This really is governed by your skill and how deep your pocket is going to be. http://www.countryplans.com/vintage_farm//boats/FoldingKayak.pdf Is an easy to do ply canoe that folds lengthways. True folding kayaks are quite difficult and expensive to make and unless well engineered may be unreliable enough to endanger the users. True folding boats rather than canoes are a different breed and even more rare. Most use canvas for the sides with a wood or plastic pipe frame to support it. Again difficult to engineer at home. Alternatives are a car topper, a light boat a single person can lift onto a roof rack, Geodesic boats - VARY light weight but strong designs http://gaboats.com/boats/ best examples I can find. http://www.pdracer.com/ - car topper http://www.woodenwidget.com/index.html A true folding dingy Have fun - Be safe - Wear a life jacket ALL THE TIME - Building and using boats is fun and adventurous as long as you come back to do it again. NEVER underestimate the dangers of water deep or not.