How to Use Fiberglass Cloth for Automobile Repairs

Lead Image
  • 2-4 hours
  • Beginner
  • 50-300
What You'll Need
Fiberglass cloth
Utility knife
Palm sander
Felt roller
Air roller
Latex gloves

When you have to make a repair on the bodywork of your vehicle, you can use fiberglass cloth to fix many different areas. Fiberglass cloth, properly applied and hardened, will leave the body ready to paint so it looks as good as new. Although bodywork can seem complex and intimidating, it's actually quite easy. It takes a little patience and it can be slightly messy, but you'll find you can easily make a repair to your car body using fiberglass cloth.

Step 1 - Prepare the Surface

You cannot start using the fiberglass cloth until you’ve prepared the surface to accept it. Start by using coarse-grain sandpaper on the entire area on and around the repair. The surface has to be scuffed until it’s smooth to the touch and dull.

Now, take a rag and acetone and clean the area you’ve just sanded. This gets rid of dust as well as oil and grease. If there are any traces of these, the fiberglass will not bond to the surface.

Step 2 - Cut the Cloth

Using the utility knife, cut one layer of the fiberglass cloth to the size of the area needing to be repaired. You’ll need to cut a number of other layers, each one smaller than the last, until you have enough layers to fill the area being repaired. Stack them to make a mat of fiberglass cloth and put it aside for a few minutes.

Step 3 - Mix the Resin

To mix the resin, pour it into a bucket along with the hardener. Use the proportions indicated on the containers. Put on a pair of latex gloves before working with the resin mix, then stir the mix very thoroughly until you achieve a smooth consistency. Take the felt roller, dip it lightly in the resin mixture and roll it lightly over the repair area to leave a very light coating.

Step 4 - Apply the Cloth

Now soak your smallest piece of the fiberglass cloth in the resin mixture until it’s taken on the color of the resin mixture with absolutely no white areas showing. Apply this piece to the damaged area. Take the air roller and roll over the piece of fiberglass cloth until there are no air bubbles.

You need to repeat this procedure with each slightly larger piece of cloth, putting one on top of the last. Roll each one until no air bubbles remain. You’ll finish with the largest piece of fiberglass cloth. Roll over this hard with the air roller. There’s no need to wipe off the excess resin.

Now leave the fiberglass cloth to cure, at least overnight. Wait until it hardens fully and feels cool against your fingers.

Step 5 - Sand

Start by using a medium-grit sandpaper on the fiberglass cloth repair, then switching to a fine grit. Sand lightly then follow up by using a palm sander. You need to keep sanding until the fiberglass area is smooth. It should be level with the area surrounding it, at which point it will be ready to be prepared, primed and painted.