Neil, Here is an interesting interview with Jim Hall and aerodynamics.
www.insideracingtechnology.com/jimhall.htm
Doug Odom in big ditch
"Albaugh, Neil" wrote:
> List;
>
> At lunch today I had an opportunity to ask John Horsman about the GT-40's
> aerodynamics and he was quite helpful. He had photographs of some of the
> Ford GT-40s and their later variants such as their Gulf Mirage. In a photo
> taken in April 1964 at the trials (practice) at Le Mans, John pointed out
> that the original GT-40 design had a rather high "pointy" nose and a tail
> with no spoiler. It was so unstable that those two cars went off into the
> weeds on the fast 3.5 mile long Mulsanne Straight (sounds like Maxton).
>
> A spoiler was added and it helped but another photo taken of that car at
> high speed showed the nose lifted by what looked like about 4 to 5 inches! A
> new nose was designed and it helped, but the early GT-40s suffered from the
> FIA regulation that required a full- width windshield and that could have
> made the lift problem even worse (my opinion).
>
> I found some data that may illustrate the point:
>
> 1967 Ford GT40 MkIV Lift:
> 213 lbs. @ 180 mph, with 554 lbs. of drag
> 263 lbs. @ 200 mph, with 648 lbs. of drag
> 318 lbs. @ 220 mph, with 828 lbs. of drag
>
> 1966 Ford GT40 MkII Lift:
> 144 lbs. @ 180 mph, with 756 lbs. of drag
> 177 lbs. @ 200 mph, with 933 lbs. of drag
>
> Compare this with a modern street- driven sports car:
>
> 2000 Porsche 911 Lift:
> 600 lbs. @ 150 mph
> Aero. Balance @ 150 mph:
> F: 228 lbs.
> R: 372 lbs.
>
> These all generate LIFT-- not a good thing! Compare those with a much later
> race car:
>
> 2001 Bentley EXP Speed 8 LMGTP
> High downforce configuration: Downforce:
> 3094 lbs. @ 150 mph
> 5500 lbs. @ 200 mph
> Low downforce configuration: Downforce:
> 2200 lbs. @ 150 mph, with 600 lbs. of drag
> 3911 lbs. @ 200 mph, with 1066 lbs. of drag
> Lift-to-drag ratio: 3.7:1
>
> Most modern competition cars have more BHP than they can deliver to the road
> so they trade off loss of horsepower (drag) for the ability to put the power
> onto the road (downforce).
>
> I realize that GT cars don't run under the same rules as SCTA but I wanted
> to pass this info along for what it's worth. I'll save the wide tire /
> narrow tire controversy for another time.
>
> Regards, Neil Tucson, AZ -- boring everyone to tears by now......
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/// what is needed. It isn't that difficult, folks.
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