In last month’s article, I talked about our race against the clock to complete the customizing of the Ford Mustang GT in time for SEMA. Now that the dust has cleared, I’ll explain in more detail the mock-up procedure for our new parts, including how our plugs were made.

The liquid foam front bumper is formed around the existing body.

Scoops, front bumper and grill mock up

A plug is a prototype part used to make a mold of the final part and subsequently to produce the part over and over again. We used the same process that has been used in the fiberglass parts industry for decades, which was actually adapted from the old process of wax molding. Wax molding goes back several centuries and used wax molds and  liquid metal to make the metal parts. In our case, we used polyurethane foam, liquid foam, and fiberglass.

Once the project was approved, my concept drawing determined that I needed to fabricate about sixteen custom parts. This was going to require some help. I called my friend Benjamin Esquivel, a master with twenty years of experience at fiberglass tooling and prototype design.

He started in the camper shell business, then moved on to making custom fiberglass parts for the motorcycle racing circuit. His talents also include architectural design and making carbon fiber bodies for funny car dragsters. With his help, we made all sixteen fiberglass parts and also have the molds to continue production.

Materials
We used 3 oz. fiberglass matting, resin, and catalyst for our splashing, which I will explain in a little bit. We used 4 lb. polyurethane foam to shape and make prototype plugs of the hood scoops, side skirts, lower parts of the bumpers, and the rear wing.

For the most part, the front and rear bumpers were made using molds made from cardboard around the car and liquid foam. For larger areas, the 4 lb. polyurethane foam is impractical. We need to mock up a quick and dirty cardboard mold to pour the liquid foam into.