You might want to take a look at a fuselage style skin on frame. They don't require much in the way of wood working, and there's a million and a half ways of putting 'em together. Yostwerks.com has some good designs, pics, and step by step instructions. The site was put together by an engineer, though, so it's recommended to read through all of the site, even if you're only building a non-folding kayak.
You don't have to use PVC to cover the kayak like Tom does, either. I used 8 oz polyester, covered it in PL Premium Construction Adhesive, then Rustoleum. There's been a lot of success using ballistic nylon and varnish, instead. I lashed all my joints, too... no need for epoxy or screws.
It'd be hard to build a 15' SoF over 50 lbs without getting really excessive on the size of the frames or stringers, unless you use absurd wood (mahogany for the stringers, for example).
Touring Kayak Paddles
Overstock Outlet Foods
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