How to make a fiberglass wing spoiler

Updated July 20, 2017

Adding a wing spoiler to your car can make it more aerodynamic and add a little extra flair to your vehicle. A fibreglass wing spoiler is very light, so does not weigh your car down even as it retains the positive benefits of a wing spoiler. Making your own wing spoiler allows you to both customise it according to your needs, and also save some money over a commercial product. Although working with fibreglass takes a lot of patience the end result will be your very own custom fibreglass wing spoiler.

Sketch the design of your spoiler with careful attention to the location where it will mount into your car. Consider rear window visibility while designing. A spoiler that is too large may make it difficult to see through the rear view mirror.

Carve a block of foam into the shape you desire. Your carving will be the mirror of what your final product will look like. You can use a knife or razor blade for the initial carvings. After carving use 180-grit sandpaper to smooth the surface. Cover the foam with Bondo and follow the directions for adequate drying time. Once dry, use 220-grit sand paper to make the surface smooth.

Apply the polyester primer by spraying it directly on top of the Bondo. After the primer has dried, sand it with 180 grit sandpaper continue to sand with finer grits until you are wet sanding with 1000-grit paper. Drying time will vary depending on the manufacturer. 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.

Separate the fibreglass sheet into strands. Lay the fibreglass directly on top of the resin. Use the roller to remove any air bubbles trapped in the resin. Repeat six times for a thick durable piece. After the resin has dried, use a wooden mixing stick to gently pry out the wind spoiler. Use a razor blade to remove any strands of glass still sticking out.


Wear a mask to keep yourself safe from the hazardous fumes. Gloves are needed to keep the chemicals and glass from your bare skin.

Things You'll Need

  • Styrofoam
  • Bondo
  • Sandpaper
  • Polyester Primer
  • Moulding Wax
  • Resin
  • Polyester resin and hardener
  • Tooling Gel
  • 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.