I'll second Delftship. If you get the free version, you'll need a separate CAD program to print the forms (part of the Pro version). I've designed and built 4 kayaks (including 2 plywood framed SOFs) and one canoe (stripper) with it.

Dan

: Hulls is probably the easiest program that I know of. Freeship and Delftship
: are very flexible. I use Delftship Pro for what I do. I like it.

: Below are three renderings from Delftship for hard chined kayaks. You'll
: probably also want a CAD program in addition to the ship design program
: for final tweaking.