Detroit Metro Soap Box Derby

DMSBD Tech Tips
Installing Cockpit Foam - by Ian Carsten

Successfully installing cockpit foam on a derby car requires planning and preparation for a neat, durable job. First, decide how much of the foam you will use.

In both the stock and superstock cars, the front piece is mandatory as a face protector. The rear piece is optional. It is useful if you are trying to close off the rear of the cockpit for a small driver. The superstock rules also allow two sidepieces to close off the cockpit even more.

The only adhesive that seems to work successfully to install foam is conventional liquid contact cement applied in two separate coats. We have had identical results with both Weldwood© and Liquid Nails© brands of contact cement.

The clear, thick Goop© brand sold in purple tubes doesn’t seem to work as well. Goop is good, however, for repairing tears in foam or re-gluing small separations between the foam and the plastic. We always carry a tube with us to races for emergency repairs.

If you have a superstock and you are going to paint it, use masking tape over the area of the lip where the foam goes. Gluing over paint doesn’t work well because the glue tends to dissolve the paint and gives a weak bond.

If you already painted the lip of the shell, you should use masking tape on the area where you want the paint to stay and use paint remover to get the paint off the area where the foam goes. You need bare plastic for the contact cement to stick to.

When you have decided how much foam you will use, you need to practice positioning the foam close to the cockpit lip and carefully pushing it against the lip a little bit at a time to adhere it. Perfecting this prior to applying the glue is important because the instant the two glued surfaces touch that is where they will stay. It is nearly impossible to lift out-of-position foam from the lip once the two glued surfaces touch.

We like to make a small reference mark with a pencil on the front center of the cockpit just above the lip and a corresponding mark on the top center of the foam. Then the foam is bent back sharply in the center. We carefully line up the marks with the center of the foam flush to the top of the cockpit and move the foam forward until it touches the lip.

If you need a second pair of hands to help steady and guide the foam into position, don’t hesitate to get help. If you get it wrong, it usually spoils the piece of foam

Our next step is to slowly work one branch of the foam away from the center and press it against the lip a little bit at a time until that half of the foam strip is against the lip. Then we do the same with the other branch until the entire length of the foam has been pressed into position against the lip.

When you are satisfied you can position the foam accurately, you can prepare the lip for gluing. Contact cement is sold in small bottles with a tiny applicator brush. It is too small for our intended purpose. It’s more practical to buy a pint or quart can. You should also purchase a one or two-inch wide paintbrush, a can of contact cement solvent to clean the brush, and some 400-grit abrasive paper.

Clean the lip with alcohol to remove any grease, oil, or fingerprints. Position the foam against the lip to determine what part of the lip has to be roughened. Mark the ends of the area with pencil. Now roughen the lip with the 400 grit paper to provide some “tooth” for the cement to stick properly.

Make the index marks on the foam and the shell as mentioned above. Use the paintbrush to apply a first coat of cement to both the lip and the foam. Since the foam is so porous, be generous when coating it. Immediately clean the brush in contact cement solvent and rub off the residue onto a rag. Allow the first coat to dry 40 ~ 45 minutes.

Apply a second coat of cement to both the foam and lip and allow it to dry 15 minutes. Re-clean the paintbrush thoroughly while the adhesive is drying. Using the positioning technique you practiced earlier, apply the foam. Press it firmly against the lip of the shell along the length of the foam.

Use the same technique to attach the rear piece if wanted. If you want side foam on a superstock, first attach the front and rear pieces. Then you can practice positioning the sidepieces before gluing them. It usually works best to first butt one end of the side piece against one of the previously installed front or rear pieces and slowly bring it against the lip a little bit at a time until the entire sidepiece has been nested into position.

Allow the bond to harden overnight before putting the driver into the car. This technique gives a neat-looking, strong bond that holds up well.

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