I coated the keels with graphite to add some protection but also wanted to add something more substantial. The Wharram plans call for a metal strip on the keel and skeg. It is also common to glue a strip of sacrificial hardwood to the keel onto the fiberglass.
However, I saw a different idea in an old issue of Sea People. Maurice Killen glued plastic water pipe to his keel. I decided to to try that idea.
Of course, I was going to have issues getting epoxy to stick to plastic pipe. A little research showed it was possible with flame treating. I decided to do a test before proceeding. For my test I glued a short piece of black polyethylene pipe to a scrap piece of hardwood. I lightly sanded the inside of the pipe and flame treated it before gluing with thickened epoxy.
To test adhesion, I just tried beating on the end of the pipe with a hammer. It stuck well and I deformed the pipe quite a bit without breaking the bond. However, by hitting the edge of the pipe with a blunt chisel I was able to break it loose. Seemed pretty good to me!
I glued pieces of 1/2” pipe onto the skegs as the next test and was happy with the results.
It turned out to be a big challenge to get the plastic pipe fitted to the keels. I started out using 1/2” pipe because it fitted the bows well. However I just couldn’t get it to lie straight along the bottom. I tried warming it overnight while clamped around straight sticks, but that didn’t help either. And I needed something that would lie down pretty well since I was using masking tape to clamp.
I tried 3/4” pipe along the bottoms and had better results. So I ended up using two pieces on each hull. 1/2” on the bow and 3/4” on the rest. In addition to sanding, I scored the insides of the pipes deeply with a utility knife to give a little more key for the glue. I glued the pieces on with thickened epoxy and clamped with tape. I did some clean up later and touched up the graphite coating where needed.