Squareback racing?

["Cooper N. Melton" <cnm4x@virginia.edu>]

On Wed, 30 Jul 1997, Melissa & Jim wrote:

> It seems that someone asked what the best possible aerodynamic
> shape was.  After some work it was determined that it was 
> approximately a cigar shape, but for it to be large enough for a race 
> car, it would have to be 40' long.  Of course this leads to the 

In that case, all ya need to do is take the Oscar Mayer Weinermobile and
just straighten it out a bit.  Voila!  Perfect race car.  :)-

>For what it's worth, I HAVE seen published explainations that the
>spoilers on the rear of race cars are there to force a high pressure
>region over the tapering rear of the car where, without the spoiler,
>a low pressure area would develop and lead to large amounts of vortex
>shedding and consequent energy loss...

If my intuitions are correct, I would be inclined to argue that the front
end of the T3, at least the post-1970 longnose model, is quite unsuited
for high-
speed running.  Remove the front bumper and the front is shaped almost
like the
prow of a ship, with the 'leading edge' way up at the headlights and
tapering back to the spare tire hump at the bottom.  The result is the
opposite of
what is desired for race cars.  At very high speeds, the wind
would have the effect of lifting the front end, like a racing boat!  Check
out the super-high-res ASCII graphic below...

              Squareback                                    Race car
   
           front       rear                                front   rear
                   _____                                      ___
 windforce     ___/_|_|_\                                 ___/   \_/|  
 ---->         \__|_|____\              windforce--->    /__________|
     


I recently read an article in I believe Car & Driver in which they tried
to run a Lingenfelter-modified Pontiac Trans Am at ridiculous speeds.  
Well, when they tried the high-speed run, they got up to like 200 and the
thing just ended up flipping nose over tail, simply because there wasn't
enough downforce to keep the front end on the ground!  Race cars need
obscene amounts of downforce at the front, which is why they have those
huge air dams.
Sorry to crush the spirits of those planning on
modifying their Squarebacks for runs at Bonneville, but I don't think the
good folks in Wolfsburg had racing in mind when they designed the T3.
Don't get me wrong, though,  I love them, and they're sporty looking cars!

Cooper
Rosie, the Indomitable '72 Squareback (which starts to get really
squirrelly at about 75 mph... but that's another story)

Cooper N. Melton, Esq.  
University of Virginia 
School of Architecture 
coop@virginia.edu
http://palladio.arch.virginia.edu/~cnm4x
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