Re: Correct fiberglass repair technique
Nicked a few holes in mine during removal. It's no real big deal. Ditto the poly vs epoxy thought. Your hull is polyester anyway, so use polyester. This whole bond thing is really a technicality if you ask me. Scuff the heck out of it. 34 grit or courser. The formula for determining the patch area is 1 to 12. IE, if you've got a 1/4" thick hull, multiply that by 12 to get the total patch area. 12 X 1/4" = 3". So. just scuff out a minimum of 3" from the slice, if your hull is 1/4" thick, in all directions, cup it if you want to, have your glass precut and ready to go. It's a lot easier than cutting and laying at the same time. The first layer should be overlapped by the second layer by at least 1" on all sides,, which is overlapped by the 3rd, and so on. The think is that the increasing size of the subsequent layers helps with the mechanical bond. The layers laminate to themselves chemically. Think about it, when they build these things, a fully cured hull comes down the line and needs to be prepped for the stringer and deck work. That whole bond, all of it, including the deck to hull layer is this much maligned mechanical bond. As I took mine apart, I was amazed at the strength of the hull to deck bond. Mine is 30 years old. There was no prying it off. Not without shearing the hull itself. It had to be cut. When I got down to the original hull glass, I noticed a pattern of ROUGH gouges about a 32nd deep everywhere deck adhered to existing hull. Must be some kind of roughing tool they use in preparation for the deck tie in. If ya can't pry it loose with a 4 foot bar and a sledgehammer, I have got believe it's a pretty good bond. And yeah, that one was mechanical. On the mat, cloth thing, the mat between layers of roving or cloth helps to integrate the layers by changing up the directions of the individual strands between layers.. All fabric has a bias. Even 18 oz roving has a bias. Mat just mixes it up. Makes it stronger. Mat is just plain lousy for an outside corner or radius or a tight inside corner or radius. The orientation of the strands will not let it lay well unless the surface is pretty flat. Mat will actually break in two if you fold it. Thats where roving and cloth come in. I had some tight outside radius work on the exterior of my new transom. Mat just turned into gooey hairballs as I tried to get it to conform the the shape I needed. The more you work it, the messier it gets. The adhesive used to hold the strands together is designed to disolve in polyester resin. Used roving next time, no problems, hugged the curves and inside corners fine, with a little patience. Finished off with 6oz cloth for a smoother look. My 2 cents worth. KR
