by William Watt  ag384@ncf.ca 

The Loonie is a one sheet boat designed for paddling and sailing by a 150 lb adult. Its made of three plywood panels and requires two saw cuts. The shape of the bottom has to be matched to the bending capability of the plywood. To do that a prototype was made in cheap lauan underlay plywood. Other types of plywood require a different bottom shape. To determine the bottom shape two 1 ft sides were cut from the outer edges of a sheet of plywood, loosely stitched together at the ends with wire, and 2 ft wide molds inserted and pushed out to the ends as far as they will go. The chords of the arcs and their depths were measured and the radius of curvature calculated. To make one of these boats of lauan underlay draw a 2x3 ft rectangle in the centre of, and parallel to the edges of, a 4x8 sheet, extend the centerline 27.5 inches beyond the rectangle at each end, and draw an arc with a radius of ninety and five eights inches (90.625") from the corners of the rectangle to the ends of the extended centrelines. Cut out the bottom and bend the sides around it. Fasten using stitch and tape or chine log methods. The photo shows the stern bent more than the bow. That was done by soaking the back ends of the plywood in a rain barrel for a week to soften them, but the plywood still creased when it was bent. I doubt most people would want to go to that much trouble. The ends of the boat will be 2 ft. high. I think that's neat but they can be cut down before assembly. They can be cut into artistic shapes to reflect the builder's individuality. The ends of the prototype are 1.5 ft high, limited by ignorance of the eventual shape of the bottom. If stems are desired leave the ends of the bottom 1" wide. Stems from 1x1.5 inch stock, 1/2 inch at the front and 1.5 inch at the back (saw blade at 25 degrees).

I used the chine log method for the prototype. The chine logs were 1/2 inch strips sliced from red cedar 2x4's salvaged when the 15 year old floor of a back yard deck was replaced. The wood was dry and brittle, cracked, had nail holes in it, and had to have soft spots sanded down. It saved a bit of money and gave me lots of trouble. Some people never learn. The photo at right shows how the end of the gunwales were gradually bent on a jig over a couple of days. They were partially sawn in two lengthwise so they could bend. They had been soaking in water for a few days. The ends were sealed in dark plastic bags to keep in the moisture and hopefully generate some heat. One gunwale was relatively free of imperfections and bent without problems, one broke, the third cracked but was used anyway. After all, it was just a prototype, right?

The bottom was cut to shape and the parts laid out to get their picture taken, sides, gunwales, chine logs, thwarts, and stems. The gunwale and chine log on the right are the ones which worked, the ones on the left the ones which didn't. The broken short left chine log was cut in the middle and a piece put in since it didn't have to bend in the middle. The broken gunwale on the left was replaced. I fastened the boat with zinc plated wood screws and a tube of polyurethane construction adhesive. The adhesive goes on easily with a caulking gun; has a long working time of three quarters of an hour; and has a wide temperature range for curing. The outside of the chines and stems were sealed and made abrasion resistant with a narrow band of polyester resin spread with a toothpick. Two coats. Its a good idea to mix in some white pigment because the paint gets scraped off the chines. The hull was painted up to the gunwales with exterior house paint. Above the gunwales and inside it was given two coats of linseed oil. The inside face of the plywood was full of worm holes. They only took 15 mintues to seal with a dab of polyester resin applied with a toothpick. When applying resin with a toothpick I mixed up 1/2 teaspoon at a time.

The sail works great. It was made from a 5x5 piece of canvas salvaged from a rummage sale. A sleeve was hand sewn in the front edge to go over the mast. The corners were already rounded and hemmed so some 1/8 braided nylon line was sewn on to square them up when rigged. Eight feet of the same braided nylon is used to control the sail. Braided nylon is preferred for hand held lines because it is so soft and gentle to the skin. Big, strong, dirty, foul-mouthed sailors swear by it. The mast and sprit are bamboo. The mast fits in two rings cut from plastic pipe screwed into the back of the back of the stem. Bamboo is very good stuff for small spars - light, hollow, strong. The bamboo plant stores silica in its skin to make itself strong and durable. In Asia they make bamboo plywood for construction forming and use it over and over. It lasts a lot longer than fir plywood. However the inside of bamboo is soft and will weaken physically and eventually rot if it keeps getting wet. The bamboo I used was salvaged many years ago from a ski slope where is was used to mark slalom courses. It spent many years propping up plants in my garden. Before recycling it a second time for spars on the boat it was cleaned and sanded. Any cracks were glued and sealed with household epoxy glue applied with a toothpick. Then the spars were given two coats of polyurethane varnish. I still would not want to let them be in the water very long. The daggerboard is not placed according to theory. It is as far back as possible and at an angle to get it back even further. It is 3 ft long and 10 inches wide. Below the waterline the front edge is rounded and the back edge is tapered. That was done with a sanding disk on an electric drill. Both edges were given two oats of polyester resin for protection. The daggerboard leaves a little lee helm when close hauled and a little weather helm on a broad reach, a satisfactory compromise. It is mounted outside the hull to save space, save weight over leeboards or a daggerboard trunk, and to save having to cut a hole in the bottom of the boat. In my experience with sailboats its always the trunk which gives the most trouble in the hull. Hanging the daggerboard outside is unique to this boat as far as I know. The slots are screwed on but not glued in case they break and have to be replaced. The interiors of the slots are coated with polyester resin to resist wear. The bottom of the daggerboard is flush against the hull so it is partially "end stopped" and more effective. The chine has been protected with some fibreglass cloth and polyester resin where the daggerboard rubs on it. 

The boat just fits on top of my small car. This is pure coincidence and not a design feature. The boat also just fits inside the car, another coincidence. When I bought the car I moved the back seat and passenger seat to make more room for my nk and the dog. The stick of wood poking out the back is the sprit for a bigger sail I wanted to try on the Loonie but it was too top heavy for the tiny boat.

The boat finally gets its bottom wet. It's too short for a canoe paddle and needs a kayak paddle. The paddle serves as a steering oar. The thwart at the back of the boat extends beyond the gunwale on the right side where there are a couple of large wood screws sticking up. The paddle rests on the thwart between the screws. The screws are padded with short pieces of plastic tubing. I guess it is a right handed boat. I wouldn't bother fitting a rudder. The extra weight isn't worth it. I dropped the steering oar once and used the daggerboard to paddle back and pick it up. The stems at the bow and stern stick up above the hull and are drilled with holes to take lines to tie the boat up with. I do love sailing this tiny boat. You get down as far as you can in the boat so your shoulders are supported by the rear thwart. That gets body weight as far down and forward as possible for trim. The boat is tippy if you sit up to sail, as I found out when I rolled the boat over in a strong wind my second time out. I was trying to see how much wind the boat could take. You don't have to jump all over inside the boat like most small sailboats. Actually it wouldn't be a good idea as you'd tip it over. I want to put some floatation along the gunwales so I can climb back in if I get careless and roll it over again. I may even put a back rest on the rear thwart. Theoretically the top speed of the boat under paddle or sail is 4 knots (4.6 mph) and the most efficient speed is about 3.25 kt (3.7 mph) and that seems about right. Draft is about 4 inches with a 150 lb. occupant. The Loonie makes the river where I've been using it seem like an ocean and provides hours of fun working the shifty breezes. I've sailed along so close to shore I could reach out and run my fingers through the grass. Not bad for an outlay of $23 ($15 US).


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