Benefits of Multihulls


Now there’s a benefit of multihulls that I hadn’t thought of.

By the way, I don’t write much about multihulls simply because I haven’t had any experience with them since I skippered a head-boat catamaran around Bermuda some forty years ago as a moonlighting job when I was a barely-making-it sailmaker. We used to load way too many people aboard, who would all congregate on the forward trampoline, and then go sailing—scared the hell out of me every time a puff hit. Definitely not recommended loading on any boat, mono or multihull. In fact my predecessor as skipper flipped her with 40 tourists aboard—by some miracle, there was no loss of life.

Anyway, other monohull sailors are often surprised to find that I have a lot of time for, and interest in, multihulls. I just don’t have much knowledge about them, so I tend to keep my trap shut—I know, unusual—on the subject.

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What make is this cat? I don’t recognize it from the rear.

Colin Speedie

And does the car go in the davits?



OK, I’ll bite on the hook!

First lesson: there are three kinds of multihulls.
Racing multihulls—the advantage is simple: Speed.

Condomarans— the benefit is that they are floating condos. Of course they sacrifice a few other things along the way like sailing for pleasure. This is the type monohullers love to hate with good reason.

Performance Catamarans (and Trimarans) The short list of benefits includes speed, level sailing, room, and safety due to unsinkability. Different designs have different combinations of these attributes. See designs by Jeff Schionning and Kurt Hughes for good examples.

I could talk in depth about the advantages (and substantial disadvantages) of this type of boat, but it would be much more fun to open the topic of whether a catamaran could be designed that would serve as an expedition yacht. Specifically could a catamaran perform the same mission that Morgan’s Cloud has over the years with an equal or better functionality and safety?

Let’s assume we have the same budget as would be required to build Morgan’s Cloud new in the US or Europe today. I’d put that at somewhere around a million US$. (While acknowledging that a bare aluminum chine boat like the Boreal 50 is substantially less expensive and more optimized for expedition work.) That budget level means we can use some ultra-strong materials and have a carbon mast to help prevent the pitching that is the bane of production catamarans.

Let’s get out our design napkin and see what we can come up with.
—50′ length with 28′ beam
—Narrow, semi-wave piercing hulls with no compromise made for queen beds and other such market “necessities”.
—Fully retractable daggerboards in crash box slots.
—Retractable kick up rudders.
—Ability to carry both a spare rudder and daggerboard and fit them while underweigh.
—Skeg protected propellers in partial tunnels
—Twin engine redundancy
—Draft only 30″
Bridge deck clearance 40″+
Displacement about 24,000# loaded.
—1 1/2″ CoreCell foam in hulls, decks and cabin for toughness and insulation.
—Enclosed dog house steering station.
—Hull bottoms heavily reinforced with Kevlar.
—Double bottoms with tankage or compartments in most parts of the hulls.
—Rotating carbon wing mast that can be fully de-powered or drive the boat at 7 knots in heavy weather with no sail up and no sail handling risk.
—Moderate sail area with highly efficient high roach main sail.
—Heavily reinforced sea anchor and drogue points.
—Auto-release load cell system for main traveler.

So before I get too long winded here, what are the potential benefits of a multihull as an expedition yacht?

— Unsinkability. The boat described could be sailed across an ocean with the bottoms of both hulls ripped open. Even inverted it will provide a stable platform much safer to await rescue in than a life raft.
—Shallow draft and beachability opens up many more areas for safe exploration and storm avoidance.
—In wind conditions under 30 knots it has close to twice the speed potential of a 50′ cruising monohull, providing more options for storm avoidance.
—Under power the same speed advantage holds.
—With a large hydraulic commercial power winch it could haul itself up on a beach and be totally secured in the face of a hurricane. The same procedure could allow it to winter over in Antarctica with greater security than a boat that has to remain locked in the ice.
— In most storm conditions it will be bridle anchored to a sea anchor from the bow, and the motion will be much more comfortable than on a monohull.
— And it can have a large and fast shore boat that is easy to launch and bring on board. (As long as Colin is willing to keep his Mini off the davits. LOL)

The first and potentially the most serious comes from the size and power of the main sail and the acceleration potential of the boat. Consider the situation of running downwind in a storm that has quickly built from 30 knots to 50 with insufficient attention by the two person crew. The combination of high roach, full battens, and large sail size means that you have no choice but to drag it down by brute force while it is plastered against the rigging, likely breaking battens along the way. You do not have the option of rounding up because you will be dangerously overpowered during the jibe. There is only one instance of a modern performance catamaran capsizing that I am aware of, and this was the likely scenario.

In ultimate storm conditions it is an open question as to which offers the best chance of survival, a broad beamed catamaran with all the underwater appendages retracted, wing mast feathered, and riding to a sea anchor or a ballasted self-righting aluminum monohull. I do know that I would prefer not to be the tester!

Sailors like John and others who have years of high latitude experience are the only ones who are really qualified to answer this question. And I expect they will be able to add some ballast to the multihull disadvantages side of the scale!

