A Laying on of Kevlar

After few days break while I awaiting another order of materials from Jamestown Distributors -- a good source of boat repair supplies -- I applied kevlar fabric to the cover the holes and cracks in the stern and amidships/bottom.

The first kevlar I ordered (top photo) was 9 oz. (per sq. yard) twill weave. This proved to be an expensive mistake. I cut a small square of it for a test, epoxying the kevlar to a piece of plywood, and I found that, due to the heavy weight and the weave, this fabric would require a great deal of epoxy to fill the weave. It's also somewhat stiff and would require a lot of fiddling to get it to lay flat on the canoe's curves. Since I had ordered a cut piece (1 sq. yd), of course I couldn't return it. I ordered a piece of 5 oz. plain weave (photo above), which has a much finer weave and smaller yarns, drapes more freely, and would require less epoxy to fill -- in other words, lower cost and lower final weight.

I made a pattern for the kevlar patch, laying a piece of stiff paper over the area at the stern and roughing out on the paper in pencil the shape and size I wanted. My objectives were to create a pleasing shape with gently curved edges that would cover the holes and the hardened filled-epoxy patch, and give at least 1" overlap all around onto sound plastic. I layed the paper pattern over the kevlar cloth, traced the shape of the pattern with pencil, and cut out the fabric. 

I also traced the shape of the pattern onto the canoe, so that I would know exactly where to place it. I masked off the hull just below the penciled lines to keep drips under control.

The hole in the stern had already been patched with filled G-Flex epoxy. This had hardened with rough spots, ridges from the spreader, and a few hollows. In order that the kevlar lie flat, I applied another moderately thick coat of thickened G-Flex, carefully smoothed it with a plastic spreader, and while it was still wet, brushed it over with liquid epoxy, working carefully so as not to disturb the smooth surface of the filled stuff.

Once I had brushed the liquid G-Flex over the still-wet thickened G-Flex base, I laid the cloth on, aligning it with the penciled guidelines. I then poured a small amount of liquid epoxy over the fabric and used a plastic spreader to spread the epoxy and force it into the weave of the cloth.

Even when wetted out, the kevlar cloth wouldn't drape over the stern stem without puckering, so I cut a dart on each side. You can see this in the photo above. As soon as the epoxy began to set, I pulled off the masking tape and paper so that it wouldn't be glued to the boat.

I followed the same process for the 'midships patch, except: a. since it was relatively smooth, it did not need another coat of filled epoxy before liquid epoxy was brushed on, and b. no masking was needed to control drips, since I was working on a flat surface.

The two kevlar patches with fresh epoxy squeegeed and brushed on.

When the epoxy on the outside was sufficiently hard that it wouldn't sag, I turned the boat over and applied another patch over the midship cracks and holes on the inside, using the same methods. I then tented the whole boat with a plastic tarp, placed an oil-filled electric radiator inside, and allowed the heat to hasten the cure.