"LU-Loonie" is a 1-sheet 2-cut double ended boat for solo sailing and paddling. "LU" is for "lauan underlay" because the plan depends on the bending radius of the plywwod used and this plan is for lauan underlay plywood because I find it cheap, light weight, flexible, and available where I live. "Loonie" is for 1. the sinking Canadian dollar which is named after 2. the loon, a water bird which swims fast under water, and for 3. the mental state of a person who would spend time designing, building, and using a boat made out of 1 sheet of plywood. "1-sheet" means it is made out of 1 sheet of 4x8 plywood "2-cut" means there are only two saw cuts, or put another way, there are three panels cut from the sheet of plywood (the bottom and two sides). The whole sheet of plywood is used. There is no waste. A canoe is usually divided into four sections of equal length. The two end ones just serve to part the water and bring it back together again. The middle two sections carry the load. The maximum length of a 2 ft wide middle section in a double ended boat made of one 8 ft sheet of plywood is 5 feet leaving 2 end sections of 1.5 feet each. Such a boat would have a draft of 3 inches. However I do not think plywood will bend to that shape, certainly not lauan underlay. I have been able to get a 4 ft middle section by soaking the plywood in water for a week to make it softer and more bendable, but I don't think many people will want to do that. It is also risky as even then the plywood can crease as it is being bent to form the bow or stern as it did on me. I have been able to get a middle section of 3 feet bending dry lauan underlay with no problems. So that is the plan which will be presented here, a middle section of 3 ft and two end sections of 2.5 feet (actually 2.25 feet bent). Here are the numbers I calculate for this boat: weight: 27 lb displacement: 230 lb draft: 4.2" wetted surface: 16.5 sq ft displacement speed: 4 mph sail area: 33 - 64 sq ft bow half angle: 25 degrees That weight is for chine log construction. For stitch and glue construction I calculate the weight to be one pound less. Sail area of 33 sq ft is twice the wetted surface for low wind speed, and 64 sq ft for a Bruce number of 1 at higher wind speed, but I think the boat would capsize under a sail of 64 sq ft. cutting plan: the middle section of the bottom can easily be marked out on the plywood - a 2x3 ft rectangle in the centre of the sheet. The end sections are 27.25" long on either end of the middle section. The bend of the plywood from the side to the centre line of the bottom is the arc of a circle with a radius of 90-and-five-eigths or 90.625 inches (about 7.55 ft). I used one of the thin 8 ft pieces I had cut for chine logs to draw the arcs but a piece of string could be used. The plywood cutting diagram follows. scale: 10 horizontal characters = 1 foot 6 vertical characters = 1 foot ---------|---------|---------|---------|---------|---------|--------|---------| feet 1 2 3 4 5 6 7 8 ------------------------------------------------------------------------------- | | | 1'| | | | | | ------------------------------- --| | / \ | | / \ 1'| | / \ | | / \ | | / 27.25" 3' 27.25" \ | --|---------------------|-----------------------------|--------------------|-- | \ / | | \ / | | \ / 1'| | \ / | | \ / | | ------------------------------- --| | | | 1'| | | | | | | ------------------------------------------------------------------------------- profile view: H /----\ H / | H < | H <-- mast \ / H | | |H--\ / \ /---| |H \ / \ / | |H \ | | / | |H \ | | / | |H \ / | / | |H \ | | / | =========================================================================== |H | \ | |H |\ ______/ | | |H | \_______/ | | |H | / | --------------------------------------------------------------------------- ---------|---------|---------|---------|---------|---------|--------|---------| feet 1 2 3 4 5 6 7 8 framing: If not using stitch and tape construction the chine logs, gunwales, and stems can be cut out of one 2x4 according to the following diagram. I found half inch thick red cedar will bend to the sides of the boat. I soaked the cedar in water for a few days to help it bend. The suggested gunwales are made of two half inch thicknesses. I cut 1x1 gunwales and only ripped those in half for the first 2.5 ft on each end to bend along the bow and stern curves. For the stems I left an inch at the bow and stern of the bottom panel (1/2" stem face plus 2x1/4" plywood thickness). The radius of curvature for drawing the arc of the bow and stern does not change. Plywood or wood thwarts have to be used to keep the sides apart at the ends of the middle section where the sides start to bend. cutting pattern for 2x4 lumber: scale: 10 horizontal characters = 1 inch 6 verticle characters = 1 inch 1" 1" 1" 1/2" ---------|---------|---------|----- chine 1/2" | | | \ | logs | | | \ | 1" -------------------| \ | | | stems | 1/2" gunwales 1" | | | / | | | / | 1" | | | / | -------------------|---------|----- stem is 1/2" exterior face, 1.5" interior face set saw blade to 25 degrees The prototype was built during the 2001 boating season using zinc plated wood screws, a tube of polyurethane construction adhesive, and a few teaspoons of polyester resin to double seal the edges of the plywood. It turned out to be a delightful boat. The hull weighs 25 lb. The sailing rig weighs 8 lb. The canvas sail is only 5x5 ft, folded over and sewn at the front to make a sleeve to go over the mast. The mast and sprit are bamboo. Two rings cut from PCV plumbing pipe and screwed to the back of the stem serve for stepping the mast. An exterior daggerboard 10" wide by 3 ft long is fit through slots on the port side, one set into the gunwale and the other screwed to the outside of the hull 4" up from the bottom (just above the waterline). The slot in the gunwale is 6" forward of the rear spreader. The slot at the waterline is under the rear spreader. Hence the daggerboard is raked aft. The boat must be paddled through each tack. The 5x5 sail is enough to capsize the boat in a stiff breeze so sponsons 3ft x 3" x 6" carved out of blue foam insulation are tied under each gunwale. The original spreaders have been replaced by 2" wide plywood ones extending 3" beyond the the hull to hold the sponsons down. Two long wood screws are in the starboard end of the rear spreader as thole pins for using the paddle as a steering oar. A home made two bladed kayak paddle is used because the boat is too short to paddle straight with a one bladed canoe paddle. The boat is sailed in strong winds on small bodies of water. The stronger the wind the lower the occupant reclines in the hull for stability. A lifejacket provides padding for the back against the rear spreader. The boat easily sails over the wakes of cruisers on the Rideau River canal. It is also sailed on a stormwater settlement pond a little bigger than a football field. The boat was used 20 times in 2001. I can't remember having so much fun for $23.00 ($15.00 US). - END -