If you are building in strip, you dont need many planks to build a set of hulls. 7-8 square meters of surface area and some bulkheads, transoms, beam seats, daggerboard wells etc. But you need some epoxy and glass, which I dont think you will find in an uncatalyzed state on a beach <img src="http://www.catsailor.com/forums/images/graemlins/grin.gif" alt="" />