How to Use Styrofoam for Fiberglass

Create custom models using Styrofoam and fiberglass.

Styrofoam can be a useful tool when creating custom models of cars, boats or airplanes. The material can easily be carved and used as the basis for a fiberglass model shell. Once the fiberglass has cured, the foam is removed, leaving a fiberglass version of the original design. This process is similar to the "lost wax" method of molding that has been in use since ancient Greece.

Things You'll Need

• Styrofoam
• Glue (optional)
• Carving tools
• Epoxy resin and catalyst
• Fiberglass mat
• Mixing bucket
• Mixing stick
• Paintbrush
• Acetone
• Protective gloves and goggles

Instructions

1. Carve the shape of the desired part out of a block of Styrofoam. Denser foams work best because they retain the most detail. You can use almost anything to carve foam, from professional tools to rasps and kitchen knives.

2. Carve an additional block or pillar of foam to attach to the bottom of the model shape with glue if a three-dimensional piece is needed (such as an airplane fuselage).

3. Put on a pair of protective gloves and goggles to protect your skin and eyes.

4. Tear the fiberglass mat into small pieces.

5. Mix a batch of epoxy resin and catalyst in a bucket. The resin's instructions will tell you the proper ratio of resin to catalyst (this can vary from product to product).

6. Brush a thin coat of catalyzed resin onto the foam.

7. Press pieces of fiberglass mat into the resin. Make sure there are no missed areas. You can overlap the pieces to be extra safe if desired.

8. Brush more resin onto the fiberglass, saturating it fully. If any air bubbles are trapped under the fiberglass, tap them out with the brush.

9. Add additional layers of fiberglass and resin for additional strength if desired.

10. Allow the fiberglass to cure for several hours. It is ready when the resin has hardened and is no longer sticky.

11. Slowly pour acetone into the fiberglass part to dissolve the foam. It's a good idea to do this over a sink or bucket so that the excess acetone doesn't damage your floor.

Tips & Warnings

• Use epoxy resin instead of polyester resin, which will begin to dissolve the foam before the fiberglass has finished curing.

• Always work in a well-ventilated area and wear protective gloves and goggles when working with acetone and fiberglass resin.

References

• RC Groups: The Lost Foam Technique for Making Fiberglass Parts
• Serious Explorations: Step by Step Fiberglass