Had an 18" crack on my hull. ground down the outside and repaired with kitty-hair Bondo. Thought I had the inside done but the fiberglass mat and resin didn't adhere. It looked good. I was going to put on another layer or two awhen I discovered that I could pull off my patch fairly easily with a set of pliers.
I had sanded it down a bit and cleaned the surface with acetone. Do I need a special bonding material or does the surface need to be really roughened up thanxs david