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Old 05-15-2008
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Singlehand Multihull 'rule of thumb'?

My sailing experience is on monohull boats in the 30' - 36' range.

As a 'rule of thumb,' I've always considered boats 35' to 40' to be 'ideal' (or at least the best compromise) for singlehanding.

Does this 'rule of thumb' apply to multihulls? Particularly catamarans?

My multihull experience is limited to 'aquacats' and 'hobies' so I don't have an appropriate feel for the subject. Also, I tend to evaluate boats based on displacement, but my understanding there, doesn't translate easily to multihulls.

I've aI'm curious to learn what aspects of multihull designs make them easier or harder to singlehand. And, whether this pushes my boat length 'rule of thumb' up or down.

My apologies if I'm asking something that already been covered, but I've tried searches and can't find anything that addresses my question directly.

Lastly, I realize that boats of every dimension CAN be singlehanded -- I'm mainly interested in the collective wisdom regarding 'ideal cruising boat size' as it applies to catamarans.

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Old 05-15-2008
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Piscator-

There isn't much different in terms of singlehanding a boat, whether it has one, two, or three hulls. However, what you learned on Aquacats and Hobies is going to be very different from what you'd experience on a cruising sized multihull. Beach catamarans are relatively overpowered and really won't teach you much about handling a cruising sized catamaran.

First thing I'd recommend is that you read the following books:
  • Chris White's The Cruising Multihull
  • Thomas Firth Jones's Multihull Voyaging
  • Mike Mullen's Multihull Seamanship
as a basic foundation of knowledge about cruising multihulls.

One of the big problems for monohullers moving over to multihulls is that some of your reactions are going to be wrong for sailing a multihull safely. Also, the speed of a multi-hull means that things can go from safe to dangerous very quickly, unless you really understand what is going on. This is especially true on large catamarans, which tend to not give as much warning when they're at the point of getting into trouble.

That said, most of the problems I've seen on multihulls, is usually human error. The biggest problem that I see with new multihull sailors is that they get so taken by how fast a multihull can go, they don't seem to realize that you shouldn't really sail one as fast as possible once conditions start to pick up. It is very difficult to capsize a cruising size multihull that is properly sailed—however, it is very easy to capsize one that is improperly sailed.

Think of a multihull as a sports car.... yes, they can do 120 MPH... but that doesn't mean that it is wise or prudent to do so all the time. For example, while it is probably reasonably safe to drive 120 MPH on a closed, private sports track that is dry and well maintained—it probably isn't as wise to do so on a wet, pot-hole ridden, icy city street in rush hour traffic.

Also, in strong winds and heavier seas, dropping the speed of the boat down a bit makes the ride for the crew much more comfortable, and reduces the risks of pitchpoling and capsize drastically.

I've taken my boat out in conditions that a lot of other boats wouldn't consider going out in, but I haven't had a problem, because I know the limits of my boat, and don't push it in those conditions.

There have been a few stories recently of Corsair trimarans capsizing—most recently, what looks like a Corsair 31 off the coast of New Jersey, on its way back to New England. The Corsairs are significantly lighter than my boat, with more sail area... and also, IIRC, have smaller amas, that are higher off the water. I believe the difference in sail area, displacement, and design contribute to the reasons why the Corsairs have capsized recently.

I also believe that the attitude of the sailors aboard the boat may contribute to the risk of capsize—if the sailors have a racing mentality and are used to flying a hull and pushing the envelope... I think they're far more likely to capsize the boat than a boat with a conservative cruising mentality crew.

Catamarans will have the most living space and stowage space out of the three types of boats—mono, cat, tri. They will also often have the worst sailing performance of the three, due to the high windage, high freeboard, low bridgedeck clearance and small sail plan that seems to be fairly common on many charter-market catamarans. Non-charter catamarans seem to have some better sailing characteristics in some cases.

Some catamarans can have problems in light air, due to the wetted surface area presented by having two hulls in the water. In heavier winds, they can have problems tacking or coming about due to the windage caused by the bridgedeck and cabintop. This is due to the designers need to make the boats exceptionally spacious and roomy as desired by the charter market.

Trimarans, especially the more modern designs, that eschew the full wing deck design that was popular in the earlier designs, will have the least amount of living space and stowage space. They will also tend to be more weight sensitive than a catamaran. There are exceptions to this of course, like the big, full wingdeck trimarans that you sometimes see in the charter trade, with 8+ berths, etc.

Trimarans tend to do a bit better than catamarans, in terms of sailing ability, since they tend to pivot on the center hull, which a catamaran can't do, and have less wetted area, since the amas are much smaller than the main hull. This is especially true on the performance oriented trimarans, which are usually designed to have only one of the two amas in the water at any time.

