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Filling big holes in the body


New member
So i've got holes where someone way before me had extra hoses running through the body. How do you guys repair them. The holes are about four-five inches. I can see where the someone tried to put a fiberglass sheet on one but it is starting to come through. I was thinking of making small square plastic flat pieces and screwing them on the body. And then, putting fiberglass putty on the other side. I know it sounds bad but i'm not sure how to fill the holes without major fiberglass work. There are about three and one big one of three holes connected.


New member
i have the same kind of holes in my "firewall" in the front. the previous owner tried to rivet pieces of sheet metal.

Brett would be the ideal fiberglass man to ask the question. that is my plan when i get back to working fiberglass, almost too cold now in kansas


New member
Keep in mind that I'm new to actually working fiberglass myself, but here's what I'd do.

As you said, cut something to fit behind the hole, like plastic. Then give that several coats of carnauba based wax. Or, you could use cardboard and cover that with that brown packing tape. Fiberglass doesn't' like sticking to it. ;)

And you'll want to prepare the 'hole'. You'll need to bevel the edges of the hole out a couple of inches at something like 30*. This is to give the new fiberglass something to grab a hold of.

Next, cut up your fiberglass matting so that you have 3 or 4 that would fit in the hole, then a few that are just larger than the hole, say by an inch, then a couple that go out to the edges of where you beveled the fiberglass.

Grab some acetone and thinly brush it on the raw fiberglass you've exposed. This will help reactivate the resin in the fiberglass and help bond the new fiberglass with the old.

Fasten your back piece in place, screwing it in (you just need to fill in the screw holes), or maybe glue it? Then start laying fiberglass in the hole, resin, then one of the smaller pieces of fiberglass you cut to fit in the hole, through to the last piece. You'll want to make it so that the final piece sits proud of the surface. That way you can sand it back flat. And don't forget to work the fiberglass as you lay it down to remove any air bubbles.

At least, that's how I'd do it given what I know. Which isn't much! lol


New member
Sounds good to me except you should have your plastic on the finished side and work from the unfinished side. That way when you remove the plastic your finished side will be smooth with maybe only minor pin holes to fill. The process description reads that way but not really stated that way. If you can get some cabosil and make a paste to start with it will stay in place better than just resin and glass.


Active member
Small screw holes I'd fill with kitty hair or just filler. Larger holes like you are talking about I would grind down one side to reduce the thickness of the lip of the hole and then start laying glass while sanding/ grinding it smooth every few layers. This will be the strongest repair and recommended for those 4-5" holes.


New member
If there's an inside area that won't be seen that you can work from, you can cut a sheet of glass cloth a little larger than the hole. Spread some resin/epoxy around the edges (like glue), lay the cloth, then spread some more over the entire cloth and let it harden. That will give you a hard bottom, then you can fill it and blend it from the other side.

Used to be a keyhole somewhere around here I think. :)