Homemade jon boat built from uncle johns plans http://www.unclejohns.com/ took me approx six months to complete. 15′ 7" long, floor is 46" wide and sides. How to make the most out of your one sheet boat. the ultimate one sheet boat, prism: discussion on maximising the displacement. free boat plans and building instructions.. Welcome to absolutely free plans, in this section you will find free boat building plans including accessories and construction techniques. free plans have a tendency.