: I'm preparing to build an 18' x 21.6" strip kayak and an 18.5' strip
: USCA spec C1 racing canoe this winter. Excluding the affects of rocks
: scraping the glass, is 2 ounce/yard cloth strong enough when applied to
: interior and exterior? I will reinforce the bow and stern areas and any
: through-bolted points. My main concern is the canoe C1 shape having
: adequate stiffness using 1/4" strips. Additional interior bracing is
: not a problem.
: Thanks, Steve.

If you are looking for cost control, then using 2 ounce cloth will save you a small amount on the glass. You'll still have to buy the entire bottle of esin, so unless you have other uses for it, there are no cost savings there.

If you are looking to saving weight, then go with thinner strips. You can use 3/16-inch-, and even 1/8th-inch-thick strips. Consider that the boat, if built exclusively with 1/8th inch strips would have 1/2 the wood (and thus half the weight) of a craft built with 1/4 inch strips. There is your real weight savings. Do you give up stiffness? Well, not so much as you might think.

Take a piece of paper. Hold it by one corner and watch it droop. That is pretty flimsy, right. Shake your hand and that corner moves with your fingers, but the rest of the sheet of paper just flaps around. Now cut the sheet of paper in half and roll up the remaining half into a tube. Grip the end of that tube, and you can see that the same sheet of paper can be directed like a dagger. And it also weighs half as much! Allow that tube of paper to unroll until it is in th shape of a "U". If you've rolled it tghtly to make your tube it should hold the "U" shape on its own. And it will be nearly as stiff.

This is roughly the shape of a canoe, and you can expect roughly this kind of stiffness strictly due to the shape of the hull--regardless of the thickness of the material.

When you were waving around that "U" shaped paper you probably didn't think much about it, but the upper edges of the paper were flapping around. If this was a canoe, you would have gunwales there to not only stiffen the upper edge, but to stiffen the entire boat.

Keep the gunwales light and stiff and your boat will also be "stiff".

If you are worried about 1/8th inch strips deforming, or shifting shape when the canoe is loaded and subjected to water pressure, you can add a few interior cedar ribs made of 1/4 inch stock, bent to fit the interior shape and epoxied in. You probably won't need them, but if you do, they are easy to fit and glue in after the rest of the canoe is completed. Paddle the boat and if you see the hull flattening out, mark the spot with a dab of duct tape, and then glue in a rib. Each rib will weigh about an ounce. You'll sweat off more than that in the 1/4 mile. Probably you won't need to do this, though.

Let me climb on my soap box for a minute: Solo canoe designs, in general, are based on the misguided idea that solo canoes are paddled completely upright. This is probably because tandem canoes tend to be fairly evenly balanced. Despite that, tandem canoes don't paddle straight. the canoe tends to point its nose slightly away from the side the stern person is paddling on. If the strern paddler is paddling on the right side, the bow starts to angle to the left. If the pair of paddlers doesn't do something about this, the boat will end up making a 90 degree turn in something under 20 strokes.

The most common ways to correct this that I know are to have the paddlers switch sides frequently, for the stern paddler to use their paddle as a rudder, to use a "J" stroke, or, as I lazily do, let the bow paddler work harder. If the guy in front doesn't look back, he'll never notice. All of these strategies waste energy or give up some speed.

We know from experimentation that double-bladed paddles are more efficient, and that rudders help, too. Unfortunately you can't use these in canoe races, 'cause they'd really be helpfull in solo canoeing where there is no bow paddler. The lone paddler must move forward to a nearly central position. That puts them in a wider part of the craft, where they must reach further to get their paddle in the water. Or, they move their body off center, and tilt the boat--lowering the gunwale closer to the waterline. Either way, by reaching over one side, the change in their center of balance tips the canoe to that side, and the canoe is essentially on its side during the power stroke. Now ALL the design work on the speed of the hull has been calculated based on the boat being upright, but that isn't how the boat actually rides. So there is a large area for design thinking, starting with giving some thought to the underwater characteristics of the hull when it is tilted. Right now, as you tilt the boat more to the right, the shape of that part of the hull which is in the water tends to push you more to the left. It is a double whammy working against the speed of the solo paddler.

I believe there is a fairly simple change to canoe design which would eliminate this. Simply design the boat as if the hull were on its side, and quit worrying about how it performs when it is upright. Then end result would probably look a bit bizarre, and might be less stable, but it should be faster. I don't race canoes, so I'm not sure if it would be legal under current rules, or if such a design would be banned at a later date.

OK. I'm off the soap box and back to your problem.

If you are worried about stiffness along the bottom of the boat you can add an interior keelson. Make this about 3/4 inch high by laminating several strips which have been bent into the shape of the hull bottom. You can make this first by notching your forms along the keel line, laying in the strips, and when the glue sets you can come back with a plane and remove any high spots.
Then lay your other strips over this. Or, build the boat first, and lay in 1/8th inch strips, building a stack slowly.

Another weight saving ideas: Use a router to hollow out the insides of your gunwale strips. Make them slightly larger than specified, particularly on the inside of the boat. On the inside use spacers to keep them 1/4 inch from the actual sidewall of the canoe.

If your boat must meet a minimum measurement at the beam, then using 1/8th inch strips on the same molds as you might build with 1/4 inch strips will make the hull 1/4 inch narrower in the water. You'd need to make the gunwales 1/8th inch thicker, at least at the middle of the boat, to come back to the design beam.

If you are going with 1/8th inch strips over most of the boat there is no reason not to use an occasional 1/4 inch strip. Recess a groove in your forms 1/8th inch deep where you want to insert a 1/4 inch strip and the outer surface will be flush with your other, thinner, strips. You might round over the edges of the inside of that 1/4 inch strip before gluing it into place so your inside glass goes over it more easily. Or, knock the corners off with a plane (or do this on the table saw) so the inside has a gradual transition for the glass to go over.

Have fun with your building. Hope these ideas help. By the way, I'm curious where you got your plans for the c-1.

PGJ