Matt Marsh

Richard, I did a little study on an expedition cruising cat a couple of years ago and came up with pretty similar specs to what you’ve suggested, albeit a touch longer and narrower. (Still hoping we’ll be able to build her someday.) It’s not terribly difficult to come up with main parameters that lead to a boat that won’t capsize in anything less than a Force 9 with 25-foot breakers, and then only if you forget to reef her.

Wing masts still make me a bit uncomfortable for short-handed cruising, mainly because they can be hard to de-power. (I do like rotating, streamlined masts, but a wing mast- one where the spar itself is a lift-generating foil- is quite a different animal.) I’m keeping a close eye on Chris White’s new “MastFoil” idea, though- they look promising.

We still see a lot of catamaran rigs that are evolved from monohull rigs, which are themselves derived from old racing rules, and while a big roachy mainsail is certainly powerful, it is also a bear to manage in a strong wind. I think there’s a lot of room for innovation in new, easier to handle rigs. Consider, for example, that you might run the standing rigging to the four corners of a cat, leaving enough room for the entire mast, sail and boom assembly to rotate forward of the beam without hitting any shrouds.

Like you, Richard, I have no desire to be the one testing the relative survivability of the two boats in a hurricane….


Hi John,
Like you I have no direct experience with wing masts, but in talking with people who do this is what I hear.
—Simply releasing the rotator control lines de-powers the bare mast so that it has less total drag than a conventional oval mast and attendant wire. And counter rotating the wing mast rapidly de-powers the main sail by spoiling the flow. Bear in mind that we are not talking about America’s cup monsters, but rather a solid carbon mast with a 3/1 or 4/1 aspect ratio.
—Being able to sail on the wing mast alone at a slow and controlled speed is a great safety factor because no sail handling is involved.
—The other advantage of a wing mast with conservative scantlings is its simplicity. Bear in mind that above the hounds it is free standing and only requires two shrouds and a forestay.
—As for the Mast-foil idea (Matt) I started a list of what I see as flaws in the concept until I ran out of space on the napkin—.


hi John,
Right you are on both counts.
Of course the overpower risk goes away if you make the rig size small enough as Matt points out. And you still have a motorsailor that will sail as fast as a similar length monohull under most conditions.

Colin Speedie

Hi John & Richard

what about the question of weight, i.e. stores tankage etc. To me the big advantages of any multihull is speed and comfort at rest. Let’s dispense with the question of comfort and simply look at speed.

A moderate to heavy displacement monohull like Morgans Cloud will swallow all of the stores, spares, fuel and water needed for a long voyage like her last one to Greenland and do so safely and without placing undue stress on the structure.

In my (admittedly limited) experience with cats you have to watch everything you put on board to avoid killing the performance and potentially over-stressing the structure. It’s a major limitation. And if there’s no speed benefit, well there goes one of the few good reasons to consider a multihull!

I love the Chris White designs and the older Outremer’s, and would happily have one for lower latitudes, but wouldn’t even think of one for higher latitudes – and there’s no shame in that, to me it’s simply horses for courses.

I sat next to a charming woman at an OCC dinner the other night who told me of her experience of being capsized in a big cruising cat on the way back from the Azores to the UK some years ago, despite having an experienced crew – they were very lucky to escape with their lives. Handling these boats in storms is really difficult.

So I think I’ll join you guys and Matt in not wanting to be the guinea pig here – and if we don’t want to try it, then do we really think it’s such a great idea?

Best wishes



Hi Colin,
Horses for courses. I too wouldn’t choose a Chris White* or Outremer (or Beneteau or Catalina) for high latitude work. And that isn’t what they were designed for. Last year a J46 hit a grey whale off Baha and sank in less than two minutes. Does that mean that monohulls shouldn’t have keels? And I had a beer in Bermuda with a delivery skipper who told a story about being hit by a wave in the Gulf Stream while delivering a well known 46′ “cruising catamaran.” The impact lifted the entire cabin top off its moorings and left halyard tails sticking in through the gap. Does that mean that all catamarans are unsafe at sea?

Anyway I’m becoming a bit polemical. I suspect that in the end we are not far apart in our opinions, and I know for certain that yours are grounded in more experience under trying conditions.
* I just heard a hilarious take-off on Chris White’s idea of putting the cockpit forward of the cabin, but unfortunately it would get me banned from this site and probably all of the internet if I repeated it. LOL


Hi again Colin,
Start with a slow, heavy, high volume condomaran with undersized rig and throw a few SubZero refrigerators and 2,000# jet drive RIBs on board and you will have a slower condomaran.

My design target for this napkin exercise was the mission that John and Phylis have put Morgan’s Cloud to over the years. Primarily double handed with occasional guests, and primarily in northern latitudes. A 50 x 28 21,000# catamaran with a design load of 3,000# should be more than adequate for extended voyages under those conditions, and an extra 1,500# would hardly stop it dead in the water. For reference, 50 people in Hawaii add 8,000# (unless they are Samoans LOL) and they are invariably in the wrong location for trim.

