yacht beam meaning

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What Is the Beam on a Boat? (Fully Explained)

Written by J. Harvey / Fact checked by S. Numbers

What is the beam on a boat ? It refers to the entire breadth of the vessel, with the widest distance between the hull’s gunwales or the port and starboard sides as the main points of reference. This is the simplest beam boat meaning.

If you want a broader definition that will expound on other considerations like beam overall, beam waterline, and beam centerline, then continue reading. You’ll also learn how to measure it and why it’s necessary for navigation and determining the direction of and from the vessel.

Table of Contents

Boat Beams Defined in Detail

How to measure the beam of a boat, how does the width of the beam impact a boat’s or ship’s performance, the role that the beam of a boat plays in nautical navigation, not to be confused with the “other” beams on a boa.

Since not all marine vessels are the same when it comes to design, it’s better to stick to the more general definition that it’s the widest distance between starboard and port.

For instance, it’s still valid for a boat owner to measure the breadth of a sailboat beam by using the windshields as the reference, instead of the gunwales. Why? Because, in the end, we’re more concerned with the widest point of the vessel when measuring the beam.

This definition only connotes the Beam Overall (BOA, in short) though. It’s just as important to dive into other considerations (usually related to measurements) connected to it such as the following:

• Beam Waterline

This refers to the width of the hull relative to the ship’s waterline. If you’re not already aware of it, the waterline connotes the point of intersection between the water surface and the sides of a vessel’s hull.

• Beam Centerline

This only applies to multihulls and refers to the distance between the vessel’s respective hulls.

A good, old tape measure will do for getting the exact boat beam measurement. Simply run it from the farthest side of the port to the starboard point that is parallel to it, and you’ll get the accurate beam measurement on a boat.

How can you be sure that you’re measuring the widest part of your boat? You can use your vessel’s line as a point of reference by using the method expounded on this site.

Ultimately, you’ll have to rely on estimations that will only be supported by using the tape measure method. When all is said and done, it’s infinitely better to just rely on a marine surveyor to take the measurement for you.

Once you get the hang of what it’s like to sail in the open sea, you’ll realize the perks of having a wider marine beam. For one, the wider or lengthier a ship gets, the more stability it enjoys – although more width often means lesser efficiency.

Certain boat makers actually design their vessels with that in mind to help them resist major stability issues like capsizing. Since both length and width are important, boatbuilders meticulously pay attention to the ideal beam to length ratio.

• The classical ratio of 3:1 is generally considered safe and solid. However, slight deviations of 4:1 or even 5:1, as evidenced by certain types of monohulls, won’t hurt.

Are you familiar with wide beam boats or widebeams as some folks in the UK refer to them? They are arguably the best example of how much beam width on a boat can impact a vessel’s perks.

For one, not only are they generally more stable, but almost anyone who has owned them or ridden in them can say that they enjoy the spacious decks that they can accommodate. “Precious real estate” is undoubtedly a phrase that gets used a lot when boat owners discuss their vessels, highlighting the importance of space in most boats and ships.

Much like how you have to be familiar with port and starboard for navigating a vessel, you should also familiarize yourself with the importance of other parts and sections. Did you know that the beam is equally vital for it?

For instance, the port beam and starboard beam are often used as points of reference.

• For example, an object, vessel, or location from the ship that is positioned at exactly 90 degrees right or left of the vessel’s head may be referred to as being spotted from the starboard beam or port beam respectively.

You might also encounter seamen using the phrase “abaft or astern the starboard beam or port beam” or “forward the port beam”. Abaft or astern only means it’s slightly behind the beam while forward connotes heading toward the head or dead ahead.

The following illustration provides a good overview of what I’ve explained above. As you can see, the first example has been encircled and represented by slanting lines to highlight its direction relative to the beam’s position.

During the latter part of the Age of Sail when pirates still plagued the high seas, ships usually had large steel or wooden beams that run athwartship. They serve highly reliable purposes both as strength members and as an effective way to trap pirates at the same time.

Sailors used to mark the main beam as the queen beam for the latter purpose. Take note that some ships still practice this, even if they already have big steel beams but they use a welding rod to mark them instead.

The fact that there are two types of it on a boat may readily create confusion as to what a beam mean on a boat, right? With that said, it’s important for any sailor to know the distinction between the actual beam of a ship and these deck-reinforcing members.

So let’s sum up our answer to “What is the beam on a boat?” It’s the widest part of a boat or ship, which, in turn, plays a pivotal role in determining its stability and storage space, and it offers referential perks for optimal maritime navigation.

If you want to make sure that your vessel is optimally stable, always take the time to measure the beam of a boat. Moreover, I hope that by adding clarificatory information here, people will finally be able to figure out what a beam means on a boat.

“My intention from the first day establishing Boating Basics Online is to provide as much help as possible for boaters who want to experience a first safe and convenient trip. So feel free to join us and share your beautiful journeys to the sea!”

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What Is Boat Beam? Understanding the Basics of Boat Beam Measurement

Boat beam, also known as the width or breadth of a boat, is an essential measurement in the design and construction of a vessel. Understanding boat beam is critical for anyone looking to purchase, operate, or design a boat.

This article will provide an overview of boat beam and its importance, discuss the different types of boat beams, explore how boat beam is measured, and examine the factors affecting boat beam dimensions. We’ll also look at the relationship between boat beam and stability, as well as regulations and standards governing boat beam dimensions. So, let’s dive in and learn about boat beam measurement!

Quick Facts

Defining boat beam: an overview.

In simple terms, boat beam refers to the width of a boat at its widest point. It is measured from the outer edge of the hull on one side to the opposite side. Some boats have a straight-line beam measurement, while others have a curved or angled measurement due to different hull designs. Boat beam is an important measurement for boats of all sizes, from small dinghies to large cruise ships. It has a direct impact on a boat’s handling, stability, and performance.

Importance of Boat Beam in Vessel Design

Boat beam plays a crucial role in the overall design and performance of a boat. A wider beam can offer increased stability, carrying capacity, and overall comfort for passengers and crew. However, a wider beam can also mean greater draft and windage, which can impact maneuverability and speed. It’s essential to strike a balance between width and performance, taking into account the intended use of the boat.

When designing a boat, naval architects consider a wide range of factors, including the intended use of the vessel, the materials used in construction, and the desired performance characteristics. Boat beam is just one of many factors that must be taken into account.

For example, a fishing boat designed for use in rough seas may require a wider beam to provide greater stability and prevent capsizing. On the other hand, a racing sailboat may require a narrower beam to reduce drag and increase speed.

Boat beam can also impact the interior layout and design of a vessel. A wider beam can allow for more spacious cabins and living areas, while a narrower beam may require a more compact layout.

Different Types of Boat Beams

There are several types of boat beams, each with unique characteristics and applications:

• Transom beam – This is the width of the boat at the transom, or the aft end of the boat. It is an essential measurement for determining the boat’s overall stability.
• Waterline beam – This measurement is taken at the boat’s waterline, which is the level at which the boat sits in the water. It is crucial for stability calculations and determining the boat’s load capacity.
• Maximum beam – This measurement is taken at the widest point of the boat, typically where the hull flares out. It is essential for determining the boat’s maneuverability and handling characteristics.

Understanding the different types of boat beams is important for anyone involved in boat design, construction, or maintenance. Each type of beam can provide valuable information about a boat’s performance and characteristics, helping to ensure that the vessel is safe, stable, and seaworthy.

How Boat Beam Measurement Works

Measuring boat beam is an important step in ensuring your boat is safe and seaworthy. The beam of a boat refers to its width at its widest point, which is typically near the middle of the boat. Here are some additional details about how boat beam measurement works:

• Flexible or Rigid Measuring Tapes: When using a flexible measuring tape, it’s important to ensure that the tape is taut and straight to obtain an accurate measurement. Rigid measuring tapes are often used for larger boats, as they provide more stability and precision.
• Laser Scanning Technology: This technology uses lasers to create a 3D image of the boat, which allows for highly accurate measurements of the beam.
• Ultrasonic Sensors: These sensors use sound waves to measure the distance between two points on the boat’s hull, which can be used to calculate the beam.
• Optical Sensors: Optical sensors use light to measure the distance between two points on the boat’s hull, which can also be used to calculate the beam.

It’s important to note that the accuracy of boat beam measurements can be affected by factors such as the shape of the boat’s hull, the presence of any obstructions or protrusions, and the conditions in which the measurement is taken.

Tools and Techniques for Measuring Boat Beam

While flexible and rigid measuring tapes are the most common tools used to measure boat beam, laser scanning technology is becoming increasingly popular due to its high level of accuracy. Ultrasonic and optical sensors are also used in some cases, particularly for larger boats where it may be difficult to obtain an accurate measurement using a tape measure.

Standard Units of Measurement

Boat beam measurements are typically expressed in feet, inches, or meters. In the United States, feet and inches are the most commonly used units, while meters are often used in other parts of the world. It’s important to use standardized units of measurement to ensure accuracy and consistency across boat measurements. When measuring boat beam, it’s also important to take into account any local regulations or requirements regarding boat dimensions.

Factors Affecting Boat Beam Dimensions

Several factors influence boat beam dimensions, including hull shape and design, boat size and purpose, and material and construction.

Boat builders must carefully consider these factors when designing and constructing a boat to ensure that it meets the intended purpose and performs optimally.

Hull Shape and Design

The shape and design of a boat’s hull can have a significant impact on its beam dimensions. A boat with a wider hull will usually have a wider beam, while boats with more rounded or tapered hulls will have narrower beams. However, the hull shape and design also affect other important aspects of boat performance.

For example, a flat-bottomed hull with a wide beam will provide greater stability and buoyancy, making it ideal for larger boats that carry heavy loads. On the other hand, a V-shaped hull with a narrower beam will cut through the water more efficiently, providing better speed and maneuverability for smaller boats.

Another important consideration is the deadrise angle, which refers to the angle at which the hull meets the waterline. A greater deadrise angle will provide a smoother ride in rough waters but may also increase beam dimensions to maintain stability.

Boat Size and Purpose

The size and intended purpose of a boat also affect beam dimensions. Larger boats designed for cruising or commercial use typically have wider beams to accommodate more passengers or cargo. This allows for a more spacious interior and greater stability when carrying heavy loads.

In contrast, smaller boats, such as dinghies or kayaks, will have narrower beams for increased speed and maneuverability. A narrow beam allows for easier handling and better performance in tight spaces.

The intended purpose of the boat also affects beam dimensions. For example, a fishing boat may have a wider beam to provide more stability when casting, while a racing sailboat will have a narrower beam to increase speed and agility.

Material and Construction

The materials and construction methods used in building a boat can also impact beam dimensions. Boats made from heavier materials such as steel or fiberglass might have wider beams to support the weight, while boats made from lighter materials like aluminum or carbon fiber might have narrower beams to increase speed and agility.

The construction method can also affect beam dimensions. Boats built using traditional methods, such as wooden planking, may have wider beams to maintain structural integrity. In contrast, boats built using modern techniques, such as vacuum infusion, may have narrower beams due to the increased strength of the materials used.

Ultimately, boat builders must carefully consider all of these factors when designing a boat to ensure that it meets the intended purpose and performs optimally. By taking into account hull shape and design, boat size and purpose, and material and construction, boat builders can create vessels that are both functional and aesthetically pleasing.

The Relationship Between Boat Beam and Stability

Boat enthusiasts know that the beam of a boat is a crucial factor in determining its stability and handling. The beam refers to the width of the boat at its widest point, which is typically near the middle of the vessel. A wider beam generally means greater stability, as it provides more surface area for the boat to rest on the water. However, wider beams can also make a boat slower and less maneuverable. It’s important to find the right balance between width and performance for safe and comfortable boating.

How Wider Beams Contribute to Stability

Wider beams contribute to stability in several ways:

• Greater surface area – Wider beams provide a larger surface area for a boat to rest on the water, which can significantly increase stability in rough or choppy conditions. This is particularly important for larger boats, which can be more susceptible to rocking and rolling in the water.
• Lower center of gravity – A wider beam can lower a boat’s center of gravity, which can improve stability and reduce the risk of capsizing or flooding. This is because a wider beam allows for more weight to be distributed horizontally across the boat, rather than being concentrated in the center.
• Increased carrying capacity – A wider beam can also increase a boat’s carrying capacity, as it provides more space for passengers and cargo. This can be particularly useful for commercial vessels or boats used for fishing or other activities that require a lot of gear.

Limitations and Trade-offs of Wider Beams

While wider beams can contribute to stability, there are limitations and trade-offs to consider:

• Draft – A wider beam can lead to a deeper draft, which can limit the boat’s ability to navigate in shallow waters. This can be a problem for boats that need to navigate in areas such as rivers, estuaries, or coastal inlets.
• Windage – Wider beams can also increase windage, or the amount of surface area exposed to the wind, which can adversely affect the boat’s speed and maneuverability in windy conditions. This can be particularly problematic for sailboats, which rely on wind power to move.
• Maneuverability – Wider beams make a boat less maneuverable, particularly in tight spaces or narrow channels. This can make it difficult to dock or navigate in crowded marinas or other areas with limited space.
• Cost – Finally, wider beams can also increase the cost of a boat, as they require more materials and labor to construct. This can be a significant factor for people who are on a tight budget or looking for a more affordable option.

Overall, the relationship between boat beam and stability is a complex one, with many factors to consider. While a wider beam can increase stability and carrying capacity, it can also lead to trade-offs in terms of maneuverability, draft, windage, and cost. Ultimately, the right beam width will depend on the specific needs and preferences of the boat owner, as well as the type of boating they plan to do.

Boat Beam Regulations and Standards

Boat beam regulations and standards exist to ensure the safety and performance of boats. The International Maritime Organization (IMO) sets global guidelines for boat beam dimensions, while national and regional regulations also apply.

International Maritime Organization (IMO) Guidelines

The IMO sets standards and guidelines for all types of boats. Their guidelines for boat beam dimensions depend on the boat’s type and size. For example, a boat over 24 meters in length must have a beam of at least 80% of its waterline length.

National and Regional Regulations

Many countries and regions have their own regulations and standards governing boat beam dimensions. These regulations vary widely depending on the type and size of the boat, as well as its intended use.

Boat beam is a critical measurement in boat design, construction, and operation. This article has provided an overview of boat beam and its importance, discussed the different types of boat beams, explored how boat beam is measured, and examined the factors affecting boat beam dimensions.

We’ve also looked at the relationship between boat beam and stability, as well as regulations and standards governing boat beam dimensions. By understanding boat beam, how it is measured, and what factors affect its dimensions, boaters can make informed decisions about boat design, purchase, and operation.

Boat Beam FAQS

What is the beam of a ship called.

The beam of a ship, also known as the breadth, refers to the widest point of the ship. It’s measured from one side of the ship to the other at its broadest part.

What is boat beam measurement?

Boat beam measurement is the process of measuring the width of a boat at its widest point. It’s measured from the outer edge of the hull on one side to the opposite side. Various techniques can be used for this measurement, including flexible or rigid measuring tapes, laser scanning technology, ultrasonic sensors, and optical sensors.

What is the purpose of a beam on a ship?

The beam of a ship serves several crucial roles. It directly impacts the ship’s stability, handling, and performance. A wider beam can offer increased stability, carrying capacity, and overall comfort for passengers and crew. However, a wider beam can also increase draft and windage, which can impact maneuverability and speed.

What is beam in naval terms?

In naval terms, the beam refers to the maximum width of a vessel. This measurement is used in designing and constructing the vessel and impacts the vessel’s stability, capacity, and performance.

Where is the beam of a boat?

The beam of a boat is located at its widest point, usually around the middle of the boat. It is measured from the outer edge of the hull on one side to the opposite side.

Do ships have beams?

Yes, all ships have beams. The beam is a fundamental aspect of a ship’s design and impacts its overall stability, capacity, and performance. It’s a critical measurement that plays a significant role in the ship’s design, construction, and operation.

John is an experienced journalist and veteran boater. He heads up the content team at BoatingBeast and aims to share his many years experience of the marine world with our readers.

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What is the Beam on a Boat? – Nautical Terms Explanation

Written by Anthony Roberts / Fact checked by Jonathan Larson

Newbie boat owners often ask, what is the beam on a boat? Although some folks might laugh, the beam of a boat is the nautical term for a water vessel’s breadth at its widest points. It is one of many words that ordinary, non-boating folks are clueless about but may want to learn.

Please continue reading to find out more about the “beam” on boats and why it matters.

Table of Contents

1. Beam Definition

2. what it means, 3. purposes/pros and cons, 4. beam dimensions, ways to measure beams, other beams on a boat, what is beam in boater’s language.

Let us understand a few nautical terms before we delve into the beam boat definition. 

A boat’s bow is its front section, while boaters call the rear “stern.” If you sit in the boat, your right side is the starboard while the left is the port. Please remember these terms because we will refer to them when defining a ships beam. 

Aside from these, you should also know about the gunwales. The gunwales make up the sides of the boat and are often made of wood or other strong materials. 

The simplest definition we could find for a boat’s beam is “maximum breadth or width.” It is a water vessel’s “cross-sectional” measurement or the distance between the starboard and port exterior surfaces.

Unfortunately, boaters do not always measure their vessel’s breadth at the gunwales. The beam width boat may be determined using the windshields or whatever widest points of the vessel are available. In any case, you may hear people call this measurement “beam overall” or BOA, which is just another term for “beam”.

If we look at a boat from the side, stern, or bow, we will notice the hull as having two portions. We have a visible section and another that’s submerged in water. The waterline marks that part of the hull where the upper section remains above water and the lower portion stays submerged. 

We can also measure the boat’s beam relative to the waterline and call it “beam waterline.”

There is also a “beam centerline,” but this term only applies to multi-hulled water vessels. Examples are a catamaran (two hulls) and a trimaran (three hulls). 

Beam centerline describes the distance between one hull’s centerline and another hull’s centerline at deck level.

You might also hear some folks using a boat’s beam and draft interchangeably. 

Unfortunately, draft differs from beam. While the beam is a boat’s starboard-to-port measurement, its draft is the vertical distance between the boat’s lowest point underwater and the waterline.

If a boat’s beam is essential for stability, a watercraft’s draft is crucial for optimum floatation. It allows boaters to avoid piloting their watercraft to areas where they could run aground.

We already know the beam boat meaning or definition. However, some folks might still ask what does beam mean on a boat.

Imagine a boat as a bus or car. The vehicle’s front-to-back measurement is its length. We call an automobile’s side-to-side dimensions its width. But in the case of water vessels, we call it “beam.” 

Hence, a boat’s beam is the equivalent of a car’s width. So, “if you ask, where is the beam on a boat?” it would be at its widest parts.

The next question you might ask is, why do you need to know a boat’s beam?

Boat builders and ship engineers design water vessels with the ideal beam to ensure “initial stability.” 

Floating on water is not as smooth or stable as a car moving on paved roads. Forces impact the boat’s sides (starboard and port), pushing it laterally and causing it to tilt.

A boat with a higher beam value is more stable, allowing the watercraft to resist overturning or capsizing. However, this has the disadvantage of making the boat harder to right once it’s flipped over and harder to maneuver around obstacles. 

The large size may also make docking tougher in small spaces, though most people will no doubt enjoy the interior area on a wide-beam vessel, where they can invite more people onboard and carry more gear during trips. 

The beam measurement on a boat depends on its aspect or length-to-beam ratio. 

For example, the ideal beam to length ratio for small sailboats (i.e trailerable sailboats and dinghies) is 2:1. These watercrafts’ beams are about half their length. For instance, if the boat measures 18 feet long, its beam should be nine feet.

Meanwhile, racing sailboats can have a 5:1 aspect ratio. For instance, a 40-foot racing sailboat will have an eight-foot water vessel beam.

Ocean-going vessels have large aspect ratios (i.e., 20:1), while rowing shells with oars have 30:1 ratios. 

The simplest way to measure a boat’s beam is by using a tape measure, latching one end on the vessel’s port (or starboard) and extending it to the starboard (or port).

Alternatively, you can do some math if you know your boat’s length. The formula is:The simplest way to measure a boat’s beam is by using a tape measure, latching one end on the vessel’s port (or starboard) and extending it to the starboard (or port).

