trimaran heavy weather sailing

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How to sail a trimaran: Expert advice for sailing with three hulls

• Theo Stocker
• February 13, 2024

For their size, trimarans can punch well above their weight in speed, cruising potential and fun. Monohull sailor Theo Stocker gets to grips with how to handle one

Humans tend to gravitate into tribes of like-minded enthusiasts, enjoying the encouragement, support and sense of identity, while often looking askance at others; sailors at motorboaters, cruising sailors at racers, monohull sailors at raft, I mean, multihull sailors, and everyone looks askance at jet-skiers.

Large cruising catamarans (40ft now counts as a small one) are a world apart from monohull sailing, but there’s a sub-tribe of sailors dedicated to life on three hulls and builders such as Dragonfly, Corsair, Farrier, and Astus give them plenty of choice.

I’ve been sailing a 22ft (7m) Astus 22.5 this season, with just enough space for a family of four and a minimum of creature comforts. Thanks to her VPLP-designed hulls and 650kg all-up weight, we can sail upwind at 7-plus knots and downwind at over 10 knots with ease, all on a roughly even keel, while the kids play Duplo down below. It can also be beached and is towable behind a car.

Having, it seems, caught the trimaran bug, I wanted to get better at sailing and handling the boat, but my monohull sailing experience and habits were proving something of a hindrance, so we sought advice from some existing trimaran owners, and well as the UK’s top multihull sailors.

Much of the advice will apply to all multihulls , whether two or three-hulled, while other parts are just for small trimarans. I also found that brushing-up some of my rusty dinghy sailing skills helped get my head around what we were trying to do.

To try out our expert tips we went out sailing to see what difference they made. On the day, we got a solid Force 4-5 southwesterly, averaging 16 knots, but fluctuating between 12 and 20 knots true.

Blasting about on a sporty trimaran is a whole world of fun, but is much calmer than it looks

Trimaran sail trim

One of the biggest differences between a cruising monohull and a multihull is how the mainsail is trimmed. Leech tension on a yacht is often largely controlled by the kicker and the backstay, while the mainsheet sheets the mainsail in and out, predominantly controlling the angle of the boom to the centreline, and there may be a short traveller.

On a mulithull, however, there’s more than enough space for a good, wide traveller. Those who sail on performance monohulls will also be used to this. The sail shape is mainly controlled by the mainsheet, and the traveller then moves the boom towards or away from the centreline.

This is exaggerated on a multihull which has wide shrouds, swept well aft with no backstay, making space for a powerful square-top mainsail with full-length battens. There’s no backstay to bend the mast and flatten what is anyway a pretty rigid mainsail.

The mainsheet purchase creates enough power to control the leech of the square-top mainsail

Depowering a trimaran

Sailing on a monohull, heel and weatherhelm and eventually a broach give loads of warning that you’re pushing too hard. With straight hulls and little heel, those warning signs don’t really apply to multihulls.

In reality, however, there are a host of warning signals that it’s time to back-off; they’re just a bit different. Even then, there’s still a large safety margin before you get close to danger.

By way of reassurance, with the boat powered up on a beat, Hein, from Boats on Wheels, the boat’s owner, stood on the leeward hull and lent on the shrouds. Even as his feet got wet and the wind gusted at the top of Force 4, the boat didn’t bat an eyelid, thanks to the huge buoyancy of the floats.

Even with a person on the leeward float the boat was extremely stable

On the water – sail trim

My first inclination was to point the boat as high upwind as possible, pin the sails in and go for height. Doing that resulted in a not-terrible boat speed of 5-6 knots and a good pointing angle.

Free off by a handful of degrees however, and ease the sails just a smidge, and the speed leapt up to 8-9 knots – over 50% more; a huge increase. So, don’t pinch. If you had a decent chartplotter on board, you could find your optimum speed to angle using velocity made good (VMG).

I was also tempted to pinch in the gusts, but it’s better to hold your course and let the speed increase until the main needs easing.

On the wind, it’s time to get the boat fully powered up

If that’s the case, drop the main down the traveller an inch or two or ease some twist into the mainsail and it makes all the difference in the world, but not so far that the top battens fall away and invert – that really isn’t fast. Push too hard and the boat will slow down, largely from the drag of submerging the leeward float and crossbeams. If you’re still overpowered and the main is luffing, it’s time to reef. Downwind is different, but we’ll get onto that later.

After we put a reef in the main, our boat speeds upwind remained largely the same, and the boat was much happier. I came away feeling reassured that even a little trimaran like this would be pretty difficult to capsize, and there were always plenty of warning signs telling me to take my foot off the pedal a little.

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Tacking and gybing a trimaran

Everyone knows that multihulls don’t tack as well as monohulls. Straight hulls and wide beam don’t lend themselves to turning, especially when coupled with the displacement and fixed keels of big cats. Trimarans are a little easier, with a single central daggerboard to act as a pivot, and one or other of the floats will generally be clear of the water. On the downside, light displacement means that there isn’t much momentum to keep you going through the turn and plenty of windage to stop you.

On a trimaran the central daggerboard helps the boat to turn by providing a central pivot point that catamarans lack

Speed is your friend. Build speed up before the tack to give you as much momentum as possible. The helm needs to steer positively into and through the turn, and if necessary, keep the jib backed on the new windward side to help the bow through the wind. Don’t worry about scrubbing speed off, but you don’t want to get stuck in irons.

When it comes to gybing, speed is again key. The turning bit isn’t going to be an issue as you’ll be scooting along, but the faster you’re going, the less load there will be on the sails. The more you slow down, the more the true wind will pile up.

Trimaran sailing skills

Tacks took a bit of practice. It felt plain wrong to jab the tiller across the boat, slamming a big break on in the water but I ended up putting us through the tacks far too slowly, losing a lot of speed. A more aggressive approach worked better. On the Astus, the traveller was between me and the tiller, so the tiller extension needed to be swung around the stern behind the mainsheet onto the new side.

Similarly, old habits of controlling a gybe needed to be modified. With the asymmetric set, we were planing at well over 10 knots, and the ideal is to stay on the plane. Heading dead downwind and centring the main lead to a more violent manoeuvre than flying into the gybe as fast as possible and, as the boom was never that far out thanks to the apparent wind angle, it didn’t need much extra controlling.

Coming up onto the wind after the gybe helped the asymmetric around the front of the jib and to fill on the new side. Stay too deep and it’ll get blanketed by the main. Once we had built up some apparent wind, we could bear away again.

You’ll be on a course deep downwind before you know it, hitting speeds in the double digits

Downwind in a trimaran

Upwind cruising may be fun in a multihull, but bearing away and going with the wind is what it’s all about. Easily-driven hulls, a generous sailplan and light weight mean you can be up and planing, leaving displacement boats wallowing in your wake.

The big difference comes from apparent wind. If you’re in a boat that can do 15 knots downwind in 20 knots of true wind, the resulting wind angles can really mess with your head.

To get going then, says Brian Thompson, ‘Use those leech tell-tales again when sailing downwind and reaching to set the correct twist through the mainsheet, and use the traveller to set the correct angle of the whole sail to the wind.’

As the wind and your speed builds, bear away and trim the main accordingly.

In theory, you shouldn’t need to ease the traveller at all, but you may need to if you want to sail deep downwind. As the gust fades, you’ll find the boat slows down, so you can come back up towards the wind a little to pick up some more breeze, and then bear away as you accelerate again.

Bear away as the boat accelerates. Your course will be something of a slalom as you look to keep a consistent wind angle

This results in something of a ‘slalom’ course, and will also be accentuated if you’re sailing down waves, but that’s all quite normal for apparent wind sailing. Ultimately, you’re looking for a consistent apparent wind angle, even if the resulting wake isn’t straight.

It’s worth remembering that apparent wind reduces the felt effect of the wind, so you need a sailplan to suit the true, not apparent wind speed.

I found that the boat was more sensitive to having a balanced sailplan and trim downwind than upwind, largely because you’ve got almost double the canvas up, with the bowsprit as an extra lever. When weather helm built, I needed to ease the mainsheet to increase twist to depower so that I could bear away. I must admit, getting the boat balanced, sailing fast and light on the helm at 15 knots was something I came away feeling I needed more practice at.

Reviewing the images, I suspect the asymmetric was sheeted in too hard, with too much twist in the main.

Getting a float fully submerged is when it’s time to back off

On the water

Unfurling the gennaker worked best on a beam reach, giving plenty of airflow over the sail to help it fully unfurl. This was also roughly the fastest point of sail, ideal for getting up some speed for apparent wind sailing. We mostly had the sails set for a close reach, even when we were beyond 120º off the true wind on a broad reach.

It was possible to soak deeper downwind, but lose the apparent wind benefit downwind and our speed dropped off dramatically, prompting us to point a bit higher to find some more speed.

As the boat powered up, it paid to hold a slightly higher angle than I would have done in a monohull for the boat to properly take off and get up into double digit speeds – topping out at 15 knots. Lymington to Cowes would have taken us just half an hour at that speed. It’s easy to give yourself a heck of a beat back!