Erik de Jong

Great post!

I’ve had the opportunity to do some offshore sailing in Cat’s and tri’s (mostly full blown racers) and definitely see the super advantages of a multihull, even for an expedition yacht and gave this a lot of thought as well.
I do however run into some great disadvantages when looking into making an expedition cat into a high latitude expedition cat.

First: anchoring at high latitudes has the problem of strong winds falling off mountains, especially in a glacier rich mountain areas. 80 knots of gusts coming down a slope are not a rarity. A catamaran has significantly more windage. I ran some computer simulations for windage while swaying behind an anchor. The loads on the tackle of the catamaran were approximately 4 times higher with the same windstrength. This would result in almost unrealistically big and heavy anchors and chains to get to the same safety factors as we would like to see on a mono. This is of course solvable, but comes at great cost of the available payload.

The second, and biggest disadvantage of a high latitude multi hull is that those are incapable of sailing in waters with icy bits. When manoeuvring through a field with brash ice, you would generally zigzag your mono between the largest bits because they are too heavy to push aside. this is doable by getting the bow on the side of the bergy bit you’d like to pass, put some throttle on it, and the speed of the boat will do the rest.
With the best effort in the world, you won’t be able to do this with a catamaran that has two bows that both should move exactly in the same direction. Therefore always messing with the ice and making it impossible for the helmsmen to get the boat where he wants it to get, one hull will experience more resistance, and make the boat turn, even with an engine and a propeller under both hulls.
I have tried this on a 40ft cruising cat on a Dutch Lake in the winter time. We did not manage to get where we needed to go, we were not able to push the boat through some ice floes and it was not possible to keep both bows more or less in the direction we needed to go. While this would not have been a problem on our mono at all.

Due to the narrow hulls of a cat, the propeller is much closer to the water surface and the vertical part of the topsides. The propeller is all of a sudden extremely vulnerable for hitting bits of ice and cause serious damage to the propulsion train. This could be solved by placing a nozzle around the prop, but this will add greatly to the resistance through the water, and that is something that catamarans are very sensitive for.

A catamaran has significantly more exposed surfaces to cold air, heating a cat would take about two times more energy compared to a monohull of the same length. Most heaters are still based on the principle of burning diesel, this means that one needs to carry twice the mount of fuel for the heater.

The cruel reality of high latitude sailing is that a significant amount of time is spend by beating upwind. Just looking through my logbooks of the last 15.000 miles, about 60% was at close angles to the wind. Multi hulls are not great beating upwind. Look at the OSTAR race for example, the mono’s finish very often ahead of multi’s of the same length.

And last, but not least. A catamaran is more limited in regards to payload. in my opinion, a good expedition yacht needs to be capable of carrying a big payload. Be it water, fuel, extra gear, spareparts, dinghys, outboards, or spare anchors.
Our “Bagheera” can carry approximately 8 tons of additional weight above her minimal “ready to sail” weight. Only adding 8 inches to the draft, the boat remains safe, stable and comfortable, and the speed does not suffer too much of it. There have been quite a few occasions we needed that much stuff on the boat. If we would do this on a 50’cat with hulls of, let’s say 4′ wide at the waterline, the cat would sink approximately 14 inches deeper, reducing the bridge to water clearance and completely eliminate the speed advantage of a cat. Of course, you’re not always sailing fully loaded, so this problem is only temporarily.

Now it sounds that a cat is the worst possible boat thinkable for expedition cruising, and that is absolutely not true, I think they are great. Most of the disadvantages I pointed out, have to do with high latitude cruising/expeditions, and if one wants to drop that aspect of sailing, and make her an expedition boat for the African, Asian and latin American continents, I think it would be an extremely good choice.

There are solutions for al problems, and it is not too hard to overcome most of what I just summed up, the only thing that remains a terrible headache to me is the manoeuvring in Ice, if anyone knows how to overcome that, I might even consider building a new boat.


Thanks Erik,
Every comment you make is spot on and comes from both reasoned consideration and direct experience. Exactly the kind of response I was hoping for when I started this post.

re windage: It isn’t just the extra total windage that is of concern, but the fact that the wind can get under the bridge deck and cause lift. The most extreme case was one of my friend Kurt’s earliest catamarans that flew more than a hundred yards ashore during a Cat 4 hurricane. Pays to partially sink the hulls under those most extreme circumstances. (that boat was repaired and is still carrying paying passengers 25 years later)

The idea of hauling out on land for wintering over is certainly not something everyone will want to do but it is an interesting concept. Not originally mine however. Years ago I knew a mountain climber couple who spent months at a time living in an elaborate ice cave part way up Mt. McKinley and cleaning up the mess left by other climbers. Their dream was to build a boat that they could motor from Alaska to Antarctica, haul out on land, man haul to the South Pole and back without support, winter over and return home. Nothing like dreaming big!


Not man haul the boat—that would really have been extreme! (LOL)


Ice? What ice? By the time I’ll be able to afford a purpose built Kevlar hulled expedition catamaran there won’t be any ice.

