Before you start grinding the hull to re-fiberglass, I would suggest using a wax remover. If the resin used to build the boat was wax based, It cured with a layer of wax on top. When you grind, it pushes the wax in all the nooks and crannys. Then when you re-glass, you get a weak bond. I never skip that step, waxed based or not, it is cheap insurance. I like to use 80 grit on a big grinder, vacuum, then clean with acetone. If there is structural damage, I only use West System Epoxy Resin with a layer of Mat and woven roving in layers. You can tell if the glass is damaged when you gind it. It will flake away with ease. The solid glass is hard to grind. Go as big around the damage as you can so you never have to deal with this again. If you are on a budget, I have a little over a half gallon of West Epoxy that you can have for your repair. The mat and roving will cost you about $80-$120+depending on how much you need. The resin is a snap to mix. It comes with metered pumps and instructions. Pm me if you want the resin, I'm local and can meet you somewhere. If you don't have structural damage, poly resin will do just fine. It is much cheaper too.