Alternatively, you can do some math if you know your boat’s length. The formula is:

• Boat’s beam = length overall (LOA) 2/3 + 1

Please note that “2/3” is an exponent. Hence, you must raise the LOA value by two-thirds power before adding one (1).

For example, suppose you have an 80-foot yacht.

• Beam = LOA 2/3 + 1
• Beam = 80 2/3 +1

First, we can square 80 to get 6400 (80 x 80 = 6400)

Next, we must find the cube root of 6400, giving us 18.57.

Alternatively, we can determine the cube root of 80 (4.31) before squaring the value to get 18.57.

Either way, you will end up with an 19.57-foot beam for the 80-foot yacht.

It is worth noting that the term “beam” does not only refer to a watercraft’s breadth or width. 

Boaters also use this word to mean the vessel’s structural support, running athwartship. 

You might hear sailors talk about “astern or abaft the port beam or starboard beam.” Some might shout, “forward the starboard beam.” 

We are more familiar with the phrase “dead ahead” than “forward the port or starboard beam,” which means the same thing. Meanwhile, “astern” implies whatever the sailors saw is slightly behind the port or starboard beam.

You are more confident now when somebody asks what is the beam on a boat. This term might mean something else in other contexts, but boaters and seafarers know it refers to a watercraft’s breadth or width.

It could be at the waterline or deck level. Regardless, a boat’s beam is essential in determining its stability in rough waters. The term should also be differentiated from other nautical concepts to avoid confusion.

Ten years of enjoying countless trips on boats never made me love them any less! So I am here to put all those experiences into good use for other boaters who want to have a safe and fun trip with their friends and families.

What Is The Beam Of A Boat (Full Breakdown)

Probably the most common way that people describe the size of a boat is in its length, measured at the centerline from the bow to the stern.  You’ll hear boaters talking about their 21, or 19 footers but hardly ever do people focus on the boat’s beam, although it is equally important.  So, what is the boat’s beam, and why should you care?

The boat’s beam is the width of the boat measured at its widest part.  As a rule of thumb, wider boats are more stable (up to a point) and have more storage space, while narrower boats are faster and easier to maneuver.  On the other hand, wider boats may also be more uncomfortable and “choppier.”

Deciding on a narrower or wider beam will depend on your personal preference and what you intend to do with the boat.  Understanding the effect of wider and narrower beams is vital to ensuring you get the most out of your boat.

The “Beam” Of A Boat

The term “beam” originates from the earliest ships constructed from wood.  The hull of those early ships kind of resembled an upside-down roof construction.  Large wooden beams formed the ribcage-like support structure on which builders fixed the hull. 

The center beam was usually the longest and thickest of the lot.  Builders used the length of this beam to determine the width of the ship as it was the widest point, requiring the most substantial beam. 

As a result, the ship’s width became known as “the beam.”  This further developed to refer to the general side of the vessel.  So, where the front is called “the bow,” the back is called “the stern,” the left and right sides became “the port beam” and “the starboard beam,” respectively.

The Relation Between A Boat’s Length And Beam

It’s probably a pretty obvious statement, but boat builders usually work around pre-determined ratios between a boat’s length and beam when building a new vessel (unless you are accidentally trying to build a barge, that is.)

For example, for boats less than 20 feet long, builders typically use a ratio of 2:1, meaning that the beam is around half the boat’s length.  However, as the boat increases in length, so does the ratio.  For example, thirty feet boats have a length-to-beam ratio of around 5:1. 

Apart from the boat’s length, the type or purpose of the boat will also affect how broad they build the beam.  The average beam of a center console boat is smaller than that of the average motor yacht.  Similarly, catamarans will have a wider beam than monohulls because they are essentially two hulls wide.

Wider Vs. Narrower Beam – Which Is Better?

Although there are ratios of length-to-beam as mentioned above, there are variations between manufacturers.  Meaning that you may find vessels with everything else being equal, but one broader than the other. 

In any case, you have to understand the difference between a broader and narrower beam to make the right choice for your particular use and needs. 

1. Wider Beams Are Generally More Stable

Think of the stability of a catamaran vs. a speed boat.  You are less likely to bob around in the wider catamaran in rolling waves and foul weather.  In addition, its wider beam acts as a strong foundation, making it less of a rock-and-roll experience. 

This added stability is one of the reasons why cats are top-rated options for sport fishing vessels.   Being anchored at a deep-sea fishing spot for hours on end is just more forgiving in a boat that isn’t rolling quite as much with the waves.  It also means that a sudden wave to the beam is less likely to capsize the vessel.

However, you should be aware that although wider vessels are generally more stable, it is not a hard and set rule as other aspects come into play, such as the hull design, the center of gravity, etc. 

A deeper hull, or chine, will add to stability, while a shallow hull coupled with a broader beam may be more unstable than if the beam were narrower. 

2. Narrower Beams Are More Comfortable

The flip side of the increased stability is that wider beams tend to have a more uncomfortable and bumpier ride than narrower hulls.  This is because that stronger foundation means that every bump in the sea is transferred through the boat’s hull, whereas a narrower hull is better at cutting through those bumps. 

Even when anchored, if the sea is choppy, you may find yourself bouncing around a little more in the wider hull.  So, you must decide whether you prefer bouncing or rolling.

3. Wider Beams Have More Space

It should go without saying, but if you have a wider beam, you have a wider boat, which means you will have more storage and cabin space. 

Keep in mind that I’m comparing apples with apples here – meaning that a wider monohull will have more storage than a narrower monohull, and the same for two cats. 

Try not to compare the beam of a cat with a monohull because their interior layouts are very different from one another.

4. Narrower Beams Are Faster

If you have two boats with the same specs, but one is narrower than the other, the speed prize will go to the narrower vessel. 

Narrow-beamed boats have smaller contact areas with the water, meaning they can cut through the water better than wider boats. 

This smaller surface area also translates to their maneuverability, meaning that (at least in the docks) they are going to be easier to maneuver in tight spaces.  Conversely, you may find them slightly harder in very few instances because of their decreased stability. 

5.  Wider Boats Have Size Limitations

OK, sure, for your average sport fishing boat, adding a foot across the beam isn’t going to force you to raise the “vessel with a restricted ability to maneuver” day shape, but it does come with a few considerations. 

Narrow channels can become more difficult to traverse with wider boats.  Especially river channels focused on small, holidaying vessels.  Similarly, the wider your boat is, the more daunting the task will be of mooring into a tight space.  You may even be required to pay more for a wider mooring if your vessel is too wide for a standard one.

The boat’s beam refers to the boat’s width at its widest point.  Having a wider beam generally means that your boat will be more stable and have more space.  However, it also means that your boat may be slower, more uncomfortable when riding, and harder to maneuver.

However, I need to add that all these pros and cons should be taken simply as guiding points in your consideration.  If you are stuck between two vessels, the best choice is to take both out to sea and choose the one that fits your needs and use best.  In the end, the boat you enjoy is the boat for you.

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What is a Boat’s Beam? Your Guide to the Beam on a Boat

A boat’s beam is the widest point of the boat. It’s an important measurement to know, just like the length of your boat is vital to know. Like many things in boat design, the beam is one of the tools that yacht designers tinker with to get just the right characteristics. But it also has lots of implications for boat owners too, so let’s take a closer look at a boat’s beam.

Table of Contents

What is “beam” on a boat exactly, beam of the boat and boat performance, boat length and beam, beam and marina choices, beam and cabin size and space, beam and navigation, beam and stability, wide boat beams pros, wide beam boat cons, narrow beam boat pros, narrow beam boat cons, trailer boat beam, narrow beam boats, measuring a boat’s beam, finding the beam sweet spot, faqs (frequently asked questions).

The beam of a boat is the widest point of the boat. It is usually located at the middle or slightly aft of the middle of the boat.

A boat’s beam impacts its performance in several ways:

• Stability : Wider beamed boats are generally more stable than narrower boats. They are less likely to capsize in waves.
• Speed and maneuverability : Narrower beamed boats are often faster and more maneuverable than wider boats.
• Comfort in waves : Narrower boats tend to slice through waves better, while wider boats are more likely to feel the impact of waves and chop.
• Living space : A wider beam provides more interior cabin space and storage capacity compared to a narrower boat of the same length.
• Trailering : Boats with beams under 8’6″ wide can be trailered on the road in most U.S. states without special permits. Wider boats may require permits.

Traditional Beam Terminology

Traditionally, boatbuilders used large wooden beams to create the boat’s frame. These beams ran laterally across the boat. As a result, a ship under construction looked like a massive ribcage, with support beams laid out. Boatbuilders would then add the rest of the wooden structure around the beam skeleton. 

The center beam was usually the longest and thickest beam. This beam’s measurement was used to measure the width of the boat. Today, the word “beam” still refers to the boat’s widest point…although sometimes it’s not in the center and it’s seldom made of wood.

Smaller boats under 20 feet often have a two-to-one ratio. Your eight-foot dinghy will probably have a beam of about four feet. Boats over 30 feet have a bigger ratio, often about three-to-one, four-to-one, or five-to-one. A sailing monohull might be 40 feet long and 12 feet wide.

These are just estimates and rules of thumb, of course. A boat’s beam is one of those things carefully considered by yacht designers and manufacturers. They want just the right handling characteristics, speed, and stability.

Beam Impacts on a Boat

Today, when someone asks about your boat’s beam, they want to know how wide your boat is. Your boat’s beam can impact your navigation possibilities, your marina choices, the size and comfort of your living space, and your comfort at sea.

Your boat’s beam can affect your marina options. Many marinas were built decades ago when narrower beamed boats were standard. Today’s more modern boats often have wider beams to provide a roomier feel in the cabin and give boaters more space. Older marinas might easily accommodate boats with a beam of 12 feet but may struggle to find a place for boats with larger beams.

If you have a large beamed boat such as a catamaran or trimaran, your marina choices will be even more limited. In addition, you might have a harder time finding a boatyard that can haul your boat and place it into dry storage. Many marina boat lifts are limited to hauling boats with beams less than 20 feet wide.

The larger the beam, the more space you’ll have in the boat’s cabin. If you are looking at liveaboard boats, you might be drawn to beamier boats with more space and storage options. Extra beam adds an enormous amount of space to the interior of the boat. This is one reason that trawlers and powerboats feel so much roomier than monohull sailboats–they have greater beams and they carry that beam all the way aft. 

In sailboats, it’s a modern design trend to make beamier boats. Plus, the beam is carried much farther aft than in traditional designs, resulting in wide-open cockpits and large, flat transoms.

The smaller your beam, the more places you can visit. In England, narrowboats have beams that are less than seven feet wide. These narrowboats can navigate England’s canal system. Some of England’s canal locks are very narrow, and only boats that can squeeze through seven-foot wide locks can successfully navigate these beautiful canals. 

There are many other examples of a boat’s beam affecting a boater’s navigation possibilities. For example, some French canals can only accommodate beams of up to 15 feet. To successfully complete America’s Great Loop, boaters should use a boat that is less than 23 feet wide.

Related: Best Boat for the Great Loop

Boats with narrower beams are often faster, especially if they have a longer waterline. However, they might be less stable than a wide-beamed boat.

Boat Design – Is More Beam Better?

In many ways, the beam of a boat is a matter of personal taste. Here’s a look at the pros and cons of wide boats vs narrowboats.

Wider boats are often more stable. For example, if you are looking for a stand-up fishing kayak, you’ll want a boat with a wider beam. A kayak with a narrow beam will be faster and more maneuverable but will be very hard to stand up on while keeping your balance.

Wider boats have more weight capacity than narrower boats of the same length. If you are hauling gear in your boat or need more room to spread out, a wider beamed boat might suit your needs better.

If you trailer your boat, a boat with a wide beam might be more challenging to tow on the road. In most states, if your boat is wider than 8’6″ you’ll need a special permit to tow your boat on the road. 

Many marinas are built with narrower boats in mind. Most marinas will find room for boats with beams less than 16 feet. Anything bigger, and you might struggle to find a traditional marina slip. 

In addition, a wide beamed boat might be too wide for older canal systems.

A narrow beamed boat is often more maneuverable and faster. Have you ever seen an Olympic sculling race? These narrow, long boats can really fly! If you are looking for a fast, fun boat, look for a boat with a narrower beam. Narrow beamed boats are often better at slicing through waves and chopping, whereas wider beamed boats are more likely to feel every bump and wave.

Narrow beams have less storage capacity and less room. If you live on your boat or plan on sleeping on your boat overnight, you might find a narrow boat limiting. 

Narrowboats are less stable and might feel more tippy than boats with wider beams.

If you want to trailer a boat on the road in the US, you’ll want to consider its beam very carefully. Trailerable boats should generally have a beam of 8-feet 6-inches or less. Forty-seven states only allow trailered loads with an 8’6″ beam or less.

However, a few states allow wider loads without permits, so check your state’s regulations. Anything larger would be considered a wide load and require special permits and additional considerations. If you want to trailer a boat on the roadways easily, buy a boat that is less than 8’6″ wide.

Narrowboats are long, narrow boats made for canal life. These boats have a beam that is less than seven feet to fit inside tiny locks easily.

Wide Beam Boats

Wide beam boats are more stable and less likely to capsize in waves. Modern boats are usually beamier than older, more traditional boats. Modern buyers are often looking for boats with extra space and condo-style amenities rather than small, camping-style interiors. If you are thinking about sleeping on your boat or living on your boat, consider how a wider beam will give you more space.

Catamarans are very popular cruising and charter boats. They have wide beams and offer couples and families additional space to spread out. In addition, their wide beam makes these boats very stable. These boats don’t heel as sailing monohulls do. This means that boaters can easily move around their boats while underway.

While monohulls and trawlers are often between 11 and 16 feet wide, cruising catamarans are usually between 21 and 26 feet wide. Monohulls vs catamarans is an ongoing debate, and of course, either choice involves compromise.

Trimarans are another style of popular wide beamed boat. These boats have three hulls and are even wider than catamarans. Cruising trimarans are up to 30 feet wide. If you have a larger trimaran, you’ll enjoy a stable ride but will have more trouble finding marina slips and haul-out yards.

Determining a Boat’s Beam

The easiest way to determine your boat’s beam is to refer to the boat’s documentation. If a factory-made your boat, you should have some paperwork that lists the boat’s beam. If your boat is Coast Guard documented, the boat’s measurements should be listed on that paperwork.

Measuring a boat’s beam might be easy or complex, depending on how big and complicated your boat is. If you have a 10-foot kayak, you can simply get a tape measure, find the widest part of the kayak, and note the measurement.

To measure a boat’s beam, first, you must determine the boat’s centerline. To do this, mark the center of the boat’s bow and the boat’s stern. Mark the centerline by tying a piece of string from the bow’s center to the stern’s center. Of course, if you have a sailboat or a boat with a bimini or other obstructions, this is easier said than done.

Now, find the widest point of the boat. The widest point is usually the middle of the boat or slightly aft of the middle of the boat. Now, measure the boat’s widest point, ensuring the measuring tape stays perpendicular to the centerline string.

Consider your plans for your boat while you consider your boat’s beam. If you are looking for a stable kayak for fishing, find a nice, wide kayak. A dinghy that needs to haul several people and all the goodies should have a wide beam. A wider beam will give you more living and storage space if you are living aboard .

However, if you want a fast and maneuverable kayak, look for a kayak with a narrower beam. If you want a fast dinghy, consider a narrower one. If you want to boat in narrow canals or access small marinas, find a boat that has a narrower beam. Finally, if you want to trailer your boat, look for a boat that has a beam less than 8’6″.

Of course, the answer to finding the perfect boat that’s stable, trailers, crosses oceans, and stores all the stuff is quite simple. You just need a flotilla of different boats!

Where is a boats beam?

The boat’s beam is its widest point. The widest point on a boat is usually in the middle or slightly aft of the middle of the boat. 

How do you measure a boats beam?

First, mark the boat’s centerline from bow to stern. Next, find the widest point of your boat and measure it, making sure that the measuring tape is perpendicular to the centerline.

What does beam on trailer mean?

A trailerable boat should have a beam of 8-feet 6-inches or less. Most states require wider beamed boats to have a special permit and follow special regulations. If your boat’s beam is 8’6″ or less, you won’t need a special permit to trailer it on the road.

Matt has been boating around Florida for over 25 years in everything from small powerboats to large cruising catamarans. He currently lives aboard a 38-foot Cabo Rico sailboat with his wife Lucy and adventure dog Chelsea. Together, they cruise between winters in The Bahamas and summers in the Chesapeake Bay.

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What is the Beam of a Boat?

Which part of a boat is the beam.

If you have recently taken an interest in boating or are a helmsman looking to buy your first vessel , navigating the different boat points can be confusing. One of the most important factors to consider is the beam, as this plays an essential part in the stability and manoeuvring of a boat.

In this boating guide, we will delve into what the beam of a boat is, how you can measure this and why it is essential to the functionality of the boat or yacht.

What is the Beam and How is it Measured?

What is the difference between the beam and the waterline beam, do wide beam boats perform better, how does the beam of a boat impact boat performance, the 3 key takeaways about the beam of a boat, what is the beam of a boat – quick summary.

The beam of a boat is most commonly known as the widest point of a boat or yacht but actually means a lot more than that. It is also used in the transportation of boats, and where you should hold your sails if you are in a sailboat or yacht. Understanding the boat’s beam will promote safety and prevent confusion on the water.

When considering the parts of a boat, the beam refers to the entire breadth / widest point of a boat or yacht starting on the port side and ending on the starboard side when standing at the back of the boat looking forward. It first originated when boats were being constructed of wood, and the overall size was calculated using the length along the beam along with the centreline dimensions. You may hear some sailors refer to the beam as the ‘BOA’ which means the beam overall. As well as the width beam, there is also a centreline beam but is only applicable for vessels that have two or three hulls such as a catamaran or a trimaran.

To measure the beam of a boat, first start on the furthest side of the hull on the port side and run a tape measure parallel across to the furthest starboard side , ensuring it is straight and in place for an accurate reading. You can follow the same method to calculate the waterline beam but we would recommend taking multiple measurements and taking an average of them all.

A beam and a waterline beam are two related terms, but they have different direct definitions. The main beam is the measurement at the highest point of the boat from the left side of the vessel to the right side when standing at the bow looking forward. 

The waterline beam is still the widest part of the boat measuring from the port side to the starboard side, but it is measured from the waterline where the boat sits when floating. The two measurements you will receive when calculating the beam will be different because of the points where you are calculating it, but both are still essential in the boating world.

Having a wide beam boat means that your overall stability will increase because it will prevent the centre of gravity from shifting towards the left or the right which reduces the chance of capsizing. However, this will make the secondary stability lower and reduce the overall speed of the yacht or boat. The wider your beam is, the further your storage is able to move from the centreline due to having more stability all around the vessel.

Purchasing a narrow-beam boat means that it will travel faster and have a higher secondary stability meaning if your boat tips, you have a higher chance of it recovering and not capsizing. However, this means that the speed of your yacht or boat will be higher. 

Depending on the size of your boat, there will be a different length-to-beam ratio. A large yacht may include a 9 to 1 ratio, whereas a smaller power boat may only have a 2 to 1 ratio. Having a narrow or wide beam boat doesn’t necessarily mean it will perform better, it just means that it is more suited to the functionality. If you are looking for a speed boat, we would recommend investing in a narrow-beam boat. However, if you are looking to buy a cruiser or larger boat, then a wide beam is the option for you.

The beam is an essential feature on a boat and affects the boat’s performance in many ways including the clearing calculation, speed, handling and stability.

Clearance Calculation

When you are travelling in your vessel, you may encounter a narrow channel or bridge and be unsure if you will be able to fit. If you find yourself in this position, you can refer to your beam dimensions as this will show if you can fit through. Because the beam is the widest measurement of the boat, you can be assured that you won’t damage your boat if this is lower than the width or height of the channel or bridge.

As mentioned previously, the size of your beam will impact the overall speed of your boat. Because a narrow beam boat requires less drag, this makes it easier to move through the water with less power. Wide beam boats are still able to move at high speeds but it just means it will require more power.

Having a boat with a narrower beam will lead to sharper turns and response times, meaning they are more manoeuvrable or if you become in a position where an emergency turn is required, this will be easier to do. Whilst large beam boats may have a larger turning circle, they have wider lateral stability and turning will be a lot smoother throughout. 