Unfortunately there is truth on both sides of that equation. (LOL)

Colin Speedie

Hi Richard

I like multihulls – the faster performance ones anyway – and think they make great (if not the best) liveaboard boats – in the lower latitudes.

I’ve sailed several including ex Class One boats and liked them a lot, but the main reasons I wouldn’t want one for higher latitude sailing is that they require far greater attention (and crew skill in extremis) than a corresponding monohull. There are too many cases of serious mishaps due to a moments inattention on the part of the crew, the sort of things that would at worst have made for a big scare on a monohull have sometimes ended very seriously with cats.

An example of a performance cat getting into trouble in this way was seen in the Sound of Sleat (the sound between Skye and mainland Scotland) in early August 2012, when a 16m high performance cruising cat (XL Catamarans) was capsized by a strong gust coming off the mountains nearby. Katabatic gusts happens all the time in high latitudes/mountainous areas, but even with a full and (apparently) capable crew, over she went, fortunately with no loss of life.

And that’s enough for me. Monohulls may be slower and less roomy than cats, but they’re predictable and safe in such an environment – so for me, at least I’d always stick with a monohull. Even though a car in davits would sometimes be useful.

Best wishes



Hi Colin,
You provide a real-life example of the negative case I mentioned. However we should agree that all “performance multihulls” are not created equal. I suspect the boat you reference was a “racer cruiser” type. The only example I know of of a more cruising oriented design with performance characteristics flipping was the Chris White 48 in the South Pacific last year. It had specific layout flaws that made it difficult to react quickly to a rapid change in conditions. The expedition design I proposed would have features specifically designed to overcome the problem of sudden overpowering: 1- smaller relative sail area and extreme beam and 2- a fully circular main traveler with a load cell that automatically blows the traveler at a pre-determined conservative load.

Doesn’t mean that acceleration and control still aren’t the characteristics that should disqualify the multihull from high latitude work—–.

Colin Speedie

Hi John

The older generation of big racing cats generally had high, arched crossbeams to keep the whole deck out of the water.

As burying the forward crossbeam is one of the worst thing that can happen with those boats (a bit like hitting a soft wall) Pete Goss and designer Adrian Thompson tried to get around this by building a design with no forward crossbeam, windsurfer rigs and wave-piercing hulls. But the limitation with that approach for the type of boat being discussed here is that it’s hard to add much in the way of accommodation. You’re generally limited to life in the hulls or in a crew pod.

Best wishes



Hi Colin,
Keep in mind that ocean racing catamarans and trimarans are a totally different species. Think a Bengal tiger vs the house kitty. Not sure how much relevance fifty knot monster windsurfers and 120′ + sizes have for a cruising or high latitude catamaran design.


Best example of catamarans with adequate bridge deck heights are the tourist cats in Hawaii that operate in reasonably high wind and sea states with 50 tourists aboard and don’t pound. On the other hand I remember sitting in the bar at the Dingy club in St. Georges Bermuda talking to the delivery crew of a 55′ condomaran who were having to go to the dentist to have fillings replaced before they continued down to the islands. (LOL)


Re. bridgedeck slamming.
A commonly cited rule of thumb is to take the greater of:
– 6% of the waterline length
– 25% of the tunnel width at midships on the waterplane
If the bridgedeck clearance (or the clearance to any large protrusions under the bridgedeck, like “pods” or “nacelles” to provide room for bigger berths) is less than this value at full load, the boat is at risk for slamming.
Surprisingly few cruising cats pass this check. But that’s perfectly OK…. as long as you stick to sheltered waters and good weather, like many tropical live-aboards and charterers do.


How about looking at the new NEEL 45 as a reference point for a recent example of the multihull option? $600k


Dear all,
I think this is a very interesting discussion, here are a couple of points I would look for;
Fwrd cockpit, aft pilot house
Tough aluminium build, shallow draft and beachable
Kick up rudder and protected propeller
Kick up centreboards
Double skinned in hulls creating fuel/water tanks in space
Watertight bulkheads, three per hull
Access to hull if upturned and from inside and out
All welded fitting for no leaks
Insulated with source of dry heat
Unpainted aluminium
Bows, no sharp angles so can sail over a log or other debris
Stern steps with climb into dinghy system
Industrial ribbing strip for docking in industrial ports.

Extra strong, preferably simple mechanical system no hydraulics, ease of access to all parts to service.
Kick up rudders
Steering position inside and out, 360 view and plan to see the rig from inside.
Self steering electric and wind designed and built in from start with redundancy.
Ready to launch built in drogue system (loop and in line depending on conditions)

High bridgedeck to avoid slamming
Front cockpit aft deck house like Chris white designs, does require planning to have 360 vision from inside steering position and also to be able to view the rig.
Toughened windows
Efficient use of space for solar panels
No big sliding door at back of pilot house
Dinghy platform
Wooden seats inn cockpit for warmth!