We were sailing on a pretty flat day, so didn’t have to contend with any waves to speak of. On the recent RTI this is what caused the capsizes of at least two multis, a sobering reminder that you need to sail much more conservatively in lumpier conditions.

The bows want to point downwind, so a stern-first approach works with rather than against the boat

Coming alongside

A 650kg boat with no draught and plenty of windage feels dreadfully skittish when manoeuvring in confined spaces. Straight hulls with no forgiving curves and fragile-looking sharp bows make berthing tricky. You’ve got a couple of advantages on your side, however. In the Astus, the floats are at pontoon height making stepping off easy.

Whether you have an engine in each hull of a cat, or one in the central hull of a tri, there’s also a lot more leverage to play with to turn the boat and drive her on or off the pontoon. A steerable outboard gives you even more options.

If the boat has a lifting keel or daggerboards, put them down if there’s enough depth to give you a pivot and to resist drifting. Think about getting corners onto the pontoon, rather than putting the boat alongside. On tris, you won’t be able to get to the bow to fend off as it’s too narrow. You can rig a fender up forwards on a line, and two fenders are enough on the flat sides.

Steering with the outboard towards the pontoon will drive the stern in more; steer away to drive the bow in more

Offshore wind

Coming onto the pontoon with wind blowing off, it worked well coming in stern first. If there’s a tide running, you’ll want to be heading into the tide, so find a spot down wind and down tide to start your approach so you come in at an angle.

On our first attempt we had a bit of tide under us to start with so we came in at a much steeper angle, almost 90º, although this worked out OK in the end.

The crew could then step ashore, taking a line from the stern quarter round a cleat.

Drive forwards against the line and the bow will obediently drive up towards the pontoon, bringing you flat alongside. Getting off was simple, releasing the bowline, and allowing the bow to swing out the before slipping the stern line.

Coming in astern and stopping upwind of the berth meant the bows blew towards the pontoon far to quickly

Onshore wind

Getting onto and off a pontoon with onshore wind proved rather trickier. On our first attempt we came in stern first. The issue was that once we were just upwind of our desired berth and stopped, we lost steerage and the bow immediately blew off with alarming speed towards the pontoon.

Going ahead would only increase the force of the impact, while going astern only increased the bow’s sideways drift. I managed to back out without smashing the bow, but only just, and ended up awkwardly stern to the wind with the bows pointing at the pontoon.

On our second attempt we came in bows first but having aimed at the berth, I had to motor the stern to leeward to stop the bow hitting, making for a rather forceful coming alongside.

On take three, I came in forwards and began ferry gliding towards the berth early, keeping the bows to windward of the stern. Being able to steer with the outboard meant I could go ahead to keep the bow up, and go astern with the engine pulling the stern down toward the pontoon. In this way, it was possible to come in pretty well controlled and parallel to the berth.

To get out, motoring astern against a bow line pulled the entire boat clear before slipping the line

Leaving was a different proposition all together, as I didn’t want to drag the bow along the pontoon, or to drive hard onto it to spring off. Instead, we rigged a slip-line from the forward cross beam. Going astern against this, and then turning the engine towards the wind, I could pull the stern, and the rest of the boat, out and away from the pontoon.

Keeping power on astern, once we’d reached a decent angle, we slipped the line and went astern, finding steerage way almost at once, with the bow following obediently in our wake with more control than I had anticipated.

Whether the wind is blowing onto, or off the pontoon, you want the engine to be driving or pulling the boat off the pontoon with a line on the corner you are going away from. That way you avoid point-loading fine ends where it’s hard to fender.

You’ll want a bridle to reduce swinging, but keep the pick up lines on the bow as backup

Anchoring and mooring a trimaran

While mooring a catamaran is complicated by the lack of a central bow, things should be simpler on a trimaran, and they are, mostly. Picking up a mooring buoy from the main hull bow with a low freeboard and dropping the pick-up line onto a cleat is easier even than a monohull.

The bow may be narrow, but for any lines that pass through a ring on the buoy, you still need to take it back to the same cleat to avoid chafe. That should be it, but windage from the two extra bows and the lack of keel mean the boat can dance merrily around the mooring buoy in a breeze.

Rig the bridle so the buoy sits to one side to stabilise the boat

In practice, we found that a trimaran benefits from a mooring bridle in the same way that a catamaran does. It can’t be rigged from the floats’ bows, as there are no mooring cleats, so a line passed around the outboard ends of the forward beams gave a pretty good angle, again with long lines passed through the mooring and back to the same side. The main pick-up lines stay as a safety backup.

The other trick is to rig the bridle asymmetrically so that the buoy sits to one side or the other, just enough to not be dead head to wind, making it much more stable in the wind.

On the plus side, the lack of draught or keel means that you’ll nearly always be lying head to wind, so the cockpit remains nice and sheltered whatever the tide’s doing.

We ran out of time on the day to try anchoring, but rigging a bridle, effectively a long snubber to a point on the anchor chain in a similar way wouldn’t be tricky.

If you needed not to swing, or to behave more like deeper boats nearby, hanging a bucket over the stern can help, or there’s always anchoring with a kedge, either out ahead in a V, or in line astern.

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Managing heavy weather in a multihull

Article published on 21/07/2019

published in n°167 sept. / oct.

Yes, bad weather! While cruising - and even during a race - almost everything is done to avoid it. Never pleasant to be caught out and/or damaged. Bad weather is anticipated in two ways: by avoiding being where it is likely to occur - sailing areas and times of year - and by preparing your multihull. A complete subject that we will be dealing with soon. But what to do when you are surprised by very strong winds and/or seas? Our 12 tips to stay operational and prevent the big three - Cold, Hunger and Fear - from taking over!

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  Suitable clothing

As long as the bad weather is manageable and the latitudes where you operate are mild in terms of temperatures, a traditional salopettes and jacket combination is perfect. But if the conditions become extreme, a survival suit will be essential.

Anticipate meals!

It’s very difficult to cook in severe weather. Prepare, if possible in advance, thermos of hot drinks, cereal bars and other dried fruits. Freeze-dried dishes are easy and quick to prepare; they allow you to eat hot food!

Keep the children safe

Children can stay in the cockpit as long as the seas are not too big. On condition that they’re wearing lifevests and harnesses.

Reef in time

Reducing the mainsail means positioning your multihull close-hauled or head to wind: easy when the sea is not too big, complicated with three-meter (10’) waves – even more-so at night. Take in a reef before you are caught out!

Furling the genoa

Reducing the genoa is possible at any speed. Remember to keep some tension on the sheet to prevent the sail and sheets from flogging too violently during the maneuver. The sailcloth, in this "half rolled" configuration, will suffer... It may be better to set a staysail on if you have a removable inner forestay, or simply to roll up the genoa completely.

Raise the daggerboards

The advantage of multihulls with daggerboards is that they can be raised all or part of the way in bad weather! The hulls can then slide more easily through the waves and make the helmsman's work easier.

Enough searoom?

The basic principle, in bad weather, is to move away from the area of strongest winds. Today, modern analysis of weather maps makes it possible to optimize its trajectory. But beware of the coasts: apart from some possible access in all weathers, many ports are inaccessible in very heavy seas. Allow yourself some searoom!

Reefed main, jib sheeted in on the opposite tack and helm hard over: this is the classic hove-to configuration. The multihull advances and drifts in relative comfort. A good formula to avoid losing too much headway and/or rest.

Lying a-hull

If the wind and sea become very strong, it may be wise to lie a-hull, i.e. stow the mainsail and furl the jib completely. Depending on the desired course, the support of one or more motors can be useful.

Trailing lines

Sometimes, extreme conditions may require you to trail lines - provided you have enough searoom. Your multihull, with no sail up, or almost (three reefs in the mainsail ideally), practically flies downwind and accompanies the waves. To remain safe, it’s sometimes desirable to limit the speed: a looped trailing line, preferably on reels, can be very effective, provided there are reinforced anchoring points.

Protect the nacelle

Par mer forte de l’arrière, les nacelles très ouvertes sur le cockpit – ou plutôt les baies vitrées – peuvent être soumises à rude épreuve. Des batardeaux sont conseillés. A ...

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Heavy Weather Sailing in a Multihull

Basic seaworthiness.

The seaworthiness of a vessel, in broad terms, is the ability of the vessel to provide safety, and comfort for her crew in all weather conditions. The concept of seaworthiness should not only be considered in storm survival conditions, because vessels can be lost in moderate conditions a well as in storms. The effects of fatigue in construction materials and rigging could result in failure in moderate winds, and crew fatigue due to extreme motion could result in errors of judgment, or exhaustion, long before a dangerous situation need otherwise have developed. Collision for instance can occur at any time, and accounts for the loss of a significant number of yachts, and in my opinion is a bigger danger than storm .

Novanet Elite in storm conditions.

The John Shuttleworth designed 80 ft. racing catamaran "Novanet Elite" in storm conditions off Plymouth at the start of the AZAB race on the 6th of June 1987. The curvature of the 27 ft whip aerial on the stern gives some indication of the wind strength. There are four slab reefs in the mainsail and a storm jib has been set on an inner forestay. Note the height of the clew of the jib - to keep the sail clear of waves breaking over the boat. Skipper Peter Phillips said boat speed was 15 to 20 knots at the time.

