I just did exa tly the same thing on a beachcomber
trailer. Here is what i did on the advice of a 35 year fiberglass veteran.
- do the repair fromthe inside uaing polyester resin, gel coat and 1-1/2 oz fg mat. Do not use epoxy.
- grind a bevel on the inside perimeter of the hole using the 1:12 rule. (Bevel width sbould be 12 times the thickness of the wall, so fpr 1/8wall,bevel back 1-1/2 inches.)
- cut three pieces of mat. One exactly the size of the hole, one 1 inch wider and higher than the hole and one 2 inch wider and higher than the hole.
Place a piece of non atick backing on the OUTSIDE. i used sheet alum like a siding installer would use. Cut the allum 1 inch wider and taller than hole. Prep it by applying at least 3 coats of paste wax, polishing in between coats. I used Minwax wood polish and it worked great.
- apply alum to outside, centred over hole and tape all around perimeter with red tuck tape wax side in of course
-apply a generous coat of get coat on the alum from the inside, allow to cure overnight.
- apply a generous coat of resin to repair area then first (SMALLEST) piece of mat. Pounce the area with your brush all over to remove any air bubbles. Apply more resin then the next piece of mat, pounce. Repeat with third(LARGEST) piece of mat.
- cure overnight.
-Next day remove alum sheet.
- the surfac
e ahould be pretty darn good. Apply filler and sand as necessary to prep for paint
- i reaired several holes using this method and it worked like a dream.