What is a Catamaran?



“ What’s that big yellow thing?”
“Oh, it’s a Catamaran. One of those fast yachts with two hulls joined together. They have lots of room but you wouldn’t catch me out at sea in one – they flip over and are too flimsy…”

We have all heard conversations like this at places where boats are moored. Its tempting to dismiss such comments as indicative of Joe Public’s ignorance of the multihull format and how much it has been developed in its current iteration, but nonetheless the above “better safe than sorry “ attitude has merit for the casual boater. Lets look more at this comment.

Catamarans, like the awesome big Cats in the wild, need to be treated with great respect or they will bite. It is true that the crossbeam to hull linkage is subject to enormous wracking forces in a seaway, and needs to be taken very seriously by both designer and builder. It is also true that despite many fine essays on ways and means of righting inverted cats, I’ve never seen a documented instance of a sizeable cat being righted at sea purely by the efforts of the shocked & battered crew, using materials carried on board. This doesn’t mean it hasn’t been done, I do hope it has, and would be heartened to hear of such a situation.

It would be a change from the usual Design competition if some Yachting Safety Conscious government (Australia with its plethora of Cats would do nicely) sponsored a competition to design a system small enough to be carried on a cruising catamaran, and deployable to right it.
The best proposals I’ve seen along these lines involve turning over floodable bows using leverage against the inertia of a deployed bag of seawater. The prize of the competition would be to build and demonstrate the Shortlisted Systems on a sizeable cheap old cat, pay for a Patent on, & publicise the best of them. There would be merit in offering a loan so the winner(s) could begin manufacturing. The cost would be negligible compared with the fortune our Australian Navy & Rescue services spends winching hapless yachties, ranging from casual fisherpersons to Hobart/Vendee competitors, out of the briny. There would be instant world-wide appreciation, and the whole business would pay for itself with the first life saved.

So Cats don’t pop up when knocked over. What’s worse is that unable to spill wind by heeling, they cop the full force of a gust. You have four defenses against capsize.

1/ A moderate sail plan that’s easily reefed. Having a furler on jib becomes a safety issue on a catamaran. If you can afford one, buy it. Keep your centre of effort low. A schooner rig is a good idea for a large cruising cat, and is actually cheaper to build than a single high mast. Gaia, Wharram’s 63ft traveling cat, is a good example – he Schooner rigged this yacht for a quarter the cost of a towering single mast.

2/ Carry as much beam as possible in the design. This of course makes the cat a liability in marinas, especially if it is both light and has high windage.

3/ The more weight in the hulls, the less chance your boat will blow about the sea like a piece of newspaper. I’ve seen a biggish cat thrown sideways by a gust, & a very well found twenty-six footer in Queensland was literally blown away by a 50 knot gust which simply picked it up and dumped it in an untidy heap upside down and half ashore. Florida residents have witnessed all sorts of atrocities committed by the wind on light cats. Of course heavy cats don’t perform, so here we have a seemingly Catch-22 situation. The solution is simple. A sealed compartment under the floor, with a screw down waterproof inspection plate and bung. When the wind rises, up comes the plate, screw out the bung, and screw the plate back down. Pretty soon you are carrying water ballast right where you want it, low in the hulls, and this will settle your skittish cat right down. Make sure your inspection plate is big enough so you can chill your beer. It also may be a good idea to use this ballasting in marinas and at anchor to keep your kitten quiet. Getting rid of water ballast by pumping is a bit of a hassle, & you can get pretty wet putting the bung back unless you beach the boat. But if it has just saved your ship you won’t curse as much.

4/ The very best defense against capsize is horse sense. Be scared. Reef early. Pick your seasons and cruising grounds, use your cat’s speed to make harbours, carry a spotlight and a decent motor. If you cant afford an inboard, a well will save an outboard being stopped by swamping. Radios, GPS's are a must. Learn all you can about the seas you are in. Carry a drogue. Read “Multihull Seamanship” by Gavin Le Seuer.

Back to our friends at the anchorage and the comment: “They have lots of room…”. This is the most common multihull misconception. Better to say “They can, and often do, have lots of internal space but it comes at extreme cost”. The “block of flats” approach to catamaranning is expensive in proportion to the extra weight and invariably tempts the owner to load his boat up to the point of not performing. The only way to stop the disease is to have not enough space. Cat Cruising on a budget means extreme minimisation. You need to consider the weight and relative importance of every item you put on board.

The economy of scale concept goes out the window with boating. A 28-foot cat with a schooner rig could be sailed without a winch, but a 40 footer with a 60-foot sloop rig will involve at least 10 grand in winch gear. Every part of the boat is likewise. I contend that once beyond the magic 28 feet, a cruising cat doubles in building cost for every 20 percent increase in length.

What is magic about 28 feet?. Nothing, its just a number that keeps coming up. For a wage slave like me, a boat over 28 feet begins to own you. Wharram's 28-foot Tanenui has safely crossed the Atlantic and will cruise anywhere at 10 knots. It has low windage, and heavy seas break through the slatted bridge deck instead of striving to tear the boat apart. Anyone with an income can afford one, and hence can cruise where they want. They have to be prepared for multihulling in its purest form, wet at times but with the option to get warm and dry in minimal accommodations. Still at just 28 feet, Richard Woods has designed the Gypsy, a fully accommodated cat that offers space and comfort in a home buildable format. Of course it will cost more to build than the Wharram, but you get the lot in a manageable package. Twenty eight footers are narrow enough to be moved by road without the extreme drama of their 40 foot 4 ton relatives, and are far more likely to be completed by the home builder who is often traumatised to a standstill upon realising the size of the building task undertaken.

If one is prepared to minimise accommodations, one can get a very fast cat for little money. Essentially if the hulls are kept small in section, one is up for building two canoes instead of two ships. A hull no higher than a 4-foot ply sheet still offers stowage, room for single berths, and (with a cunning hatch) the opportunity to provide a private head. Such hulls can even be shaped in section shaped so the windage holds them down. Combined with a small pod that gives seating round a table and cooking, even with your head and shoulders sticking out of a hatch, you have all the comfort accommodation you need. You will never have all the accommodation you want, that’s at home for lucky humans born in some countries. Such pods can gain seating space in a structure only a metre high by putting the sole in a nacelle which can break up underwing slamming, and shelter a motor behind the cockpit. A tent at anchor can provide a heap of space and enable you to strip your cat to an efficient high-speed sailing machine when its time to move. Further, the small section hull enables you to work with waterline length to beam dimensions of over ten, providing real speed without the extra building effort of stepped hulls.

One must also consider the old devil windage. If you insist on being able to strut up and down 40-foot hulls without banging your head, you present 200 square feet of wind-catching panel right where you don’t want it. A cat at speed is almost always on a reach, so you’ll be fighting to keep from being blown off course. A good sail lead and daggerboards will help, but when you pull them up to berth you can finish up bouncing around a marina like a nightmare game of pinball. And needing a football field of space to simply hang off a mooring.

So what is a Catamaran? Since the Polynesians discovered they could fish or travel more efficiently by lashing canoes together, a catamaran has been a double canoe. Joining the canoes with a slatted deck to let the water through adds space without danger. If you want to build a cat, you are building a double canoe. Keep this idea in the forefront of your mind, & I reckon you’ll be on the water sooner, for less money & in a better-performed and safer yacht. And if you think you’ll miss your TV, forget the whole idea!

Jeff Gilbert 2003.