Making a Fiberglass Bumper

Updated July 20, 2017

If you have been in a car accident and have damaged your bumper, you will find that it is very costly to replace it. However, you can learn to work with fibreglass to make your own bumper rather than spending hundreds of dollars on a new one. You can even add in personalised customisation in your design, making your car one of a kind. Although working with fibreglass can be rather messy and time consuming, with a little patience anyone can make a fibreglass bumper.

Draw out how you want your piece to look. Pay special attention to the location of where bolts and screws will be. Although you can throw in your own personal flair to the design, do not take any focus away from the dimensions.

Carve a block of foam into the shape you desire. If you cannot find a chunk large enough to cover the entire bumper, use smaller pieces and glue them together. You can use a knife to cut out the large pieces and sand it into the design you would like. Cover the foam in Bondo and sand it down.

Spray on polyester primer. It should be very think and is made specially for moulds. After the primer has dried, sand it with 180 grit sandpaper and progress to 1000 grit wet sandpaper. After you are done sanding, polish it to a high gloss. Let it sit for 3-4 days while waxing it every day with mould wax. Spray three coats of tooling gel and let it sit until tacky. Once tacky, brush on the resin.

Break the fibreglass mat and into small even pieces. Lay it on top of the resin, you can use a roller or brush to smooth out any air bubbles underneath. Repeat three times, making sure the fibreglass is thoroughly soaked with the resin. After you let it dry, you can use a razor blade to smooth out any glass. Once the fibreglass has cured, use a wooden mixing stick to gently pry out your piece.


Use gloves at all times. You are dealing with glass and chemicals and do not want any of those on your hands.

Things You'll Need

  • Styrofoam
  • Bondo
  • Sandpaper
  • Polyester Primer
  • Moulding Wax
  • Resin
  • Polyester resin and hardener
  • Plastic mixing cups
  • Brushes
  • Fibreglass roller
  • Fibreglass mat
  • Razor blade
  • Wooden mixing stick
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About the Author

Quyen Tong began writing professionally in 2006 when he launched a nutrition information website named Complex Nutrition. He has graduated from Purdue University with a degree in aeronautical engineering and has submitted technical papers regarding the NextGen project and future flight trajectories for air travel within the United States.