Fiberglass Repair?

[bigastrout]

I need to do some fiberglass repair to a below the waterline crack in my boat. I don't want the band-aid fiberglass job that fails because its poorly bonded to the gel coat. I want to do it right by cutting the damaged area completely out replacing it. Does anyone have any tips?

[jmay]

I've done my own fiberglass repairs on an old snowmobile cowling that cracked. I also used to work a marina. We sub out glass work because it is so labor intensive however this is my 2 cents

If you are going to cut out the bad spot I would cut a little bigger than just the problem area as all fiberglass repairs are secondary bonds, so they rely upon the adhesive quality of the resin for their strength. Marine applications where chopped mat is most prevalent probably best fix is to use a general purpose polyester resin. When Prepareing the surface for the addition of gel coat wipe the surface with acetone and a clean rag to remove any wax, oil or grease which might contaminate the repair by messing up the adhesion