Skirts....

[Sumner]

   

We are trying to improve on the center of pressure on Hooley's Stude.  

The rule (4.CC.5 Skirts) says:

Streamling devices.........................thick.  The skirt shall be in a single plane, mounted to the bottom of the body but cannot modify the contour of the body.  The skirt may extend from the centerline of the front axle to a vertical plane at the rearmost point of the original bodyline.

We don't want to do anything between the front and rear axle, just behind the rear axle where the pan slopes up.

Does the cardboard mockup below the rear quarter panel in the picture above meet the requirements to be considered a skirt?

Does it have to be parallel with the ground on the bottom?

Can it be any size vertical we want as long as it isn't on the ground and doesn't extend past the rear of the car?

The car runs Competition Coupe.

Thanks,

Sum

[dwarner]

Sum,

Those look OK to me. The skirts need not be parallel or perpendicular to the ground. You may want to ask a more aero savy person than I as to the most efficient mounting.

Warner

[Sumner]

 

Thanks Dan for the info.  The picture above is getting closer to what we will do.  

The skirt will be less than 1/2 inch thick, but we want to know if any bracing is allowed on it.  We would like to come down at an angle from the rear bumper area with a small brace to the lower back corner of the skirt to support it and keep it stiff so that it can do it's job if the car starts to get sideways.

Would that be allowed?

Thanks and a good 4th to you and everyone else here,

Sum

[PorkPie]

Looks too short for me, so you get the whole turbulences from the rear wheels between and outside of the skirt. Your idea is to get a clean downforce airflow between the two skirts. This is only possible if you extend the skirt forward between the wheels - axle? driveshaft? - best would be a extension to the "front" of the wheels.
Height is ok for your idea.

Think fast....always

Pork Pie

[Sumner]

Looks too short for me, so you get the whole turbulences from the rear wheels between and outside of the skirt. Your idea is to get a clean downforce airflow between the two skirts. This is only possible if you extend the skirt forward between the wheels - axle? driveshaft? - best would be a extension to the "front" of the wheels.
Height is ok for your idea.

Think fast....always

Pork Pie

We've moved it out so that it is on the outside plane of the rear tire.  That is the best we can do for this year.

I still am trying to find out if a 45 degree support rod coming from the rear of the car to the bottom rear of the skirt is permissible according to the rules?  

Does the skirt have to get all of it's stiffness from the root area only where it attaches to the car?

Does anyone know?

Thanks,  Sum

[PorkPie]

If you mean a support bracket to hold the skirt better it had to come from the outside, due to this that the "vaccum" would be between the skirts.

To my opinion is this not necessary, the "vaccum" would be only a small percentage, due to your current design.

If the skirts are fixed properly to the body it will be strong enough.

Use a proper flange against the bodywork and its fine, if you screw them, get the screws on the outside into the tire turbulence.

See ya

Pork Pie