"Here's one I made earlier..." A single layer of chopped strand mat, glassed with
polyester resin, cut out with scissors from a much larger piece. This will be the blind backer, about the size and
weight of a credit card. You can also see the hole has been chamfered back along the surface with a sanding drum on
Mr. Dremel. This provides a greater area of adhesion for the fibreglass repair in a few minutes. The blind
backer must be placed inside the hull and glued to the inside to provide a surface to build upon.