I like the unstayed aero rig type mast with emergency release mechanism to depower in Katabatic winds, this will require engineering input as the mast ‘plants’ on the deck beam, I am sure wouldn’t be insurmountable.
Looking for larger roach on main to lower rig height, also trysail set up in high winds.
Easily handled by one person from cockpit (I would prefer no reliance on electric winches)

keep it simple
looking for self sufficiency in power generation through solar , PV’s on roof deck and side, wind turbine x2 aft and dragged marine generators one on each hull, Tag yachts and green motion have done some work in this area. One diesel generator and battery bank with say 8 hours power, for electric engines, if you need to power further use generator.

Big anchor on foward beam (rocna) with other for in line service stored back by mast. Long chain on roller by mast for weight centraling, simple bridle system.
Aft anchor, and lines on rollers for tying to shore.
strong simple oversized cleats

Apologies for such a long post I have been researching this for a while!

John Lundin

For a completely tangential topic – this catamaran pic reminds me I need to learn more about the A-frame main sheeting arrangement. Any real-world (mono) cruising experience with these? I see the Boreal using the system and am considering it myself. I understand there can be some windward trimming consequences, but curious to hear thoughts.

Evan Gatehouse

Cat Payload: we have a 40′ cruising cat. A Richard Woods design that is faster than the condo cats. Very heavily loaded (sigh). 4 scuba tanks, 400 lbs tools, spares, 100’s of paper charts, scuba compressor, RIB with 15 HP engine, 3 anchors, hundreds of books (my daughter reads a lot). The usual cruising gear and then some. I suspect 3000# payload – at least.

Bridgedeck clearance is 28″ loaded – and her bridgedeck starts 18′ aft of the bow or so, so slamming is very rare.

And she still _easily_ averages 160 m/day in light to moderate conditions. 180/day is achievable but we are more interested in comfort so while we can go that fast it is not as comfortable. But we did it 3 days out of 19 on a Pacific crossing when the wind was a bit stronger. And we’ve done it when chasing the sun to arrive at an anchorage before sunset. Having that extra speed potential is nice.

So scaling this up to 50′ means easily go for a 5000# payload and it still will be a quickish boat. Just have to design the hulls and sail plan accordingly.

But not 2x the speed of a comparable mono except when the wind is strong and astern. 200 miles a day – yes. 250 – quite a bit harder unless you really scale up the rig and the loads.

Yes, I think the idea of beaching a boat (if you carry a bunch of big inflatable fenders) as an ultimate storm tactic in an anchorage could work. Interesting idea. We beach our boat all the time.

I think the capsize of the XL catamaran and “Anna”, a Chris White 57 were both ‘user error’. When you’re sailing a very powered up performance cruising catamaran you have to watch out for katabatic wind conditions and have the main sheet &/or traveller hand held, not in a self tailer jaw. And if you see a squall coming (Anna) you reef proactively and early. And you’re in the cockpit, not sheltering inside the nice cabin.

Our Genoa is much bigger than the mainsail. After the Anna capsize we added cam cleats beside our genoa sheet winches. The tails are removed from the self tailing mechanism and put into the cam cleats if sailing in anything other than settled weather. Flick the sheet from the cam cleat and the sail flogs and you are instantly depowered.

Evan Gatehouse

2011 Arc Rally results, a year that was known to have fast crossing times.

Phaedo, a all carbon Gunboat 66 catamaran, with full crew aboard did 2680 (rhumb line) miles in 11.75 days – or 228 miles /day. This included 59 hours of motoring.

Rothmans, an ex-Whitbread Maxi did it in very similar time (within an hour or so of Phaedo) without any motoring hours. In the racing division, with full crew.

It’s very hard to _average_ 250 miles/day. Unless you’re a modern racing mono of 60’+ like a Volvo 60 or a similar size ORMA 60 trimaran. which routinely exceed these numbers.


Ah yes, the speed question!

First some generalities:
—Reaching in 20 knot conditions a good performance 50 ft catamaran can easily double a monohull’s 7-8 knots.
—Beating to weather in 30 knots it will struggle to equal the monohull’s VMG.
—Dead downwind in 6 knots it will rarely be able to keep up with the monohull. (which is why cats are never sailed dead downwind)

A downwind transatlantic crossing is the worst possible measure of a catamaran’s speed potential as it will spend most of its time at its least efficient point of sail.

But why are we interested in speed anyway? Don’t we go to sea to enjoy the experience? If getting there were the only goal we would take a 747. No, we are interested in speed for the safety it brings by being able to plan around and avoid dangerous weather.

So let’s return to the design mission statement— providing equal or better functionality for the voyages Morgan’s Cloud has undertaken over the years. John reports that 50% of that time at sea was spent with the motor running, motoring or motorsailing. So if we want to discuss speed we should look at speed potential for the mission at hand, not how a three million dollar Gunship performed on a downwind transatlantic passage.

