> While I'm sure the Aleut kayaks were very efficient, some of the
> conclusions people have made from reading contemporary accounts of their
> performance are a little far fetched.

I have a hunch that some of the attributes of skin on frame design are the result of cumulative lucky coincidences more than rigorous design.

If the origianl kayak builders were emulating large sea mammals, like whales, seals and walruses -- and using the bones from these animals as components of their crafts, then a good deal of the design would be determined by the materials at hand. If you use the ribs from a walrus as the ribs of your boat then you can hardly take credit for the curvature.

Many years ago I saw an exhibit on soap bubbles in a mathematics exhibit at the local museum. One of the points being made was that the soap film would follow the shortest distance between all the surrounding points. Dip in the plain, circular bubble wand and you get a plane. Dip in a 3-D wire frame, and you get an interesting shape. I think that with the Inuit kayaks, the flexibility of the skin would allow it to work like a stiff soap film. when the boat was placed in the water the pressures would bend the skin into a concave shape on each side of the boat. Like a soap film, this shape should be close to the minimum size needed. That would mean a minimum wetted area, and a minimum of drag. The effect of having the left and right sides being convex, from keel to the edge of the bottom, should give a nice skeg-like effect, which would enhance tracking, too.

Strangely, when I read about design specs for skin covered boats they mostly seem to assume that the hull material is rigid. I'm not sure what kind of fudge factors are involved, but the skin DOES flex once the boat is in the water and the paddler gets in the boat -- and that absolutely changes the underwater shape of the boat, so either the performance is going to change from the design specs, or you have to rethink whether the ideas behind the design were valid in the first place.

This whole thread should probably be in the kayak design area.

Just adding my 2 cents.

Paul G. Jacobson