By M. G. Fisk, updated by Dave Gray
I’ve often thought that a little heavier version of our white polytarp might make a decent substitute for 12 oz. Boat canvas. Recently, I came across this set of plans for a small, lightweight, canvas-covered sailing canoe/dinghy by M. G. Fisk and decided to try to prove the concept. However, instead of using our 8 oz. Polytarp, I simply used some of my leftover 6 oz. white polytarp sail material for the hull covering. (I would use our 8 oz. tarp if I built another PolyBoat.) Here’s my version below with a hull weight of 25 pounds as shown. No effort was made to sand or finish the wood. However, I did plane rough edges on the chines, stem, and stern; and I did reinforce the keel with vinyl tape on both sides. There are more construction photos at the end of the instructions. The sail rig, skeg, and leeboard are yet to be completed.
Simply substitute polytarp for canvas in the instructions which follow, and you can construct a PolyBoat in about one weekend! You will need a rectangular piece of polytarp about 6’ 6” x 10’ 6” for the boat and another piece about 6’ 6” x 8’ 6” for the sail. You can easily get enough for both sail and boat out of one of our 7’ x 20’ 8 oz. white polytarps. Our colored vinyl tape can be used to dress up the finished product, but it needs to be heated and rolled to stay in place. (I used a special heated blower and roller to firmly attach the vinyl tape to the polytarp.) I’d also recommend foam flotation.
This boat would make an inexpensive project and could be paddled or sailed on small ponds for hours of outdoor fun. Notice that a detachable lee board is dropped over the side and that a paddle is used for a rudder when sailing. It’s not a good boat for open waters with strong winds, rocky bottoms, or lots of snags, so use by youngsters should be supervised.
Finally, a few additional words of advice are in order. Please don’t try this project with a lightweight blue tarp from the hardware store—the lightweight (3 oz.) tarp rips too easily and tends to disintegrate in the sun. And, don’t forget the personal flotation device (PFD) when you launch. The covering could rip on a snag or sharp rock leaving the sailor in the water with either a sinking boat or a light boat blowing away in the wind. Therefore, PolySail International disclaims all responsibility for property losses, injuries, or deaths related to the use of this boat.
HERE is the answer for the beginner in boat construction who is looking for a craft that is easy to build, low in cost and at the same time as safe as possible to use. The boat can be built in one week end-in fact, the original was built in one day while the designer was on vacation at the shore. Some of the materials needed can be picked up around the workshop; and are easily attainable, and inexpensive.
The boat is 8′ long by 29″ wide at the center frame and the measurements are variable depending on whether a boy or man intends to use it. The wider model is best for sailing.
In the keel, stem and stern assembly and also the middle cross frame, you will note that wherever possible all sawing is done after the pieces are nailed together. Also stem, stern and frames are made longer than necessary and cut off later. This procedure makes for much easier sawing, and there is little possibility of wood splitting when joints are so made. The end frames are made after the hull frame is partly assembled. Sizes of the various pieces’ for these frames are taken from the space into which they are to fit. This is easier than making these frames as a separate unit. ‘
Attaching the battens over which the canvas is spread is the next task, and if you follow the suggestions given herewith you will have no trouble doing a good job. Test each piece of wood for bending before using. (1” x 2” vinyl strips bend easily if you want to avoid steaming wood to bend it.) Mark stem and stern posts for heights, that you desire to make your boat. Drive in temporary nail supports on middle frame uprights (as per sketch). Cut off one end of a batten at the proper angle, drill hole and attach batten to stem post at place marked. Tighten screw just enough to hold the batten in place. Attach another batten to the opposite side of the same post. Now bend both battens at the same time over temporary nail rests in frame uprights until they meet the stern post.
Hold the battens in this position with a light cord or other means, saw off at angle in line with post (without taking batten. off of the boat), drill hole and insert screw. True up the middle frame both ways, drill holes in battens, insert screws and fasten battens to frame upright.
Check over the job at this point and if everything looks in line tighten screws all the way. The lower side (chine) battens go on in the same manner. The bottom battens are not put on until you have built in the end frames. Note that the bottom battens are not as wide as the side battens and that they are attached upright instead of flat.
The canvas covering is put on in one piece. In the event that your canvas is made up of two strips sewn together, be sure that the seam is placed over the keel. Lay canvas over the boat so that it is centered all ways. Stretch the canvas and tack the ends first. (Don’t tack the polytarp to the keel or bottom anywhere.)
Next pull the canvas down tight across the middle frame and tack at top through battens. “Now pull canvas straight down at stem and stern and tack to these posts. Do not cut off any of the surplus canvas at the stem and stern but fold it over instead. (See pictures below.) Grasp the canvas overlapping at the stem and stern faces and fold and crease it until you have two overlapping creases which you can fold over one another on the face of the post. Apply double-faced tape to these folds and then tack securely to posts with tacks placed no further than one inch apart. The folds inside the boat at the stem and stem will keep out any water that leaks past the joint in case you do not get it perfectly watertight.
After canvas is attached to stem and stem posts, work the canvas back as smooth as possible from the ends, tacking only to the top batten. Smooth out about three feet on each side of the boat from each end, working toward the middle frame. In the region of the middle frame you will have considerable surplus canvas to dispose of along the top edges of the boat. Take up this surplus evenly by leaving a small loop of canvas between each tack. When molding trim is attached these loops will flatten out.
The extra canvas at the ends of the sides is folded over to cover the end decks. A small piece of lattice nailed over the canvas at this point will trim the cockpit.
Miscellaneous Construction Notes:
- I used strips of towels dipped in boiling water to help bend the wood 1” x 2”s for the gunwales and chine logs.
- I used a combination of screws, nails, tacks, and glue in assembly.
- The ends of the frame bottoms are attached to the insides of the chines, or “battens” as Fisk calls them, not to the undersides of the chines. Screws hold the frames in place.
- The plywood braces on the middle frame must be fairly large to support the gunwales.
- I used some 3/8” x 2”-wide plywood strips for the floorboards.
- I recommend flotation foam be included in the bow and stern.
**The actual construction cost was only about $60.00 since I had most of these materials on hand.
See more details on the following pages….