i have a fiberglass boat that the previous owner either had a bad keel roller on his trailer or beached the boat a lot. on the keel there is a section about 18 in long that is worn thin and then about a 4-5 in section where the fiberglass has broken off the cloth. i checked on the inside and the hull is sound. the damage appears to be strictly to the gel coat and the outside resin. can i use epoxy putty to fill the hole and cover the thin spot? and if i do, do i need to cover it with a layer of cloth with epoxy resin? or is the putty strong enough? or do i need to use resin, mat and cloth to do the repair? i do not have a keel roller in the same spot but when loading and unloading the repaired spot will roll over a keel roller. i am assuming that i need to use an epoxy resin to stick not a polyester resin.