The beam of a boat is a key element in providing stability which is essential when cruising on the seas. If you are facing potentially rough conditions, the size of your yacht or boat is essential. Large beam boats tend to be more stable due to the bigger surface area contact with the water.

If you are looking to buy a new boat or are interested in the sailing components, here are 3 key takeaways to consider regarding the beam of a boat:

1. The beam is the widest part of the boat and is measured from the port side to the starboard side.

2. Boat beams are essential to the stability of a vessel.

3. The ideal beam size is dependent on the boat’s purpose.

Knowing the components of a boat, particularly the beam, is crucial for navigating, functionality, and in emergency situations. By using the tips mentioned above, you can easily measure the beam of a boat, apply this to your specific needs and avoid any confusion.

Clipper Marine Mailing List

Beam: Definition (Boat)

The beam of a boat refers to the greatest width of a boat when measured between its two sides. Sailors use the beam measurement to determine a sailboat’s capsize ratio for offshore suitability, while marinas use it to assign appropriately sized dock slips. The beam measurement may also be used when calculating handicaps for yacht regattas .

Things to know about the beam of a boat:

• Wider beams typically result in a more stable boat.
• This stability is sacrificed for recovering from a capsize scenario (a boat with a wider beam will be harder to recover if it flips).
• A boat with a wider beam will tend to heel (tilt when sailing or facing pressure from the wind) less easily.

The beam is what some might consider the opposite of the Length Overall (LOA), which refers to the length of the boat from the bow (the front) to the stern (the back) of the boat.

Beam Measurement Variations

While the simplest term of “beam” refers to the boat measured at the widest point, there are a few important distinctions that may be used in specific circumstances such as shipbuilding or racing, such as:

• Beam (max): the overall widest measurement of the boat from side-to-side.
• Beam (hull): the measurement of the beam, as measured at the hull.
• Beam (waterline): the measurement of the beam at the waterline.

Similar and Related Terms

Since the term “beam” covers a fairly basic aspect of boats, it should come as no surprise that other nautical terms incorporate the use of the term “beam” as well. These are:

• Beam reach: When you are sailing at a roughly 90 degree angle to the wind.
• Beam sea: When waves are hitting the boat on its side or beam.

The word “beam” is one of many that are specific to boats and boating. New boaters and sailors often remark that it’s difficult to feel confident when learning to sail with so much new vocabulary thrown into the mix, but with time and experience, you will likely find that using terms such as “ helm “, “ helm’s a-lee “, “ jibe ho “, and “beam” become second nature.

Listing your boat with Yachtlify provides several unique benefits, including:

• List once, post on multiple platforms (Yachtlify.com, Facebook Marketplace, Instagram, and others).
• Schedule showings and sea trials with our calendar and reminders.
• View listing engagement analytics across platforms.
• eSign, state forms, and Coast Guard forms to manage closing documentation in once place.

What Is the Beam of a Boat

Key Take­aways:

• The boat’s beam is the widest part of the boat’s hull and mea­sures the boat’s width at its widest point.
• Under­stand­ing the boat’s beam is cru­cial for free­dom and com­fort on the water.
• Accu­rate beam mea­sure­ment deter­mines max­i­mum sta­bil­i­ty and maneu­ver­abil­i­ty.
• A wider beam allows for more inte­ri­or space and free­dom to move around inside the boat.

Have you ever won­dered about the beam of a boat?

Well, get ready to set sail into a world of knowl­edge! In this arti­cle, we’ll dive into what the beam of a boat is and why it’s impor­tant.

You’ll dis­cov­er how boat beam mea­sure­ments are cru­cial for sta­bil­i­ty and how they impact the inte­ri­or space.

So, if you’re ready to explore the won­ders of boat beam, hop on board and let’s embark on this exhil­a­rat­ing jour­ney togeth­er!

Table of Con­tents

The Definition of Boat Beam

The boat’s beam is the widest part of the boat’s hull. It’s the mea­sure­ment of the boat’s width at its widest point.

For those of you who crave free­dom on the open water, under­stand­ing the boat’s beam is cru­cial. Imag­ine your­self stand­ing on the deck of a boat, feel­ing the wind in your hair and the waves beneath your feet . You want a boat that gives you the free­dom to move around com­fort­ably, with­out feel­ing cramped or con­fined.

This is where the boat’s beam comes into play. A wider beam means more space to move around, to spread your wings and enjoy the vast­ness of the sea. It allows you to take in the breath­tak­ing views with­out feel­ing restrict­ed.

You can check this video we have found on Youtube:

Importance of Boat Beam Measurement

Mea­sur­ing the width of your ves­sel is cru­cial to ensure prop­er sta­bil­i­ty and maneu­ver­abil­i­ty. The beam, or width, of a boat plays a sig­nif­i­cant role in its over­all per­for­mance on the water. By accu­rate­ly mea­sur­ing the beam, you can deter­mine the max­i­mum sta­bil­i­ty and maneu­ver­abil­i­ty of your boat, allow­ing you to enjoy your time on the water with peace of mind.

To help you under­stand the impor­tance of boat beam mea­sure­ment, here is a table that high­lights the rela­tion­ship between beam width and stability/maneuverability:

As you can see, a nar­row beam pro­vides high­er maneu­ver­abil­i­ty but low­er sta­bil­i­ty, while a wide beam offers high­er sta­bil­i­ty but low­er maneu­ver­abil­i­ty. Find­ing the right bal­ance is essen­tial to ensure your safe­ty and enjoy­ment while boat­ing.

Factors Affecting Boat Beam

To ensure prop­er sta­bil­i­ty and maneu­ver­abil­i­ty on the water, con­sid­er fac­tors that affect the width of your ves­sel.

The beam, or width, of your boat plays a cru­cial role in its per­for­mance and your over­all boat­ing expe­ri­ence.

One impor­tant fac­tor to con­sid­er is the type of water you’ll be nav­i­gat­ing. If you plan to pri­mar­i­ly cruise calm lakes or rivers, a nar­row­er beam may be suf­fi­cient. How­ev­er, if you’re an adven­tur­ous soul seek­ing the free­dom of open seas or rough waters, a wider beam is essen­tial for sta­bil­i­ty and safe­ty.

Anoth­er fac­tor to take into account is the pur­pose of your boat. If you’re an avid fish­er­man, a wider beam can pro­vide more sta­bil­i­ty when reel­ing in that big catch. On the oth­er hand, if you’re look­ing for speed and agili­ty, a nar­row­er beam can reduce drag and improve maneu­ver­abil­i­ty.

The num­ber of pas­sen­gers you plan to accom­mo­date should also influ­ence your choice of beam width. More pas­sen­gers may require a wider beam to ensure every­one’s com­fort and safe­ty.

Ulti­mate­ly, find­ing the right beam for your ves­sel is about bal­anc­ing sta­bil­i­ty, maneu­ver­abil­i­ty, and per­son­al free­dom on the water.

Understanding Boat Stability and Beam

Under­stand­ing boat sta­bil­i­ty and beam is cru­cial for your safe­ty and enjoy­ment on the water. When you’re out on the open sea, you want to feel free and in con­trol. Know­ing how sta­bil­i­ty and beam work togeth­er can help you achieve that sense of free­dom.

Here are a few things to con­sid­er:

• Bal­ance : A wider beam can pro­vide bet­ter sta­bil­i­ty, allow­ing you to feel con­fi­dent and secure as you nav­i­gate the waves. It gives you the free­dom to move around the boat with­out feel­ing off-bal­ance.
• Han­dling : A boat with a nar­row­er beam may be more maneu­ver­able, giv­ing you the free­dom to explore tight spaces or nav­i­gate through crowd­ed areas with ease. It allows you to take con­trol and enjoy the thrill of the ride.
• Com­fort : A wider beam means more space inside the boat, giv­ing you the free­dom to bring along friends, fam­i­ly, and all the gear you need for a day of adven­ture. It pro­vides room to relax and enjoy the jour­ney.
• Ver­sa­til­i­ty : Depend­ing on your pref­er­ences, dif­fer­ent boat beams offer dif­fer­ent advan­tages. Whether you pre­fer sta­bil­i­ty, maneu­ver­abil­i­ty, or spa­cious­ness, under­stand­ing boat sta­bil­i­ty and beam gives you the free­dom to choose the ves­sel that best suits your needs.

How Boat Beam Impacts Interior Space

When it comes to inte­ri­or space, a wider beam allows you to have more free­dom to move around and bring along all the essen­tials for your day on the water. A boat’s beam refers to its width at its widest point, typ­i­cal­ly mea­sured in feet. The wider the beam, the more space you have inside the boat. This means you can bring more friends, fam­i­ly, and gear with you on your adven­tures.

To give you a bet­ter idea of how boat beam impacts inte­ri­or space, let’s take a look at this table:

As you can see, as the beam increas­es, so does the avail­able inte­ri­or space. With a wider beam, you have the free­dom to move around com­fort­ably, whether it’s to access the stor­age com­part­ments, stretch your legs, or enter­tain guests. You can also bring along all the essen­tials for your day on the water, such as cool­ers, fish­ing gear, and water toys.

So, now you know what the beam of a boat is and why it’s impor­tant to mea­sure it accu­rate­ly. Fac­tors like hull design, weight dis­tri­b­u­tion, and sta­bil­i­ty are all influ­enced by the boat’s beam.

Under­stand­ing how beam impacts inte­ri­or space can help you make informed deci­sions about the lay­out and func­tion­al­i­ty of your boat.

So, next time you’re out on the water, take a moment to appre­ci­ate the sig­nif­i­cance of boat beam and its role in the over­all boat­ing expe­ri­ence.

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What is The Beam of a Boat? (Precisely Answered)

The beam of a boat is an important part of its stability. A wider beam increases speed, reduces water resistance and makes a vessel less likely to capsize. On the other hand, a narrower beam cuts through the water more efficiently.

Table of Contents

How Are Boat Beams Defined in Detail?

There are a few different ways that a boat beams can be defined in detail. The way that they are defined is important to ensure that the structure of the vessel is structurally sound and that it can support the weight of the crew. For example, the beams can be defined in terms of speed to length ratio and underwater volume.

Measurement

Boat beams are important to understanding the stability of a vessel. They can help you safely navigate through a narrow passageway and even determine whether or not a boat is able to sail through an obstacle.

Boat beams can be measured at several points on the hull. The most accurate boat beam measurement is the one at the widest point of the vessel. This is typically located in the watercraft’s center.

Beams can be made of wood, metal, or concrete. Generally, these are used in conjunction with a draft to provide structural support and balance loads on the vessel.

A beam can be measured by using a tape measure. The width is measured from the hull to the hull. It is usually listed in feet and inches.

Speed-to-Length Ratio

A speed-to-length ratio of boat beams is a way to determine the stability of a boat. This can be determined through mathematical equations, but is also dependent on a number of factors. It is important to understand the pros and cons of both narrower and wider beams before purchasing a new boat.

A lower ratio indicates greater boat stability. Higher ratios mean that the hull is prone to roll. If the hull is too wide, it can cause more bouncing in rough seas. On the other hand, a narrower beam means that the hull cuts through water better.

An L:B ratio of around seven is a good rule of thumb for stability, but a higher ratio could make a boat roll uncomfortably. However, a high L:B ratio has been shown to increase fuel efficiency.

Underwater Volume

The underwater volume of a boat is a measure of the amount of hull under water. It’s usually expressed in cubic feet or meters. Depending on the ship’s size and weight, the volume can be measured in a variety of different units.

This measurement may be complicated to calculate, but naval architects can usually get a pretty good idea of the volume of the underwater part of the hull with a bit of tinkering. There are a few ways to do this, but the simplest is to simply divide the boat’s length by its width.

When measuring the volume of the hull, it’s important to pay attention to the beams. They are essential to the stability and speed of a boat. A narrower beam makes it easier for the boat to cut through the water and is less likely to be swept away by large waves.

How to Measure the Beam of a Boat?

Boat beams are measured at several different points on the hull. These points are generally referred to as the stern, the bow, the gunwale, and the centerline.

Using a carpenter’s square to check the angle of the tape, you can then determine which point is the widest on the hull.

Typically, the beam is listed in inches and feet. It is usually the widest part of the hull, but the width may also be indicated as the distance between two parallel gunwales at that point.

You should measure the beam of a boat three times to ensure accuracy. This measurement is important in determining the stability of the vessel, its ability to pass through passages, and the storage space available.

To measure the boat’s beam, you need a carpenter’s square, a tape measure, and a ball of twine. Firstly, mark the centerline of the boat on a piece of twine.

After doing this, move the tape a few inches forward and a few inches to the rear. Once you’ve done this, you can then use a measuring tape to measure the boat ‘s beam.

How Does the Width of the Beam Impact a Boats Or Ships Performance?

The width of a boat’s beam is a critical part of its performance. This is because it determines its stability in rough waters and how fast it can travel. It is also important in tight passages. In addition, it relates to the way in which the ship handles.

There are several ways to measure the beam. For example, one may simply place a ruler on the widest point of the boat. However, it is more convenient to measure the beam from the back of the boat.

Another measurement to check is the angle of the buttocks. These can be measured visually from abeam, or with a profile drawing. If the angle is too large, the flow will separate, and eddy making can occur.

Some ships are designed to have low angles of entrance, like Darts. This reduces wave-making drag and helps maintain streamline flow of water. On the other hand, a yacht with a larger angle will create more wave resistance, and generate a larger wake full of eddies.

Hull shape is also a factor. A V-shaped displacement hull is often used for catamarans. They have a fine stern, which is crucial to low wave resistance.

Hull shape is also a matter of personal preference. For example, a wide, flat stern gives planing lift, which allows the vessel to surf through waves without getting bogged down.

One thing to keep in mind is that a narrower beam can increase speed. But a wider beam can be better in rougher waters because it provides a better handling.

Why Does A Boat’s Beam Matter?

The boat beam affects the stability of the boat. It also determines how safe a passage is around obstacles. Knowing the boat’s beam can help you understand the type of boat that would be ideal for your needs.

Boat beams are vital components of the structure of a boat. They provide a platform for other structures, like masts, and they distribute weight evenly. Modern beams are made of light materials.

Wider beams are generally more stable. However, it’s important to consider the length, size, and weight of your boat to determine which beam will work best for you.

A wider beam allows volume to be distributed farther away from the centerline. This helps to reduce drag, allowing the boat to move faster. In addition, the extra weight increases the righting moment, which is the force that the center of gravity generates.

The boat’s beam also impacts the interior space of the boat. As a result, a narrower beam will have less room for passengers and cargo. On the other hand, a wider beam will have more storage space.

The Role That the Beam of a Boat Plays in Nautical Navigation

The beam of a boat is a key element in navigation. This is because it determines how stable the boat is. It also impacts the handling of the vessel and its speed. In addition to this, it can determine the direction of the boat.

For example, a wide beam can increase the stability of the vessel. It can also improve its fuel efficiency. However, a wide beam can make it harder to maneuver in tight spaces. Therefore, certain boat makers design their vessels with wider beams in mind.

In general, the boat beam is measured at the midpoint of the vessel. To measure the beam, you need a tape measure. You also need the line of the vessel as a reference. Once you have these measurements, you can begin making estimations.

Boats come in all shapes and sizes. But one thing remains the same: they all need space. People who own boats enjoy spacious decks.

A wider beam means more space. In addition, a longer beam means more stability and less water resistance. Depending on the length of the boat, the beam can be anywhere from 8 feet to 20 feet.

Besides being a crucial element in navigation, the beam is a necessary factor when determining the direction of a boat. Ship motions can have serious consequences on the vessel’s structural integrity.

Some of these motions include pitching, rolling, and yawing. These motions are important to understand because they have material and secondary load responses.

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What Is A Boat’s Beam?

If you are new to boating, there are many terms to familiarize yourself with.

You may have come across the term ‘beam’ and wondered, ‘’what is a boat’s beam?’’.

Well, you have come to the right place! I wrote this article to define a boat’s beam. I will explain everything you need to know about this aspect of your watercraft.

Later in the article, you will learn the importance of knowing what your boat’s beam is. Hint: it is all about your safety while in the water.

So, let’s dive in and answer the question: what is a boat’s beam?

Table of Contents

Definition of A Boat’s Beam

How to measure a boat’s beam, why does a boat’s beam matter, 1.  wide beam boats, 2.  narrow beam boats, summary: what is a boat’s beam.

A boat’s beam is the widest part of a boat .

The term ‘beam’ originated from the structure of wooden boats used in the past. Back then, boats were constructed so that large pieces of wood flanked the watercraft and helped strengthen the wooden boat . These wood pieces were placed on the boat’s rib, starting from the keel to the gunwale.

The boat’s deck was made of smaller pieces of timber. For ships with two floors, the underside of the deck acted as the ceiling of the first-floor cabin. You could see the wooden planks on the deck’s underside when on the first floor.

The pieces of wood on the deck’s underside were used to approximate the boat’s size. One could tell how big a boat was just by looking at the wooden planks underneath the deck, i.e. the roof beams.

Today, a boat’s beam is the measurement of the widest part of the vessel. Knowing how to measure or calculate the beam can help you decide whether your boat can navigate obstacles in water or pass through certain passageways.

Next, let us look at how to measure a boat’s beam.

Measuring a boat’s beam is a simple skill you can learn quickly. You could always hire a marine surveyor to calculate the measurements for you. But, as with most things, it helps if you can do it yourself.

Still, if you need a boat’s beam measurements for official purposes such as state or federal registration, it is good to acquire a marine surveyor’s services.

Knowing your boat’s beam measurement can help you understand the vessel’s stability in water, storage capacity, and ability to navigate obstacles in the water or along certain passageways.

To measure the beam, you first need to identify the boat’s centerline. Then, you can measure the perpendicular distance from one gunwale to the other.

For this process, you will need:

• A ball of string
• Tape measure
• Carpenter’s square

Follow these simple steps to measure your boat’s beam.

Step 1: Measure the boat’s stern

The stern is the rear end of the boat. Measuring the stern and the bow, which is the boat’s tip, will help you determine the centerline.

Use a tape measure to measure the width of the stern. Then, calculate the central point of the stern by dividing the width by two. For example, if the stern’s width measures 50 feet, the center point would be 25 feet.

Use a pencil to mark the center point of the stern. Place one end of the string at this center point and hold it down with duct tape.

Step 2: Determine the bow’s center

The bow is the front-most part of the boat. It is usually tipped and curved, so measuring its width using a tape measure can be cumbersome.

Instead, simply find the most pointed part of the boat. This should serve as the bow’s center point. Mark this point using a pencil.

Step 3: Determine the centerline

Once you find the stern and bow’s center, determining the boat’s overall centerline is easy.

One end of the string should be taped to the stern’s center. Then, pull the ball of string toward the bow’s center. Tape the string to the bow’s marked center point.

The boat’s centerline is the string’s entire length from the bow’s center to the stern’s center. Leave the string taped in place.

Step 4: Select the widest part of the boat

Examine your boat carefully and identify the widest part from one gunwale to the other. A gunwale is the top edge of the vessel’s hull.

In most boats, the widest part is closer to the center of the watercraft. It is also where the waterline meets the hull.

Step 5: Measure the beam

Once you visually identify the widest part of the boat, place the tape measure on one gunwale and stretch it out to the gunwale on the other side.

The measuring tape should be perpendicular to the taped centerline. Use the carpenter’s square to check that the tape measure is at a 90-degree angle to the centerline.

Step 6: Check the accuracy of the beam’s measurement

The boat’s beam is the distance between the two parallel gunwales at the widest point. It is always good to take at least three beam measurements for accuracy.

Once you take the first beam measurement, with the tape measure still in place, move it slightly forward and take the beam measurement there.

Move the tape measure back to the first beam measurement. Then, move it slightly backward and take the beam measurement there too.

Check the widest measurement out of the three-beam measurements. The widest measurement is the most accurate boat beam measurement.

Now that you know the answer to the question: what is a boat’s beam ? You might be wondering, “why does a boat’s beam matter?” How does this simple measurement help me?

A boat’s beam matters in many situations. But, the most important reason to know about the beam is to understand the vessel’s stability.

