Welcome to spira international home-built boat plans. spira international offers a wide variety of different power, rowing, and sailing skiffs, dories, and other boat. Wooden boat plans developed by a boat design expert & naval architect. all boat plans come with free 3-d computer models & free master boat builder course.. 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..