yacht breadth

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.