Speed under power with a displacement hulled 50′ catamaran is almost anything you want it to be up to about 24 knots. There is virtually no change in the slope of the power requirement curve when you reach theoretical hull speed, and the curve doesn’t really start to steepen until you start going over 2.5 times that reference point. Drag is a nearly linear function of skin friction. At the upper end of speed potential, Kevin Manhoney’s HoloHolo 65′ power catamaran, built on two displacement sailing catamaran hulls, runs at 28 knots from the minute it leaves the harbor, and operates daily in open ocean offshore conditions on the North Shore of Kauai.

So with our theoretical 50′ catamaran we can choose low powered engines that will enable us to motor at twice the speed of a monohull with similar fuel consumption per mile, or about 250 hp. that will push us over the 20 knot barrier. We can use that speed advantage to decrease passage times when the wind is light, or increase safety by being able to run for cover or head for a different patch of ocean.

So under the conditions of 50% motoring set by the design brief, I stand by my statement that a 50′ catamaran has twice the speed potential of a 50′ monohull.

Erik de Jong

I do believe that a cat is faster than a mono under most conditions. But looking at the logs of our own recent sailing history, we averaged about 170 miles a day on our 50′ mono. From which more than half was upwind or at very close angles. And about 15% while motoring/motor sailing.

I can simply not believe that with a cat it would have been 340 miles a day on average, especially not if you need to carry so much stuff as you need for an several month long High Latitude cruise. I do believe that it would be not too difficult to pump the average up from 170 to a bit over the 200, but not much more than that, not with several thousands of kilo’s of gear and liquids on board.


Hi Erik,
The key word here is “potential”, not average over a typical year of sailing. My point is that in motoring conditions and some sailing conditions a properly designed cat can use its ability to motor or sail at twice the speed of a monohull to bring an added measure of both safety and comfort.

Eric Klem

Richard (or Matt or anyone else),

I have been watching this thread intently as my experience with cats has not been of the type that you are discussing, only condomarans and small performance ones. From an engineering perspective, they have many things about them that make a lot of sense as well as some interesting structural challenges.

I am curious as to your thoughts about the comfort of a cat that operates at the speeds that you are talking about. I realize you are not talking about flying along all the time but even doing 15 knots on a reach is a very different beast than doing 8. What would it feel like on a cat at these speeds and likely wave heights to be close reaching, beam reaching or broad reaching? The condomarans that I have been on in these types of conditions have felt like they are trying to dart all over the place and they do a weird diagonal pitch when at an angle to the waves. Will a good design optimized for offshore performance make double digit speeds comfortable for long passages or will it be fun for a few hours before the crew gets tired and decides to slow down?

Hopefully this isn’t too silly of a question.



Hi Eric,
Fly to Hawaii. Go on to Kaui and join the tourists on Kevin’s 50′ Lelia sailing catamaran. Or if you can’t stand the idea of warm tropical trade winds, go to San Francisco and do the same on the larger and heavier Adventure Cat. Stand on one of the hulls at a position several feet forward of the mast as it motors or sails into a 6′ chop or seaway at 16 knots. Don’t hold onto anything. Question answered. Hulls that are shaped to penetrate and progressively build buoyancy don’t behave anything like ones that are designed to be broad enough to fit a walk-around queen berth.

Will broad reaching at 16 knots be as comfortable as at 8? Nope. Unless you are in really flat water there will be a lot more spray and more vertical motion. And in conditions like you often encounter crossing the Gulf Stream you’ll purposely slow everything down. Sometimes the combination of sea state and heading will bring out some of the racking motion you observed, telling you it is time to change heading a bit.

On the other hand, is sailing a monohull hard pressed at eight knots with the rail down comfortable? Nope

Like others have pointed out if you expect to double your average speed on extended passages or over the course of a year you will be sorely disappointed. On the other hand if you want the safety of double digit speed when you really need it, especially under power, and the fun of being able to sail really fast when the conditions are right for it, then a real catamaran is for you.

Since it hasn’t been brought up yet, the biggest disadvantage of a multihull is that they are damn expensive to do right because of their large surface area and high structural loading. And the demand for those that are is so limited that the world ends up filled with condomarans that become the standard by which everybody judges all multihulls.

Eric Klem

Hi Richard,

Thank you for those thoughts. It sounds like the two cats that you mention are truly impressive boats. One of my favorite days of sailing of all time was a little daysail on a 122′ boat I was working aboard to go watch a race that included several smaller multihulls. The wind was around 30 and the waves were probably only 10-12′ as they hadn’t had time to build but they seemed almost completely square, so much so that we couldn’t tack without full throttle on the engine. While we were busy getting completely soaked because the bow was barely rising to these square waves, the multis were trying to beat to weather and getting seriously airborne on every wave. They seemed to travel as far sideways while airborne as they were moving forwards but what struck me was how level they stayed throughout and how comparatively soft the landings looked. I don’t remember the exact results but probably half the multis finished and less than a quarter of the monos finished.

And you bring up a good point about cost.



Hi Eric,
Actually the boats I mentioned are 15 year old designs intended as work boats. They were built from low tech materials and by no means are state of the art. They just happen to be accessible to the public and good enough examples to answer your question about motion of a properly designed multihull in common offshore conditions at speeds far higher than a monohull of the same size could attain.

