Re: Epoxy or Polyester ?
If you are patching polyester resin you can probably just use polyester resin. Its less expensive and cures faster so you can put multiple layers on in 1 aftenoon. If you are working with wood and polyester I would go with epoxy. When working with wood epoxy bonds better to wood than polyester. Epoxy is also more flexible than polyester which is another reason it works better with wood. Boats are usually built out of polyester resin because it has adequate moisture impermeability, is less expensive, and easier to work with in production lines. High end composites for boats, race cars, and airplanes are usually made out of epoxy because it is stronger and has a higher bond strength.