A lot of the rules for monohulls don't really apply to multihulls. For instance, the scantlings for monohulls are often much, much heavier than what you'd find on a similar LOA catamaran or trimaran. This is due to the fact that catamarans and trimarans don't have to support the weight and mass of a heavy metal keel.
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Last edited by sailingdog; 05-15-2008 at 11:45 PM.
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Old 05-16-2008
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Piscator, you've asked some intelligent questions, and I will defer to the multihull sailors who know a lot more about multihulls than I do, which is slightly greater than zero, but not much.

I have the monohuller's prejudice in favor of hulls that will seek to right themselves if everything else has gone wrong. I may be sadly misinformed (as was Humphrey Bogart about "the waters") but everyone has an opinion, and that's mine.

I don't think the number of crew is a whole lot different between a mono or multi hull of similar length, but my experience in this regard is limited to monohulls. I'll agree that 35 feet is close to ideal for monohulls, but can't opine about multihulls.
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Old 05-16-2008
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When you look at the size of machines that tiny Dame Ellen navigates, it doesn't look like there is a single handed limit. However, for most cruisers, I expect it's cash rather than length that limits the choice.

There are also practical cruising problems in marinas, not all can accommodate really big multihulls and not too many of them fit in simultaneously.

Mooring a big multihull into a tight space could also be more stressing single handed, than mooring an equivalent length monohull. Being lighter, I would guess they are more wilful in cross winds, but a cat could have two engines to help.

Bigger boats need bigger anchors and at some point single handed anchor laying and recovery becomes an issue. Lots of automation helps, when all is well, but when things go wrong being at both ends of the boat can prove difficult.

Big boats need big sails, and cruising sails tend to be heavier to take the chaff and have longer lives than their racing brethren. Big sails present single handed handling problems. Multihulls probably need more sail handling to sail safely and still use their speed.

Certainly, multihulls get from A to B faster, and cruisers usually want to be at A or B and the bit in between is a time consuming necessity. However, when most time is spent at A or B, the live-aboard qualities play a big role. A big cat is a bit more like a condo, than the narrow hull of a tri, or the submarine like interior of a monohull. Being a condo, the accumulation of junk is likely to be larger and those cat like high speed sailing characteristics don't like the weight.

Anyway, I still drool over pictures of the Dragonfly 1200.
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Old 05-16-2008
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A few points re: Idiens and Nolatom

You have to remember that Dame Ellen's boat was essentially a very expensive machine tailored to her specifications and designed so that she could single-hand the boat. Most production boats won't be setup up to single hand specifically. Modifications, like having multiple headsail furling units, etc... aren't typically found on production boats.

Idiens' points about marina space and the size of boats is an excellent one...which is one reason I went with a Telstar. Most Farrier designs are not stored in the water folded, primarily due to the design of their ama folding system, which would leave the outer topsides of the amas and the hull-deck join immersed. This is why most are parked at moorings, or in the rare case an end slip, where beam is less of an issue. My boat can be stored in the water with no trouble, since the amas don't change orientation during the folding process.

As for manueverability... most big catamarans have dual engines and dual props... and as such can make turns much tighter than a monohull of the same size, once the captain and crew are used to using two engines for manuevering.

Size is generally a limitation. While powered winches and windlasses can help with raising, lowering or otherwise controlling larger sails and anchors, they do little for the rest of operating a larger boat. As Beth Leonard points out in her book, The Voyager's Handbook, a powered windlass or winch won't help you carry a 90 lb. anchor from the anchor locker to the bow roller or flake a 600 sq. ft. genoa. It won't help a small person coil up 50' of 5/8" dockline either. And then what do you do if the powered winch or windlass fails. On a smaller boat, you can often manually horse the sail down or haul the anchor up... with a large enough boat, that no longer becomes an option.

Windage can be a big problem for multihulls, especially since they don't have the mass and inertia that a monohull does. Without the centerboard a third of the way down, the bow of my boat blows around like a kite. This is also a major problem for them during a RTS-type storm.

The monohuller's prejudice against boats that don't self-right doesn't make much sense IMHO. Most of the boats and ships that go out to sea don't self-right—monohull sailboats are the majority of the exceptions to this. Capsizes and knockdowns are a reality. However, the incredible form stability of the multihull makes it generally a far lower probability than it is on a ballasted monohull. While a multihull can't be knocked down, it will capsize, and usually, won't right without outside assistance. A monohull can and often is knocked down or rolled, but will often right itself—but not always.

