I had the privilege of being taught composite fabrication by one of the most knowledgeable and dedicated fabricators I think I will ever work with. Rich Alvarez, the owner and operator of TrackLife Composites, was introduced to me by a mutual friend and became my first sponsor in exchange for real-world R&D feedback on his new business endeavor: composite automotive aerodynamic fabrication. Out of respect for the effort and learning that it took Rich to get to where he is, and the unbelievable shortcuts he taught me that took him years of experience, I won’t share his secrets, but I can share our discussions on what and how aerodynamics help your car.
What does aero actually do?
The function of aerodynamic pieces can actually vary, but generally speaking, aero on a racecar is to either create handling force or manipulate the airstream around the vehicle to reduce resistance and turbulence. Sounds pretty straight forward right? It’s actually pretty scientific, which means I FUCKING LOVE IT.
Think of an airplane. You may have seen or heard that the shape of a plane’s wing generates lift by changing the speed of the air around it. There’s obviously more things going on, but let’s stick with this example. Just like a plane, the aero on your car creates variable wind speeds to create suction and push, which means poor aero can really fuck you up under the wrong conditions. When done properly, however, aero can make a huge difference on the drivability of your car. Let get into the different types.
Front end aero is the most common and includes common pieces like splitters, lips, and canards. If you want to get real fancy, full bumpers, fenders, and even hoods can improve performance by using the air as secondary cooling systems along with their aerodynamic benefits. Lips and splitters function mostly to create a smoother initiation in the deflection of the air around the vehicle. In a sense, they are the most important piece because they guide the air to all the places your other aero is waiting to manipulate it. Splitters can also start the under-end aero, but we’ll touch on that later.
Canards, along with some lips and bumpers that incorporate canard-style grooves and shapes, are meant to provide front-end down force. They create an angled ramp that the air pushes down on, sending it sliding up and over the car, so the angle is very important. Too steep, and you’re creating a wall that’s pushing the car backward. Too narrow, and the air is just slipping through it. Most canards and similar components have their angle built-in with their curvature, and others sweep up into their angle of attack. Angles of attack don’t vary by much, but feel free to research variations and their effects.
For the fancy folk, extra aero work can be done for things like engine and brake cooling. Fender cutouts can seriously reduce brake fade and even act as secondary aero with molded canards to create a slipstream along the side of the car. The faster and closer the air moves along the body of the vehicle, the better. Bumpers can have the same effect with cooling ducts to direct air towards radiators, intercoolers and even brakes. Hoods can further engine cooling by keeping bays cool through negative pressure vacuums. Air traveling quickly over hood scoops/vents pulls air out from the engine bay, creating a vacuum that pulls cool air in from the front. Front end aero is usually the first type of aero mod because it’s often the most immediately useful. SCIENCE, BITCHES!
Get the giggles out, I know “rear-end” tickled your funny spot. For the adults that are ready to continue reading, rear-end aero incorporates pieces like wings, spoilers, extensions, and diffusers. Just like water coming off a spoon in the sink, air can either slide off your car smoothly in one stream, or splatter everywhere and soak your shirt just below your belly button. Similar to how that water splatter might make you jump back, the path the air takes can help or hurt the way the car moves. How the air comes off the back end of your car is just as important as how the air initiates its path on the front end.
Spoilers (fully attached to the car) and wings (lifted on mounts/stilts) serve to provide down-force to the rear end of the vehicle. These parts are pretty common on most RWD/AWD vehicles, even from the factory, but are the stereotypical mod for all drive-train racecars for good reason. Rear end downforce can greatly improve handling and traction. However, there is also such a thing as “too much” downforce, where you essentially weigh down your car with the force of the air. Extensions, like those seen on drag cars, are often a middle ground between the function of a wing and the aerodynamic benefit of sending a smooth, clear stream of water off of your spoon. However, whereas wings and spoilers taper or curve at their edges, extensions tend to only operate in a single direction, and as such are usually only seen on drag cars.
Turbulence (splatter-spoon) off the back end creates bounciness and instability as the air randomly pushes and pulls the back end of your car while it tries to find a way back into a stream. Roof top diffusers try to comb the air traveling over the top of the car, while bottom end diffusers do the same for the air traveling along the sides and under your car. You may see rear end side diffusers with curls in them. These spin the air into a vortex so that it can find its path back to normality in any direction. However, many bottom end diffusers and air passes (I’m looking at you, hole-cut bumpers) are non-functional at best because of the air traveling under the car BEFORE it gets to the back end.
Remember the splitters we talked about earlier? They are often modified to extend into the bottom of the engine bay. This can be considered a “skid pan” to protect the bottom end of the motor from bumps and debris, but many people believe it helps stabilize the air traveling under the car. Unfortunately, while some splitters even have grooves like diffusers to guide the air, the second it hits the pockets of the engine bay, it creates turbulence all over again. This turbulence acts like a bumpy road of air all the way to the back of the car, where the diffuser combs it back in the big wide world. In reality, the best splitter/diffuser combination is one that starts at the furthest forward point of the vehicle and ends at the furthers back point, covering the ENTIRE bottom end. In fact, it’s so beneficial, most host organizations will bump you into a higher class just for having a full bottom end plate. MORE SCIENCE, BITCHES.
With all the mods and options, you’re sure to come across various material that make up these components. Working in a shop and actually creating these pieces with someone experienced in the practice gave me a lot of insight. Mostly, the difference between the composite material.
Fiberglass is probably the most common material, but it’s often regarded as the “cheaper” material. This is partially true. The same amount of fiberglass compared to carbon fiber or carbon Kevlar is definitely cheaper, but it’s also because it’s easier to mold than the latter two. Fiberglass usually comes in either spools, bolts, or “chop”, giving the fabricator a lot of different options on how to lay the material. This also means it’s significantly easier to repair if it breaks, which is why most body components are made of fiberglass, not carbon fiber or Kevlar. Fiberglass also flexes significantly compared to carbon fiber and Kevlar, but what a lot of people don’t know is that, when made properly and tediously, fiberglass is actually stronger (more tear-resistant) than carbon. Unfortunately, it takes a lot of work to get the resin out (the syrupy mix that hardens around the fibers and creates brittleness), so it’s not cost-effective to try for the ultra-strong fiberglass on a large scale.
Carbon fiber and carbon Kevlar, on the other hand, create very strong, inflexible pieces and are actually pretty inexpensive to purchase in spools. The associated higher cost of carbon composites comes from the more difficult process of laying whole sheets of inelastic material into curves and shapes. It often causes air bubbles that manufacturers deem unsellable, since the look of carbon fiber and Kevlar are part of the appeal. Because carbon composites are so much stiffer and unyielding than fiberglass, aerodynamic, suspension, and even engine components are often exclusively made from carbon. This also means that they are significantly more difficult to fix inconspicuously, since most carbon composites are left to show the pattern and are less flexible, which affects its ability to be “stitched” back together with more material.
Decisions, decisions, decisions.
Aerodynamics have become a key part of competitive automotive sports, and for good reason. Bad aero can cause handling issues, instability, and even cause racecars to become airborne, which is probably not as fun as it sounds. Depending the courses and disciplines you’re driving in, aero may or may not be super noticeable, but it’s become as much an aesthetic component as a performance mod. Materials and the function of each vary, so hopefully this has given some insight into your choices. Best of luck to you, and gods’ speed, drivers!