In this chapter I shall explain some of the many factors that affect the seaworthiness of multihulls. Including windward ability, stability, motion in waves, and pitching and rolling. I will describe the broad outlines of a number of distinct types of multihull that have emerged over the past 30 years, and go on to indicate how these different types of multihull can be handled in heavy weather, and then describe how a multihull can be made safe if the worst happens and the vessel capsises. The most informative technical work on seaworthiness in modern yachts to date is Seaworthiness the Forgotten Factor by C.A. Marchaj.1 Unfortunately the book concentrates almost exclusively on monohull design and very little is mentioned about multihulls. Since space is limited, I will not redefine the formulae and criteria for seaworthiness, which are explained clearly in the book, instead I will just go straight on to show how a multihull fits into the picture. On reading through Seaworthiness the Forgotten Factor, I could not help constantly thinking how few of the vices and problems, attributed to monohulls, were applicable to modern multihulls.

Ocean going multihulls have been designed and built for at least 2000 years. And it is now an accepted fact that the Pacific was colonised from the West (i.e. to windward) by early navigators in outrigger canoes. These vessels were different from the general types of multihull that are being developed today, in that they had a main hull for the living quarters and stores, and a stabilising outrigger (or ama) which was always to windward while sailing. The mast was stepped on the main hull, and the vessel was 'shunted' end for end during a tack. This requires that there is a rudder at each end of the vessel, the hulls are symmetrical, and the sails can be set from either end. Making long ocean voyages aboard these craft required great skill and experience, and a high degree of 'toughness', since for the most part the accommodation was on deck, exposed to the elements, and weight carrying capacity was relatively limited.

Modern yachtsmen in general require more creature comforts than the hardy navigators of the Pacific, and while some will accept spartan living as a necessary part of the adventure of going to sea, there are others to whom a fully equipped laundry, huge freezers, scuba equipment, speed boat, jaccuzzi, and dog kennel, are minimum requirements for simple living afloat. Therefore although the basic form of the multihull is derived from the polynesian vessels, we have had to develop a new form that can carry weight without loss of seaworthiness, and requires less skill to sail, since the modern sailor does not have a 'navigator' aboard who was born to the task with several generations of knowkedge behind him.

Weight carying capacity. payload, safety.

Thus over the past 30 years a number of distinct types of multihull have emerged all having different sailing qualities, and seaworthiness. There has been a steady improvement in the understanding of the factors required to make a multihull both safe and fast, resulting in boats that are extremely seaworthy, as will be demonstrated in the following pages.

The basic types of Multihull are as follows. Obviously these are the extremes, and many boats will fall between the categories. The groupings given here represent a chronological order in only a very general way. Boats having some of the characteristics of the most modern types can be found in multihulls whose designs date back over 1000 years. On the other hand boats of all types are still being designed and built. From a subjective point of view, the order given here follows my own muiltihull sailing and design experience closely. I first sailed across the Atlantic some 17 years ago in type 1, later I crossed again in a type 2, and a few years ago in a type 3. Recently most of my long distance ocean voyaging has been aboard a type 6 catamaran. So the order given is more applicable to my own rather than general criteria, even though most observers of the development of the modern multihull will agree with the broad outline of each type.

A keel in the sense used below is a foil for resisting leeway. The keel is not balasted as in a monohull, and may be fixed, or retractable either vertically (daggerboard) or by pivoting (centerboard). A few multihulls have been built with ballasted keels, but current practice is to make the boats wider to increase stability, and to keep weight low, to improve windward performance. Amas are the outer hulls of a trimaran, sometimes referred to as outriggers, or the smaller hull of a proa.

Type 1. Early trimaran. Relatively heavy. High Windage. Inefficient underwater and keel shape, often with either a fixed keel or no keel at all. Small sail area. Hard chine with high wetted surface. Poor pitching control. Medium buoyancy amas (around110% of the displacement of the boat). Amas usually both in the water at the same time. Narrow beam (length to beam ratio = 2). Construction sometimes doubtful often in sheet plywood. Low long term fatigue.

Type 2. Trimaran. Becoming lighter. Larger sail plans. Less accommodation. Low buoyancy amas (75 to 90%). Wide beam (L/B = 1.3). Considerably reduced windage. Improvement in structural design.

Type 3. Trimaran. Light weight (due to the use of composite materials). Large Sail areas. Wide beam (L/B < 1.5 to as low as 1.0 in smaller boats.). High buoyancy amas (up to 200% of displacement). Pitching very well controlled by use of different hull shapes on main hull and ama. Sailing attitude well controlled on all points of sail. Low windage. Dramatic improvement in structures due to use of Computer aided design, and better understanding of composite materials.

Type 4. Early catamaran. Relatively heavy. Narrow beam (L/B often over 2). Small sail area. Inefficient underwater shape with low aspect fixed keels or no keels at all. Cruising cats very heavy by today's standards. Bridgedeck saloon versions with large flat windows in coachroof causing high windage. Often prone to hobbyhorsing and pitching due to rocker and symmetry of hulls.

Type 5. Catamaran. Open bridgedeck designs. All accommodation in the hulls. Greatly reduced windage. Keel shapes improved. Retractable daggerboards. Large sterns and fine bows causing bow burying tendencies on a reach. Greatly improved windward performance. Pitching control still poor, some attempts to reduce pitching by using bulb bows. Wider than early designs. Larger sail plans.

Type 6. Catamaran. Open bridgedeck designs with large accommodation in hulls. Hobbyhorsing eliminated by hull shape. Windage greatly reduced by rounding and streamlining deck edges. Powerful efficient rigs. Sophisticated retractable daggerboards and rudders. Minimum wetted surface hulls. Excellent windward performance. Fast easy motion through sea. Very stable with wide beam (L/B < 1.5). Similar structural design improvements taking place as for trimarans.

Type 7. Catamaran. Basically as 6 above but with very streamlined bridgedeck cabin for large accommodation and low windage. Light weight maintained, with large weight carrying ability for fast cruising.

8. Other types. Proas (Atlantic, ama to leeward, and Pacific, ama to windward) and trimaran foilers. In general these are development types almost exclusively for racing, as far as modern multihulls are concerned, and they have special problems that require particular knowledge, experience and seamanship for handling in heavy weather. Due to lack of space these types will not be dealt with in any detail in this chapter.

Although I am concentrating primarily on cruising designs, many of the design concepts have been derived from successful racing designs. Indeed the racing designs which push the limits of performance to the edge, are an excellent test bed for cruising boats, particularly racers designed for the long offshore events like the OSTAR and the 2STAR, which are both predominantly to windward across the North Atlantic. In these races, ease of handling and motion, windward ability, structural integrity, and seaworthiness are of paramount importance.

It is interesting to note that this development, resulting in a dramatic increase in seaworthiness and speed, has taken place over virtually the same time period as the monohulls have been deteriorating in seaworthiness. The primary reason for this has to be the fact that the development of multihulls has taken place without the restriction of any rating rules, with the only criteria for successful design being to improve seakeeping qualities and overall performance - resulting in the development of extremely seaworthy cruising designs.

Boat Motion in a Seaway, and the effect on the ships crew.

1. Rolling. With the exception of type 2 above, multihulls are virtually immune to rolling. This means that the boat sits on the water like a raft - following the surface of the sea, giving great crew comfort while sailing, particulartly down wind. When lying ahull, cats and tris exhibit different characteristics. Firstly catamarans have a very high roll moment of inertia ( Ir ), because the weight of the boat is primarily concentrated at the hull centerlines. The buoyancy of the boat is also concentrated at the extremity of the hull centerline beam, giving massive roll damping. Open bridgedeck cruising cats benefit most from this effect, and low buoyancy ama trimarans (Type 2) least. In a tri the weight is concentrated closer to the center of gravity (CG), reducing Ir , and the amas take longer to pick up buoyancy as the boat heels, thereby reducing damping. In a low buoyancy ama tri this effect can lead to capsize in waves, (when lying ahull) as will be shown later, and different techniques of seamanship are required to ensure the safety of this type of multihull in a storm.

2.Pitching and hobbyhorsing. Many early multihulls were prone to hobbyhorsing, and pitching. This was caused by too much rocker on the hull profile, and fine V sections both fore and aft. U shaped sections forward help to reduce pitching, however too flat a forefoot will slam. As hull shapes improved tending towards more U shaped underbodies particularly aft, pitching still remained a problem, because the large width of the stern sections caused the sea to lift the sterns as the boat passed over the wave, driving the bow down. However we now know that pitching can be dramatically reduced by finer sections at the stern combined with the center of buoyancy being moved forward in the immersed hull, and aft in the lifting hull (ref 2 and 3). This effect can be achieved in both cats and tris, giving a very comfortable and easy motion upwind. At the same time windward performance is improved, because the apparent wind direction is more stable across the sails.

