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 designs that are simple to build, rugged and seaworthy.. Thai inspired longtail boat; free stitch and glue plan for a simple to build cruising kayak from spira international; free plans for doris the dory from in the boatshed. combination building methods. herring skiff free stitch and glue boat plans 12 ft motor skiff; 4. metre dayboat by radoslaw werszko. can be use with outboard. nice contruction photos.. Open/dayboat, free sailboat plans. hobby kat. everyone who digs boating has heard of the hobie cat, the sleek little catamaran that burst on the scene and captured the attention of all the fast-action sailors. marked by asymmetrical hulls and special trampoline supports, the hobie can reach speeds above 20 mph and perform with a rare agility..