Repairing cracks in fiberglass is something you can do at home
By Tommy Lee Byrd – Photography by the Author
Whether you install a fiberglass body panel because of weight savings or because certain steel replacement panels are hard to find, be prepared to make a few repairs somewhere along the way. Without question, fiberglass work can be hazardous to your health, so before grinding out the cracks, we made sure to grab a respirator. You may want to take additional precautions, like gloves and long sleeves.
As soon as the grinder hit the major crack in our fiberglass bumper, we realized how thin the material is in the damaged area. The backside had been repaired with body filler, so we used the grinder to get rid of it entirely. Having finished the grinder work to rough-up the surface for proper adhesion, we can blow off the damaged areas, as well as our clothes. Before mixing the resin, we take a piece of loose strand mat and cut it in small pieces to fit our application. Loose strand mat is much easier to work with than some of the tight weave mats. Sometimes, hairline cracks can be repaired using only resin, but we chose to use the mat as well, just to be safe.
When the surface is ready, pour a small amount of resin into a mixing cup and then add the proper amount of liquid hardener, per the product instructions. Mix it with a paint stir stick or a paint brush. You’ll use a paint brush to coat the area with resin before applying the mat. Once the damaged area is saturated, apply the mat and then re-coat it with resin to work in the fibers. For most repairs, more than one layer of mat is necessary, as you’ll be grinding away some of the material after it cures. In our case, we applied resin and mat to the inside and outside of the panel for additional strength. After applying the resin and mat, it’s time for more grinding, to prepare the fiberglass for body filler and eventually primer. MR