When handling a boat, you want to ensure that it is stable enough to navigate the waters you want to explore. A small, narrow boat lacks the stability to withstand deep waters with large waves; the boat will likely capsize.

The stability of a boat with a wide beam is different from a boat with a narrow beam. Let’s take a deeper look at how a boat’s beam affects stability.

Boats with a wider beam are generally more stable. Stability, in this case, is a measure of a boat’s resistance to the center of gravity. As a boat moves through the water, the center of gravity may shift sideways due to the weight of the cargo in the boat, waves, or the wind’s direction.

Aside from these external forces, a boat’s stability will also depend on its volume, which is also a factor of the boat’s beam.

The vessel volume of wide-beam boats is distributed further away from the centerline, increasing the boat’s stability. When the vessel’s volume is concentrated toward the centerline, the boat’s stability generally decreases.

As the boat’s beam increases, its secondary stability decreases. A watercraft’s secondary stability is its resistance to capsizing if it is titled sideways.

Aside from the beam, the shape of the keel also determines a boat’s secondary stability. Boats with a curved keel have higher secondary stability but may lose their primary stability. On the other hand, boats with a square keel have lower secondary and greater primary stability.

Pros and cons of wide-beam boats

• Higher primary stability, making them the best choice for deep-sea boating
• More interior space so you can carry more cargo and passengers
• Difficult to pass through narrow passages and get around obstacles
• Finding marinas that accept large boats can sometimes be difficult, depending on where you want to dock

Boats with a narrow beam are generally less stable and can easily capsize in the face of external forces such as waves and winds.

On the upside, narrow beam vessels move faster in water than boats with wider beams. Another advantage of narrow beam vessels is that they can easily pass through narrow waterways, and you can safely navigate obstacles in the water.

Pros and cons of narrow beam boats

• Can easily pass through narrow passages and around obstacles, especially in coastal and inland waters where maneuvering large boats can be difficult
• Moves faster, especially in small and calm water bodies
• Easy and more affordable to access marinas
• Lower stability
• Smaller interior space. The amount of cargo and people you can have onboard is limited.

A boat’s beam is its widest point. When buying or renting a boat, the beam is among the most important factors to consider. Your vessel’s stability, space, and speed will depend on the beam. You should select a vessel that meets your boating needs, including whether you need more interior space and the types of waterways you plan on exploring to ensure that you navigate the vessel safely.

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1 thought on “What Is A Boat’s Beam?”

Interesting! I didn’t know that the beam of a boat refers to its width. Thanks for sharing this information on your blog post.

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Beam and Draft

For many voyagers, trying to define of the "ideal" voyaging boat is one of the sport’s greatest debates. It is far easier said than done in that there are a large number of factors to be taken into consideration, many of them contradictory.

As a result, every boat is the result of a series of compromises that will differ according to the priorities of the person driving the decision-making process. At one extreme, performance under sail may be the overriding concern; at another, gunkholing in shallow anchorages may be the primary interest. These differing priorities should (if the yacht designer does his or her job) result in very different boats.

When exploring design choices, we can look at a number of commonly quoted numeric parameters that are often used to compare boats and their implications. One excellent place to start is with beam and draft calculations.Contemporary boat trends

Almost all voyaging boats, including world-girdling boats, spend the majority of their time either anchored out, on a mooring, or secured to a dock. At such times the boat is little more than a floating condominium. It is natural to want to make it as comfortable a floating home as possible. This, in turn, calls for space, and as a result yacht designers and boat builders are always under pressure to create as much volume as possible in any given design.

Volume nowadays typically translates into a wide beam, carried as far aft as possible, with high freeboard. The boat owner is sometimes going to want to be able to take this floating home into relatively shoal anchorages. This requires a shallow draft. To get a beamy boat with little draft, the boat must have a flat bottom. Even though this boat will probably not spend much of its life at sea, the builder and owner are still going to want it to perform reasonably well. A couple of keys to maximizing performance are to keep the overall weight, and thus the displacement, as low as possible (lightweight construction), and to minimize wetted surface area by using the minimum keel area necessary to achieve reasonable upwind performance (a fin keel), together with the minimum rudder size and supporting structure necessary to maintain control (a smallish spade rudder).

The kind of boat that is taking shape should be familiar; it can be seen at every major boat show. There is nothing wrong with this boat; it is built to fit a certain formula that is market driven, and by and large it does an excellent job of fitting this formula.

When it comes to voyaging boats, and indeed any boat that may be used offshore, we have to add at least one more criterion to the mix. This is the ability to safely deliver the crew, together with all stores and belongings, to its chosen destination in the worst conditions that might be encountered, and to do this at an acceptable speed and with as little discomfort as possible.

Among other things, this translates into a boat that is reasonably fast but with an easy motion at sea (a seakindly boat), that tracks well and has a light helm, that is stiff enough to carry sufficient sail area to keep moving to windward in heavy weather, and that has, in an extreme situation, the ability to claw off a lee shore under sail alone in heavy seas and gale-force winds. It must, of course, be built strongly enough to survive the gale.Form stability

Just about any boat can be pushed to windward in smooth water, but when things start to get rough it requires a great deal more power to counteract the boat’s windage and motion. Power requires sail area. Sail area requires a stiff boat- i.e, one that resists heeling: all the sail area in the world won’t do a bit of good if the boat rolls over and lies on its side!

One way to achieve stiffness is to increase beam. As the boat heels, the immersed volume shifts rapidly to leeward, keeping the boat more-or-less upright. This is known as form stability. A lightweight, beamy boat generally has excellent form stability. However, when the going gets tough the wide, flat sections, combined with the relatively light weight, are not only likely to make it pound and roll uncomfortably, but also will have a tendency to cause its keel to stall out. As it stalls out, if the boat has a relatively shallow draft and minimal lateral surface area in the keel and rudder, it will offer little resistance to making leeway. If it also has high freeboard, the windage will simply exacerbate problems. In other words, many of those features designed to improve comfort at the dock or on the hook, and to ensure a sprightly performance in relatively protected waters, can become a handicap. A less extreme design approach is needed. The first thing to reconsider is the wide beam.Length-to-beam ratio

The "beaminess" of a boat can be quantified by calculating its length-to-beam ratio – a number obtained by dividing the length by the beam. Often the length overall (LOA) – although in this case it should not include a protruding bow pulpit – and the maximum beam (Bmax) are used, although I prefer to use the waterline length (abbreviated to LWL) and waterline beam (BWL). Note that the two different formulas produce quite different values, so when making comparisons between boats it is essential to see that the same methodology is used to derive the numbers. For example, our Pacific Seacraft 40 has a LOA (excluding the bow pulpit) of 40.33 feet and a Bmax of 12.42 feet, giving a length-to-beam ratio using these numbers of 40.33/12.42 = 3.25 (note that the inverse ratio is sometimes given by dividing the beam by the length, in which case we get a beam-to-length ratio of 12.42/40.33 = 0.308). But if we use the waterline length (LWL) and waterline beam (BWL), we get a waterline length-to-beam ratio of 31.25/11.33 = 2.76.

As noted, for comparison purposes it is preferable to use the LWL and BWL to derive a waterline length-to-beam ratio, but unfortunately, although the waterline length is commonly published, the waterline beam is almost never published. As a result, yacht designer Roger Marshall, in The Complete Guide To Choosing A Voyaging Sailboat (published by International Marine, 1999) suggests that a way to use available data is to work with the waterline length and Bmax x 0.9, which will approximate the waterline beam on many boats (note, however, that when looking at a range of boats, I found this factor varied from as low as 0.75 to as high as 1.00, so this is a pretty crude approximation). When we apply these numbers to the Pacific Seacraft 40, we get: LWL/(Bmax x 0.9) = 31.25/(12.42 x 0.9) = 2.80. This is pretty close to the actual waterline length-to-beam ratio (2.76). Lower length-to-beam ratios indicate proportionately more beam; higher ratios less beam. A higher ratio is desirable both in terms of windward performance in difficult conditions, and also as an indicator of handling characteristics and seakindly behavior.Beam and stability However, this is not the whole picture. Beam affects stability on a cubic basis, which is to say that any increase in beam has a disproportionate effect on stability. If the length-to-beam ratio is kept constant, as length increases, the increase in beam needed to maintain a constant ratio produces a disproportionate increase in stability. For example, a 36′ LWL boat with a 3:1 ratio will have a 12′ waterline beam while a 48′ boat with the same ratio will have a 16′ beam; the 48′ boat will be considerably stiffer, even though it has the same ratio. What this means is that if two boats have the same length-to-beam ratios, the one with the longer waterline is likely to have greater stability and sail-carrying ability, and better performance to windward. Or, put another way, as length increases the syme relative sail-carrying ability can be maintained with a proportionately narrower beam and thus a higher length-to-beam ratio. As a result, to improve stability and sail-carrying ability, shorter boats need proportionately more beam, resulting in lower length-to-beam ratios. Consequently, there is no absolute length-to-beam ratio “magic number” that can be used for comparing boats; length must also be taken into account: the shorter a boat’s waterline length, the lower its length-to-beam ratio is likely to be. Nevertheless, when looking at the 35-foot to 45-foot boat range (the “norm” for offshore voyaging these days), for a comfortable offshore voyager I like to see a waterline length-to-beam ratio of 3.00 or higher (using LWL/[Bmax x 0.9]). Shorter boats may have a lower ratio; longer boats should have a higher ratio. Looking at a sampling of contemporary European and American boats (see table on page 88), we see that the only two boats below 40 feet LOA that have a ratio of over 3.00 are the Alerion Express 38 and the Shannon 39. At 40-feet and above, many of those boats that follow the current fashion of short overhangs, which maximizes the waterline length, have ratios of 3.0 and higher, whereas more traditional voyaging boats, with longer overhangs, for the most part do not. Our Pacific Seacraft 40, for example, has a waterline length-to-beam of 2.80. This is the price that has to be paid for its long overhangs combined with the beam necessary to provide a more spacious interior as compared to voyaging boat designs of a generation ago. Many older, but nonetheless highly successful, voyaging boats in this same size range have waterline length-to-beam of 3.0 and above (based on LWL/[Bmax x 0.9]). Steve Dashew, the designer of the Deerfoot and Sundeer series of boats, has taken the length-to-beam ratio to extremes. His boats commonly have ratios of 4:1, 5:1 and up. This is all to the good except that, because of the relatively narrow beam, in order to establish a reasonable interior volume, the boat has to get longer and the costs start to soar. He writes in the second edition of the Offshore Voyaging Encyclopedia that he and Linda, his wife and partner, decided to see just how small a boat they could design that would contain what they felt to be their minimum requirements for just the two of them, including accommodating a couple of guests for a week or two a year. They arrived at 56 feet in length! Unfortunately, however desirable it may be, such a boat is beyond the budget of most of us, not only up front but also in terms of mooring or dockage fees, gear replacement costs, maintenance, and so on.Keel types A narrower beam results in less form stability, which can translate into greater heeling when on the wind. To counteract this tendency to heel it’s necessary to put a lot of weight down low. In its extreme form this results in the 14-foot fin keels, with massive lead bulbs, seen on some narrow racing boats. Clearly, such a keel is not practical on a voyaging boat, but the principle is the same – to get as much weight as possible as low as possible. How low is primarily a function of where the boat is intended to sail. In general, a six-foot draft is acceptable, still allowing access to most of the world’s finest voyaging grounds. However, a boat specifically intended for voyaging in shoal areas such as the Bahamas might be designed with less draft, whereas one intended for Pacific voyaging might have a deeper draft. A voyager/racer, with an emphasis on the racing side of things, is likely to exceed six feet, trading access to some voyaging grounds for improved performance when racing. For a given draft, the use of a bulb keel keeps the weight as low as possible. A wing keel does the same, but needs to be carefully designed if it is not to foul lines and seaweed, or get stuck in the mud in a grounding. (A wing keel has a shape much like a Bruce anchor. Wing keels originated as a rule-beating device in the America’s Cup, and have since become something of a fad. I doubt that any advantage over a bulb keel outweighs the disadvantages in a voyaging environment.) On our new boat we chose a bulb-keel option, with a draft of five feet two inches, as opposed to the standard deep-keel of six feet one inch. We get a significantly reduced draft with a small loss of windward performance. The advent of bulb and wing keel types has pretty much put paid to the old debate as to whether it is preferable to have internal or external ballast: the bulb or wing must be external (it’s hard to mold them into fiberglass). Clearly, lead, with its great density, should always be used as the ballast material (as opposed to iron, which is sometimes used to save cost yet it’s only a little more than 60% of the density of lead). We’ve hardly started looking at the process of choosing an “ideal” voyaging boat, and already we are beginning to sense that there are a complicated series of trade-offs between, for example, beam and draft, interior accommodation and windward ability, and comfort on the hook and at sea. Based on my own experience, which is primarily bluewater voyaging, if I were to settle on two numbers that provide an acceptable beam and draft middle ground for 35- to 45-foot voyaging boats, it would be a waterline length-to-beam ratio of 3.0 or higher, and a draft of six feet or less. Longer boats should have a higher waterline length-to-beam ratio, and may require more draft.

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Nautical + Sailing Terms You Should Know [578 Phrases]

June 5, 2019 2:05 pm

A seaman’s jargon is among the most challenging to memorize. With over 500 terms used to communicate with a captain, crew, and sailors regarding navigation and more, there’s a word for nearly everything. No need to jump ship, this comprehensive list will have you speaking the lingo in no time.

Abaft the beam: A relative bearing of greater than 90 degrees from the bow. e.g. “two points abaft the port beam.”

Abaft: Toward the stern, relative to some object (“abaft the fore hatch”).

Abandon Ship: An imperative to leave the vessel immediately, usually in the face of some imminent danger.

Abeam: “On the beam”, a relative bearing at right angles to the centerline of the ship’s keel.

Aboard: On or in a vessel. Close aboard means near a ship.

Above board: On or above the deck, in plain view, not hiding anything.

Accommodation ladder: A portable flight of steps down a ship’s side.

Admiral: Senior naval officer of Flag rank. In ascending order of seniority, Rear Admiral, Vice Admiral, Admiral and Admiral of the Fleet (Royal Navy). Derivation reputedly Arabic, from “Emir al Bath” (“Ruler of the waters”).

Admiralty law: Body of law that deals with maritime cases. In the UK administered by the Probate, Divorce and Admiralty Division of the High Court of Justice.

Adrift: Afloat and unattached in any way to the shore or seabed. It may also imply that a vessel is not anchored and not under control, therefore goes where the wind and current take her, (loose from moorings, or out of place). Also refers to any gear not fastened down or put away properly. It can also be used to mean “absent without leave”.

Affreightment: Hiring of a vessel

Aft: Towards the stern (of the vessel).

Afterdeck: Deck behind a ship’s bridge

Afterguard: Men who work the aft sails on the quarterdeck and poop deck

Aground: Resting on or touching the ground or bottom.

Ahead: Forward of the bow.

Ahoy: A cry to draw attention. A term used to hail a boat or a ship, as “Boat ahoy!”.

Ahull: With sails furled and helm lashed to the lee-side.

Aid to Navigation: ( ATON) Any device external to a vessel or aircraft specifically intended to assist navigators in determining their position or safe course, or to warn them of dangers or obstructions to navigation.

All hands: Entire ship’s company, both officers and enlisted personnel.

All-Round White Light: On power-driven vessels less than 39.4 feet in length, this light may be used to combine a masthead light and sternlight into a single white light that can be seen by other vessels from any direction. This light serves as an anchor light when sidelights are extinguished.

Aloft: Above the ship’s uppermost solid structure; overhead or high above.

Alongside: By the side of a ship or pier.

Amidships (or midships): In the middle portion of the ship, along the line of the keel.

Anchor ball: Black shape hoisted in the forepart of a ship to show that ship is anchored in a fairway.

Anchor buoy: A small buoy secured by a light line to anchor to indicate the position of the anchor on the bottom.

Anchor chain or cable: Chain connecting the ship to the anchor.

Anchor detail: Group of men who handle ground tackle when the ship is anchoring or getting underway.

Anchor light: White light displayed by a ship at anchor. Two such lights are displayed by a ship over 150 feet (46 m) in length.

Anchor watch: Making sure that the anchor is holding and the vessel is not drifting. Important during rough weather and at night. Most marine GPS units have an Anchor Watch alarm capability.

Anchor: An object designed to prevent or slow the drift of a ship, attached to the ship by a line or chain; typically a metal, hook-like object, designed to grip the bottom under the body of water.

Anchorage: A suitable place for a ship to anchor. Area of a port or harbor.

Anchor’s aweigh: Said of an anchor when just clear of the bottom.

As the crow flies: A direct line between two points (which might cross land) which is the way crows travel rather than ships which must go around land.

Ashore: On the beach, shore or land.

Astern: Toward the stern; an object or vessel that is abaft another vessel or object.

ASW: Anti-submarine warfare.

Asylum Harbor: A harbor used to provide shelter from a storm.

Athwart, athwartships: At right angles to the fore and aft or centerline of a ship.

Avast: Stop! Cease or desist from whatever is being done.

Awash: So low in the water that the water is constantly washing across the surface.

Aweigh: Position of an anchor just clear of the bottom.

Aye, aye: Reply to an order or command to indicate that it, firstly, is heard; and, secondly, is understood and will be carried out. (“Aye, aye, sir” to officers).

Azimuth circle: Instrument used to take bearings of celestial objects.

Azimuth compass: An instrument employed for ascertaining the position of the sun with respect to magnetic north. The azimuth of an object is its bearing from the observer measured as an angle clockwise from true north.

Back and fill: To use the advantage of the tide being with you when the wind is not.

Backstays: Long lines or cables, reaching from the rear of the vessel to the mast heads, used to support the mast.

Baggywrinkle: A soft covering for cables (or any other obstructions) that prevents sail chafing from occurring.

Bale Cube (or Bale Capacity): The space available for cargo measured in cubic feet to the inside of the cargo battens, on the frames, and to the underside of the beams.

Ballaster: One who supplies ships with ballast.

Bank (sea floor): A large area of elevated sea floor.

Banyan: Traditional Royal Navy term for a day or shorter period of rest and relaxation.

Bar pilot: A bar pilot guides ships over the dangerous sandbars at the mouth of rivers and bays.

Bar: Large mass of sand or earth, formed by the surge of the sea. They are mostly found at the entrances of great rivers or havens, and often render navigation extremely dangerous, but confer tranquility once inside. See also: Touch and go, grounding. Alfred Lord Tennyson’s poem ‘Crossing the bar’ an allegory for death.

Bargemaster: Owner of a barge.

Barrelman: A sailor that was stationed in the crow’s nest.

Beacon: A lighted or unlighted fixed aid to navigation attached directly to the earth’s surface. (Lights and daybeacons both constitute beacons).

Beam ends: The sides of a ship. “On her beam ends” may mean the vessel is literally on her side and possibly about to capsize; more often, the phrase means the vessel is listing 45 degrees or more.

Beam: The beam of a ship is its width at the widest point or a point alongside the ship at the mid-point of its length.

Bear away: Turn away from the wind, often with reference to a transit.

Bear down: Turn away from the wind, often with reference to a transit.

Bearing: The horizontal direction of a line of sight between two objects on the surface of the earth.

Bee: Hardwood on either side of bowsprit through which forestays are reeved

Before the mast: Literally, the area of a ship before the foremast (the forecastle). Most often used to describe men whose living quarters are located here, officers being housed behind (abaft) the mast and enlisted men before the mast. This was because the midships area where the officers were berthed is more stable, being closer to the center of gravity, and thus more comfortable. It is less subject to the up and down movement resulting from the ship’s pitching.

Belay: To secure a rope by winding on a pin or cleat

Belaying pins: Bars of iron or hardwood to which running rigging may be secured, or belayed.

Berth: A bed on a boat, or a space in a port or harbor where a vessel can be tied up.

Best bower (anchor): The larger of two anchors carried in the bow; so named as it was the last, best hope.

Bilge: The bilge is the compartment at the bottom of the hull of a ship or boat where water collects so that it may be pumped out of the vessel at a later time.

Bilged on her anchor: A ship that has run upon her own anchor.

Bimini: Weather-resistant fabric stretched over a stainless steel frame, fastened above the cockpit of a sailboat or flybridge of a power yacht which serves as a rain or sun shade.