Erik de Jong

One book that I found particularly interesting was “catamarans” written by Tarjan, the book is only a couple of years old if i’m not mistaken, and is a wealth of information on pretty much all aspects of catamarans for cruising.
Call it a multi hull bible of you will, definitely worth reading, to me it was a real eye-opener.


I just wanted to thank everyone who responded to this red flag waved in front of the bull with such civility! In particular Eric de Jong, whose contributions didn’t loose sight of the big picture while cutting right to the chase.

And perhaps apologize for hogging so much space on the comments board! (LOL)
Fair winds, everybody.

John Tynan

If I were to consider a multi, then I would start with a Neel Trimaran. This company was set up by Eric Bruneel who spent 26 years with Fountaine Pajot culminating as General Manager. He also ocean races trimarans.

The concept is to have all the living space on one level with technical and stockage zones contained in the central hull maximizing stability. The boats were designed by Joubert-Nivelt. They are considered to be about 20% faster than an equivalent sized cruising catamaran.

The protype was a 50′, followed by a 45′ version with a 60′ under development.

(I have no connection with the company.)

Waiting for that lottery win….


Michael Roberts

Good evening all
This has been a most valuable discussion, and such civility!

About five years ago a flash of something bright came out of the clouds and said: “You must design and build a catamaran, one that can take you through the Straits of Magellan, and maybe Antarctica”.

So I learned about Maxsurf, Rhino, Scan and Solve. Then read Skene, Marchaj, Chris White and Gougeon. Eight 44 gallon drums of epoxy later and the project is … well sort of … underway. Hull two will be finished by Christmas.

Is there enough bridge deck clearance? hope so, maybe another 50mm would be good; rotating wing mast? for sure; retracting foil rudders? yes; brushless DC motors? not sure.

I hope I have not made too many big mistakes. All of your comments have helped me considerably. Long may this discussion continue.

PS can’t see where I can post a picture of my boat – she’s 62 feet and looks like a stealth swan. On target for lightship weight of 10 tonnes.


I’m pretty convinced that the longer and narrower a hull, the more comfortable it is because it slices through everything rather than over and around. So multis are attractive, but the problem is connecting the long narrow hulls together without introducing components that stop the boat from slicing through everything.

In my opinion the best designer of multihulls for life at sea is still James Wharram. Just one example of the thought that has gone into every aspect of his designs: Decks are slatted so when green water sweeps the deck any crew person out there will be pressed down onto the deck rather than swept overboard.

Wharram’s load carrying “Islander 55” could be built in aluminium and make a perfect expedition boat. Not too expensive either. But Erik’s observation about needing to thread through bergy bits convincingly rules out anything with more than one bow I think.

So we’re back to a long, narrow monohull. It could never be as narrow as a good multihull’s hulls so won’t have the same speed potential unless we can get it to exceed it’s displacement speed i.e.; plane. Surely not possible in a load carrying expedition yacht. Unless perhaps you deploy lateral under water foils to provide righting moment and lift, like these guys:
They appear to be onto something: Long narrow hulls that can also climb out of the hole between bow and stern waves and go even faster. Apparently the foils stabilise the ride as well.

Sure it’s something else to go wrong and you’d probably not have the foil extended when threading through berg fields, but it would appear to offer some significant benefits on passage.


Infinity Yachts’ “DSS” system looks like a standard motor-yacht’s fin-based dynamic stability system using a couple of retractables oversised fins and configured & servo-piloted in order to give some lift and some counter-heeling moment as well as classic roll & pitch stability.
I understand that classic (motor-yacht’s….) active-fin-based dynamic stability systems can be installed in sailing yachts and should reduce their roll & pitch. Point is that those systems are expensive, and that fins’ size should be somewat larger on sailing-yachts vs. motor-yachts because of the lower speed.
Technically, the idea of using oversised stability fins and servo-piloting them to obtain some lift & counter-heeling as well as stability seem good, although sophisticated and probably expensive (looks like an aircraft’s active computerised flight control system….), but I am afraid that the amount of lift and counter-heeling moment you can obtain that way on a sail-boat heavy enough for long-range cruises and associated equipments load should be much lower than on the very light “Infinity 60 GT” prototype….

Nikolas Andersen

Would require a lot of electricity for a sailing boat?

Michael Korndeld

What a great discussion thread about catamarans! Let’s forget about catamarans and ice and high latitudes where strong monos clearly dominate. Instead let’s look at the various aspects of heavy weather sailing and seamanship in world cruising catamarans where the 95% of the rest of the worlds cruising sailing goes on. Any takers?


John, this aluminum offshore cat use many of the features of Chris White’s Atlantic Catamaran 47. Beside dogging icebergs, would this fit your criteria for an offshore capable vessel?


I’m a strong proponent of boats of that general type for long-range cruising. I’m not familiar enough with this specific one to give a meaningful opinion on it, though.