3 Yawing. Any tendency to yaw has been virtually eliminated in the modern multihull due to the shallow draft of the hull (because of the U shaped sections and the light weight), and by the use of retractable daggerboards. Once the keel is removed when sailing downwind, there is virtually no chance of broaching, as long as the forefoot does not dig in. This can be prevented by firstly reducing the forefoot, and by picking up buoyancy quickly in the forward sections of the boat above the waterline. Computer simulations of the hull in different bow down trims, and at varying waterline positions, are now an essential part of the design process to control sailing attitude properly, both on and off the wind. see Fig 1. (ref 4).

4. Surfing. A modern multihull will surf very easily, making for fast passage making in the open ocean. Sailing downwind in winds up to 40 knots can sometimes be quite comfortable and easy depending on the steepness of the seas. The apparent wind being reduced by the high boat speed. Once the wind speed becomes so strong, or the seas so steep, that surfing downwind is dangerous, and if the boat will not make progress to windward or lie ahull, (this could well be the case for types 1,2,and 4) It will be essential to deploy a sea anchor to control the boat speed. Much has been written on this subject, and certainly is an accepted way of surviving a severe storm in a multihull. From the designer's point of view it is essential to provide adequately strong attachment points on the bows and sterns.

One of the main problems when sailing at 20 knots or over in the open sea, (even if this is just caused by surfing on the odd occasion), is that the boat will overtake the wave train, which is usually moving at around 18 knots. When this happens there is a danger that the bows could bury into the back of the wave ahead. If the true windspeed is say 35 knots and the boat is sailing at 16 to 20 knots as she surfs down the wave fronts. The apparent wind speed will be between 35 - 16 = 19 and 35 - 20 = 15 knots. So the "feel on the boat will be that you are sailing in a force 4. The danger here is that you may think you can carry full sail, and indeed you can, until the boat buries the bow and slows right down. Suddenly the wind across the deck will increase to nearly 35 knots, and the boat will be massively overcanvassed. At this point a jib sheet can be released, which may be enough to save the boat from capsise, but a mainsail cannot be depowered in the same way when you are sailing downwind. Therefore it is very important to be familiar with the static stability of the boat, and when sailing downwind ensure that you never have more sail area up than if you were sailing with that true wind from abeam.

The bows can also be prevented from burying if there is adequate reserve buoyancy forward. This can be achieved by flaring the hull above the waterline, and by rounding the decks so that if the bow goes under, the build up of water pressure on the deck is reduced. The stern or transom should not be large, to prevent a following wave from lifting the aft end, thereby increasing the possibility of pitchpoling.

Particular attention has to be paid to rudder size and design to maintain good control at surfing speeds that may be in excess of 20 knots. Elliptical balanced spade rudders of airfoil section reduce helm loads and drag at high speeds. Rudder stocks have to be very strong to be able to steer consistently at such high speed. I used to favour using stainless steel or titanium, rather than carbon for rudder stocks, because at least the rudder will bend if overloaded (by grounding or hitting and object, instead of shearing off. However recently we have designed carbon rudders for some catamarans, because we have found that a bent rudder stock can jam in position, and cause more problems than if it had simply sheared off. It is important to design the rudders large enough so that the boat will steer with one rudder only. A couple of years ago I made a voyage from Corunna to the Canaries in a 42ft Cat with only one rudder, in wind speeds of 30 to 40 knots, without any problem.

The factor of safety for the rudder design should be at least1.5 with rudder at 90 degrees to the waterflow at 25 knots. This situation is quite possible if the boat starts to broach and slew down a wave, and the helm is turned to full lock (35 degrees). A quick sketch will show you that the rudder is then presented at 90 degrees to the water flow.

5. Swaying. Fig 2 shows the righing moment of a Catamaran and a Trimaran of similar displacement.

A modern light displacement multihull lying sideways to the seas with no sails up (i.e. lying ahull), and with the daggerboards up, will surf sideways very easily in a breaking crest. It will be demonstrated later that this is a very important feature in the seaworthiness of multihulls lying ahull in a storm. Multihulls with fixed keels and tris of type 2, have the possibility of tripping over their keels or amas when struck by a breaking crest. Narrow beam increases the danger of capsize in this situation. In a recent tank test programme we dragged a 65ft cat sideways with no keels, two shallow keels, and two deep keels. The increase in sideways resistance, at 3.4 knots was : no keels 100% Shallow keels 123% Deep keels 132% Although we did not test a daggerboard, I would estimate that a daggerboard on the downwind hull would be in the order of 145% to 150%. Fig 3 shows the effect of the tripping action of a board or low buoyancy outrigger that has become immersed. If sideways motion of the yacht needs to be stopped, for instance because of a danger to leeward, this can be done by either deploying a sea anchor abeam, or by putting down the upwind board. (this only applies to a cat) The upwind board can act as a brake without imparting rotational momentum to the boat. If the boat does not rotate - it will not capsize.

6. Heaving. This is a complex problem to define clearly for a multihull, because the two immersed hulls are at different places on the wave front at any given time. Nevertheless, they heave less than monohulls because the hulls are slimmer, allowing the yacht to cut through the water when sailing. Loss of apparent displacement at the wave crest and rotational momentum imparted to the boat by heaving on the upwind hull will assist in capsizing an overcanvassed multihull due to wind and wave action. Heaving assisted capsize has been experienced particularly in tris of type 2, and cats of type 4. This is of particular importance and will be dealt with more fully in the next section.

This is generally a very contentious and little understood subject when multihull seaworthiness is discussed, and is probably the biggest fear that inexperienced sailors have about this type of vessel. And while it is true that certain multihulls have capsized, it is clear from the above that there are many different types of multihull, and indeed there are different ways in which they can capsize. I will endeavour to show that with a real understanding of the factors that contribute to capsize vulnerability, it is clear that some multihulls are extremely difficult to capsize, and therefore are very safe in all conditions provided that the correct amount of sail is carried in relation to the wind and the sea state, and when sail can no longer be carried, correct storm techniques are adopted. (Bearing in mind that there may be a wave out there that will overwhelm any vessel).

Stability in wind. Static stability is a measure of the stability of the boat in flat water, and is given by the following formula. (ref 2 )

• d= displacement (lbs).
• CE = height of the center of effort above the center of lateral resistance (CLR) in feet. Use C of E to Waterline for quick calculation.
• SF = windspeed in MPH that the boat has to reduce sail.
• SA = sail area in square feet.
• B = beam between the centerlines of the outer hulls in feet.

Fig 4 shows the paramaters as they apply to a cat and a tri.

This formula gives designers a measure of stability as an indication of the power to carry sail. i.e. the ability of the boat to resist capsize by wind action alone. This formula accounts for gust loading, the actual static stability is 40% higher. See Technical Q&A's for more information on why we reduce the stability factor in waves. There are two factors that can reduce SF. Firstly if the boat has a high angle of heel at the point of maximum stability, (worst in trimarans of type 2, and minimal in all catamarans) the correct SF is given by replacing beam in 1 with beam overall x cos(angle of heel).

Typical values for SF can vary between 12 mph for a Formula 40 racing catamaran, to over 50 mph for cruising multihulls. Modern light cruiser racers would be in the range of 24 to 30 mph. So it is clear that in addition to the different types of multihull listed above the initial static stability can vary enormously.

Stability curve and stability in waves.

Righting moment is the distance from the center of buoyancy to the center of gravity x the apparent weight of the vessel. This is basically the vessel's inbuilt static resistance to heeling. The forces that heel the boat could come from the wind and/or the waves. Fig 2 shows the curve of righting moment versus angle of heel for a typical modern 35ft catamaran and trimaran racer cruiser to my design.

It is important to note that the maximum stability of the tri occurs at around 20 degrees angle of heel, while the cat has a max at about 6 degrees. If the buoyancy of the ama is reduced below 100 % of the weight of the boat (as in type 2 above), the maximum stability will be reduced not only in proportion to the reduction in buoyancy in the ama, but also by the effect of added apparent displacement from the downward pressure from the sails at high angles of heel.

At 20 degrees this would cause a loss of righting moment in the order of 20%. If the ama buoyancy was only 80% in the first place, the total righting moment would be only 60% of an equivalent trimaran of type 3. Fig 6 shows the same righting moment curve for the cat versus a typical modern cruiser/racer monohull. The energy required to be input into the yacht in order to roll it from 0 degrees to the point of capsize (90 degrees in the cat and 135 degrees in the Mono) is given by the area under the curve. From the graph it is clear that the energy required to roll the cat over is 50% higher than the monohull. Of course in either case the initial angle of heel will reduce the available reserve of stability, and in the trimarans this reduction in energy resistance to roll will be greater than a cat. The energy to roll a tri to 90 degrees is much greater than a cat provided it is of type 1 or 3.

However in all cases, in order to a capsise to occur, the energy from the wind and the waves (which is equal to the area under the righting moment curve) has to be transferred to the vessel in the form of rotational energy. In waves alone, if the energy of the wave impact is not changed into rolling energy the boat can not capsise.

The following table gives the dispalcement and dimensions of the cat, tri, and monohull shown in the graphs.

Firstly if we consider the action of the waves alone. Tank testing has shown (ref 1) that capsise due to the action of unbroken waves is impossible. Therefore when a vessel is lying ahull the impact of the breaking crest is the primary means of energy entering the system which may be transformed into roll energy. A multihull follows the slope of the wave face exactly like a raft as shown in fig. 7. However, because the buoyancy and the weight of the vessel is concentrated at the extremities of the beam (particularly in cats of type 6,) multihulls will be more stable against rolling than a simple raft.