Bimmy: A punitive instrument.

Binnacle list: A ship’s sick list. The list of men unable to report for duty was given to the officer or mate of the watch by the ship’s surgeon. The list was kept at the binnacle.

Binnacle: The stand on which the ship’s compass is mounted.

Bitter end: The anchor cable is tied to the bitts when the cable is fully paid out, the bitter end has been reached. The last part of a rope or cable.

Bitts: Posts mounted on a ship for fastening ropes

Bloody: An intensive derived from the substantive ‘blood’, a name applied to the Bucks, Scrowers, and Mohocks of the seventeenth centuries.

Blue Peter: A blue and white flag hoisted at the foretrucks of ships about to sail.

Boat: A craft or vessel designed to float on, and provide transport over, water.

Boatswain or bosun: A non-commissioned officer responsible for the sails, ropes, and boats on a ship who issues “piped” commands to seamen.

Bobstay: Rope used on ships to steady the bowsprit

Bollard: From “bol” or “bole”, the round trunk of a tree. A substantial vertical pillar to which lines may be made fast. Generally on the quayside rather than the ship.

Boltrope: Strong rope stitched to edges of a sail

Booby hatch: A sliding hatch or cover.

Booby: A type of bird that has little fear and therefore is particularly easy to catch, hence booby prize.

Boom vang: A sail control that lets one apply downward tension on the boom, countering the upward tension provided by the mainsail. The boom vang adds an element of control to mainsail shape when the mainsheet is let out enough that it no longer pulls the boom down. Boom vang tension helps control leech twist, a primary component of sail power.

Boom: A spar used to extend the foot of a fore-and-aft sail.

Booms: Masts or yards, lying on board in reserve.

Bosun: Boatswain

Bottomry: Pledging a ship as security in a financial transaction.

Bow: The front of a ship.

Bower: Anchor carried at bow of a ship

Bowline: A type of knot, producing a strong loop of a fixed size, topologically similar to a sheet bend. Also, a rope attached to the side of a sail to pull it towards the bow (for keeping the windward edge of the sail steady).

Bowse: To pull or hoist.

Bowsprit: A spar projecting from the bow used as an anchor for the forestay and other rigging.

Brail: To furl or truss a sail by pulling it in towards the mast, or the ropes used to do so.

Bream: To clean a ship’s bottom by burning off seaweed.

Bridge: A structure above the weather deck, extending the full width of the vessel, which houses a command center, itself called by association, the bridge.

Bring to: Cause a ship to be stationary by arranging the sails.

Broaching-to: A sudden movement in navigation, when the ship, while scudding before the wind, accidentally turns her leeward side to windward, also use to describe the point when water starts to come over the gunwale due to this turn.

Buffer: The chief bosun’s mate, responsible for discipline.

Bulkhead: An upright wall within the hull of a ship. Particularly a load bearing wall.

Bulwark: The extension of the ship’s side above the level of the weather deck.

Bumboat: A private boat selling goods.

Bumpkin: An iron bar (projecting outboard from a ship’s side) to which the lower and topsail brace blocks are sometimes hooked. Chains supporting/stabilizing the bowsprit.

Bunt: Middle of sail, fish-net or cloth when slack.

Buntline: One of the lines tied to the bottom of a square sail and used to haul it up to the yard when furling.

Buoy: A floating object of defined shape and color, which is anchored at a given position and serves as an aid to navigation.

Buoyed Up: Lifted by a buoy, especially a cable that has been lifted to prevent it from trailing on the bottom.

Burgee: Small ship’s flag used for identification or signaling.

By and Large: By means into the wind, while large means with the wind. By and large, is used to indicate all possible situations “the ship handles well both by and large”.

By the board: Anything that has gone overboard.

Cabin boy: attendant on passengers and crew.

Cabin: an enclosed room on a deck or flat.

Cable: A large rope; also a measure of length or distance. Equivalent to (UK) 1/10 nautical mile, approx. 600 feet; (USA) 120 fathoms, 720 feet (219 m); other countries use different values.

Cabotage: Shipping and sailing between points in the same country.

Camber: Slight arch or convexity to a beam or deck of a ship.

Canister: A type of anti-personnel cannon load in which lead balls or other loose metallic items were enclosed in a tin or iron shell. On firing the shell would disintegrate releasing the smaller metal objects.

Cape Horn fever: The name of the fake illness a malingerer is pretending to suffer from.

Capsize: When a ship or boat lists too far and rolls over, exposing the keel. On large vessels, this often results in the sinking of the ship.

Capstan: A huge rotating hub (wheel) mounted vertically and provided with horizontal holes to take up the capstan bars (when manually rotated), used to wind in anchors or other heavy objects; and sometimes to administer flogging over.

Captain’s daughter: The cat o’ nine tails, which in principle is only used on board on the captain’s (or a court martial’s) personal orders.

Careening: Cause the ship to tilt on its side, usually to clean or repair the hull below the water line.

Cargo Deadweight Tons: The weight remaining after deducting fuel, water, stores, dunnage and such other items necessary for use on a voyage from the deadweight of the vessel.

Carlin: Similar to a beam, except running in a fore and aft direction.

Cat Head: A beam extending out from the hull used to support an anchor when raised in order to secure or “fish” it.

Cat: To prepare an anchor, after raising it by lifting it with a tackle to the Cat Head, prior to securing (fishing) it alongside for sea. (An anchor raised to the Cat Head is said to be catted).

Catamaran: A vessel with two hulls.

Catboat: A cat-rigged vessel with only one sail, usually on a gaff.

Centreboard: A removable keel used to resist leeway.

Chafing Gear: Material applied to a line or spar to prevent or reduce chafing. See Baggywrinkle.

Chafing: Wear on the line or sail caused by constant rubbing against another surface.

Chain-wale or channel: A broad, thick plank that projects horizontally from each of a ship’s sides abreast a mast, distinguished as the fore, main, or mizzen channel accordingly, serving to extend the base for the shrouds, which supports the mast.

Chine: A relatively sharp angle in the hull, as compared to the rounded bottoms of most traditional boat hulls.

Chock: Metal casting with curved arms for passing ropes for mooring ship.

Chock-a-block: Rigging blocks that are so tight against one another that they cannot be further tightened.

Clean bill of health: A certificate issued by a port indicating that the ship carries no infectious diseases.

Clean slate: At the helm, the watch keeper would record details of speed, distances, headings, etc. on a slate. At the beginning of a new watch the slate would be wiped clean.

Cleat: A stationary device used to secure a rope aboard a vessel.

Clew: Corner of sail with a hole to attach ropes.

Clew-lines: Used to truss up the clews, the lower corners of square sails.

Club: hauling the ship drops one of its anchors at high speed to turn abruptly. This was sometimes used as a means to get a good firing angle on a pursuing vessel.

Coaming: The raised edge of a hatchway used to help keep out water.

Cocket: Official shipping seal; customs clearance form.

Cofferdam: Narrow vacant space between two bulkheads of a ship.

Cog: Single-masted, square-sailed ship with a raised stern.

Companionway: A raised and windowed hatchway in the ship’s deck, with a ladder leading below and the hooded entrance-hatch to the main cabins.

Compass:   Navigational instrument that revolutionized travel.

Complement: The full number of people required to operate a ship. Includes officers and crewmembers; does not include passengers.

Cordage: Ropes in the rigging of a ship.

Corrector: a device to correct the ship’s compass.

Courses: The mainsail, foresail, and mizzen.

Coxswain or cockswain: The helmsman or crew member in command of a boat.

Cringle: Loop at the corner of a sail to which a line is attached.

Crosstrees: Horizontal crosspieces at a masthead used to support ship’s mast.

Crow’s nest: Specifically a masthead constructed with sides and sometimes a roof to shelter the lookouts from the weather, generally by whaling vessels, this term has become a generic term for what is properly called masthead. See masthead.

Cube: The cargo carrying capacity of a ship, measured in cubic feet.

Cuddy: A small cabin in a boat.

Cunningham: A line invented by Briggs Cunningham, used to control the shape of a sail.

Cut and run: When wanting to make a quick escape, a ship might cut lashings to sails or cables for anchors, causing damage to the rigging, or losing an anchor, but shortening the time needed to make ready by bypassing the proper procedures.

Cut of his jib: The “cut” of a sail refers to its shape. Since this would vary between ships, it could be used both to identify a familiar vessel at a distance and to judge the possible sailing qualities of an unknown one.

Cut splice: A join between two lines, similar to an eye-splice, where each rope end is joined to the other a short distance along, making an opening which closes under tension.

Cutline: The “valley” between the strands of a rope or cable. Before serving a section of laid rope e.g. to protect it from chafing, it may be “wormed” by laying yarns in the cuntlines, giving that section an even cylindrical shape.

Daggerboard: A type of centerboard that is removed vertically.

Davit: Device for hoisting and lowering a boat.

Davy Jones (Locker): An idiom for the bottom of the sea.

Daybeacon: An unlighted fixed structure which is equipped with a dayboard for daytime identification.

Dayboard: The daytime identifier of an aid to navigation presenting one of several standard shapes (square, triangle, rectangle) and colors (red, green, white, orange, yellow, or black).

Deadeye: A round wooden plank which serves a similar purpose to a block in the standing rigging of large sailing vessels.

Deadrise: The design angle between the keel (q.v.) and horizontal.

Deadweight Tons (DWT): The difference between displacement, light and displacement, and loaded. A measure of the ship’s total carrying capacity.

Deadwood: Timbers built into ends of a ship when too narrow to permit framing.

Deckhand: A person whose job involves aiding the deck supervisor in (un)mooring, anchoring, maintenance, and general evolutions on deck.

Deck supervisor: The person in charge of all evolutions and maintenance on deck; sometimes split into two groups: forward deck supervisor, aft deck supervisor.

Deckhead: The under-side of the deck above. Sometimes paneled over to hide the pipework. This paneling, like that lining the bottom and sides of the holds, is the ceiling.

Decks: the structures forming the approximately horizontal surfaces in the ship’s general structure. Unlike flats, they are a structural part of the ship.

Demurrage: Delay of the vessel’s departure or loading with cargo.

Derrick: A lifting device composed of one mast or pole and a boom or jib which is hinged freely at the bottom.

Directional light: A light illuminating a sector or very narrow-angle and intended to mark a direction to be followed.

Displacement, Light: The weight of the ship excluding cargo, fuel, ballast, stores, passengers, and crew, but with water in the boilers to steaming level.

Displacement, Loaded: The weight of the ship including cargo, passengers, fuel, water, stores, dunnage and such other items necessary for use on a voyage, which brings the vessel down to her load draft.

Displacement: A measurement of the weight of the vessel, usually used for warships. Displacement is expressed either in long tons of 2,240 pounds or metric tons of 1,000 kg.

Disrate: To reduce in rank or rating; demote.

Dodger: Shield against rain or spray on a ship’s bridge.

Dog watch: A short watch period, generally half the usual time (e.g. a two-hour watch between two four hour ones). Such a watch might be included in order to slowly rotate the system over several days for fairness  or to allow both watches to eat their meals at approximately normal times.

Dolphin: A structure consisting of a number of piles driven into the seabed or riverbed in a circular pattern and drawn together with wire rope.

Downhaul: A line used to control either a mobile spar or the shape of a sail.

Draft, Air: Air Draft is the distance from the water line to the highest point on a ship (including antennas) while it is loaded.

Draft: The distance between the waterline and the keel of a boat; the minimum depth of water in which a boat will float.

Dressing down: Treating old sails with oil or wax to renew them, or a verbal reprimand.

Driver: The large sail flown from the mizzen gaff.

Driver-mast: The fifth mast of a six-masted barquentine or gaff schooner. It is preceded by the jigger mast and followed by the spanker mast. The sixth mast of the only seven-masted vessel, the gaff schooner Thomas W. Lawson, was normally called the pusher-mast.

Dromond: Large single-sailed ship powered by rowers.

Dunnage: Loose packing material used to protect a ship’s cargo from damage during transport. Personal baggage.

Dyogram: Ship’s chart indicating compass deflection due to ship’s iron.

Earrings: Small lines, by which the uppermost corners of the largest sails are secured to the yardarms.

Embayed: The condition where a sailing vessel is confined between two capes or headlands, typically where the wind is blowing directly onshore.

Ensign: Large naval flag.

Escutcheon: Part of ship’s stern where name is displayed.

Extremis (also known as “in extremis”): The point under International Rules of the Road (Navigation Rules) at which the privileged (or stand-on) vessel on a collision course with a burdened (or give-way) vessel determines it must maneuver to avoid a collision. Prior to extremes, the privileged vessel must maintain course and speed and the burdened vessel must maneuver to avoid a collision.

Fairlead: Ring through which rope is led to change its direction without friction.

Fardage: Wood placed in the bottom of the ship to keep cargo dry.

Fathom: A unit of length equal to 6 feet (1.8 m), roughly measured as the distance between a man’s outstretched hands.

Fender: An air or foam filled bumper used in boating to keep boats from banging into docks or each other.

Fiddley: Iron framework around hatchway opening.

Figurehead: Symbolic image at the head of a traditional sailing ship or early steamer.

Fireship: A ship loaded with flammable materials and explosives and sailed into an enemy port or fleet either already burning or ready to be set alight by its crew (who would then abandon it) in order to collide with and set fire to enemy ships.

First Lieutenant: In the Royal Navy, the senior lieutenant on board; responsible to the Commander for the domestic affairs of the ship’s company. Also known as ‘Jimmy the One’ or ‘Number One’. Removes his cap when visiting the mess decks as a token of respect for the privacy of the crew in those quarters. Officer i/c cables on the forecastle. In the U.S. Navy the senior person in charge of all Deckhands.

First Mate: The Second in command of a ship.

Fish: To repair a mast or spar with a fillet of wood. To secure an anchor on the side of the ship for sea,otherwise known as “catting”.

Flag hoist: A number of signal flags strung together to convey a message, e.g. “England expects…”.

Flagstaff: Flag pole at the stern of a ship.

Flank: The maximum speed of a ship. Faster than “full speed”.

Flatback: A Great Lakes slang term for a vessel without any self-unloading equipment.

Flemish Coil: A line coiled around itself to neaten the decks or dock.

Flog: To beat, to punish.

Fluke: The wedge-shaped part of an anchor’s arms that digs into the bottom.

Fly by night: A large sail used only for sailing downwind, requiring little attention.

Following sea: Wave or tidal movement going in the same direction as a ship.

Foot: The bottom of a sail.

Footloose: If the foot of a sail is not secured properly, it is footloose, blowing around in the wind.

Footrope: Each yard on a square-rigged sailing ship is equipped with a footrope for sailors to stand on while setting or stowing the sails.

Fore: Towards the bow (of the vessel).

Forebitt: Post for fastening cables at a ship’s foremast.

Forecabin: Cabin in the fore part of a ship.

Forecastle: A partial deck, above the upper deck and at the head of the vessel; traditionally the sailors living quarters. Pronounced “foc-sle”. The name is derived from the castle fitted to bear archers in time of war.

Forefoot: The lower part of the stem of a ship.

Foremast: Mast nearest the bow of a ship

Foresail: The lowest sail set on the foremast of a square-rigged ship.

Forestays: Long lines or cables, reaching from the front of the vessel to the mast heads, used to support the mast.

Forward: The area towards the bow.

Founder: To fill with water and sink → Wiktionary.

Frap: To draw a sail tight with ropes or cables.

Freeboard: The height of a ship’s hull (excluding superstructure) above the waterline. The vertical distance from the current waterline to the lowest point on the highest continuous watertight deck. This usually varies from one part to another.

Full and by: Sailing into the wind (by), but not as close-hauled as might be possible, so as to make sure the sails are kept full. This provides a margin for error to avoid being taken aback (a serious risk for square-rigged vessels) in a tricky sea. Figuratively it implies getting on with the job but in a steady, relaxed way, without undue urgency or strain.

Furl: To roll or wrap a sail around the mast or spar to which it is attached.

Futtock: Rib of a ship.

Gaff: The spar that holds the upper edge of a fore-and-aft or gaff sail. Also, a long hook with a sharp point to haul fish in.

Gaff-topsail: Triangular topsail with its foot extended upon the gaff.

Galley: The kitchen of the ship.

Gangplank: A movable bridge used in boarding or leaving a ship at a pier; also known as a “brow”.

Gangway: Either of the sides of the upper deck of a ship

Garbled: Garbling was the (illegal) practice of mixing cargo with garbage.

Garboard: The strake closest to the keel (from Dutch gaarboard).

Genoa: Large jib that overlaps the mainsail

Global Positioning System (GPS): A satellite-based radio navigation system providing continuous worldwide coverage. It provides navigation, position, and timing information to air, marine, and land users.

Grain Cube (or Grain Capacity): The maximum space available for cargo measured in cubic feet, the measurement being taken to the inside of the shell plating of the ship or to the outside of the frames and to the top of the beam or underside of the deck plating.

Grapnel: Small anchor used for dragging or grappling.

Gross Tons: The entire internal cubic capacity of the ship expressed in tons of 100 cubic feet to the ton, except certain spaces which are exempted such as: peak and other tanks for water ballast, open forecastle bridge and poop, access of hatchways, certain light and air spaces, domes of skylights, condenser, anchor gear, steering gear, wheelhouse, galley and cabin for passengers.

Groundage: A charge on a ship in port.

Gudgeon: Metal socket into which the pintle of a boat’s rudder fits.

Gunnage: Number of guns carried on a warship.

Gunwhale: Upper edge of the hull.

Gybe: To swing a sail from one side to another.

Halyard or Halliard: Originally, ropes used for hoisting a spar with a sail attached; today, a line used to raise the head of any sail.

Hammock: Canvas sheets, slung from the deckhead in mess decks, in which seamen slept. “Lash up and stow” a piped command to tie up hammocks and stow them (typically) in racks inboard of the ship’s side to protect the crew from splinters from shot and provide a ready means of preventing flooding caused by damage.

Hand Bomber: A ship using coal-fired boilers shoveled in by hand.

Handsomely: With a slow even motion, as when hauling on a line “handsomely.”

Hank: A fastener attached to the luff of the headsail that attaches the headsail to the forestay. Typical designs include a bronze or plastic hook with a spring-operated gate or a strip of cloth webbing with a snap fastener.

Harbor: A harbor or haven is a place where ships may shelter from the weather or are stored. Harbors can be man-made or natural.

Haul wind: To point the ship so as to be heading in the same direction as the wind, generally not the fastest point of travel on a sailing vessel.

Hawse: Distance between ship’s bow and its anchor.

Hawse-hole: A hole in a ship’s bow for a cable or chain, such as for an anchor, to pass through.

Hawsepiper: An informal maritime industry term used to refer to a merchant ship’s officer who began his or her career as an unlicensed merchant seaman and did not attend a traditional maritime college/academy to earn the officer license.

Hawser: Large rope for mooring or towing a ship.

Head of navigation: A term used to describe the farthest point above the mouth of a river that can be navigated by ships.

Head: The toilet or latrine of a vessel, which for sailing ships projected from the bows.

Headsail: Any sail flown in front of the most forward mast.

Heave down: Turn a ship on its side (for cleaning).

Heave: A vessel’s transient up-and-down motion.

Heaving to: To stop a sailing vessel by lashing the helm in opposition to the sails. The vessel will gradually drift to leeward, the speed of the drift depending on the vessel’s design.

Heeling: The lean caused by the wind’s force on the sails of a sailing vessel.

Helm: Ship’s steering wheel.

Helmsman: A person who steers a ship.

Hogging or hog: The distortion of the hull where the ends of the keel are lower than the center.

Hold: In earlier use, below the orlop deck, the lower part of the interior of a ship’s hull, especially when considered as storage space, as for cargo. In later merchant vessels, it extended up through the decks to the underside of the weather deck.

Holiday: A gap in the coverage of newly applied paint, slush, tar, or other preservatives.

Holystone: Sandstone material used to scrape ships’ decks

Horn: A sound signal which uses electricity or compressed air to vibrate a disc diaphragm.

Horse: Attachment of sheets to the deck of the vessel (Main-sheet horse).

Hounds: Attachments of stays to masts.

