Does the word fiberglass intimidate you? When you think of fiberglass maybe you are thinking you need a whole new set of skills. If you have ever used, or should I say mixed bondo, you are halve way there. Working with fiberglass can be very effective and very simple. The key to a solid fiberglass repair is to plan ahead of time. Make sure you have the proper equipment. You will need:
* Fiberglass mesh, or preferably a fiberglass kit. It includes enough material to fix a rather large area
* Get yourself a decent pair of rubber gloves
* Depending on the size of the repair you'll need a piece of cardboard, for mixing the resin/hardener
* Another piece of cardboard and some duct tape, (read below)
* A good industrial or at least a sharp scissors
* A old small paint brush, or some cheap acid brushes for applying the resin
When preparing to repair fiberglass, and you have your supplies as far as fiberglass necessities, of course you'll want to analyze the damage very good. This gets overlooked very easily. When fiberglass is damaged in an accident it usually cracks, even if they are hair line cracks. They may not seem like much, but when it comes time to paint and certainly over time they will show up. You cannot build a bridge over cracked fiberglass with primers nor does bondo (body filler) hold forever. You will need to grind down all the damaged areas!
To Start wipe the area off where you are now going to grind. You'll want to grind the area and all the little cracks down, at least a 1/16 of an inch. If you can grind further go ahead. If you can get behind the damage like say on a hood of a semi, then you can grind the inside as well. This is the proper way to do it, but I have had great success either way.
Take a tape measure and measure the area you have ground. If it's ten inches then you will need 30 inches of fiberglass matting. When repairing fiberglass it is essential to lay down 3 layers of mesh intertwined together to get the proper strength to hold the repair together, forever. You do not want vibrations or minor bumps to crack your repair again. Of course you cut it wide enough to fill the hole. Most fiberglass repairs will need some sort of backing plate behind the huge hole. This is where the other piece of cardboard comes in. Cut the piece an inch or so larger than the damaged area all the way around. Now the duct tape. Tape it in there real good for now. You are gonna have to find a way to get behind it. Use what works. I have had it where I can't get behind So I tenderly have had to nurse it from the front side, holding it tight in place until it is set up, wear your gloves, you'll be in good shape..
Now for the mixing of the fiberglass with the resin. Resin is the bonding agent, mixed with the hardener so it sets up. It is somewhat like mixing body fillers. It basically uses the same hardener, same principle in mixing. There are a few different ways to do the next few steps:
* Pour out enough resin to be sure to coat all the pieces of mesh completely. You'll normally need a 1/2 cup or more for most repairs. Don't be skimpy here, you want to have enough to coat the glass. If you pour it in a container try to keep an idea how much is in there. Apply a few inches of hardener in the container and get mixing. If it's hot you have about 10 minutes to to work so again have your fiberglass mesh ready to go. Take your mixture of resin over to the vehicle you are working on and brush liberally around the damaged are with the resin, put it as thick as will hold, but try not to let it go running onto the floor or the tires:)
* Another more messy technique I've seen is to pour out the resin on the cardboard and mix it there. Take your mesh and dredge it in it till it is coated... like chicken. Caution though, this is very messy, I shake my head when I see this, but it will coat the mesh and probably the work bench and you really well. Use the first method and paint it on.
* Take the cut mesh and press it around the outside where you put the resin, you want it to soak in there together. Apply one piece of mesh at a time, this will allow you to soak each piece real good for a strong fix. If you have your cardboard backer it's probably gonna be a permanent part of the repair. If you want it off you have to work at it carefully before the resin is set, but avoid allowing the fiber glass to fall in the hole, so let it set up a little and work quickly. Once you have the first piece on apply resin over the entire mesh, do these steps with all 3 pieces. Don't worry if the fiberglass matting seems to be falling apart, it's a good thing. The more intertwined the pieces are the stronger the repair.
* Let the repair set till it is hard as a rock. You want to grind on it or use a sander with 36 grit sandpaper to begin to flatten and form it out. DO NOT sand through the fiberglass around the edges of the repair, that's why we ground it down another 1/16". It should hold and be able to sit there without any problems, you'll be grinding and finishing off with a couple coats of bondo.
* With the repair set up and ground down it may not hurt to test the strength of the repair. It should not give in, you should be able to push on it and see the rest of the panel moving in and out with you. If not repeat the fiberglass steps again, add a few more pieces and bond it to the strongest areas.
* If you feel the repair is strong enough, blow it off good and begin with the bondo. If you haven't read Bondo Basics - The Art Of Bondo, now would be a good time, you'll want to read that before you begin with fiberglass.
Those are the basics for you, you can repair almost anything with fiberglass. Done properly you'll patch boats, be able to put a front end on a Corvette, fix or replace a headlight bucket on your beloved Semi, I've even fixed bumper covers with it, to hell with the bumper repair kits!
