Aerodynamics in off road racing

[bajaxp]

I am curious, why there is not much consideration for aerodynamics when building off road cars today. I have asked a few opinions and the overwhelmingly consistant theme that comes back is that 'it doesn't matter.' Really? Most desert race cars and trucks look about as aerodynamic as a bathroom door (haha). I find it odd that 800 hp Trophy trucks 'only' go 140-ish, and 120 hp 1600 lb Class 12's can't even break 100 mph. Back in the 70's and 80's you had Big Oly and MT's Challenger with big wings and Parnelli even went so far as to have his driving lights hidden and tucked into the leading edge of the aforementioned 'wing.'

So what say you Desert Familia...could better aerodynamics improve current desert rigs? Traction, cornering, top speed, comfort, etc.

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[Will_Higman]

This should be a good thread I think opinions have changed greatly over the last 10 years.

The more aero the better…

[martein]

A lot of people are changing to smaller lights and LED's and finding another 5-7mph of top speed I know we did. It is hard to get an aerodynamic package up front with arms swinging 30". If you look at a lot of the class 1 cars they make an attempt to smooth the curves behind the tires and suspension but bottom line is your aerodynamics are shot by the time it reaches the body. I know our car builder has moved just about everything around on the car trying to free up some air flow but there is only so much he can do. The full body classes have it a lot easier

[Ol' Curmudgeon]

The ground clearance issue certainly complicates any aerodynamic improvements.

Has anyone tried skirting to direct airflow out from under the vehicles?

The frontend of the Class 1 I raced got pretty light over 110 MPH, with the front skid plate ramming air under the floorpan.

[GunnSlinger]

I am curious, why there is not much consideration for aerodynamics when building off road cars today. I have asked a few opinions and the overwhelmingly consistant theme that comes back is that 'it doesn't matter.' Really? Most desert race cars and trucks look about as aerodynamic as a bathroom door (haha). I find it odd that 800 hp Trophy trucks 'only' go 140-ish, and 120 hp 1600 lb Class 12's can't even break 100 mph. Back in the 70's and 80's you had Big Oly and MT's Challenger with big wings and Parnelli even went so far as to have his driving lights hidden and tucked into the leading edge of the aforementioned 'wing.'

So what say you Desert Familia...could better aerodynamics improve current desert rigs? Traction, cornering, top speed, comfort, etc.

Ive always wondered the same myself, and have always heard the same line "it doesn't make that much of a difference" but personally I think it would. To be quite honest, I think it has a lot to do with the way it would make a car/truck LOOK and thats why some people forgo the thought entirely.

If im not mistaken, Andy Mac took his Geiser into a wind tunnel when they first got it and tried a couple different things out to reduce the wind resistance.. shortly after, the front valiance became widely popular with TT teams running Geisers. Im prob way off on my info but I recall hearing him talk about this topic before..

[mike mcqueen]

I went to the GM wind tunnel with the SPD chevy of BJ Baldwins, with the collins crew. We learned quite a lot. They start off with a given number with the first pull (air) then you make changes for each pull. We managed to get the number way down with a lot of changes, Then we put the light bar on which brought it back to the starting point. The new small lights are a good help. The front air dam aka spoiler,or cow catcher(its original name from SCCA) is a plus, To be more effiecient
it has to have a forward pointing lip at the bottom. One big plus is to seal the bottom as in DAKAR cars. The tires are always a problem in any race vehicle. "think like the wind"

[bajaxp]

I went to the GM wind tunnel with the SPD chevy of BJ Baldwins, with the collins crew. We learned quite a lot. They start off with a given number with the first pull (air) then you make changes for each pull. We managed to get the number way down with a lot of changes, Then we put the light bar on which brought it back to the starting point. The new small lights are a good help. The front air dam aka spoiler,or cow catcher(its original name from SCCA) is a plus, To be more effiecient
it has to have a forward pointing lip at the bottom. One big plus is to seal the bottom as in DAKAR cars. The tires are always a problem in any race vehicle. "think like the wind"

Mike McQ...great info and thanks! Can you elaborate on 'One big plus is to seal the bottom as in DAKAR cars.' Are you talking skid plate or side skirts?

[mike mcqueen]

Most of it is sealing the bottom from the front lower a arms back. shielding the bottom so air will not get up into the car.
Air will blow the hood off almost any car that the hood is not latched down. I know from experiance. The A arms are done with flexable material that will move with suspension. Smooth is slippery.

[Rory]

Heard the same story from Robbie Goerke from Collins. Robby Gordon has also done wind tunnel testing and you can see the added material behind the "cow catcher" down to the bottom of the front skid plate, i believe BJ has the same sort of design. Light bars up top are almost like a mini parachute but with the Rigid/Vision X type lights being used now it helps.
Rumor was when Challenger IV was first built did a 150mph on the asphalt at the Mexico races (Per Danny Thompson and John House the builder) but was VERY squirrely and scared the hell out of Mickey Thompson. They kept playing with the narrow wing on top of the car then finally took off the back of the narrow part and put on a "top fuel" type wing and that seemed to calm it down. Talking with Bob Gordon and Parnelli about wings, they said they worked great but you constantly had to adjust them (electric actuator) for the terrain or it would upset the vehicle. Not sure what a wing would look like on a TT but 'd love to see some on a couple class 1 cars.......

[smt racing]

Here is a good link to some basic principles, in a nut shell its more important how you leave the air then how you enter it... good post

http://www.gmecca.com/byorc/dtipsaer...ml#AeroGeneral