How to repair automotive fiberglass

As more and more auto parts are made of fiberglass, it is important to know how to make repairs on the material. Gouges and holes can be fixed in a body shop, but often the cost is very high. The idea of ‚Äč‚Äčautomotive fiberglass repair may seem intimidating, but in reality it is much simpler than most people think. The most important things you should have are patience and attention to detail.


Prepare the car

  • Sand the area around the hole to be repaired with a palm sander using coarse sandpaper. You want sand through the layers of paint up to the fiberglass. You will know it is there when the white fiberglass layer shows. Keep it as rough as possible to ensure good adhesion with the new fiberglass.
  • Cut a piece of sheet metal a few centimeters larger than the hole if it is a large one. If it is a small hole, you can skip this and go to section 2.
  • Place the metal sheet on the bottom of the hole and shape it to fit the contours of the car. This will give the fiberglass something to rest against.
  • The holes of the drill through the fiberglass of the car and the metal sheet around the damaged section.
  • Place the metal sheet for the car with bolts and nuts. The heads of the screws must be on the outside, the nuts guaranteed on the bottom.
  • Grind the bolt heads flush with the surface of the car.

The addition of fiberglass

  • Cut the fiberglass cloth and tear the fiberglass mat into pieces slightly larger than the hole to be repaired.
  • Mix a batch of fiberglass resin with the catalyst in a disposable bucket. The exact proportions will be in the resin container.
  • Painting a catalyzed resin layer in the sanded area around the hole (and on the metal sheet if used).
  • Add a layer of fiberglass to the resin. Start with a cloth if it is a large hole with metal sheet; for a small whole start with mat. Cloth is thicker than the mat and is good for filling in larger areas, but it is easier to soft sand mat and should always be used for outer layers.
  • Touch more resin in the fiberglass with a brush to saturate completely. Touching (unlike brushing) eliminates trapped air bubbles, which greatly weaken the fiberglass.
  • Allow the fiberglass to heal completely (until it is no longer sticky) if the hole is small with no sheet metal. This first layer will provide a basis for the rest of the fiberglass. If it is a large hole, go directly to the next stage without letting the resin cure.
  • Add more layers of fiberglass and resin until it is flush with the surface of the car. Remember to use a mat for the outer layers.
  • Allow the fiberglass to cure for a few hours for maximum hardness.
  • The fiberglass of the soft sand with the surface of the car, from coarse sandpaper and move to increasingly thin grains. As the sand, feather the edges of the repair area in toward the center.
  • Seal fresh fiberglass with fiberglass enamel.
  • Fiberglass base paint over the repair work to make it ready for painting. Two to three thin layers are better than a thick layer.
  • Allow the primer to dry and wet sand with a fine sandpaper to remove any late imperfections.
  • Paint the repaired area to match the rest of the car.

Tips and warnings

  • Only work with fiberglass in a well-ventilated area.
  • Wear gloves and a paper suit. Resin fiberglass and dust can severely irritate the skin.