Secondly, particularly in the case of the open bridgedeck cruising cat (type 6), the roll moment of inertia is very high because of the hull configuration. Also the inertia of the water entrained by the hulls is high. Therefore this type of cat has the least energy transferred from the the wave impact into rolling energy. On the other hand a trimaran with the board up will still have a small capsise lever and hence a low impact moment, but the roll moment of inertia (Ir ) is much lower than a cat, because the weight of the yacht is concentrated closer to the center of gravity. Therefore more roll energy will enter the trimaran lying ahull than the cat. (ref 17)

Most mopdern multihulls have low draft, and if the keels are retractd, or not too dep, virtually all the energy of the wave impact is absorbed by surfing sideways. This is exactly the same effect that saves the older type of monohull from capsising in waves, the only difference is that the monohull has to experience a knockdown before the keel is almost parallel to the surface of the water, thereby reducing the lever arm (r) and allowing the energy to be dissipated into sideways motion.

The multihull that fares worst in this situation is the trimaran with low buoyancy amas. When a wave hits the side of the boat, firstly it will roll quicker and much more than a cat, and if the ama immerses to the point where it digs in, thereby stopping sideways movement, all the energy will be transferred into rolling and a capsise is possible. Also having deep fixed keels or leaving the downwind board down will greatly increase the risk of capsise in waves for all types of multihull.

Of course the situation may arise when it may be necessary to limit the sideways drift of the boat, for instance if there is a danger to leeward. In a cat this can be achieved safely by lowering the windward daggerboard. All other types will have to use a sea anchor. Whether to deploy the sea anchor from the bow or the side of the vessel depends on the type of boat, and the conditions. Several people have written on the subject including the Cassanovas, and Dick Newick, who both have used and favour this method of controlling drift and rolling in a storm.

Wind and wave action.

When you combine the action of wind and waves, a catamaran is more vulnerable than a tri, because when a boat is sailing the heaving action of the wave on the windward hull imparts rolling momentum to the boat, reducing the energy reserve left under the righting moment graph in fig 2. If the boat has a low static stability, and is being sailed close to the limit, with the daggerboard down, it will be possible to capsise in waves in a wind speed that would be safe in flat water. Cats are more vulnerable than tris because in general the static stability of the cat is less than an equivalent tri. This is the main reason that tris are considered to be safer for short handed racing - they can be sailed harder in waves with a greater margin of safety. On the other hand this is a very good reason to make cats as wide as possible to increase the static stability and thereby increase the safe sail carrying power.

Windward ability

Another area of traditionally poor performance in multihulls is their windward ability. And indeed it is true that the older types of multihull (types 1 and 4) would tack through 100 degrees or more, and had very inferior pointing ability when compared to their monohull counterparts. Today however modern multihulls are designed paying careful attention to weight saving in the structure, aerodynamic drag of the hulls and superstructure, with efficient rigs and wide overall beam to give good sail carrying power. All these features combine together to give a windward performance better than any equivalent sized monohull. In a force 4 wind, a modern 60ft racing trimaran will sail upwind at 16 knots tacking through 75 degrees. While an open bridgedeck cruising cat like the Spectrum 42 will tack through 80 degrees, at around 10 knots.

The implications of this sort of performance is also an indication that modern multihulls will sail upwind in a gale long after the monohulls have had to heave to. Indeed this superior windward ability has been conclusively demonstrated in all the windward races of the North Atlantic and is a factor of major significance in the improved seaworthiness of modern designs. Windward ability is a very important measure of seaworthiness, and can prove vital if there is a danger to leeward in a gale.

Computer Aided Design.

We now have the ability to design a hull and decks for a complete multihull directly on a computer screen (ref 4). The computer allows us to rotate the hull and draw sections at any angle across the boat. We can therefore see the shapes that the wind is going to flow over in the exact direction that the wind strikes the boat. Remember that the wind never comes from dead ahead in a sailing boat. In fact the boat is really moving crabwise through the air, at best the wind crosses the boat at and angle of around 30 degrees from the bow. Fig 8 shows the perspective view on the computer screen of a bridgedeck cabin for a 43ft cat. It will be obvious that this is a very useful aid in achieving aerodynamically clean 3 dimensional shapes like this. And the next step will be to test the complete hull and bridgedeck in a wind tunnel.

Total potential loss of windward ability due to Drag.

Theoretical calculations of the aero, and hydrodynamic drag of various types of multihull shows the following effect of keel efficiency, weight, sail are, and aerodynamic drag.

25% decrease in keel efficiency = total loss in tacking angle of 5 degrees.

Double hull weight = total loss in tacking angle of 6 degrees.

If we include the lift to drag factors of the sails.... 16% decrease in sail area = total loss in tacking angle of 4 degrees. 35% increase in aerodynamic parasitic drag = total loss in tacking angle of 6 degrees.

The total of all these factors is a loss in tacking angle of 21 degrees.

If we compare an open bridgedeck cat of type 6 to an older type of multihull, this is exactly the sort of difference in pointing ability we observe.

When compared to a design of type 1 or 4 the modern multihull is much more streamlined, about half the weight, has an efficient keel, wide width for high stability and sail carrying power, and larger rig. Where the older designs tacked through 100 degrees, a modern design will be sailing considerably faster and tacking through 80 degrees or less.

In order to achieve large volume in a cruising cat without increasing windage, the hull can be flared above the waterline. This flare can also be used to increase the reserve buoyancy forward, and to control the movement of the center of buoyancy as the boat heels. The same applies to the main hull of a trimaran.

Safety in the event of collision or capsise.

Even though it has become extremely unlikely that a properly designed multihull will capsise, the possibility still exists, in much the same way as it exists for any monohull. The monohull's escape valve is that there is a chance that the boat will right itself before it sinks. The multihull on the other hand can be made into a safe raft for the crew to live on in the inverted position, provided that proper provision for this eventuality has been made at the design stage. In terms of ultimate safety of the crew in the most extreme storm - I believe that a habitable inverted multihull offers better survival prospects than a partially flooded - dismasted monohull that has rolled through 360 degrees, and is in imminent danger of doing so again.

If possible watertight compartments should be built in to the amas of a trimaran, and where ever possible in a cat. A trimaran can be made virtually unsinkable by making the cross beams watertight, and by dividing the ama up into watertight compartments, in such a way that if any section is holed, the remaining volume is over120% of the displacement of the main hull. The bows should be backed with foam, and a watertight collision bulkhead can usually be placed about 6 feet back from the bow, without affecting the accommodation.

The structural cross beams of a cat should be designed to be watertight, with their combined volume large enough to support the whole weight of the vessel. In the unlikely event of a capsise, this will ensure that the boat floats high out of the water, which reduces stress on the structure, and allows the crew to live in the upturned hull. Escape hatches should be incorporated in all designs as a matter of course.

Construction and Fatigue.

- Integrated structure. During the lifespan of a multihull it is subjected to many cycles of a complex array of loads, and if the boat is to survive in all conditions without damage careful attention has to be paid to avoiding stress concentrations in the structure, and to the long term fatigue of the materials used to build it. Fig 9 shows a generalised stress diagram for an open bridgedeck catamaran. By using a computer to analyze the loads at any point in the boat, and then laying appropriate amounts of fibers aligned in the direction of the stress, the stiffness and the strength of the boat can be greatly increased. While at the same time weight can be saved by removing excess material where it is not required. This weight saving actually increases the strength of the boat, because it not only reduces the loads that the boat experiences, but it reduces stress concentrations, which are a major cause of fatigue failure. If the structural design is carried out in this way, and adequate allowance is made in the fiber stress levels in the all parts of the boat to account for long term fatigue, the lifespan of the boat will be greatly increased.

At present, research indicates that if a composite laminate can survive over 10 million cycles, it will last indefinitely. In general in order to achieve this, a factor of safety of at least 10 is required. In all my cruising designs I use at least 10 as a factor of safety in areas of maximum stress. For carbon in particular the laminate is strain limited because the material is so stiff, has a relatively low strain to failure, and an extremely high notch sensitivity. However the material can be very successfully used in areas where great stiffness is required, like the cross beams of a multihull. There are many racing and cruising multihulls sailing that have been designed in this way, and that have suffered no structural failure what so ever, in thousands of miles of hard ocean sailing.

Conclusion.

In the past 20 years the level of understanding of the factors that affect the seaworthiness of multihulls has increased enormously. I hope that the above discussion makes it clear that there are many different types of multihull, and that different techniques are required to handle thes different types of multihull in a storm. Indeed many of the problems and vices associated with the older designs have now been eliminated, and the new generation of cruising designs are very exciting boats to sail, while still offering vast accommodation, crew comfort, and most important of all - safety at sea.

References.

Technical papers..

• Race Results
• Owners' Comments
• Safety at Sea

Heavy Weather Tactics

Scores of books have been written about heavy weather sailing, but few of them address the particulars of multihulls and their individual considerations. Monohulls have more commonalities as a group, therefore there are more general guidelines. Storm tactics for multihulls will depend more on the capabilities of crew and vessel than any other factors.

