How to Mold a Fiberglass Hood

A fiberglass hood will never be as sturdy as a metal hood.

A fiberglass hood can be made for a car or truck to replace a damaged fiberglass hood. Fiberglass hoods are also used to provide customized looks to vehicles. In some cases, a fiberglass hood can be used as a less expensive way of replacing a damaged metal hood. When crafting a fiberglass hood it is important to have a mold that matches your vehicle to ensure a proper fit. You can use an existing undamaged metal hood if it is the same body style as your vehicle.

Things You'll Need

• Hood mold
• Fiberglass
• Mold release wax
• Mold release wedges
• Epoxy
• Epoxy brush
• Gloss epoxy or polyvinyl acetate
• Razor
• Expanding foam
• Chopped strand mat
• Fine grit sandpaper

Instructions

1. Apply several coats of mold release wax to your hood mold. The amount of wax required will depend on your mold, but ten coats of wax should provide adequate protection of your mold in most cases and will prevent air bubbles.

2. Mix up epoxy and apply evenly to the surface of the mold to form the gel coat. Let this set for about 30 minutes. When it is ready it will feel slightly tacky.

3. Roll out and cut the fiberglass while you are waiting for the gel coat to dry. Cut four separate pieces of fiberglass.

4. Lay one piece of fiberglass over the mold at a 45-degree angle. Coat the entire piece of fiberglass with epoxy. Lay another piece of fiberglass over the first, again at a 45-degree angle. Coat that layer with epoxy before laying the third layer on at a 45-degree angle. Coat the third layer with epoxy then place the fourth layer on at a 9- degree angle. It is fine if the epoxy extends beyond the mold as this part will be trimmed off later.

5. Coat the hood with polyvinyl acetate or with gloss epoxy. This will help to seal out the oxygen and allow the epoxy to cure. This will need to sit overnight to cure.

6. Trim off any excess fiberglass before the epoxy fully cures, using the razor. You should trim off anything that extends beyond the mold.

7. Use the mold release wedges to remove the hood from the mold. Sand the edges of the hood.

8. Turn the hood over. Use expanding foam to create structural ribs. Apply the foam in a grid pattern that will look a bit like window panes. Trace a line of foam around the outline of the hood then add vertical and horizontal lines to create the grid. Allow the foam to dry. If the grid lines do not seem thick enough, add a second coat of foam.

9. Sand and grind down the dried foam to remove any sharp angles. Apply chopped strand mat to the ribs using epoxy to glass the ribs.

Tips & Warnings

• Epoxy can release strong fumes and should always be used in a well-ventilated area.

References

• CST The Composites Store, Inc.: Molding Fiberglass Parts
• Fiberglass Hood Project: 1994 Chrysler Concorde