Sidepods Vs Barge Boards on race car

[andy2503]

Hi there,

Is there anybody out there who can give me some very basic aerodynamic advice on a racing car?

I have a sports racing car which is unusual in that it does not have the all enveloping bodywork normally associated with sportscars, but instead has been built with a needle-nose front end and push-rod front suspension. However, the rear end bodywork is as wide as the wheels.

The first diagram at

http://www.btinternet.com/~teslock/car1.htm

shows the basic layout, with front (A) and rear (B) sidepods down each side attached to the main chassis. The front sidepods house the radiators, but these could be moved.

My main question is this:
The needle-nose layout is supposed to take advantage of having a low frontal area. However, because the front sidepods (A) are immediately after the front wheels, I feel this configuration is not taking full advantage of that benefit. When the air goes between the wheels and the nose, it immediately hits the sidepods, some goes through the sidepod for cooling, and some will get pushed around the sidepod. I think this is inefficient.

I am thinking of removing the front sidepods altogether, moving the radiators to the rear sidepods, and fitting some form of barge-board to deflect some of the air around the rear sidepods, as shown in the second diagram at

http://www.btinternet.com/~teslock/car2.htm.

However, this is quite a large amount of work.

Before I embark on such a drastic change, can anyone tell me whether this change in the car will produce:
1. no benefit whatsoever,
2. only a slight benefit and possibly not worth the effort.
3. a significant benefit that would make it worthwhile.

Note: this car is a low powered car (70-80bhp), low weight (<400kg), and average race lap speeds are about 80mph.

Any advice would be gladly welcome.

Thanks in advance.

Andy Spencer

 

[GregLocock]

If I were you I'd go and buy a book on aerodynamics of road vehicles, but removing the sidepods is probably not a good idea.

http://www.normas.com/SAE/pages/R-177.html

or

Race Car Aerodynamics: Designing for Speed (Engineering and Performance)
by Joseph Katz

are both very readable.

Note that you may lose some downforce.

You should bear in mind that the wheels have already blasted a hole in the air.

One way to estimate the effect would be to measure the pressure on the front of the sidepods with a water tube manometer.

By the way the needle nose argument is all wrong. The frontal area is not changed by the needle nose, the most efficient solution is to fit bodywork over the front wheels.







Cheers

Greg Locock

 

[MikeHalloran]

You also need a current copy of the complete rulebook under which you intend to race the car.

Cars that are designed for aerodynamic efficiency tend to look like airplanes. Unfortunately, they don't have the appropriate control surfaces and systems for controlled flight, so they make very bad airplanes, in the sense that they tend to fly, and then crash, with unfortunate consequences.

So as to reduce the incidence of those unfortunate consequences, modern racecar rules tend to require or prohibit specific aero details, which is why the cars look so odd, and so similar to each other within a given series.

;---

The needle nose doesn't change the frontal area of the car, but it may actually work to reduce drag. Google the words "aerospike" and "shkvall" for some interesting reading about needle noses.



Mike Halloran
NOT speaking for
DeAngelo Marine Exhaust Inc.
Ft. Lauderdale, FL, USA