Barreling along at 18 knots in strong winds can be thrilling and is a highlight of multihull sailing. Making no seamanship errors will be as important as the simplest rules of keeping all lines neatly organized and kink free. Often tangled lines have gotten sailors into more trouble than anything else. Keeping a neat cockpit and thinking ahead are the cheapest insurances against mishaps.

In heavy weather the boat should be set up with appropriate safety lines and attaching yourself to them must be mandatory, even if one only ventures briefly into the cockpit. All crew should wear full gear and always have their life jackets at the ready. Each member should have a strobe, knife and whistle permanently attached and there always should be a big knife with a serrated edge mounted in the cockpit to quickly cut a jammed line, if necessary. Basic safety drills, location of life saving equipment, rafts and throw-able MOB devices must be known to each crewmember. Everyone on board must understand the crucial function of EPIRBs, VHFs, firefighting equipment, as well as engine operation and bilge-pump system. It is all really common sense.

If in the highly unlikely event that you capsize, stay with the boat at all costs. Rig one life raft or dinghy to the underside of the bridge deck, fly a kite and wait for help. Never, ever separate from the mother ship as your chances of being spotted will be close to zero in a raft. Staying warm, hydrated, and clear headed will be as important as keeping crew morale up. Salvage as much food and water as you can and secure them, as waves in the interior will wash them out any opening. It has been suggested to await help in the upturned vessel, but unless it is a perfect calm, it will be impossible. Wave surges in the cabins will be violent and there will be leaking battery acid, foul smells and floating objects that will force you onto the upturned platform of the bridge deck.

Storm strategies will depend on the sea state. The shorter and higher the wave faces, the more critical correct seamanship will be. It is my opinion that the use of sea anchors should be carefully weighed and avoided if one can actively deal with the conditions. In theory, they work well if conditions do not change. The crew can rest and the multihull will make nominal drift downwind, provided there is minimal searoom. But the sea is a chaotic environment and waves do not always remain in one and the same pattern, direction, and period. The forces and loads on the boat when tied to a parachute type device can be huge.

True and Apparent Wave Height

Imagine your boat hanging off a sea anchor and suddenly a wave from a different direction slams into the boat from the side. As the boat is not moving, actually drifting slightly backwards, it will not have any possibility to handle this odd rogue wave. The catamaran might be overwhelmed and rotate around its longitudinal axis and flip. Most cruising catamarans that have capsized were constricted by sea anchors. In one well-documented incident, the parachute's lines caught under the rudders and turned the boat.

A sea anchor might lull you into a false sense of security and your vigilance will be reduced. Being caught with your guard down is the most dangerous situation, and I feel it is better to actively deal with storm conditions, rather than letting the boat drift off a sea anchor. Besides, retrieval and deployment are risky, and if not done properly the first time, they can subject crew and boat to more risks.

This is not to say that a parachute anchor does not work. On the contrary, many multihulls have ridden out hurricanes with these devices. Personally, I would want to position the boat to sail with the seas if there is sea room. The vessel's speed should be adjusted to the wave period and therefore would reduce the relative impact of waves. If one's cat sails too fast, even without sails up, a drogue or warps could be dragged behind the boat. Streaming warps off a stern bridle will also be helpful if the boat has lost steerage. It will keep the bows pointing downwind. Ideally, seas should be taken off the rear quarter in order to present the longest diagonal axis to them. This will be the most stable attitude, and a good multihull will be able to handle the most severe conditions. A well-working autopilot, an alert crew, and a strong boat will get you through anything. Concentration will deteriorate as the conditions worsen and any mistake will be very difficult to rectify. Your margin for error will be minimal and advance thinking and anticipation will be key. Approaching a safe harbor during heavy weather can be nerve-wracking and should be carefully weighed with the risk of running aground and encountering much rougher than usual inlets. Often standing off will take discipline but be safer.

Again it should be mentioned that everyone manages differently with storm conditions and there is not necessarily only one right or wrong way to do it. Making the vessel's speed work for you and being able to

Wave heights make great subjects for sea tales, but the altitude of seas are often overestimated. Especially on smaller vessels, when the horizon is hidden, one feels that the seas are steeper than they actually are. The apparent gravitational pull makes one think that the boat is sailing parallel on the horizontal plane. Usually however, the boat is already ascending the next wave, leading to estimation errors as high as 50% in judging wave heights.

Safely slowing the multihull is accomplished by streaming warps or trailing a special drogue. A large bridle is either fastened to the windward hull or to the sterns.

Streaming Warps or a Drogue to Slow Down

Streaming Warps or a Drogue to Slow Down outrun a system will reduce your exposure time. Drifting slowly downwind tied to a sea anchor will expose you to bad weather longer. The advantage of a fast catamaran should be used to get you out of trouble, or even better, by using today's advanced meteorological forecasts, you might be able to avoid it entirely. Yet, once you are in storm conditions, slowing down the boat to retain full control will be challenging.

If there is no sea room, or one is forced to claw upwind, reducing speed to minimize wave impact is imperative to the comfort of the crew and safety of the boat. Finding the right groove between stalling and too much speed is important. You do not want to be caught by a wave slamming into you, bringing you to a halt. This could end up in a lack of steerage and, in the worst case, you could be flipped backwards. Always keep on sailing at a manageable speed and if your boat has daggerboards, both boards should be down one third only. Head closer to the wind towards the top of the wave, and fall off as the boat sails down the slope. This will aid in keeping the sails drawing and boat speed in check. Structural shocks upwind in very strong winds can be very tough, so find the right speed. Reducing your main to 3 or even 4 reefs and furling your headsail for balance will drive you to weather. We all know that this will not be comfortable, but if there is no choice other than to windward, one will manage until conditions have abated. Flatten sails as much as you can to depower the boat. If you need to tack, plan ahead, do it decisively, and with plenty of momentum. You do not want to be caught in irons while drifting backwards. Loads on the rudders with the boat going in reverse can damage the steering, leaving you crippled.

Running off at a controllable speed is the safest way to handle a storm. If you are deep reaching or sailing downwind with the storm, retract both boards if your boat has daggerboards. In the event that the catamaran is skittish and hard to steer, lower one foot of daggerboard on both sides. Long, well balanced, high-aspect-ratio hulls, especially ones equipped with skegs far aft, will track well, even without boards. A tiny amount of jib sheeted hard amidships might be all that is needed to point the boat downwind. Reduce the boat to a speed where you are just a fraction slower than the waves.

Keep in mind that the term "slow" is relative as this could still mean that you are traveling at well over 15 knots!

Sailing with the beam to the storm and seas should be avoided at any cost. If, because of say navigational issues, one has no choice, both daggerboards must be lifted to assure sideways slippage.

Heaving-to is a tactic which lets the boat sail controlled, almost stationary, and should be used only if one has no more alternatives.

This could be caused by crew exhaustion or mechanical issues with the boat. When heaving-to, the helm is locked to windward, a tiny scrap of jib sheeted to weather, and/or a heavily reefed mainsail can be set. The traveler should be let off to leeward and, theoretically, the multihull will steadily work herself to windward. At 40 degrees, she will either be stationary or slightly fore-reach. This does not work on all multihulls and different mainsail and jib combinations should be tested. Also letting the main or jib luff slightly will take speed off the boat, if

far right Boarding via the transom platform, any guest will easily find his/her way to the spacious cockpit by walking down wide, teak-covered steps. Notice the lack of any sail controls or helm station - they are all located out of the way, on the flybridge above.

so desired. Catamarans with daggerboards should only have very little windward board down to avoid tripping.

Similar to "heaving-to" lying-a-hull differs from boat to boat. In this attitude the boat will carry no sails at all and fend for herself. In case of daggerboards, retract them. Most boats will take the seas on their beams (not my favorite) and let the waves pass under them by surfing sideways. Just as trying to avoid the use of sea anchors, this tactic should only be reverted to if one has exhausted every other possibility.

There are a few generalities that will help you learn about heavy weather sailing tactics. Fine-tuning the sails will help depower the boat. As the wind increases, move the mainsail sheeting point to leeward. This is one of the best features of multihull sailing. Multihulls have wide travelers and an extensive sheeting base which allows for more choices for sail trim than narrow boats. Ease off the traveler to move the main to leeward and use a strong outside rail attachment point, such as a cleat or toe rail track to move the jib to leeward. As the wind strengthens, reduce camber and flatten the sails. Double up preventers and reef lines to create backups and divide the loads. In the end, knowing when to reef and how to control your cat is the most important skill to develop to prepare for heavy weather sailing. Practicing maneuvers in strong conditions will raise your level of confidence and prepare you for the worst Mother Nature might have in store for us.

Heaving-to is an important "parking" technique that should be practiced by every catamaran owner. One tacks from a close-hauled position and either luffs the mainsail or furls it completely. Once on the other tack, the jib is left on the "wrong" side and the helm is turned hard to windward. Every multihull will behave differently, and one has to experiment how hard the headsail must be sheeted in or how far the rudders must be turned. Keel catamarans will behave slightly differently than daggerboard cats. The headsail will keep the bows turned away from the seas, while the rudders will prevent the boat from presenting her beams to the waves. In the heave-to attitude, the catamaran will fore-reach and slightly drift to leeward.

