Instructables

Outrigger canoe with freestanding mast

A sailboat built out of luan plywood, fiberglass, epoxy, and a little mahogany. Mostly plywood though. It's an outrigger canoe modeled roughly after a proa, but with a more western style hull shape and sail. I think it took around 200 person-hours to finish, although a boat with less finish work and slightly less laminated mahogany, could be finished in half that time.

I should give a general outline of what sort of sailboat this is. A proa is a double-ended outrigger canoe. The sail is rigged up so that it can rotate fully forward of the mast, and the rudder can be moved. The boat never tacks, and instead just stalls and starts going backwards. We didn't want to mess with the rudder for this sort of design, so we opted for a single ended outrigger canoe. This has the downside that one tack is different than the other, which in moderate winds is not especially troublesome.

The most interesting thing about this boat is probably the construction technique. We tried to make everything extremely easy to build, as well as tolerant of a lot of slop, but still lightweight enough to carry single-handedly, and as strong as is necessary for a freestanding mast. We compromised a small amount on hydrodynamics to do this (as we have a sharp chine). The high aspect ratio of the hull (5-6) makes this less of a compromise.

The basic design is very simple; The main hull has a flat deck which forms the backbone on which the rest of the boat is built (upside-down). The ribs, mast box, and centerboard box, are glued to the bottom of the deck. The sides and bottom of the boat are then glued to the ribs. To make the boat comfortable with a flat top, we put benches out over the water to sit on instead, which facilitates hiking as well. The bottom and sides are all single sheets of quarter-inch luan plywood, but the top is two sheets laminated together (this would have preferably been a sheet of 3/8" or 1/2" marine ply)

We wanted to minimize how many pieces we needed to cut and how many numbers we had to crunch (though we still crunched a laborious number of numbers), so we made the outside of the hull out of five pieces: the deck, two side pieces, and two bottom pieces. And a rear transom, which is more of a glorified bulkhead.

our side panels were constant width along the boat (they are rectangular). We then simply cut the top and bottom to fit the angle and curve of the side panels.

To make sure everything would fit together simply, we only made planks bend along a single axis, and always in parabolic shapes (this is roughly how a uniform stiffness beam wants to bend, at small angles. Since we wanted side planks that could be cut on a table saw, and only bent along their long axis, in a parabolic shape, this became the starting point of the boat. Simply define the boat length, the vertical slope of the side planks, and the maximum width of the boat, and the boat is fully defined in terms of camber and planview. All that remains to be determined is the vertical slope of the bottom planks on the hull. Just pick something pleasing to the eye here, unless you are interested in a particular ratio in the tradeoff between hull drag and static stability. With the above chosen, the hull is fully designed. Now build! wait, no. Now plug everything into any plotting program and figure out all your bulkhead cross sections, taking into account the thickness of your planks.

Now build! You'll probably need about a gallon and a half of epoxy, and a gallon of titebond 3 or comparable 'waterproof' woodglue (this can be replaced with epoxy if desired, but is a lot healthier to work with, and sets up quicker. Any wood-wood joint which is only going to encounter splashes, or which will be coated with a protective coat of paint in the end, can be glued in with a waterproof wood-glue)


 
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kleinjahr3 years ago
Very nice. Never saw one built from the deck up.
Suggestions. Make another outrigger for the other side,won't dump you in the water then. By using brackets/slots you can run the outriggers in, makes it easier for trailering. Through bolts and wing nuts will hold them in position. A water proof hatch in each hull might also be useful, allows you to check for leakage and gives some storage for kit.
DavidM453 years ago
Great project, really unique sailboat I'd love to have a proa.

I sail a Europe Class 11' 98lbs monohull, un-stayed rotating cat rigged with 75 sq ft.

I would say that it's SOLID your all-up must be over 170 lb. I really think this could be made completely using 1/8" doorskin (about $10-12 sheet) for an el-cheapo version and half as many bulkheads at least cut out the bulkheads leaving 2.5" on the edges. as long as you encapsulate all the wood with epoxy.

Take a look at the schedule for 11' "Classic Mistral Moths", they often us 1/4" ply with bulkheads at 2 feet. and weigh about 50-60 lbs.
Just a thought, great job.
geno-995 years ago
how long is it??
mister25 years ago
Beautiful. I envy your boat making prowess.
Leon Close5 years ago
Nice little boat, I don't know why I didn't notice this earlier.
interesting! I haven't heard of the dacron step before. does it ruin the dacron?