Minimalist Long-Distance Cruising: Designing a Tacking Proa (PT1)
Article by Stephen Ladd
A year and a half ago SCA ran my article, Design Tips Gleaned from Long Voyaging. Now I will relate how I have been following my own advice with respect to a new boat: a tacking proa.
A boat the hulls of which have a length-to-beam ratio (measured at the waterline in both cases) of at least 10 has no “hull speed” limit. Skinny hulls are fast, and their speed isn’t achieved through energy-costly planing but rather by not creating a bow wake that the boat must continually climb uphill against. I didn’t have to start from scratch; I came across a prototype Pacific proa that had been intended for the Race to Alaska but which never entered. Pacific proas keep their outrigger (or ama) always to weather, and “shunt” rather than tack. But I am radically re-working it. It will no longer be a Pacific proa but rather a tacking proa: it will have a bow that is always the bow and a stern that is always the stern, and will tack like most sailboats. It will still be a proa, though, because the main hull is much larger than the outrigger. In effect, it will be much like a trimaran missing one of its amas.
Besides speed (or little need for power at a given speed), a multihull inherently has shallow draft. This is because its stability comes from widely spacing its skinny hulls. They don’t need to hang a ballast keel down low, where it will hit rocks.
The boat I bought was thirty feet long yet weighed only 450 pounds! This seeming impossibility was due consisting of slender stringers on abbreviated bulkheads, covered with fabric skin. I have removed the fabric and replaced it with foam-core fiberglass: a half inch of Divinycell coated with a single layer of bi-directional knitted (not woven) 18-ounce glass on the outside and 12-ounce on the inside, the resin being epoxy. This is so light that weight didn’t increase much. (The new construction also includes some wood components where appropriate.)
I have also removed the main hull’s original superstructure and have built something quite different. It originally had a kayak-like deck that you couldn’t walk on, and the beam on deck was the same as at the waterline: only two feet! (She has a rather extreme length/beam of 15.) Instead, looking at her frontally, above the waterline she now swells out to six feet wide, and she has a normal deck, with conventional shear and crown.
Like the original boat, she has a bulkhead every 30 inches, and she has no cabin per se. Most of the bulkheads are now watertight, so she consists of many watertight compartments. Holing any one compartment won’t much embarrass her, and even if she breaks up, the pieces will bob like corks. How, then, do I achieve accommodation? Principally, by giving her a large central cockpit (six feet wide, seven and a half feet long) over which a custom tent (or a bimini if you just want sun protection) can be swiftly erected because the sockets for the poles will be permanently attached. Secondarily, an almost-cabin is achieved by combining two compartments, plus a foot of another, into a single compartment which I call the passage berth. This is six feet long and two feet wide where your body rests on the keel. Here you can sleep prone and dry while someone else (or just your autopilot?) steers for a few hours during a long passage. Once you’ve arrived, you erect the cabin for greater comfort.
This boat is intended for minimalist long-distance cruising. True, she won’t be as minimalist as Squeak of Three Years in a 12-Foot Boat fame or the Sea Pearl in which Ginny and I sailed to Argentina (see The Five-Year Voyage). But she will be more minimalist than is usually associated with a 30-foot sailboat. She will be very light. And though the widening of the superstructure above the waterline has given her much more interior volume, the purpose is not to fill that space with heavy stuff, but to achieve deck space to work the boat and cockpit space for practical indoor/outdoor living.
She has two carbon-fiber masts in a stay-less cat ketch configuration. The masts are intended to be in place only under sail. When motoring (with a four-horse outboard mounted on a crossbeam) or moored they will be lashed down onto the crossbeams. The idea is this: you reach up into the sky only when needed (by raising masts or erecting the tent) and you reach down into the sea only when needed (by lowering the rudder blade and by lowering a leeboard if sailing to windward). Otherwise everything is on a flat plain, which stretches out extravagantly in the horizontal dimension.
The reader will understandably wish he had a picture or drawing to look at, but I prefer to focus on concepts for now. I will come back with other articles as I finish her, which will take quite a while (this is a very part-time build). •SCA•
Of like minds....almost.
QB (Questing Beast) is a tad shorter and lighter proa, 21' and ~ 320# on the trailer.
Has twin stayed masts with cambered panel staysails. A domed tent with the bottom cut out provides standing room camping at night. I've only been out on the boat for three nights for a a first attempt at the Texas 200 but there's nothing major I'd change and the little bits to modify will happen over the winter and hope to campaign it regularly thereafter as long as I'm able though not as vigorously as Steve probably would.
Look forward to seeing more about upcoming adventures.
I would love to see this craft in the Texas 200!