Hull: The shell and framework of the basic flotation-oriented part of a ship.

Hydrofoil: A boat with wing-like foils mounted on struts below the hull.

Icing: A serious hazard where cold temperatures (below about -10°C) combined with high wind speed (typically force 8 or above on the Beaufort scale) result in spray blown off the sea freezing immediately on contact with the ship.

Idlers: Members of a ship’s company not required to serve watches. These were in general specialist tradesmen such as the carpenter and the sailmaker.

In Irons: When the bow of a sailboat is headed into the wind and the boat has stalled and is unable to maneuver.

In the offing: In the water visible from on board a ship, now used to mean something imminent.

Inboard: Inside the line of a ship’s bulwarks or hull.

Inboard-Outboard drive system: A larger Power Boating alternative drive system to transom mounted outboard motors.

Jack: Ship’s flag flown from jack-staff at the bow of a vessel.

Jack-block: Pulley system for raising topgallant masts.

Jack-cross-tree: Single iron cross-tree at the head of a topgallant mast.

Jacklines or Jack Stays: Lines, often steel wire with a plastic jacket, from the bow to the stern on both port and starboard. The Jack Lines are used to clip on the safety harness to secure the crew to the vessel while giving them the freedom to walk on the deck.

Jackstaff: Short staff at ship’s bow from which the jack is hoisted.

Jackyard: Spar used to spread the foot of a gaff-topsail

Jib: A triangular staysail at the front of a ship.

Jibboom: Spar forming an extension of the bowsprit.

Jibe: To change a ship’s course to make the boom shift sides.

Jigger-mast: The fourth mast, although ships with four or more masts were uncommon, or the aft-most mast where it is smallest on vessels of less than four masts.

Junk: Old cordage past its useful service life as lines aboard ship. The strands of old junk were teased apart in the process called picking oakum.

Jurymast: Mast erected on a ship in place of one lost.

Kedge: Small anchor to keep a ship steady.

Keel: A boat’s backbone; the lowest point of the boat’s hull, the keel provides strength, stability and prevents sideways drift of the boat in the water.

Keel: The central structural basis of the hull.

Keelson: Lengthwise wooden or steel beam in ship for bearing stress.

Kentledge: Pig-iron used as ballast in ship’s hold.

Killick: A small anchor. A fouled killick is the substantive badge of non-commissioned officers in the RN. Seamen promoted to the first step in the promotion ladder are called “Killick”. The badge signifies that here is an Able Seaman skilled to cope with the awkward job of dealing with a fouled anchor.

Ladder: On board a ship, all “stairs” are called ladders, except for literal staircases aboard passenger ships. Most “stairs” on a ship are narrow and nearly vertical, hence the name. Believed to be from the Anglo-Saxon word “hiaeder”, meaning ladder.

Lagan: Cargo jettisoned from the ship but marked by buoys for recovery.

Laker: Great Lakes slang for a vessel who spends all its time on the 5 Great Lakes.

Landlubber: A person unfamiliar with being on the sea.

Lanyard: Rope or line for fastening something in a ship.

Larboard: The left side of the ship.Derived from the old ‘lay-board’ providing access between a ship and a quay.

Lastage: Room for stowing goods in a ship.

Lateen: Triangular sail rigged on ship’s spar.

Lateral System: A system of aids to navigation in which characteristics of buoys and beacons indicate the sides of the channel or route relative to a conventional direction of buoyage (usually upstream).

Laveer: To sail against the wind.

Lay down: To lay a ship down is to begin construction in a shipyard.

Lay: To come and go, used in giving orders to the crew, such as “lay forward” or “lay aloft”. To direct the course of the vessel. Also, to twist the strands of a rope together.

Lazaret: Space in ship between decks used for storage.

League: A unit of length, normally equal to three nautical miles.

Lee shore: A shore downwind of a ship. A ship which cannot sail well to windward risks being blown onto a lee shore and grounded.

Lee side: The side of a ship sheltered from the wind (opposite the weather side or windward side).

Leeboard: Wood or metal planes attached to the hull to prevent leeway.

Leech: The aft or trailing edge of a fore-and-aft sail; the leeward edge of a spinnaker; a vertical edge of a square sail. The leech is susceptible to twist, which is controlled by the boom vang and mainsheet.

Lee helm: If the helm was centered, the boat would turn away from the wind (to the lee). Consequently, the tiller must be pushed to the lee side of the boat in order to make the boat sail in a straight line.

Leeward: In the direction that the wind is blowing towards.

Leeway: The angle that a ship is blown leeward by the wind. See also “weatherly”.

Length at Waterline (LWL): The ship’s length measured at the waterline.

Length Overall (LOA): The maximum length of the ship.

Length: The distance between the forwardmost and aftermost parts of the ship.

Let go and haul: An order indicating that the ship is in line with the wind.

Lifeboat: A small steel or wood boat located near the stern of a vessel. Used to get the crew to safety if something happens to the mothership.

Line: The correct nautical term for the majority of the cordage or “ropes” used on a vessel. A line will always have a more specific name, such as mizzen topsail halyard, which describes its use.

Liner: Ship of The Line: a major warship capable of taking its place in the main (battle) line of fighting ships. Hence the modern term for most prestigious passenger vessel: Liner.

List: The vessel’s angle of lean or tilt to one side, in the direction called the roll.

Loggerhead: An iron ball attached to a long handle, used for driving caulking into seams and (occasionally) in a fight. Hence: “at loggerheads”.

Loxodograph: Device used to record the ship’s travels.

Lubber’s line: A vertical line inside a compass case indicating the direction of the ship’s head.

Luff: The forward edge of a sail. To head a sailing vessel more towards the direction of the wind.

Luffing: When a sailing vessel is steered far enough to windward that the sail is no longer completely filled with wind. The flapping of the sail(s) which results from having no wind in the sail at all.

Lugsail: Four-sided sail bent to an obliquely hanging yard.

Lutchet: Fitting on ship’s deck to allow the mast to pivot to pass under bridges.

Lying ahull: Waiting out a storm by dousing all sails and simply letting the boat drift.

Mainbrace: The brace attached to the mainmast.

Mainmast (or Main): The tallest mast on a ship.

Mainsail: Principal sail on a ship’s mainmast.

Mainsheet: Sail control line that allows the most obvious effect on mainsail trim. Primarily used to control the angle of the boom, and thereby the mainsail, this control can also increase or decrease downward tension on the boom while sailing upwind, significantly affecting sail shape. For more control over downward tension on the boom, use a boom vang.

Mainstay: Stay that extends from the main-top to the foot of the foremast.

Man overboard: A cry let out when a seaman has gone overboard.

Manrope: Rope used as a handrail on a ship.

Marina: A docking facility for small ships and yachts.

Martingale: Lower stay of rope used to sustain the strain of the forestays.

Mast: A vertical pole on a ship which supports sails or rigging.

Master: Either the commander of a commercial vessel, or a senior officer of a naval sailing ship in charge of routine seamanship and navigation but not in command during combat.

Masthead Light: This white light shines forward and to both sides and is required on all power-driven vessels.

Masthead: A small platform partway up the mast, just above the height of the mast’s main yard. A lookout is stationed here, and men who are working on the main yard will embark from here. See also Crow’s Nest.

Matelot: A traditional Royal Navy term for an ordinary sailor.

Mess: An eating place aboard ship. A group of the crew who live and feed together.

Midshipman: A non-commissioned officer below the rank of Lieutenant. Usually regarded as being “in training” to some degree.

Mizzen staysail: Sail on a ketch or yawl, usually lightweight, set from, and forward of, the mizzen mast while reaching in light to moderate air.

Mizzen: Three-masted vessel; aft sail of such a vessel.

Monkey fist: A ball woven out of line used to provide heft to heave the line to another location. The monkey fist and other heaving-line knots were sometimes weighted with lead (easily available in the form of foil used to seal e.g. tea chests from dampness) although Clifford W. Ashley notes that there was a “definite sporting limit” to the weight thus added.

Moonraker: Topmost sail of a ship, above the skyscraper.

Moor: To attach a boat to a mooring buoy or post. Also, to a dock a ship.

Navigation rules: Rules of the road that provide guidance on how to avoid collision and also used to assign blame when a collision does occur.

Net Tons: Obtained from the gross tonnage by deducting crew and navigating spaces and allowances for propulsion machinery.

Nipper: Short rope used to bind a cable to the “messenger” (a moving line propelled by the capstan) so that the cable is dragged along too (Used because the cable is too large to be wrapped around the capstan itself). During the raising of an anchor, the nippers were attached and detached from the (endless) messenger by the ship’s boys. Hence the term for small boys: “nippers”.

Oakum: Old ropes untwisted for caulking the seams of ships.

Oreboat: Great Lakes Term for a vessel primarily used in the transport of iron ore.

Orlop deck: The lowest deck of a ship of the line. The deck covering in the hold.

Outhaul: A line used to control the shape of a sail.

Outrigger: Spar extended from the side of the ship to help secure mast.

Outward bound: To leave the safety of the port, heading for the open ocean.

Overbear: To sail downwind directly at another ship, stealing the wind from its sails.

Overfall: Dangerously steep and breaking seas due to opposing currents and wind in a shallow area.

Overhaul: Hauling the buntline ropes over the sails to prevent them from chaffing.

Overhead: The “ceiling,” or, essentially, the bottom of the deck above you.

Overreach: When tacking, to hold a course too long.

Overwhelmed: Capsized or foundered.

Owner: Traditional Royal Navy term for the Captain, a survival from the days when privately-owned ships were often hired for naval service.

Ox-Eye: A cloud or other weather phenomenon that may be indicative of an upcoming storm.

Painter: Rope attached to the bow of a boat to attach it to a ship or a post.

Pallograph: Instrument measuring ship’s vibration.

Parrel: A movable loop, used to fasten the yard to its respective mast.

Patroon: Captain of a ship; coxswain of a longboat.

Pay: Fill a seam (with caulking or pitch), or to lubricate the running rigging; pay with slush (q.v.), or protect from the weather by covering with slush. See also: The Devil to pay. (French from paix, pitch).

Paymaster: The officer responsible for all money matters in RN ships including the paying and provisioning of the crew, all stores, tools, and spare parts. See also: purser.

Pilot: Navigator. A specially knowledgeable person qualified to navigate a vessel through difficult waters, e.g. harbor pilot, etc.

Pipe (Bos’n’s), or a Bos’n’s Call: A whistle used by Boatswains (bosuns or bos’ns) to issue commands. Consisting of a metal tube which directs the breath over an aperture on the top of a hollow ball to produce high pitched notes. The pitch of the notes can be changed by partly covering the aperture with the finger of the hand in which the pipe is held. The shape of the instrument is similar to that of a smoking pipe.

Pipe down: A signal on the bosun’s pipe to signal the end of the day, requiring lights (and smoking pipes) to be extinguished and silence from the crew.

Piping the side: A salute on the bos’n’s pipe(s) performed in the company of the deck watch on the starboard side of the quarterdeck or at the head of the gangway, to welcome or bid farewell to the ship’s Captain, senior officers and honored visitors.

Pitch: A vessel’s motion, rotating about the beam axis, so the bow pitches up and down.

Pitchpole: To capsize a boat end over end, rather than by rolling over.

Pontoon: A flat-bottomed vessel used as a ferry or a barge or float moored alongside a jetty or a ship to facilitate boarding.

Poop deck: A high deck on the aft superstructure of a ship.

Port: Towards the left-hand side of the ship facing forward (formerly Larboard). Denoted with a red light at night.

Preventer (Gybe preventer, Jibe preventer): A sail control line originating at some point on the boom leading to a fixed point on the boat’s deck or rail (usually a cleat or pad eye) used to prevent or moderate the effects of an accidental jibe.

Primage: Fee paid to loaders for loading ship.

Privateer: A privately-owned ship authorized by a national power (by means of a Letter of Marque) to conduct hostilities against an enemy. Also called a private man of war.

Propeller walk or prop walk: Tendency for a propeller to push the stern sideways. In theory, a right-hand propeller in reverse will walk the stern to port.

Prow: A poetical alternative term for bows.

Purser: Ship’s officer in charge of finances and passengers.

Quarterdeck: The aftermost deck of a warship. In the age of sail, the quarterdeck was the preserve of the ship’s officers.

Quartering: Sailing nearly before the wind.

Quayside: Refers to the dock or platform used to fasten a vessel to.

Radar reflector: A special fixture fitted to a vessel or incorporated into the design of certain aids to navigation to enhance their ability to reflect radar energy. In general, these fixtures will materially improve the visibility for use by vessels with radar.

Radar: Acronym for Radio Detection And Ranging. An electronic system designed to transmit radio signals and receive reflected images of those signals from a “target” in order to determine the bearing and distance to the “target”.

Rake: The inclination of a mast or another part of a ship.

Range lights: Two lights associated to form a range (a line formed by the extension of a line connecting two charted points) which often, but not necessarily, indicates the channel centerline. The front range light is the lower of the two, and nearer to the mariner using the range. The rear light is higher and further from the mariner.

Ratlines: Rope ladders permanently rigged from bulwarks and tops to the mast to enable access to topmasts and yards. Also, serve to provide lateral stability to the masts.

Reach: A point of sail from about 60° to about 160° off the wind. Reaching consists of “close reaching” (about 60° to 80°), “beam reaching” (about 90°) and “broad reaching” (about 120° to 160°).

Reef points: Small lengths of cord attached to a sail, used to secure the excess fabric after reefing.

Reef: To temporarily reduce the area of a sail exposed to the wind, usually to guard against adverse effects of strong wind or to slow the vessel.

Reef-bands: Long pieces of rough canvas sewed across the sails to give them additional strength.

Reef-tackles: Ropes employed in the operation of reefing.

Reeve: To pass a rope through a ring.

Rigging: the system of ropes, cables, or chains employed to support a ship’s masts and to control or set the yards and sails.

Righting couple: The force which tends to restore a ship to equilibrium once a heel has altered the relationship between her center of buoyancy and her center of gravity.

Rigol: The rim or ‘eyebrow’ above a port-hole or scuttle.

Roach: Curved cut in the edge of sail for preventing chafing.

Roband: Piece of yarn used to fasten a sail to a spar.

Roll: A vessel’s motion rotating from side to side, about the fore-aft axis. List (qv) is a lasting tilt in the roll direction.

Rolling-tackle: A number of pulleys, engaged to confine the yard to the weather side of the mast; this tackle is much used in a rough sea.

Rostrum: Spike on the prow of warship for ramming.

Rowlock: Contrivance serving as a fulcrum for an oar.

Royal: Small sail on the royal mast just above topgallant sail.

Running rigging: Rigging used to manipulate sails, spars, etc. in order to control the movement of the ship. Cf. standing rigging.

Sailing Certification : An acknowledgment of a sailing competence from an established sailing educational body (like NauticEd).

Sail-plan: A set of drawings showing various sail combinations recommended for use in various situations.

Saltie: Great Lakes term for a vessel that sails the oceans.

Sampson post: A strong vertical post used to support a ship’s windlass and the heel of a ship’s bowsprit.

Scandalize: To reduce the area of a sail by expedient means (slacking the peak and tricing up the tack) without properly reefing it.

Scud: To sail swiftly before a gale.

Scudding: A term applied to a vessel when carried furiously along by a tempest.

Scuppers: An opening on the side rail that allows water to run off the deck.

Scuttle: A small opening, or lid thereof, in a ship’s deck or hull. To cut a hole in, or sink something.

Scuttlebutt: Cask of drinking water aboard a ship; rumour, idle gossip.

Scuttles: Portholes on a ship.

Sea anchor: A stabilizer deployed in the water for heaving to in heavy weather. It acts as a brake and keeps the hull in line with the wind and perpendicular to waves.

Sea chest: A valve on the hull of the ship to allow water in for ballast purposes.

Seaman: Generic term for a sailor.

Seaworthy: Certified for, and capable of, safely sailing at sea.

Self-Unloader: Great Lakes slang term for a vessel with a conveyor or some other method of unloading the cargo without shoreside equipment.

Shaft Horsepower (SHP): The amount of mechanical power delivered by the engine to a propeller shaft. One horsepower is equivalent to 746 watts in the SI system of units.

Shakes: Pieces of barrels or casks broken down to save space. They are worth very little, leading to the phrase “no great shakes”.

Sheer: The upward curve of a vessel’s longitudinal lines as viewed from the side.

Sheet: A rope used to control the setting of a sail in relation to the direction of the wind.

Ship: Strictly, a three-masted vessel square-rigged on all three masts, though generally used to describe most medium or large vessels. Derived from the Anglo-Saxon word “scip”.

Ship’s bell: Striking the ship’s bell is the traditional method of marking time and regulating the crew’s watches.

Ship’s company: The crew of a ship.

Shoal: Shallow water that is a hazard to navigation.

Shrouds: Standing rigging running from a mast to the sides of ships.

Sickbay: The compartment reserved for medical purposes.

Sidelights: These red and green lights are called sidelights (also called combination lights) because they are visible to another vessel approaching from the side or head-on. The red light indicates a vessel’s port (left) side; the green indicates a vessel’s starboard (right) side.

Siren: A sound signal which uses electricity or compressed air to actuate either a disc or a cup-shaped rotor.

Skeg: Part of ship connecting the keel with the bottom of the rudderpost.

Skipper: The captain of a ship.

Skysail: A sail set very high, above the royals. Only carried by a few ships.

Skyscraper: A small, triangular sail, above the skysail. Used in light winds on a few ships.

Slipway: Ramp sloping into the water for supporting a ship.

Slop chest: A ship’s store of merchandise, such as clothing, tobacco, etc., maintained aboard merchant ships for sale to the crew.

Small bower (anchor): The smaller of two anchors carried in the bow.

Snotty: Naval midshipman.

Sonar: A sound-based device used to detect and range underwater targets and obstacles. Formerly known as ASDIC.

Spanker: Sail on the mast nearest the stern of a square-rigged ship.

Spanker-mast: The aft-most mast of a fore-and-aft or gaff-rigged vessel such as schooners, barquentines, and barques. A full-rigged ship has a spanker sail but not a spanker-mast (see Jigger-mast).

Spar: A wooden, in later years also iron or steel pole used to support various pieces of rigging and sails. The big five-masted full-rigged tall ship Preussen (German spelling: Preußen) had crossed 30 steel yards, but only one wooden spar—the little gaffe of its spanker sail.

Spindrift: Finely-divided water swept from the crest of waves by strong winds.

Spinnaker pole: A spar used to help control a spinnaker or other headsail.

Spinnaker: A large sail flown in front of the vessel while heading downwind.

Spirketing: Inside planking between ports and waterways of a ship.

Splice: To join lines (ropes, cables, etc.) by unraveling their ends and intertwining them to form a continuous line. To form an eye or a knot by splicing.

Sponson: Platform jutting from ship’s deck for gun or wheel.

Sprit: Spar crossing a fore-and-aft sail diagonally.

Spritsail: Sail extended by a sprit.

Squared away: Yards held rigidly perpendicular to their masts and parallel to the deck. This was rarely the best trim of the yards for efficiency but made a pretty sight for inspections and in the harbor. The term is applied to situations and to people figuratively to mean that all difficulties have been resolved or that the person is performing well and is mentally and physically prepared.

Squat effect: Is the phenomenon by which a vessel moving quickly through shallow water creates an area of lowered pressure under its keel that reduces the ship’s buoyancy, particularly at the bow. The reduced buoyancy causes the ship to “squat” lower in the water than would ordinarily be expected.

Standing rigging: Rigging which is used to support masts and spars, and is not normally manipulated during normal operations. Cf. running rigging.

Starboard: Towards the right-hand side of a vessel facing forward. Denoted with a green light at night. Derived from the old steering oar or ‘steerboard’ which preceded the invention of the rudder.

Starbolins: Sailors of the starboard watch.

Starter: A rope used as a punitive device.

Stay: Rigging running fore (forestay) and aft (backstay) from a mast to the hull.

Staysail: A sail whose luff is attached to a forestay.

Steering oar or steering board: A long, flat board or oar that went from the stern to well underwater, used to control the vessel in the absence of a rudder.

Steeve: To set a ship’s bowsprit at an upward inclination.

Stem: The extension of the keel at the forward of a ship.

