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. Skin on frame boatbuilding method. skin on frame refers to a method of boatbuilding that has been around for a very long time. typically a light frame often made of. Links to boat plans some free boat plans, boat building information including plywood stitch and glue. full range of boat plans from sophisticated yachts to plywood.