I have three places that are damaged on my keel that go all the way through. One at the front right where it starts to turn under. Second one in the middle below the livewell. And a third place at the rear near the drain plug. I have cut them out and sanded them down to a 12:1 taper. Next I am going to put a form on the inside, cardboard or pvc pipe or use a pool noodle to get the shape I need then start the repiar. I thought I would put the first layer as CSM, then follow up with biaxial cloth, CSM, biaxial cloth etc and build it out and make each patch progressively larger. I sanded down the gel coat over the entire length of the keel and I am going to use two layers of 4" biaxial cloth offset by 1". So what am I missing. I know there must be something else I need to do. I have done some fiberglass work before but not to this extent. The one question I have is the proverbial poly vs. epoxy. I am going to coat the entire bottom with truck bed liner so I was wondering of poly would work since it will be coated (I always heard that you must use epoxy below the water). But then why in the world if you need to use epoxy below the water line then why do boat manufacturers use poly?