The wide body on the No. 43...
The wide body on the No. 43 Lumina helps push the car's nose down, but the car would be much cleaner if the builder dropped the air cleaner down and tried to feed it with a duct at the base of the windshield. Photo by June Boone
Consider how an airplane wing looks. That is in essence what you are trying to accomplish with the body if you looked at it from directly overhead.
The air behaves the same no matter how the "wing" travels through it, and a shape that gives an airplane lift can also help a car turn better in the corners.
"A few years ago, body shapes got pretty outrageous in the Cup garages," he says. "Now, with all the multiple templates, NASCAR has been able to limit what fabricators can do."
You, on the other hand, may have more latitude.Realistically, it may be more trouble than it is worth, but the concept is fun to consider.
The next area to address is the shape of the fenders. Make them as flat as possible. Given the same amount of air moving over a car, a flat surface will produce more downforce than a round one.
Properly shaped wheelwell openings can create downforce by helping suck air from beneath the car.
"Let's say you have a 28-inch tire and the fender opening is 32 inches," he says. "What you want is as much of that 32-inch opening in front of the tire as you can possibly achieve. You have 4 inches to work with, so try to get at least 3 inches in front of the tire-more if you can find a way to do it."
Then push the front of the opening out as far as you can.
If you want to work with aerodynamics,...
If you want to work with aerodynamics, consider what you pick to race. These three cars have nearly stock body shapes on the front, and each moves the air in entirely different ways. Photo by June Boone
The air rushing along the body will hit the flare and be forced away from the car. That creates low pressure-partial vacuum-in its wake. Air that's already beneath the car will rush to fill the vacuum, creating additional low pressure beneath the car and adding to the downforce.
He says it is common for front tire changers on Nextel Cup and Busch cars to bang the tire against the leading edge of the fender during pit stops in order to flare the edge of the opening further.
"It is all very subtle," he says. "But it happens all the time."
Breeze says to keep the top of the fender as close to the tire as you can when shaping the bodywork on a short track car.
"It should be just short of rubbing on the bodywork," he says. The object is to make the fit as tight as possible at the top and rear of the tire.
If possible, the rear of the fender opening should be a couple of inches inboard of the front.
"If you looked along the side of the car from the rear, you want to see as much as an inch of the tire's tread stick out from the bodywork in the back of the fender opening. In the front, the fender should extend beyond the tire."
Try your best to match the same type of configuration on the rear fenders, he says.
Door pillars should be as smooth as possible.
The body on this car, being...
The body on this car, being driven by Ken Schrader, shows what can be done when the rules allow moving the greenhouse around to dump more air onto the rear spoiler. Photo by June Boone
"If you look at a Cup car, you will see the B-pillar [the ones at the rear of the front doors] is beautifully radiused to try to keep the air from flowing inside the car."
Fabricators press the pillar post into a gentle curve to direct the air along the outside of the bodywork.
Breeze suggests adding a thin piece of aluminum bent at a 30-degree angle to the B-pillar to push the air away from the inside of the car.
"It doesn't have to be very big to have an impact," he says.
You have probably seen how little things in a stream can make a big difference. When you put even a thin stick in a flowing stream, you can see how the water flows around it and creates a wake behind the stick. Air works like water, and the same thing happens with even a little change in the flow of air around a car.
He cautions not to go overboard on moving air along the side of the car. You want air to flow along the quarter windows so it will end up against the rear spoiler.
"Make the deck low and flat," he says. "You can probably gain a bunch of rear downforce just by sitting on the decklid."
It isn't uncommon for a Cup crew to roll the car to the pits-after passing template inspection-with a heavy toolbox on the trunk.
"Maybe it's just a convenient place to rest their gear," he says.
Maybe not.
The last bit of aerodynamic help has nothing to do with downforce.
Although they may look crude...
Although they may look crude when parked next to a Late Model designed for pavement competition, the body shape of a Dirt Late Model shows how to effectively use the air to give bite on a slippery surface. Photo by June Boone
Breeze says that-other than at the very nose of the car-the most air pressure anywhere is in the area where the windshield and hood meet and form an angle.Air rushing along the hood slams into the windshield and builds pressure that can be used to force-feed air to the engine.
If the rules allow it, build an inlet box in the cowl at the base of the windshield to use that source of pressurized air. It's pretty easy to do. You can build a sheetmetal box off a stock air cleaner to extend the cleaner's housing to the opening. Seal the edges tightly so you don't lose any pressure.
"It doesn't have to be pretty to be effective," he says.
None of the changes he suggests are very high tech. Many of them are legal -or at least there are no rules saying they are illegal-in local racing divisions.
You may already be familiar with most of these changes, but you probably never thought they'd help much on a short track.
"They are all common sense things," he says.
But, Breeze cautions, every change creates another change.
If you build the airbox, be prepared to rejet the carburetor. If you create more downforce by working with the body, be ready to change springs and suspension settings to accommodate them.
"If you have to make changes, you know what you did is working," he says. "That's the real proof."
And what can you expect if you do everything he suggests?
"Two-tenths," he says. "I'll just about guarantee it."
Jerry F. Boone can be reached at Jfboone@aol.com.
Perhaps one of the best books on the subject is New Directions in Race Car Aerodynamics by Joseph Katz. Although Katz is a college professor, most of his book is easy to understand, even if you can't do the math. It is available at most online book outlets.