Testing Your Aero Efficiency
Clean the car and the wings very well. Tape 2- to 3-inch pieces of yarn about every 10 inches all over the top and bottom of both wings and take video or still photos of the yarn at different speeds and different slide angles. If the yarn is waving all over the place and is not against the surface of the wing, it is stalled. When it is stalled, it's making less downforce and much more drag.

Get the wing angle down until the yarn is stable and against the wing surface. It should not be wiggling more than 1/4-inch. Watch what happens to the yarn as you start to slide the car versus going straight.

The endplates on Sprint Cars are primarily advertising space. They add very little to the efficiency of the wing. You may not be able to even measure the additional efficiency. The vertical endplate stiffeners should be blended as best as possible and should all be on the left side of the endplate to give the best drag reduction. The endplates act more as rudders in the turns and reduce downforce.

Mid-Turn Aero
In the turns, the aerodynamics of a Sprint Car make a radical change. The exception to this are with those who drive like Danny Lasoski usually does. If a car tracks through the turn or has a very small drift angle, the aerodynamics stay pretty close to the same as they are on the straights. If you throw the car into a slide, something very different happens.

As the car goes into a slide, the outside endplate blankets a section of the wing at an angle, reducing its downforce. There is more reduction in downforce at the rear of the wing than the front. As the slide angle increases, the downforce reduces more and the side plate acts more like a rudder.

On the left side of the wing, the endplate increases pressure on itself, acting more like a rudder and it increases pressure on the wing surface some, adding more downforce. As the slide angle in the turn increases, the more the downforce decreases, and the rudder force increases. The car is going through a transition from cornering with traction, to cornering with rudder force and reduced traction. The rudder force, or leaning on the side plates are holding you in the turn, but you are losing traction.

The more you lose traction, the harder it will be to get a good drive off the corner. If you slide a car in smoothly, like Dave Blaney does, the transition will be easier to manage. If you throw the car into the slide, the transition will be radical and upset the car. If you can anticipate the violent upset, you will be OK. The smoother the upset, the faster you should be. The less the slide angle, the more traction you will have.

Load Transfer Due To Drag
Bob Bolles and I have talked in length about something else going on here. The wing is stalled, creating a huge amount of drag. This drag is centered far above the car. There is a leverage arm from the ground to the center of the drag force. This drag causes load transfer to the back and is shifting its force causing what appears to be downforce on the rear wheels.

It is not airfoil induced, but drag induced from load transfer. It takes a tremendous amount of wasted horse power to make this work. This force is also trying to lift the front wheels off the ground. This force goes up with the square of your speed, meaning if you double your speed, you have four times the drag and a similar increase in load transfer.

The stalled wing also has other affects. It creates a large force trying to stop the car all the way around the track. When you lift the throttle the car has a tremendous stopping force. This stopping force may make up for the lack of braking power needed to enter the turn. The problem is it eats up your horsepower everywhere else. It could be using up more than 30 percent of your power. The drag also makes your speed more constant all the way around the track, constantly slower.

If you clean up the angles of the wings, which will take some testing, you will get more downforce and less drag. You will get a much higher straightaway speed if you do this. My question is; if you make the aerodynamics more correct, will you have the stopping power to make the turn? You may not. On the other hand, if it puts you in front on the straight, the other racers have to find a way around you.