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How to Design Your Own Custom Body Kit

Sometimes you can't get the car body you want, even with the growing selection of aftermarket parts. If you have the skills, you can design a DIY body model that will make your car truly unique.


  • Step 1: Remove any dust, overlay the finish with a coat of glazing putty, and, when it's dry, sand the entire surface with fine-grit sandpaper until it is smooth.
  • Step 2: Apply a coat of epoxy resin to the mold, and lay the first layer of fiberglass on it, smoothing the material down around the corners and edges. Repeat with the second and third layers of resin and fiberglass, pressing out any bubbles with a squeegee or blunt metal tool as you go.
  • TIP: Let the fiberglass and resin cure for at least 48 hours before proceeding.
  • Step 3: Make sure the part fits properly on the car. Trim or file the edges with shears or a grinding wheel if necessary.
  • FACT: BMW's concept car, called GINA, has an almost seamless skin exterior made of flexible fabric, rather than metal and fiberglass.
  • Step 4: Drill holes for mounting the piece to your car's frame, apply primer and paint, ant then mount the piece on your car. Congratulations, your custom design is complete.
  • Step 5: Cut three plies of fiberglass or matting to a size slightly larger than is needed to fit around your foam mold.
  • Step 6: Prep your chiseled foam for fiberglass by applying a layer of water-based contact glue to the front and sides and covering it with a layer of aluminum foil or duct tape.
  • TIP: Make sure your custom modifications are compliant with local vehicle laws and regulations before you go any further.
  • Step 7: Sketch your design or make a computer graphic model of your car body. Include detailed measurements of where each line and indentation will go.
  • Step 8: Remove the bumper, trim, or any other existing car parts that will be replaced by your custom attachments.
  • Step 9: Attach high-density foam to the place that you want to modify, and then draw the lines where you will cut the foam to match your design.
  • TIP: Cut the foam a little thinner than the desired thickness of the final product, since the addition of fiberglass layers will add thickness.
  • Step 10: Use cutting and carving tools and a medium-grit sandpaper to shape the foam to appear exactly as it does in your design. Measure the depth of your cuts on opposing sides to ensure symmetry.
  • : Wear protection, including a respirator and non-porous disposable gloves, when working with fiberglass, resins, and epoxies.

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