Stemson: Supporting timber of a ship.

Stern tube: The tube under the hull to bear the tail shaft for propulsion (usually at the stern).

Stern: The rear part of a ship, technically defined as the area built up over the sternpost, extending upwards from the counter to the taffrail.

Sternlight: This white light is seen only from behind or nearly behind the vessel.

Sternpost: Main member at the stern of a ship extending from keel to deck.

Sternway: Movement of a ship backward.

Stevedore: Dock worker who loads and unloads ships.

Stokehold: Ship’s furnace chamber.

Strake: One of the overlapping boards in a clinker-built hull.

Studding-sails (pronounced “stunsail”): Long and narrow sails, used only in fine weather, on the outside of the large square sails.

Stunsail: Light auxiliary sail to the side of principal sails.

Supercargo: Ship’s official in charge of business affairs.

Surge: A vessel’s transient motion in a fore and aft direction.

Sway: A vessel’s motion from side to side. Also used as a verb meaning to hoist. “Sway up my dunnage.”

Swigging: To take up the last bit of slack on a line such as a halyard, anchor line or dock line by taking a single turn round a cleat and alternately heaving on the rope above and below the cleat while keeping the tension on the tail.

Swinging the compass: Measuring the accuracy in a ship’s magnetic compass so its readings can be adjusted – often by turning the ship and taking bearings on reference points.

Swinging the lamp: Telling sea stories. Referring to lamps slung from the deckhead which swing while at sea. Often used to indicate that the storyteller is exaggerating.

Swinging the lead: Measuring the depth of water beneath a ship using a lead-weighted sounding line.

Taffrail: Rail around the stern of a ship.

Tail shaft: A kind of metallic shafting (a rod of metal) to hold the propeller and connected to the power-engine. When the tail shaft is moved, the propeller may also be moved for propulsion.

Taken aback: An inattentive helmsmen might allow the dangerous situation to arise where the wind is blowing into the sails “backward”, causing a sudden (and possibly dangerous) shift in the position of the sails.

Tally: The operation of hauling aft the sheets, or drawing them in the direction of the ship’s stern.

The Ropes: Refers to the lines in the rigging.

Thole: Pin in the side of a boat to keep an oar in place.

Three sheets to the wind: On a three-masted ship, having the sheets of the three lower courses loose will result in the ship meandering aimlessly downwind.

Tiller: Handle or lever for turning a ship’s rudder.

Timberhead: Top end of ship’s timber used above the gunwale.

Timenoguy: Rope stretched from place to place in a ship.

Timoneer: From the French, “timonnier”, is a name given on particular occasions to the steersman of a ship.

Ton: The unit of measure often used in specifying the size of a ship. There are three completely unrelated definitions for the word. One of them refers to weight, while others refer to volume.

Tonnage: A measurement of the cargo-carrying capacity of merchant’s vessels. It depends not on weight, but on the volume available for carrying cargo. The basic units of measure are the Register Ton, equivalent to 100 cubic feet, and the Measurement Ton, equivalent to 40 cubic feet. The calculation of tonnage is complicated by many technical factors.

Topgallant: Mast or sail above the topmast and below the royal mast.

Topmast: The second section of the mast above the deck; formerly the upper mast, later surmounted by the topgallant mast; carrying the topsails.

Topsail: The second sail (counting from the bottom) up to a mast. These may be either square sails or fore-and-aft ones, in which case they often “fill in” between the mast and the gaff of the sail below.

Topsides: The part of the hull between the waterline and the deck. Also, Above-water hull.

Touch and go: The bottom of the ship touching the bottom, but not grounding.

Towing: The operation of drawing a vessel forward by means of long lines.

Traffic Separation Scheme: Shipping corridors marked by buoys which separate incoming from outgoing vessels. Improperly called Sea Lanes.

Tranship: To transfer from one ship to another.

Transire: Ship’s customs warrant for clearing goods.

Transom: A more or less flat surface across the stern of a vessel.

Travellers: Small fittings that slide on a rod or line. The most common use is for the inboard end of the mainsheet; a more esoteric form of traveler consists of “slight iron rings, encircling the backstays, which are used for hoisting the top-gallant yards, and confining them to the backstays”.

Treenail: Long wooden pin used to fix planks of the ship to the timbers.

Trice: To haul in and lash secure a sail with a small rope.

Trick: A period of time spent at the wheel (“my trick’s over”).

Trim: Relationship of ship’s hull to the waterline.

Trunnel: Wooden shipbuilding peg used for fastening timbers.

Trysail: Ship’s sail bent to a gaff and hoisted on a lower mast.

Tuck: Part of the ship where ends of lower planks meet under the stern.

Turtleback: Structure over ship’s bows or stern.

Turtling: When a sailboat (in particular a dinghy) capsizes to a point where the mast is pointed straight down and the hull is on the surface resembling a turtle shell.

Under the weather: Serving a watch on the weather side of the ship, exposed to wind and spray.

Underway: A vessel that is not at anchor, or made fast to the shore, or aground.

Underwater hull or underwater ship: The underwater section of a vessel beneath the waterline, normally not visible except when in drydock.

Unreeve: To withdraw a rope from an opening.

Vanishing angle: The maximum degree of heel after which a vessel becomes unable to return to an upright position.

Wake: Turbulence behind a ship.

Wales: A number of strong and thick planks running length-wise along the ship, covering the lower part of the ship’s side.

Walty: Inclined to tip over or lean.

Wardroom: Quarters for ship’s officers.

Washboard: Broad thin plank along ship’s gunwale to keep out sea water.

Watch: A period of time during which a part of the crew is on duty. Changes of watch are marked by strokes on the ship’s bell.

Watching: Fully afloat.

Watercraft: Water transport vessels. Ships, boats, personal watercraft.

Waterline: The intersection of a boat’s hull and the water’s surface, or where the boat sits in the water.

Waveson: Goods floating on the sea after a shipwreck.

Wear: To turn a ship’s stern to windward to alter its course

Weather deck: Whichever deck is exposed to the weather—usually either the main deck or, in larger vessels, the upper deck.

Weather gage: Favorable position over another sailing vessel to with respect to the wind.

Weather side: The weather side of a ship is the side exposed to the wind.

Weatherboard: Weather side of a ship.

: If the helm was centered, the boat would turn towards the wind (weather). Consequently, the tiller must be pulled to the windward side of the boat in order to make the boat sail in a straight line. See lee helm.

Weatherly: A ship that is easily sailed and maneuvered; makes little leeway when sailing to windward.

Weatherly: Able to sail close to the wind with little leeway.

Weigh anchor: To heave up (an anchor) preparatory to sailing.

Wells: Places in the ship’s hold for the pumps.

Wheelhouse: Location on a ship where the steering wheel is located, often interchanged with pilothouse and bridge.

Whipstaff: Vertical lever controlling ship’s rudder.

White Horses: Waves in wind strong enough to produce foam or spray on the wave tops.

Wide berth: To leave room between two ships moored (berthed) to allow space for a maneuver.

Windage: Wind resistance of the boat.

Windbound: A condition wherein the ship is detained in one particular station by contrary winds.

Windlass: A winch mechanism, usually with a horizontal axis. Used where mechanical advantage greater than that obtainable by block and tackle was needed (such as raising the anchor on small ships). Modern sailboats use an electric “Windlass” to raise the anchor.

Windward: In the direction that the wind is coming from.

Xebec: Small three-masted pirate ship.

Yard: Tapering spar attached to ship’s mast to spread the head of a square sail.

Yardarm: The very end of a yard. Often mistaken for a “yard”, which refers to the entire spar. As in to hang “from the yardarm” and the sun being “over the yardarm” (late enough to have a drink).

Yarr: Acknowledgement of an order, or agreement.

Yaw: A vessel’s motion rotating about the vertical axis, so the bow yaws from side to side.

Yawl: Ship’s small boat; sailboat carrying mainsail and one or more jibs.

Zabra: Small Spanish sailing vessel.

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What Do Boat Measurements Mean? 11 Terms Explained!

Boat measurements are more than just numbers; they are the essence of maritime safety, efficiency, and compatibility.

Navigating the intricate world of boat measurements is crucial for anyone in the boating industry, from manufacturers to enthusiasts.

Understanding these measurements ensures proper vessel selection, compliance with marina requirements, and safe navigation in various water conditions.

Below we delve into the key aspects of how boats are measured and the main terms used, providing you with the essential knowledge to engage with the maritime world confidently.

11 Main Boat Measurement Terms

These are 11 main boat measurement terms with expanded descriptions and examples for better understanding:

• Length Overall (LOA) : This is the total length of the boat from the tip of the bow to the end of the stern. It’s the most common way to describe the size of a boat. LOA is important for determining mooring space, marina fees, and navigating in confined waters. For example, a boat with an LOA of 30 feet will need a berth slightly longer than 30 feet. For stability calculations, you should refer to LBP or length between perpendiculars .
• Length on Deck (LOD) : This measures the horizontal length of the boat’s hull excluding any extensions like bow sprits or swim platforms. LOD is used to provide a more accurate measurement of the usable space on the boat. A boat might have an LOA of 35 feet but an LOD of 30 feet if there’s a 5-foot bow sprit.
• Beam : The beam is the width of the boat at its widest point. It’s crucial for stability; wider beams generally provide greater stability. The beam also affects a boat’s capacity and maneuverability. For instance, a boat with a beam of 10 feet might be more stable but less maneuverable than a boat with an 8-foot beam. More about boat beam read here .
• Draft : Draft measures the minimum depth of water a boat requires to float. It’s key for determining where a boat can safely navigate. A sailboat with a draft of 6 feet can’t enter waters less than one fathom or 6 feet deep without risking running aground.
• Displacement : This is the weight of the water displaced by the boat’s hull. It roughly equates to the boat’s weight when fully loaded. Displacement impacts how a boat handles and its fuel efficiency. A boat displacing 5 tons will handle differently than one displacing 2 tons.
• Freeboard : The distance from the waterline to the upper deck level, indicates how much of the boat is above water. A higher freeboard can mean a drier and potentially safer ride in rough conditions. For example, a boat with 4 feet of freeboard will handle choppy water better than one with 2 feet of freeboard.
• Deadrise : This is the angle of the boat’s hull relative to a flat surface. A higher deadrise (sharp angle) helps cut through waves, providing a smoother ride in choppy conditions. A boat with a 20-degree deadrise will generally perform better in rough water than one with a 10-degree deadrise. Learn more about boat deadrise in a detailed article.
• Air Draft : This is the height of the boat from the waterline to its highest fixed point. It’s important to determine if a boat can fit under fixed bridges or other overhead obstructions. A sailboat with a mast height (air draft) of 50 feet needs to consider bridge clearances on its route.
• Gross Tonnage : This volume measurement is used for large vessels and is calculated based on the total internal space of the ship. Ship tonnage is important for regulatory, safety, and commercial purposes. A cargo ship with a gross tonnage of 50,000 indicates its large size and capacity.
• Ballast : This is the weight (often lead or water) added low in the boat to improve stability. Ballast is particularly important in sailboats to counterbalance the force of the wind. A sailboat with 2,000 pounds of ballast will heel (lean) less and be more stable than one with 1,000 pounds.
• Waterline Length (LWL) : The length of the boat at the waterline, can be shorter than the LOA due to overhangs. LWL affects speed and stability; longer waterline lengths generally allow for higher speeds. For instance, a boat with an LWL of 25 feet may be faster than one with an LWL of 20 feet.

Each of these measurements plays a critical role in the design, functionality, and performance of a boat. They are essential for builders, designers, and users to understand the capabilities and limitations of a vessel in various conditions.

How Do You Measure A Boat Hull?

Measuring a boat hull involves determining several key dimensions that are critical for understanding the boat’s design, performance, and suitability for certain conditions. Here are the main measurements taken for a boat hull:

• Length Overall (LOA) : Measure from the furthest point forward ( bow ) to the furthest point aft ( stern ), including any overhangs.
• Length on Deck (LOD) : Measure the length of the deck, excluding overhangs.
• Waterline Length (LWL) : Measure the length of the boat at the waterline, which may be different from the LOA due to the hull shape and overhangs.
• Beam : Measure the widest part of the boat hull, which is usually found at or near the midpoint of the boat’s length. The beam measurement is crucial as it affects stability and interior space.
• Draft : Measure the vertical distance from the waterline to the lowest part of the hull (usually the bottom of the keel ). This tells you how deep the water needs to be for the boat to float without hitting the bottom.
• Freeboard : Measure the distance from the waterline to the upper edge of the hull. This measurement gives an idea of how high the boat sits in the water and can affect how dry the boat stays in rough conditions.
• Deadrise : This is the angle between the hull bottom and a horizontal plane at the boat’s beam. It’s measured in degrees and indicates how the hull will handle different sea conditions. A higher deadrise usually means better performance in rough water.
• Hull Depth : Measure the distance from the deepest point of the hull to the top of the deck. This gives an idea of the overall volume of the hull.

These measurements are typically made using measuring tapes, laser measuring tools, or, in the design phase, through CAD (Computer-Aided Design) software. Accurate hull measurements are essential for boat builders, designers, and owners, as they influence the boat’s capacity, stability , speed, and seaworthiness.

How Does the Coast Guard Measure Boat Length?

The U.S. Coast Guard measures boat length primarily based on the Length Overall (LOA) method. This approach involves measuring the boat from the tip of the bow in its most forward position to the end of the stern in its most aft position.

This includes all structural and integral parts of the boat but does not include removable attachments and fittings such as outboard motors, bow pulpits, rudders , and similar extensions.

It’s important to note that the Coast Guard’s measurement for boat length can differ from how length is defined for registration or documentation purposes, or how it might be described by manufacturers or in boating literature.

For instance, Length on Deck (LOD) or Waterline Length (LWL) might be used in different contexts but are not the standard measurements the Coast Guard uses for defining a boat’s length.

The Coast Guard’s method of measuring boat length is significant for regulatory and safety reasons. For example, certain boating laws, safety requirements, and regulations apply differently to boats depending on their length class. Therefore, accurate measurement is crucial for compliance with federal and state boating laws .

About the author

I worked as an officer in the deck department on various types of vessels, including oil and chemical tankers, LPG carriers, and even reefer and TSHD in the early years. Currently employed as Marine Surveyor carrying cargo, draft, bunker, and warranty survey.

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Do you know your numbers when it comes to sizing up your boat? Accurate measurements for figures like length, draft, beam and clearance will keep your boat free from damage in marinas and private boat dock slips as well as while traveling beneath fixed bridges.

Boat length is measured from the bow to the stern. However, the number is not as set in stone as it may seem. It can vary depending on whether there’s a swim platform, a bow pulpit, a dinghy on a davit or other things that contribute to the length overall (LOA). Knowing the correct length of your boat is just as important as knowing how to properly operate it. We’re not talking about that number the manufacturer says it is … the one that’s part of the model name. For example, a Hatteras GT45X is 45 feet long, but with a swim platform and a bow pulpit, it could technically come closer to a total of 47.5 feet. This number can change from boat to boat (even among the same model and manufacturer) as well as type of boat. Correct length is especially useful when docking or choosing a private boat dock rental. Trying to fit a boat into a slip that’s too small can result in damage to the boat, the dock and other property around it.      

Example Average Length

• Cruising Sailboat: 16’ – 50’
• Catamaran: 32’ – 47’
• Cabin Cruiser: 25’ – 45’
• Motor Yacht: 29’- 65’
• Center Console: 18’ – 32’

Another important factor is draft. A boat’s draft refers to the vertical distance from the waterline (where the hull touches the water) to the bottom of the hull, or keel on a sailboat. It determines the minimum depth of water a boat can safely navigate without running ashore (which, by the way, is very bad). Put simply, it helps you know how deep the water needs to be. Like length, it can vary from boat to boat. A sailboat can have a very large draft based on whether it has a keel (and whether the keel is removable). Each dock has its own specific draft allowance, which is based on things like water level, tides and how flat or angled the ground is under the water. One dock can be vastly different than others in the area. Dock draft measurements can be taken by dropping a long length of rope (weighted) or chain into the water, marking it at the water level and then measuring from the bottom up out of the water. Private docks on our site are listed at the low tide water level. This way, you know the absolute minimum depth of water. It’s always best to be conservative by one or two feet if you’re not completely sure you’ll be able to dock at that boat slip – due to things like changing tides, weather and boat wakes. 

Boat Size vs Draft

• Low Draft: A boat 32 feet long and under needs 3 feet or less of water
• Medium Draft: A boat 45 to 65 feet long needs 4 to 5 feet of water
• High Draft: A boat 65 feet long or greater needs 5 to 7.5 feet of water

To throw a wrench into these statistics, there are instances where this might vary. Sailboats can be an exception as they may have a non-retractable keel, which gives them the need for a larger draft (since the keep gives them a bigger draft measurement). On the other hand, since catamarans are wide and displace water very efficiently, they may only need 4.5 feet of draft even if it falls into a bigger category.

Average Boat Draft

• Cruising Sailboat: 5’ (but could be more if it has a non-retractable keel)
• Catamaran: 2’ – 4’(large cats could need more)
• Cabin Cruiser: 3’
• Motor Yacht: 4’ (the bigger the yacht, the bigger the draft)
• Center Console: 2’

As a general rule, the bigger the boat is, the deeper the draft will need to be. Factors like weight and beam play into this concept. The hull shape can also play a part. A flat or multi-hull boat (like pontoon boats, jet skis and dinghies) has a low draft. A deep V-shaped displacement hull (like most power boats and cruisers) allows the boat to sit deeper in the water, resulting in a high draft.

Beam refers to the distance from the widest point of the boat to the other side (think: middle of the boat from side to side). Catamarans are very wide compared to that of center consoles and cabin cruisers. Most boats fall into the 18 to 20-foot beam category, but cats can be as wide as 22 to 30 feet.

The beam of a boat will determine how wide of a boat slip rental you need. You’ll want to measure the dock to make sure it’s wide enough that your boat won’t bang against the sides.

Average Beam

• Cruising Sailboat: 12’
• Catamaran: 22’ to 30’
• Cabin Cruiser: 8.5’
• Motor Yacht: 13’
• Center Console: 9’

Clearance, or vertical clearance, is important for sailboats and catamarans with a fixed mast, as well as sportfish boats with tall towers. It refers to the height of the boat from the waterline to the top of the mast or flybridge (or any non-removable part). Some masts can be lowered, so that would not be included in your clearance number.

Out in the wide-open ocean, clearance isn’t too much of an issue. The time it becomes an issue is when you’re sailing under a fixed bridge. A drawbridge is no problem. You just need the patience to wait till it opens. Sailboats can require anywhere from 35 to 75 feet of vertical clearance, so you’ll want to check out those fixed bridge heights when charting your course or choosing a boat dock for rent. Be sure to take into account low tide when determining clearance.

Average Boat Clearance

• Cruising Sailboat: 50’
• Catamaran: 39’
• Express Cabin Cruiser:  9’ 10 “ with tower up / 7’ 7” with tower down
• Motor Yacht: 14’ to 15’
• Center Console: 9’ 6”

Whether you’re docking your boat at a marina, a mooring or a private boat dock rental, the correct measurements play a big factor. Hopefully this has given you some good advice to make the whole docking process a bit easier. Now if you could just control the wind while docking.  

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• Call Us: +44 (0) 23 8045 8737

How to sail: A-Z of Yachting Terms

When learning how to sail have you ever wondered when you are on a yacht what some of those yachting terms mean, we have asked our RYA Training Centre pupils which ones confuse the most. Here are a selection, which includes the obvious to the more obscure!

A baft: A location on the boat but further to the rear of the boat. “The tiller is abaft the mast.”

A beam: The beam is the widest part of the boat. When another boat is abeam, it is at a right angle off the beam to either the starboard or port side of the boat you are on.

A ft: When on a boat you refer to the stern part of the boat as being aft or to the rear of the boat.

A head: A term used to describe the area in front of the boat you are on. “Look ahead.”

A ids to Navigation: This includes all external systems like channel markers, preferred route buoys, danger and safe water buoys, isolated danger and regulatory markers etc. that help determine a boats position or course, the presence of dangers or obstructions and the preferred route to navigate.

A midships: In the middle of the boat between the stern and the bow.