The risk of a wave filling a big, deep cockpit like that should not be ignored, and in a way, this is a strike against the design. Whether this is important depends on how the designer calculated the cockpit drainage area. Most “standards” for cockpit scuppers are an order of magnitude too lax, in my opinion. Always check what full-to-empty drainage time was used as the design basis; I like 10 seconds, although other opinions may differ.

To be fair, I have never heard of a case of an offshore forward-cockpit cat being damaged or capsized from cockpit flooding. Fully one-third of the length of the de Villiers 525 is trampoline, which dissipates breaking waves very effectively. By the time a wave reaches the cockpit crossbeam, you already have about eight tons of reserve buoyancy forcing the bows up and clear of it.

The flip side of the risk coin is that sail handling is much easier, and man-overboard risk greatly reduced, in a good forward-cockpit cat design. The speed of these vessels also gives you many more options for dodging risky conditions in the first place.


Hi John and Matt, after speaking with several owners of Chris White designs, who did high latitude sailing, I was shocked to hear how dry the cockpit was, even in a storm. As Matt mentioned the position of the cockpit seems well protected from green water. All said the forward cockpits were drier than any of their previous aft cockpits. Because the forward cockpit has a few inches of bridgedeck to drain through, any water is quickly returned to the sea, it should be quite easy to empty any water faster than a center cockpit and most all aft cockpits. As Matt mention the easy and protected access to the mast and the ability to step inside for further protection, the added bouncy of the multihulls, and the greater passage speed, make for a compelling combination. John as you and I age and do not want to consider a power option. The multi-hull seems to give us everything we did not find in the Nordhaven: greater stability, speed, ease of sail handling, and if constructed like Chris White’s or the design above, great structural strength and reasonable sail management if not overdriven (which is true of every sailboat). The only high latitude issue I see is the wider beam make iceberg dodging difficult and that could be a deal breaker if all you want to do is high latitude sailing. Otherwise, I have still not read a compelling reason, backed by experience, to make a monohull a better voyaging vessel, other than familiarity. I read all the posts here about multi-hulls and find some criticisms inaccurate, when compare to real experience of those who sail them. I enjoy this website for its reasoned examination of techniques and equipment and was hoping more multi-hull advocates (Richard is the exception) who would enter the dialogue. Trying to make a decision about whether to go to the dark-side or not. Thank you all, and especially John and Phyllis for this outstanding resource.

Marc Dacey

This is precisely the logic of our “outside helm” and its modest footwell (about 150 litres in volume, or about one-quarter of a bathtub), which is drained via two four-inch, angled pipes open to the stern about a metre and a half above the WL. Another older idea not common enough on purportedly ocean-capable boats are a decent, water-shedding camber to the deck and sufficiently large freeing ports. Both elements let water leave the boat promptly. Large aft cockpits are excellent for entertaining and large cockpit lockers are convenient, but both represent potential failure points and are compromises in a following/breaking sea.


Marc, you make a great point. The forward cockpits in Chris White’s cat are large enough to be comfortable and small enough to be safe in the most important way. I am surprised that the forward cockpit is not an overwhelmingly accepted idea since John and others stress the importance of working at the mast and remaining on the boat. What could be safer than having access to all your lines and the mast at the helm in a forward cockpit the sits in near wher a center cockpit sits onna monohull and avoid walking inches from the 500 foot cliff so often. It seems from a probability standpoint, avoiding the necessity of leaving the cockpit to work the sails and avoiding the complexity and friction of lines going aft would outway the rare freak wave that capsizes a nearly unsinkable cat. I imagine more risk is taken on a regular basis in leaving the cockpit in a storm at night to adjust sails, than the risk of a wave flooding the cockpit enough to threaten a similar displacenent cat, to capsize and if it did the lead bottom monohull is probably upright at the bottom of the sea while the cat is floating upside down, high and dry. I wish some monohull sailor would read The Cruising Multihull by White and explain where the logic breaks down. He us not talking about a BVI floating condo, but an ocean going passage maker and build the the same displacement as the monohull I see more disadvatages and safety issues in dealing with the monohull, that the multihull solves by its very nature. Trying to better understand the logic behind monos in a multi world. The older technology (ie multi) renewed just seems more logical, though the lines on a Herrshoff are more lively. And one last point in this long reply. Why a main sail? It is the most inefficient square footage on the boat for its intended use. Forget the mast foil and just have two masts with roller jib and roller staysail. I think this is the greater innovation that Chrus brought to the table, but it goes against all convention. Reefing is no longer an issue. The mast does not imped the airflow at the cuting edge of the sail. You can still hoist light sails up front or run wing on wing without wisker pokes because of the wider beam. All the difficulty of sail handling is removed and without the 15% advantage in speed from the mastfoil you are in a simple low aspect rig that is still fast. But now tacking and jibbing are easy and less stressful. I thought thus rig would have been wide soread by niw among shorthanded cruisers. Thank you for discussing this further.


Correction: “this rig would have been wide spread by now”


Thanks John, great clarification. I think I confused everything talking about dodging icebergs.