The world of composites can be confusing, especially when you're dealing with new terms, new materials and countless different construction techniques. The difficulty that arrises is the fact that composites are used for many different applications in both the racing and non-racing worlds.
For example, the technilogy to build something like a tub for a Fomula 1 car is far different than what's required to build a lightweight, lift-off hood for a warmed-over Honda street car. On a similar note, the level of sophisitication & engineering required to fabricate something as simple as a rowing shell (which is basically an Olympic-style raciing rowboat) is again far different from the needs of the average tuner car enthusiast.
In order to cut through this confusion, we spoke with Joe Van Overbeek Race Car Bodies in Ontario, Canada (519-264-9899), in regard to composite body panels. Van Overbeek proved candid in his responses.
HCI: How do carbon fiber composites compare to traditional fiberglass in terms of weight?
Van Overbeek: Depending on the weight, a typical fiberglass hood will weight in the range of 16-22 pounds. That same hood in carbon fiber weighs between 10-16 pounds. A raw, unmounted fiberglass pro nose can weight between 15-35 pounds. That same nose in carbon fiber weights 5-10 pounds less.
HCI: Why are some fiberglass parts sold in the aftermarket heavier than others?
VO: In many cases, the ultimate weight of the fiberglass is offset by the strength requirements. As an example, we can use a high-strength woven fabric instead of our conventional fabrics. This typically adds 10% to the overall component weight, but increases the strength considerably. Keep in mind that some fiberglass components are manufactured with a chopper gun. These pieces are always heavier than a hand lay-up; but even though they are heavier, they're not as strong.
HCI: We notice on some cars where the carbon fiber literally caves in at high speed. What is the cause of this?
VO: The primary reason is the carbon fiber component in question was constructed too light. This is very easy to do. I have a theory about this, and it stem from my background as a chassis builder. Virtually all pieces, such as a Pro nose, require some form of aluminum monocoque and chrome-moly bracing to support the structure. Why make the carbon fiber piece one pound lighter than it needs to be, only to have to add another 2 pounds of bracing so it doesn't collapse? When I build a specific component, I always try to visualize how the part will react to the forces placed upon it on the car. These forces can be aerodynamic or they can simply be created by things like pit maintainance.
HCI: How does carbon fiber compare to fiberglass when it comes to price?
VO: It depends on the component. For instance, we charge $235 for a typical lift-off fiberglass hood. That same hood in carbon fiber costs $415. A typical fiberglass Pro nose costs $630, while the same nosepiece in carbon fiber costs $1250. An entusiast can save money by mixing and matching fiberglass and carbon fiber. For exampe, we sell a complete body package for certain applications. In carbon fiber, the package sales for $5,350. In fiberglass, that same package sells for $2,950. We also offer the same package with a fiberglass main body along with carbon fiber hood, nose and doors. We charge $4,075 for this package. Mixing carbon fiber pieces with the main fiberglass body can reduce the weight by 10-20 pounds.
HCI: What precautions should racers take when handling carbon fiber components?
VO: Carbon fiber is more brittle than fiberglass. Think of carbon fiber as a pane of window glass in your house and think of conventional fiberglass as a sheet of Plexiglas in the same house. During a severe hailstorm, the Plexiglass won't shatter. The sheet of "real" glass will. Typically, carbon fiber racecar parts have thinner edges and as a result, are a bit on the dainty side. Pnce carbon fiber is locked into place Dzus fasteners, it keeps its shape and is very strong. On the other hand, fiberglass is very resilient and more forgiving.
HCI: Are there appearance considerations with carbon fiber when compared to fiberglass?
VO: Yes carbon fiber has a characteristic called "print-through." You can see the carbon fiber check pattern coming through the finish. This isn't common in a quality fiberglass part, and to be honest, it is extremely difficult to get as nice a job in carbon fiber because of it.