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Canoe Building: Fiberglassing the inside of the hull
After the inside is all planed, sanded, wet sanded, and essentially made smooth (faired), it's time to encase it in fiberglass. But before you start, get an epoxy solvent and wipe down the inside of the hull one last time. This will eliminate any oils or other contaminants that will prevent full adhesion of the epoxy. Be sure to wear a respirator while you do this! The low vapor pressure of the solvent makes it evaporate very quickly and be nasty stuff if it gets into your lungs! Spreading the fiberglass cloth on the inside isn't as easy as it was on the outside. Bits of exterior fiberglass want to snag the cloth as you spread it, and you're trying to fit it in a hole instead of over the outside of a dome. The stiffness of the cloth is your friend as you spread it.
Take your time spreading the cloth, Make sure the fibers going across the canoe are as straight as reasonably possible. The fibers going lengthwise will align themselves. Along the way, a good pair of scissors will help as you cut strips in the cloth hanging over the sides to help the rest of the cloth lay flat. For the ends, I cut straight in from the end and folded and tucked the cloth so it overlapped with the other side, essentially giving two layers of cloth right at the end of the boat, but only overlapping a total of 3-4 inches. Once the cloth is smoothed to your liking, it's time to apply the epoxy.
Fiberglassing the inside is much the same as fiberglassing the outside. Start about 1/4 down from the end, in the middle of the canoe and work toward the ends and sides. I worked to cover the far end first, then came back to the middle and worked to the closer end, as shown in the picture above. Work quickly, but consistently. I found that about 1 to 1 1/2 cups of epoxy with hardener in it was about the right amount for each batch for me. Also, if you're ever tempted to squeegee from the side to the middle- don't! Remember- always work from the center of the canoe to the sides!
Here's a picture of the canoe once the inside has been epoxied. Let the first coat mostly cure, then repeat it another two times. Think of it like a waffle breakfast. The first coat makes the waffle, the second coat fills in the holes in the waffle, and the last coat makes it smooth. Ted Moores in his book advocates only doing two coats of epoxy on the inside so you have a little texture to stand/walk on. He must be super amazing when it comes to epoxying. After two coats for me, the bottom was full, and the sides of the inside were blotchy and irregular in the amount of epoxy there. If you're a newbie like me, it might be easier just to plan on doing three coats and having a smooth finish.
Once the epoxy has cured and hardened, you can go back and trim off all of the excess cloth around the top of the canoe.