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Spoiler Dynamics - Quick Tech: Wings And Things

We've all seen them-those large objects sitting atop trunk lids and (gasp) hatchbacks-and wondered just what they hell they were doing there. "It's a front-wheel drive car," we've all thought to ourselves, "so why the hell do you need downforce in the rear?" Next came the inevitable jokes about shopping carts, table tops and drag -racing fwd cars in reverse.

So, just what is the point of having a rear-mounted wing on a front-wheel-drive car? If there was an appropriate answer, we're sure many of you would be glad to hear it; that way you could probably even pull out a few technical terms here and there as your Mom hands you her credit card and says, "OK-but just that spoiling wingy thing and nothing else!"

We scoured the earth for an answer to our embarrassing dilemma and came up with Ryan Pogy. Ryan Pogy of Wingmaster/Pogy Wings isn't the reason you can get away with that super-commando F1 wing on the back of your car, but he sure did know how to explain it pretty well.

The answer to any aerodynamic question can be complex, but there are a few things to understand about wings and how they affect a vehicle in different situations.

The automotive engineers who designed your car have a specific operating range they target in order to balance looks, safety, price and feasibility in an operating range that maxes out at about 80 mph. Owners of modified sport compact cars tend to move beyond those parameters, especially with respect to speed. That's where modifications become necessary to gain the performance and safety needed at those higher speeds.

Balance is the key to any racing vehicle. While a vehicle might be ideally balanced at the scales, aerodynamic forces at differing speeds change that equation.

Looking at Figure 1 (page 113), you can see the tremendous amount of down pressure at the front of the car (roughly 200 lb of force), and in Figure 2 the "uplifting" effect at the rear of the car (due to lower air pressure in that region). This lift causes the car to become unbalanced; the faster you go, the more these forces become pronounced. This effect is known as "bias." From there, checking out the wing placement and subsequent aerodynamic benefit on Figure 3 is a no-brainer.

Professional racing teams spend thousands of dollars on wind-tunnel design, working on the overall shape of a car to gain the desired balance. Rules and budgets often prevent too much modification to the shape of the body, but still allow the use of a wing, so a wing is usually the preferred method. Even so, the fact that you can adjust many wings (and therefore compensate for different track conditions) sometimes makes it more preferable than "permanent" body modifications.

In terms of drag racing, the best vehicle combines a balance of horsepower, traction and the least amount of weight and aerodynamic drag. If you're building a drag racer, it's important to work on all of these factors, not just horsepower.

The addition of a properly tuned wing can help increase the amount of downforce and reduce the amount of turbulent air reaching the back of the car (one of the many causes of instability) without introducing negative aerodynamic drag effects. In road racing the same rules apply, except the downforce produced by the wing helps keep your wheels planted on the ground during hard and fast cornering maneuvers.

Will any kind of wing will do? Not exactly. Weight is an issue, especially when it comes to racing. Sure you want additional downforce, but you don't want dead weight sitting on the back of your car. The aluminum wings produced by Pogy are among the lightest in the market, even amidst their carbon-fiber counterparts. And, the wings are engineered to perform, not just to look good. If looks are what you're after (and really who isn't?) you can order custom-cut wing endplates through Pogy to perfectly match your style or budget.

OK, now you know all there is to know about aerodynamic performance wings. Order a side of mashed potatoes and cole slaw and pick up a couple of those Little Bucket Chocolate Parfaits and drive up to the second window.

Aerodynamic GlossaryRear Wing:The function of a rear wing is to reduce lift or create downforce. The upturned shape is reverse compared to an airplane wing, which is intended to create lift.

Rear Spoiler:These are another means of creating rear downforce or reducing lift. Many production cars have movable rear spoilers.

PUR Polyurethane Foam: A common material used for rear spoilers and wings. There are different levels of rigidity based on purpose. Older cars used a very soft compound; newer versions are more rigid. If the part is to be painted, a high percentage of flex prep is added to keep the paint from chipping, although parts such as these are often left black.

Polyurethane RIM (aerolastic):This is created by a chemical reaction between urethane components. Common uses for polyurethane RIM include front spoilers, bumper covers, fender flares, side skirts and rear aprons.

ABS thermoplastic (Acrylonitrile-Butadiene-Styrene):A hard, rigid plastic used in a similar fashion as RIM. Parts are constructed by warming a flat piece of Lurran and then drawing it over a positive mold. When the part has cured, it is trimmed at the edges. Common uses for ABS plastic include spoilers, gauge housings, bumper covers, fender flares, side skirts and rear aprons.

Injection molding:This is accomplished by melting thermoplastic granules and forcing the liquid into a mold where it is cured. Small pieces such as headlamp covers and trim are made from injection molds.

GFRP Glass Fiber Reinforced Plastic:This stuff is often called a generic term-fiberglass, though constructed by a few different methods. With the wet lay-up method, a gel coat is sprayed into a negative mold. followed by layers of resin-soaked glass pads, mats and cloth. Cheaper methods of construction involve using a chopper gun that builds up thickness by mixing resin and chopped glass fibers and spraying them onto the mold. Dry lamination uses a pre-preg mat that is heated with a heat gun and pressed into a mold. Dry lamination is most commonly used with carbon fiber, a material much lighter than glass fiber or Kevlar. Large pieces such as wide body kits, fenders, bumpers and spoilers are made with glass fiber-reinforced plastic.

Pogy Products Inc. 11 Herbs & Spices
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