There is a monohuller's argument that the multihull has a position of ultimate stability—floating upside down, with the rig as keel. This is true, but most modern multihulls are made of positively buoyant materials and as such can't sink, since they have no ballast to pull them under. Then there is the multihuller's position that a ballasted monohull has a position of ultimate stability—upright, sitting on the bottom of the ocean. If I have a choice of being on a floating inverted multihull or on a sunken monohull, I know which I'd choose.

One of the key things to taking full advantage of a well designed multihull is keeping them relatively light. Taking full advantage of all the stowage space available on a catamaran is a serious problem.
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You know what the first rule of sailing is? ...Love. You can learn all the math in the 'verse, but you take
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Old 05-16-2008
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Good points SD - so what would you give as a direct answer to the size of multihull that, shall we say, is the maximum practical comfortable size to single hand on a fairly continuous basis. I'm guessing 40 ft long might be the answer, much the same as for a monohull.
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40' is probably a good basic limit for most people. A larger boat can certainly be single-handed, if the boat is rigged for it specifically, but it wouldn't be for the average sailor.
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You know what the first rule of sailing is? ...Love. You can learn all the math in the 'verse, but you take
a boat to the sea you don't love, she'll shake you off just as sure as the turning of the worlds. Love keeps
her going when she oughta fall down, tells you she's hurting 'fore she keens. Makes her a home.

—Cpt. Mal Reynolds, Serenity (edited)

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Old 05-16-2008
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I've just come off a six month single-handed cruise from the Chesapeake to Florida and back. My boat is an old Gemini Catamaran. I don't know that there are many issues specific to single-handing a catamaran. Most of the issues are general to the performance of a catamaran compared to a mono-hull.

One thing I've found useful is that when I have crew aboard, I keep the mindset of single-handing. I always assume that I'll have to do everything myself. Regardless of the boating experience of the crew, a cat is just a lot different from what they've been on before and they're apt to make misjudgments about the performance of the boat.

In regards to size, I've appreciated that the boat is something that I can push off from grounding. I've never needed a tow (knock on teak). With my cat's tiny draft, I am often tempted into the skinny water. I'll ignore markers if they would cause a long detour from a straight line cruise. And I like to gunkhole and search out secluded anchorages. Some say that a catamaran has a natural attraction to the skinny water.

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Old 05-16-2008
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Scott's point about the ability of most multis to sneak into water that other boats would have trouble with is a good one. I've anchored in 6' of water at high tide and been able to sail off at low tide. It also means that I can hide from storms in more choices of "hurricane" holes than a monohull.

However, the shallow draft doesn't really affect how you sail a multihull vs. a monohull.

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You know what the first rule of sailing is? ...Love. You can learn all the math in the 'verse, but you take
a boat to the sea you don't love, she'll shake you off just as sure as the turning of the worlds. Love keeps
her going when she oughta fall down, tells you she's hurting 'fore she keens. Makes her a home.

—Cpt. Mal Reynolds, Serenity (edited)

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Thanks to everyone for such thoughtful replies!

Nolatom, I agree that 35' is a 'sorta' magic monohull number, thanks for the confirmation.

Idiens, "practical crusing problems" as you phrase it, is exactly my curiosity. 'What's easier?' 'What's harder' about singlehanding a multihull and how does that influence boat length/size. You're points regarding sail area and weight, anchoring, etc. are precisely what interests me.

Sailingdog, you write wonderful stuff and I appreciate it. I've read both Chris White and Beth Leonard; and think you might consider publishing yourself!

Sailingdog, your points regarding manueverability, windage, etc. are the kind of issues I'm trying to discover. What other multihull 'plusses' and 'minuses' do you perceive? And, when all is said and done -- where do your 'lines get drawn' when it comes to size limits and singlehanding multihulls?

A 'quasi-related' example: I once worked on charter fishing boats. My 'take' is that boats around 35' are handy and still comfortable. At 44' - 46' it gets to be a damn long trip up to the flying bridge about the 7th time you make it. 36' to 42' is my 'rule of thumb' for day charter fishing boats.

I'm trying to cultivate a similar 'rule of thumb' for multihulls, or, at least, to understand what factors (like windage, manueverablity) contribute to the practical limits inherent to the design.

How boat size relates to safety in multi-hulls (and where a singlehander might 'draw the line' there) is an important consideration. But, I'm not focusing on the mono vs multi controversy.

Lastly, for 'practical cruising with moderate dispatch' an undercanvassed multihull seems like it would have advantages over a monohull maximized to acheive equivalent speeds. Maybe even safety advantages. Any comments?

How design effects the compromises sailors have to make is endlessly fascinating, to me. Since I'm new to that discussion as it relates to multihulls, I do appreciate your comments.

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