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Readers' Questions

What size waves can a caramaran handle?

The size of waves that a catamaran can handle depends on various factors, including the design and build quality of the specific catamaran, the experience and skill of the captain and crew, and the conditions of the sea and weather. In general, catamarans are known for their stability and ability to handle moderate to large waves. Some larger, more robust catamarans are designed for offshore sailing and can handle rough open ocean conditions, including large waves of several meters in height. However, smaller or lighter catamarans may be more suitable for calmer or sheltered waters and may have limitations in handling very large waves. It is important to consult the manufacturer's recommendations and consider the specific characteristics of a catamaran before taking it into rough seas. Additionally, it is essential to have proper training and experience to safely handle a catamaran in challenging wave conditions.

Are catamarans good in rough water?

Yes, catamarans are generally considered to be good in rough water. The design of a catamaran with two hulls provides better stability and maneuverability compared to a monohull. The wide beam and low center of gravity of a catamaran make it less prone to capsizing in rough conditions. Additionally, the dual hulls help reduce the wave impact, making catamarans more comfortable in rough seas. However, it's important to note that extreme weather conditions can still pose challenges for any type of boat, including catamarans.

How to sail in a storm?

Secure all loose items in and around the cockpit. Reef main sail if possible. Lower the jib, or furl it tightly if possible. If a storm jib is aboard, hoist it. If single handed, rig a preventer to hold the boom in place if a sudden gust should cause an accidental jibe. Double up all sail sheets, halyards, and control lines. Reduce windage by dropping the mainsail traveler and vang. Keep an eye out for squalls. Wear your life jacket and a wet suit or dry suit if the weather is cold enough. Trim the helm to keep the bow into the waves. Try to maintain a consistent speed and course to avoid broaching. Monitor the boat, keeping it free of water and heeling as little as possible. Be prepared to take evasive action, such as dousing the sails, heaving to, or running off.

Can catamarans handle rough seas?

Yes, catamarans can handle rough seas. They are designed with a shallow draft and wide beam that make them more stable, allowing them to handle the waves better than a traditional monohull boat. Additionally, modern catamarans have been designed to be more resistant to adverse weather conditions, which helps them perform better in rough seas.

Are catamarans safe in heavy weather?

It depends on the type of catamaran, its size and design, but generally catamarans are considered to be very safe in heavy weather. They have a wide beam, low center of gravity and are relatively stable in rough seas. A good quality catamaran will have also good deck drainage and self-draining cockpits, adding to their safety in bad weather.

How well are catamarans in heavy waves?

Catamarans usually have good stability in heavy waves, as their wide, shallow hulls help to provide good lift and reduce rolling. However, the size and weight of a catamaran will determine how well it handles in heavier waves, with larger catamarans generally being more stable in larger waves. It is also important to note that catamarans may not perform as well as monohulls in heavy waves as they often have less grip in the water due to their shallow draft. Therefore, it is important to consider the size and weight of the catamaran when planning to take it out in heavier seas.

How to park a catamaran heavy weather?

Ensure that the sea state is suitable for anchoring and that the area is suitable for your catamaran. Set the anchor and let out chain or rope depending on the type of anchor you are using. Monitor the anchor and the mooring lines for any signs of distress. If possible, secure more anchors or mooring buoys to the sea floor away from the catamaran to increase the overall stability and security. Use fenders to protect your catamaran from the sea swell. Make sure that the crew is off deck and has safety lines in place if they are on deck. Aim to park the catamaran in a sheltered area and away from the prevailing winds. Check regularly to make sure the anchor stays in place and that the mooring lines and fenders remain secure.

Why catamaran rotate beam on wave?

Catamarans rotate their beam on waves in order to remain stable and reduce drag. When a catamaran is moving through the water, its hulls can act like wings, causing the boat to tip sideways. By rotating the beam, the catamaran can counter the sideways motion, allowing it to remain relatively level and cut through the water more effectively. Rotating the beam also helps to reduce drag, helping the catamaran to move faster and more efficiently.

The Storm Jib Technique

Discover the benefits of using a storm jib for heavy weather sailing, including improved balance and control, reduced heeling, and increased safety for you and your crew.

Sailing in heavy weather can be both exhilarating and challenging. It requires a combination of skill, experience, and the right equipment to safely navigate through rough seas and strong winds. One essential piece of equipment for heavy weather sailing is the storm jib. In this article, we will explore the storm jib technique, its benefits, and how to properly set it up and use it in various conditions.

Table of Contents

What is a storm jib, benefits of using a storm jib, choosing the right storm jib, setting up the storm jib, using the storm jib in different conditions, storm jib safety tips.

A storm jib is a small, heavy-duty sail designed specifically for use in heavy weather conditions. It is typically made of a strong, durable material like Dacron or Spectra and features reinforced corners and edges to withstand the forces of strong winds and rough seas. The storm jib is usually set on the inner forestay or a removable stay, and it is designed to work in tandem with a reefed mainsail or trysail to maintain balance and control in challenging conditions.

There are several benefits to using a storm jib in heavy weather, including:

Improved Balance and Control: A storm jib helps to balance the forces on the boat, making it easier to maintain control in strong winds and rough seas. This is particularly important when sailing downwind, as it helps to prevent the boat from rounding up into the wind or broaching.

Reduced Heeling: By reducing the sail area forward of the mast, a storm jib can help to minimize the boat’s heeling angle, making it more comfortable and safer for the crew.

Enhanced Performance: A well-designed storm jib can improve the boat’s performance in heavy weather by providing additional drive and reducing drag.

Increased Safety: A storm jib can help to reduce the risk of damage to the boat and injury to the crew by minimizing the forces on the rig and sails.

When selecting a storm jib for your boat, there are several factors to consider:

Size: The size of the storm jib should be appropriate for your boat’s size and displacement. As a general rule, the storm jib’s luff length should be approximately 50-60% of the boat’s “J” measurement (the distance from the mast to the headstay attachment point).

Material: Choose a storm jib made from a strong, durable material like Dacron or Spectra. These materials are designed to withstand the forces of heavy weather and will provide better performance and longevity than lighter materials.

Construction: Look for a storm jib with reinforced corners and edges, as well as heavy-duty stitching and hardware. These features will help to ensure that the sail can withstand the rigors of heavy weather sailing.

Compatibility: Make sure that the storm jib is compatible with your boat’s rigging and hardware. This may include the type of hanks or luff attachment system, as well as the location and strength of the inner forestay or removable stay.

Properly setting up the storm jib is crucial for its effectiveness and safety. Follow these steps to ensure a successful setup:

Inspect the Sail: Before setting up the storm jib, inspect it for any signs of damage or wear. Check the stitching, corners, and edges for any tears or fraying, and ensure that the hardware is in good condition.

Attach the Hanks or Luff System: Attach the storm jib to the inner forestay or removable stay using the appropriate hanks or luff attachment system. Make sure that the hanks or luff system is properly secured and in good working order.

Secure the Tack: Attach the tack of the storm jib to the designated attachment point on the boat, ensuring that it is properly secured and tensioned.

Hoist the Sail: Hoist the storm jib, making sure that it is properly tensioned and free of any twists or tangles. Adjust the halyard tension as needed to achieve the desired luff tension.

Set the Sheet: Attach the sheet to the clew of the storm jib and lead it through the appropriate blocks and winches. Adjust the sheet tension to achieve the desired sail shape and trim.

The storm jib can be used in a variety of heavy weather conditions, including:

Upwind Sailing: When sailing upwind in heavy weather, the storm jib can help to balance the boat and reduce heeling by providing additional drive and reducing drag. Trim the storm jib for optimal performance by adjusting the sheet tension and halyard tension as needed.

Downwind Sailing: In downwind conditions, the storm jib can help to prevent the boat from rounding up into the wind or broaching by providing additional balance and control. In these conditions, it may be necessary to ease the sheet tension and adjust the halyard tension to maintain the desired sail shape and trim.

Reaching: When sailing on a reach in heavy weather, the storm jib can help to maintain balance and control by providing additional drive and reducing drag. Adjust the sheet tension and halyard tension as needed to achieve the desired sail shape and trim.

To ensure the safety of your crew and boat when using a storm jib, follow these tips:

Monitor the Weather: Keep a close eye on the weather conditions and be prepared to set the storm jib when necessary. This may include monitoring weather forecasts, observing changes in wind speed and direction, and watching for signs of approaching storms.

Practice Setting the Storm Jib: Regularly practice setting and using the storm jib in a controlled environment to ensure that you and your crew are familiar with the process and can perform it quickly and efficiently in an emergency.

Inspect the Sail and Rigging: Regularly inspect the storm jib and associated rigging for signs of wear or damage, and address any issues promptly to ensure the safety and effectiveness of the sail.

Use Proper Safety Gear: When setting and using the storm jib in heavy weather, make sure that you and your crew are wearing appropriate safety gear, including life jackets, harnesses, and tethers.