A pparent Wind: The apparent wind is a combination of the true wind and the wind caused by the boat travelling through the water. On an windex, the apparent wind will cause the windex to show wind direction just in front of the true wind.

A stern: A location off the boat and behind it.

B ulkhead – Refers to an often watertight, interior wall on the boat

Backing Wind: Refers to the wind shifting direction in a counter-clockwise direction. This usually means that bad weather is approaching.

Backstay: A wire running from the top of the mast to the stern of the boat. The backstay stops the mast from falling forward and also helps to control the degree of mast bend when tuning a boat.

Battens: Wood, fiberglass or plastic strips slid into pockets along the leech of the sail. Battens help to shape and strengthen the sail to increase overall performance.

Beam: The widest part of the boat.

Beam Reaching: One of the points of sail. You are ‘beam reaching’ when sailing directly sideways to the wind on either a port or starboard tack. Think of a clock face – if the wind is blowing from 12 o’clock, sailing at between 3 o’clock or 9 o’clock would be a beam reach.

Bearing Away: Turning away from the wind or turning downwind.

Beating: Sailing towards the wind by tacking back and forth across the wind.

Belayed: Secured, tied to, made fast to.

Bend On: To secure one thing to another. Tieing two lines together.

Bifurcation: A channel junction (two channels meeting) usually marked by a ‘bifurcation buoy’ indicating the perferred channel to follow.

Bight: A loop or bend in a line.

Bilge: The lowest inner part of a boats hull.

Bitter End: The utmost free end of a line. (The other end is referred to as the ‘Standing Line’).

Boat Wind: The wind created by the boat moving through the water. The true wind and the boat wind combine to create the apparent wind direction.

Boat Fall: Rigging used to raise or lower a ship’s boat.

Boat Painter: Rope tied to the front end of a boat used to either tow a boat or to secure it to a dock.

Bollard: Wooden or iron post on a pier to which the boat is secured.

Boom: The boom is the pole running aft from the mast to which (among other things) the foot of the mainsail is attached.

Bowline: A very strong and yet easy to untie knot that creates a loop in the end of a line.

Breastlines: Mooring lines that run from the bow and the stern at right angles to the dock to stop the boat from drifting out from the dock.

Broad Reach: One of the points of sail. Sailing downwind off to the port or starboard side. Think of a clock face – if the wind is blowing from 12 o’clock, sailing at between 4-5 o’clock or between 7-8 o’clock would be a broad reach.

By the Lee: Sailing downwind with the mainsail remaining on the same side of the boat that the wind is hitting. If you are sailing downwind on a port tack, typically the mainsail would be off the starboard side of the boat. When sailing ‘by the lee’, the mainsail in the same situation would remain on the port side of the boat out at a 90 degree angle to the boat.

C lew – The lower aft corner of a sail

Cabin: The below deck living quarters.

Cable: Measurement of distance equal to 0.1 nautical mile.

Cam cleat: A fitting through which a line is run through. The cam cleat consists of two cams that wedge against the line stopping it from being pulled out.

Cardinal Aids to Navigation: Buoys with indicate the location of hazards, safe water or deep water by reference to the four cardinal points of a compass (North, South, East, West).(See our section on buoys for a more complete explanation.)

Catboat: A boat with one mast flying no foresail (jib).

Cast Off: To release the lines allowing the boat to leave it’s mooring.

Chainplates: Very strong metal plates affixed to the hull to which the forestay, backstay and shrouds are attached.

Chart Datum: For navigational safety, depths on a chart are shown from a low-water surface or a low-water datum called chart datum. Chart datum is selected so that the water level will seldom fall below it and only rarely will there be less depth available than what is portrayed on the chart

Chock: a metal fitting, either oval or U-shaped, through which mooring lines are passed. Chocks help reduce abrasion saving the lines from excessive wear and tear.

Cleat: A small, metal deck fitting with horns used for securing lines (belaying).

Clew: The lower rear corner of a sail.

Close Reach: Point of sail – sailing against the wind at an angle somewhere between a Beam Reach and Close Hauled. Think of a clock face – if the wind is blowing from 12 o’clock, sailing at 2 o’clock or 10 o’clock would be a close reach.

Close Hauled: Point of sail – sailng as close to the wind (sharp angle to the wind) as possible without the sailings luffing (fluttering).

Cockpit: The open inset area from where the boat is steered.

Companionway: Stairs or ladder on a boat usually leading down to the cabin.

Cringles: Open metal rings inserted into the sail (also called grommets) used as reefing points for a sail but also found at the clew, head and tack of the sail to attach halyards, lines, outhauls etc.

Cunningham: A line used to adjust the forward edge of the mainsail. Usually runs from the tack of the sail to the front area of the boom.

Current: The horizontal flow of water. (Tide is the vertical flow of water.)

Cutter: A cutter has one mast but sails with two foresails.

D raft – This describes the depth of a boat measured from the deepest point to the waterline

Davit: A crane onboard that can be swung out over the side for hoisting or lowering boats.

Dead Reckoning: Navigational term – method used to plot the course already travelled by measuring speed and time to calculate distance.

Deep Six: A slang term meaning to discard something over the side of the boat.

Degree: A distance of measurement on a nautical chart. One degree equals 60 nautical miles. Each degree is broken down into 60 minute intervals. One minute of one degree equals 1 nautical mile.

Deviation: A ship’s magnetic compass reading can be affected by metal objects on the boat (electronic equipment etc). The difference between the correct magnetic reading and the ships compass magnetic reading is called deviation. Deviation will vary depending on the direction of the boat.

Dog: A metal fitting used to secure watertight doors, hatch covers and scuttles.

Downhaul: A line attached to the tack of the sail and used to pull down or tighten the mainsail to increase sale efficiency.

E ase: To let out or ‘ease off’ a line.

E nsign – The national flag of the boats home country

F Fairleads: A metal fitting through which lines are run to in order to change the direction of the lines while reducing friction on the lines.

Fairway: Sailing on inland waters, fairway means an open channel or being in midchannel.

Fast: To make fast. To secure (snugly tie) a line to something.

Fathoms: A unit of measurement. One fathon equals 6 feet.

Fenders: Cylindrical air filled plastic or rubber bumpers hung off the side of a boat or dock to prevent damage to both dock and boat.

Fetch: The distance over open water the wind has blown.

Faked: A line is faked by zig zagging it back and forth so that when it is used it will not tangle on itself.

Flaked:A sail is flaked when lowered. Flaking a sail is the process of folding the sail back and forth upon itself like the blades on a paper fan. Flaking a sail will help prolong the sail life.

Foot (Sail): The foot of a sail is the lower part of the sail. In the case of a mainsail, this is the part of the sail that runs along the boom.

F orepeak- The cabin most forward in the bow of the boat

Forestay: The forestay is a wire that runs from the top of the mast (or near the top of the mast) to the bow of the boat. The forestay supports the mast from falling backwards and is also used in shaping the bend in the mast for maximum efficiency. The luff (front) of the foresails (jib, genoa) are also generally attached to the forestay depending on the rigging system.

Forward: When on a boat, forward means towards the bow. “Move forward” – move towards the front of the boat.

Galley: The boat’s kitchen.

Genoa: The Genoa is a foresail that is larger than a jib. The clew (lower corner at the foot of the sail) extends aft of the mast unlike a jib.

Give-way Boat: Navigational rules – the boat not having the right-of-way. The Give-way boat must stay clear of the Stand-on boat. The Give-way boat must make it’s intentions known by making a decisive maneuver to alert the Stand-on boat.

Gooseneck: This is a metal fitting that attaches the boom to the mast.

G oosewinging – To sail downwind with the mainsail set on one side and the foresail on the other

Gybing: Sailing down wind and turning through the wind causing the sails to move from one side of the boat to the other.

Gybe ho: Term used by the helmsman to let his crew know that he has started to turn the boat into a gybe.

H alyard – A line which is used to raise things on a boat, so the main halyard line would be used to raise the mainsail

Halyards: Lines used to lower and raise sails.

Hanks: Clips found along the luff (front) of the foresail used to clip the sail onto the forestay (wire running from the bow to the top or near the top of the mast).

Hard over: Turning the wheel or pushing the tiller all the way over.

Head: Generally used to refer to the boat’s toilet. When talking about a sail, the Head is the top of the sail.

Head to Wind: The bow of the boat is pointed directly into the wind.

Heading up: Turning up more into the wind.

Heaving to: A way to, in effect, stall a sailboat by backing the jib, easing out the mainsail and turning the rudder hard into the wind. The forward wind pressure on the foresail wants to force the bow downwind. The rudder turned towards the wind wants to force the bow windward. These two counter effects balance each other causing the boat to hold it’s position with little movement. The mainsail is eased out all the way so that it does not catch any wind and therefore has no bearing on the boats postion.

Heeling: Leaning or heeling over caused by wind pressure on the sails.

Helm: The Helm is the steering mechanism of the boat (wheel or tiller). The person at the helm is called the helmsman.

Helms Alee: A term used by the helmsman to notify the crew that he has started to tack. Hypothermia: A dangerous condition where the body core temperature has been lowered causing extreme shivering, loss of co-ordination, in ability to make decisions and in extreme cases, loss of conciousness and even death.

I nlet – A recess, such as a cove or bay, along a coastline

In Irons: This occurs where the boat has been turned directly into the wind and has lost all forward momentum. Without forward momentum the boat loses it’s ability to steer.

J ackstay – A strong line, that can be made of wire, which runs fore and aft alongside the boat that can be used to attach your safety harness to.

Jacob’s ladder: A light ladder made of rope or chain with metal or wooden rungs used over the side or aloft.

Jib: The jib is a foresail (smaller than a genoa). The jib is about the same size as the triangular area between the forestay, mast and foredeck.

Jiffy reefing: This is a way to make the mainsail smaller by partially lowering it, tying or reefing the lower slack part of the sail onto the boom through gromets (holes in the sail) called reefing points. This is done in high wind conditions to power down the sail.

Jury rig: Makeshift – adapting parts and materials for a use not specifically designed for in order to get by until proper parts or repairs can be obtained.

K etch – A sailboat with 2 masts

Kedging: A method used to free a grounded boat by dropping it’s anchor in deeper water and then pulling on the anchor rode to attempt to free the boat.

Keel: The large heavily weighted fin like structure secured to the bottom of the boat. The keel helps to keep the boat upright and also reduces leeway (side slipping across the wind).

Ketch: A two masted boat. The second and smaller mast (mizzen) is positioned just forward of the rudder post.

Knot: Rate of speed. On land it is miles per hour, on the water it is knots (nautical miles) per hours. One knot equals 1.15 land miles – so one knot is just a bit faster than one mph.

L eeway – The sideways movement of a boat caused by wind and currents

Lateral Aids to Navigation: channel buoys (Red & Green), isolated danger buoys (Black & Red), safe water ahead (Red & White), regulatory buoys (Yellow), bifurcation buoys (Black & Yellow) plus channel identification markers and navigation markers are all considered Laterial Aids to Navigation.

Lazarette: A storage compartment, usually under the seats of the cockpit.

Lee Helm: Also called Weather Helm, this is the tendancy of the boat to turn into the wind once it has heeled over at a sharp angle.

Lee Shore: Feared by most sailors, this is the downwind shore from the boat.

Leech: The rear edge of the foresail or the mainsail running from the head (top) to the clew (rear corner) of the sail.

Leeward: Downwind.

Leeway: When a boat sails across the wind, the force of the wind causes the boat to slip sideways. This drifting or sideway motion is known as Leeway.

Lifelines: The lines running around the outside of the deck creating a railing. The lines are attached to stanchions (upright metal posts).

Luff: The forward edge of a sail running from head to tack (front corner of the sail).

Luffing: A sail is luffing when it starts to flutter in the wind. The term Luff is also used to describe the same situation. “The sail is starting to luff.”

Luff Up: To turn into the wind to cause the sails to start luffing.

M ultihull – Any boat that has more than one hull, such as a catamaran.

Made fast: Secured to.

Mast: The upright pole supported by the shrouds, forestay and backstay to which the sails are attached.

Masthead fly: A windvane attached to the top of the mast to show which direction was wind is coming from.

Monkey fist: A type of knot, heavy in nature and tied to the end of the rope. The weighted knot makes it easier to throw the rope a farther distance.

Mooring ball: An anchored ball to which you can secure your boat. Safer alternative to anchoring provided the mooring ball and lines are in good condition.

Mooring lines: Lines used to secure a boat to a dock or mooring ball.

MSD: Marine sanitation device (toilet).

N eap tide – When during the four week tidal cycle, the tide rises and drops the least.

Nautical mile (NM): International standard for measuring distance on water. One nautical mile equals one minute of latitude. (One nautical mile equals 1.15 land miles.)

O uthaul – This is a line used to tension the foot of the sail, to better control the curvature of the sail

P ulpit – A sturdy rail around the deck on the bow, normally surrounding the forestay

Pad eye: A metal eye (ring) through which lines can be passed in order to stop chaffing.

Painter: The bow line of a dinghy.

P-effect (Prop Walk): When a boat is in a standstill position and put into forward or reverse, the resistance of the boat to move and the motion of the propeller creates a paddlewheel effect pulling the stern of the boat to either port or starboard side depending on the spin of the propeller. This paddlewheel effect is known as P-effect or Prop Walk. P-effect is especially noticable in reverse where there is greater boat resistance to move backwards thus making it easier for the prop to pull the boat sideways.

PFD: Personal Floatation Device – life jacket.

Pintle and gudgeon: The pintle and the gudgeon together form a swinging hinge usually associated with the installation of the rudder on smaller tiller steered boats. The pintle has pins that fit into the holes on the gudgeon thus creating a hinge like fitting.

Points of sail: A reference for the direction the boat is travelling in relation to the wind. (in irons, close hauled, close reach, beam reach, broad reach, running)

Port: When on a boat and facing forward, the left hand side of the boat.

Port tack: Sailing across the wind so that the wind hits the port (left) side of the boat first.

Pulpit: Located at the bow of the boat, this area is enclosed by a metal railing.

Pushpit: Located at the stern of the boat and like the pulpit, this area is enclosed by a metal railing.

Q uadrant – This is a device connected to the rudder that the steering cables attach to

R egatta – Boat races

S hroud – The wires at the side that hold the mast up

Schooner: A sailboat that has two masts both the same height or on some schooners, the aft mast is higher than the fore mast.

Scope: Expressed in terms of a ratio, it is the length of the anchor rode let out compared to height above the sea bed. Height is measured not from the water line but from the top of the deck to the sea bed. A safe anchoring ratio is 1:7 which translates to 7 feet of anchor rode for every foot of height. Many sailors incorrectly assume that height means water depth and therefore find themselves dragging the anchor for lack of proper scope.

Seaworthy: A boat that is fit to be sailed at sea.

Self-bailing cockpit: A cockpit that allows water to drain automatically from the cockpit to the outside of the boat.

Shackles: Metal fittings (often U shaped) that open and close with a pin across the top of the ‘U’. Lines and halyards often use shackles. The mainsail halyard is secured to the head of the mainsail with the use of a shackle.

Sheave: A roller/wheel to guide a line or wire.

Sheets: Lines that are used to adjust sails by either pulling them in or by letting them out.

Shrouds: Also called sidestays, shrouds are the metal wires found on both sides of the mast running from the deck to the top or near top of the mast. The shrouds support the mast by providing lateral support.

Slack water: The period between the flood (tidal water moving in) and the ebb (tidal water moving out) where the water has in effect stalled – little or no movement.

Slides: The groove in the mast to which the luff (front side) of the mainsail is inserted. The slides hold the sail tight against the mast and allows the sail to be easily raised or lowered.

Sloop: a sailboat that has one mast and sails with the mainsail and one foresail.

Soundings: Water depths.

Spar: A spar can refer to any of the following: mast, boom or a pole.

Spinnaker: A large balloon-like foresail used for sailing downwind (running or broad reach).

Spinnaker pole: The spinnaker pole is boom-like in nature, but smaller and lighter, and attaches to fore part of the mast a few feet up from the deck. The other end of the spinnaker pole attaches to the leeward (down wind) base of the spinnaker.

Spreaders: Bars extending sideways from the mast (gives the mast a cross-like appearance). The spreaders hold out the shrouds so that they do not interfer with the rigging.

Springlines: Springlines are used to secure a boat to a dock and stop the boat from moving forward or backwards. The aft springline runs from a point on the boat near the bow to a point aft on the dock. The forward springline runs from a point on the boat near the stern to a point forward on the dock.

Squall: A sudden isolated storm associated with potentially high wind gusts.

Stanchions: Upright metal posts running around the outside of the deck supporting the lifelines.

Stand: This refers to the short period of time where the tide is neither rising or falling. (At a stand still.)

Standing rigging: Standing rigging includes the forestay, backstay and the shrouds. Unlike the ‘running rigging’, the standing rigging is generally only adjusted when the boat is not underway.

Stand-on boat: The boat that must retain her current course and rate of speed in order to avoid a potential collision with an approaching give-way boat.

Starboard: As you face towards the bow on a boat, starboard is the right hand side of the boat.

Starboard tack: Sailing across the wind with the wind hitting the starboard (right) side of the boat first.

Steerage: The ability of the boat to be steered. In order for a rudder to be effective in steering a boat, there must be boat movement. A boat not moving cannot be steered.

Stern: The most aft part of a boat (the very back of the boat).

Storm jib: Same as a jib but not as big. The smaller sail is used in high wind conditions.

T ender – A small boat or dinghy used to ferry crew between the boat and shore

Tack: The front lower corner of a sail. Also means to sail back and forth across the wind in either a port or starboard tack.

Tacking: Also called “Coming About”. Tacking is when the bow of the boat is turned through the wind onto the opposite tack.

Tail: The bitter end of a sheet tailing out from a winch.

Tang: A metal fitting used to affix the stays to the mast.

Telltails: (Also called Ticklers) These are small strings (wool, plastic) attached to both sides of the luff of the sail. When the telltails on both sides of the sail are blowing straight back, this indicates that the sail has been properly trimmed.

Through hulls: Through hulls are holes that go through the boat. Each through hull will have a shuttle cock (value) to stop the flow of water. An example of a through hull would be the head (bathroom). A through hull value is opened so that water from outside the boat can be pumped into the MSD (toilet). The value is closed and the toilet pumped empty into a holding tank.

Tide: The vertical rise and fall the oceans.

Tide rips: This is an area of rough water where the wind is blowing across the water in the opposite direction from which strong tidal current is flowing.

Tiller: In boats that are not steered by a wheel, a tiller (long handle) is attached to the top of the rudder in order to facilitate steering.

Toe rail: A small metal railing running around the outside of the deck used to support your feet.

Topping lift: A line running from the top of the mast to the end of the boom. The topping lift supports the boom when the sail has been lowered.

Topside: The portion of the hull above the water line.

Transom: The flat area across the stern of the boat.

Trim: To trim or adjust the sail to make it more effective against the wind.

True wind: The actual wind felt wind the boat is not moving.

Turnbuckles: Adjustable fittings usually attached at the end of shrouds and stays. Turning the turnbuckle one way or the other tightens or loosens the wire.

U nfurl – To unroll a sail

Upstream: Moving from seaward into harbor, moving with the flood of the tide, moving up river toward the headwaters.

V ane – A wind direction indicator

Veering: A wind shift in the clockwise direction usually indicating that good weather is approaching.

W inch – A mechanical device for pulling in a line

Wake: The waves created behind a boat as a result of the boat moving through the water.

Way: Movement of the boat.

Weather helm: The tendancy of the boat to turn up wind after heeling (leaning over).

Wheel: Controls the rudder. Taking control of the wheel is taking the helm.

Winch: Provides a mechanical advantage. Used to raise the sails, tighten the sheets and other lines.

Windward: Towards the wind.

Wing to wing: Running (sail directly downwind) with the mainsail out one side of the boat and the foresail out the other side of the boat.

X marks the spot on the treasure map!

Y awing – The side to side movement of a boat on an uneven course

Yawl: A sailboat that has two masts. The aft mast (mizzen) is shorter than the foremast. The mizzen mast is located aft the rudder post. (On a Ketch, the mizzen mast is located fore of the rudder post – this is the distinquishing factor between the two.)

Z ephyr – A very light westerly wind

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