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. Free houseboat plans, and almost free boat building plans the free houseboat plans section is here as a starting point to the world of building a house boat, and the. For reasons that escape us, there are few production boats like our chinook. but if you’re like us, there are times when you want.