The storm jib is an essential piece of equipment for heavy weather sailing, providing improved balance, control, and safety in challenging conditions. By choosing the right storm jib for your boat, properly setting it up, and using it effectively in various conditions, you can enhance your sailing experience and ensure the safety of your crew and vessel. Remember to practice setting and using the storm jib regularly, monitor the weather conditions, and always prioritize safety when sailing in heavy weather.

Trimaran Seaworthiness Explained! Will it Flip?

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Trimarans are known for their speed and excellent performance. However, not every vessel performs well in the ocean’s rolling waves, which begs the question – are trimarans able to handle rough seas?  

Trimarans are seaworthy because their tri-hull construction makes them incredibly stable, even in the roughest sea conditions. They are lightweight, very buoyant, easy to handle, fast, and resistant to capsizing. Trimarans also have a shallow draft. 

So, let’s get into the details and discuss why trimarans are an excellent choice for seafaring. I’ll tell you more about the features that make them safe and ideal for traversing the oceans. So, let’s get into it. 

Table of Contents

What Makes A Trimaran Seaworthy? 

A trimaran is seaworthy because of its wide base giving it capsize resistance, its high speeds allowing for outrunning storms, and good maneuverability, making transiting stormy areas with precision, safer.

I’ll describe these factors in more detail below: 

Buoyant Construction

One of the most important factors making trimarans seaworthy is their buoyant construction. 

Modern trimarans are made from two lightweight fiberglass layers with a foam core, giving them exceptional buoyancy. 

This should be seen in comparison to their lead keel counterpart, the monohull.

Trimarans also consist of various sealed parts, allowing them to remain afloat if one or more parts become damaged in a collision. If the worst came to the worst and the ocean obliterated the entire trimaran, there would still be buoyant pieces to act as rafts for the crewmembers to hold onto. 

Many trimarans also have watertight crossbeams between the hulls, further increasing their buoyancy. 

If the trimaran were to become filled with water, any of its hulls would be able to keep it afloat. 

Catamarans are known for their excellent stability, and if they heel (lean over with wind-filled sails), they can right themselves up to a 12° angle before flipping over. 

To understand when a catamaran or trimaran will capsize, I suggest you read this article: Why Catamarans Capsize .

On the other hand, Trimarans are well-known for their righting torque (the ability of a vessel to right itself before flipping over). These vessels can reach a 27° angle before they flip over, but the trimaran will likely remain floating even if this happens. 

So, although they heel more than cats, and studies suggest they would capsize “more easily”, they are very stable.  

This stability and ability of trimarans to keep themselves upright are due to their wise base. Just like when someone pushes you, you take a step to widen your base, so do the trimarans amas (the floats to either of the side of the center hull).

This means that the wind’s force can push harder on the sails before it flips, harder than if it had a narrow base (monohull or cat).  

With its tri-hull design, a trimaran’s weight is distributed primarily on the middle hull. This mid-central balance provides a lot of vertical stability for the vessel, but the two outrigger hulls (a.k.a. amas, connected via lateral beams) give added sideway stability. Its multi-directional strength allows a trimaran to remain stable even in the roughest seas. 

While monohulls are heavy and tend to go through the waves, trimarans are light and go over. This means higher speeds but also a different more bumpy ride, at least while going into the wind. 

A trimaran’s three hulls will contact the wave at different points. However, because their hulls are slimmer than a monohulls, they can slice through waves more easily but will lack the kinetic energy to drive through.

Shallow Draft

A boat’s draft refers to the distance between the bottom of the boat and the waterline. Trimarans have a very shallow draft due to their lightweight construction, hull design, and buoyancy. 

A trimaran’s shallow draft means that it will be able to sail in waters that monohulls can’t. This allows for more shallow water harboring options, something that can be very useful when a storm is approaching.

Maneuverability

Lightweight and responsive steering means not only that a trimaran is fun to sail, but it also allows for more precise maneuvering. This is not only useful in marinas when navigating tight quarters, but it is also essential when transiting large waves at the right angle. 

Capsizing Resistance

A trimaran’s design makes it very unlikely to capsize as it has a fast-draining deck, open-weave wing nets, and a wide base. 

The fast-draining deck and cockpit have drainage holes to help prevent waterlogging in extreme conditions.

Trimarans also have open-weave wing nets to help decrease windage and reduce the amas susceptibility to digging into the water when waves crash over it.

As noted above, the trimarans main feature, the wide stance, allows for more power to the sail before there is a need to reef. This means higher speeds!

Speed is not a primary factor contributing to seaworthiness, but speed can improve a boat’s safety in storms. 

If the trimaran encounters a dangerous storm, its high-speed capability allows it to move out of the stormy area faster, decreasing the chances of an accident. 

Safe Cockpit

Trimarans usually have sealed or partially sealed cockpits with windshields, allowing the captain and crew members to navigate the vessel comfortably, even in extreme weather conditions. 

A trimaran’s protected cockpit also helps keep the vessel’s essential navigational equipment safe during stormy conditions, contributing to its seaworthiness. 

Final Thoughts

So are trimarans safe in rough seas.

Are you in the market for a new boat and considering a trimaran? If so, you may wonder how safe they are on rough seas. 

Trimarans are safe in rough seas because they have high righting torques, and conditions have to be extreme before they flip over. They have excellent vertical and lateral stability due to their tri-hull design, and their buoyant construction helps keep them afloat. 

Trimarans are some of the speediest vessels out there, and in rough seas, they can move out of the stormy area and into safety. They are also easy to handle and have protected cockpits, making them safer to use on rough seas. 

Trimarans are seaworthy because they have three hulls, giving the vessel excellent stability, even in extremely rough seas. They consist of lightweight and buoyant foam-core material with multiple sealed sections to allow them to float if one or more parts become damaged. 

Trimarans can quickly move to shallow harbors in storms with their shallow drafts and high-speed ability. 

Trimarans are easy to handle, and their sheltered cockpits make it easy for the crew to navigate them expertly through the sea. The cockpit or deck is unlikely to become waterlogged because of the drainage. 

• Shuttleworth Design: Multihull Design Considerations for Seaworthiness
• Yachting & Boating World Forum: Are trimarans safe? 
• Chemical & Engineering News: What’s fiberglass, and how does the delicate material reinforce thousands of products?
• The Free Dictionary: Heeling
• Wordnik: Outrigger
• Discover Boating: What is Boat Draft?

Owner of CatamaranFreedom.com. A minimalist that has lived in a caravan in Sweden, 35ft Monohull in the Bahamas, and right now in his self-built Van. He just started the next adventure, to circumnavigate the world on a Catamaran!

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Carnival cruise ship's funnel catches fire for second time in 2 years

A fire in the exhaust funnel of the Carnival Freedom this weekend has disrupted a cruise on the Florida-based ship for the second time in less than two years.

Carnival said there are no reports of injuries to passengers. Two firefighting crew members were treated for minor smoke inhalation.

Carnival said the fire, which was confined to the funnel area, is not expected to affect the ship's next scheduled sailing out of Port Canaveral on Monday.

In a statement provided to FLORIDA TODAY, part of the USA TODAY Network, Carnival said that, at about 3:15 p.m. Saturday, the Carnival Freedom reported a fire on the port side of the ship’s exhaust funnel. The ship was 20 miles off Eleuthera Island, Bahamas, heading to Freeport after a canceled call to the Carnival private island of Princess Cay due to adverse weather.

"The ship’s fire response team was quickly activated, and the ship’s captain also turned the vessel towards the heavy rain in the area to maximize the efforts to put out the flames," the statement said. "Eyewitnesses reported the possibility of a lightning strike, and that is being investigated, but cannot yet be confirmed."

By 5:20 p.m. Saturday, the fire was extinguished. 

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Carnival said the ship's captain made multiple announcements to passengers and crew, and advised all but essential safety personnel to stay away from balconies and all open decks. 

The port-side portion of the funnel had fallen onto Deck 10, and the firefighting response put out any flames. 

The U.S. Coast Guard has been notified of the fire, and Carnival activated its incident response team to support the ship’s crew. 

Carnival said there are no operational issues with the ship’s systems, and the ship, which was on a four-night cruise, was visiting Freeport on Sunday.

A cruise ship funnel generally serves as a smokestack to lift emissions above the deck, thus away from passengers and crew.

On Saturday evening, "Carnival Freedom guests enjoyed the Elegant Night dinner as planned, and, with the exception of the open decks, all areas of the ship are fully functioning," Carnival said in its statement. 

Carnival said it does not expect any impact to the next Carnival Freedom voyage, scheduled to depart from Port Canaveral on Monday afternoon on a five-night cruise.

In May 2022 , a fire broke out in the funnel area of the Carnival Freedom while it was docked in Grand Turk, which is part of Turks and Caicos.

In October 2023, the Carnival Freedom debuted a new iconic winged funnel after returning from a 16-day dry dock refurbishment in Cadiz, Spain.

Dave Berman is business editor at  FLORIDA TODAY.  Contact Berman at  [email protected] , on X at  @bydaveberman  and on Facebook at  www.facebook.com/dave.berman.54