Repairing Fiberglass Panels - Glass Act

Mention "fiberglass" and "Chevy" in the same sentence, and most people immediately think "Corvette." It's a natural reaction, since fans of Chevy's sports car have been wrapping their, uh, persons in fiberglass for more than 50 years. On the other hand, Vettes certainly aren't the only Chevys running around with fiberglass body panels. Thanks to the aftermarket, thousands of other Bow Tie models run the streets--and the strip--wrapped in this lightweight composite material. All these 'glass hoods, fenders, bumpers, and front clips are at least as prone to battle damage as their metal kin, so we decided to look at what it takes to smooth over a fiberglass crackup.

The first item on the agenda, however, is deciding whether or not a panel should in fact be repaired. In most cases, this isn't an issue of whether or not the panel is repairable--it'll usually be pretty apparent if a panel has been damaged too badly for repairs. As with many things, to repair or not to repair comes down to the bottom line. Fiberglass is simply strands--or fibers--of glass that have been formed into mats, which are then bonded into structures. The structures favored by gearheads are lightweight and inexpensive, and therefore popular. The low cost of many 'glass panels makes repairing and repainting them a bad investment.

"You have to decide if repairing the part is cost effective," declared John Morrow, bodywork honcho at Johns Customz & Performance in Torrance, California. For instance, a typical fiberglass cowl-induction hood may cost $300-400, with bumpers and fenders running even less. A new part would cost less than the repairs, and there's still paint to pay for. On the other hand, a front clip can cost $800, and a "fancy" hood can approach this amount. At this point, repair becomes cost effective. Our guinea pig, an '84 Corvette, fell into this range. This Vette had an unfortunate encounter with the rearend of a Buick, leaving a hole in the hood. A used clamshell hood for a C4 Corvette can cost $900 (and quality may be iffy), while a new lid runs well over a grand. The cost of this repair, $400-500, made fixing the old a better investment than replacement.

Say you've come to the same conclusion--now what? The first tip Morrow gave us was on material--Johns Customz uses marine-quality fiberglass mat for the simple reason that it's designed to handle continual exposure to the elements. The second tip he gave us is to always work with clean material. This applies to both the new mat you're laying on and the old 'glass you're repairing. "The strands should be solid white," Morrow told us. "Fiberglass is like a sponge--it soaks things up." Once a panel is damaged, it's exposed to the elements, as well as dirt, oil, and other contaminants. The new fiberglass actually bonds with the old--picture the fingers of both hands interlaced. New strands intermingle with old. A repaired fiberglass panel should be just as strong as the original. For this reason, these impurities must be removed before new material can be laid on.

Speaking of fiberglass' sponge-like quality, the mix of resin and hardener used to bond in new fiberglass mat is critical. "The rate of hardening can varies according to the mix," Morrow told us. "But add too much hardener, and the material will crystallize, making it brittle and breakable." Be safe, we say, and follow the manufacturer's instructions until you've gained some experience working with these materials. Experience, of course, can make a job look easy, so we knew we were in good hands when Morrow turned us over to his top-notch 'glass man, Adrian Herrera. Herrera has been working with fiberglass since he was a child, building models and even a bicycle out of glass mat and resin. One of his specialties is creating custom body panels, so the prospect of repairing our Vette's broken nose didn't intimidate him in the least.

Herrera's skill at working in fiberglass proved impressive, so we weren't worried about the strength of his repairs. During the process, however, we did fret a bit about how the repairs would look. When the decision is made to repair a damaged 'glass panel, we all want more than a mere repair; we also want the part to look as good as new. Our expert bodyman achieved this as well. Skill and experience in working with fiberglass are crucial, but so is something of an artistic touch, the ability to form new material into an existing fender- or hoodline. We also replaced our subject Vette's tweaked urethane front bumper cover with a replacement from Mid America Motorworks, just to see how good the hood repair came out. As you'll see below, finding any of these repairs will be near impossible once the car is painted--and isn't that how it should be? Follow along, and we'll take some of the mystery out of the mysterious art of working with fiberglass.