I went over and talked to our aerodynamics guy here at MD Helicopters about
this one. He said he could speak to aerofoils but not necessarily for cars
because of the ground plane effect, but ...
It seems that as the car (airfoil) penetrates the air the, sharper the
leading edge radius the sharper the pressure gradient. As the air moves aft
from the leading edge the pressure initially is below ambient and then as
the it continues aft the pressure increases until it is actually above
ambient. For a "needle nose" configuration the difference between the lower
pressure (still positive, but below ambient) is greater than for a more
rounded leading edge. Because the low pressure is relatively greater, the
center of pressure (resultant of all aero forces) would move forward with a
"needle nose." By the way, the point at which the pressure increases above
ambient may not be the same location if nothing else is change except the
leading edge radius, so its not totally black and white as to how far it
will move forward. (That's why we still have wind tunnels and flight
testing, I guess.)
This could still be compensated with additional areo devices aft, too.
Hope that made sense ...
Dale
-----Original Message-----
From: Nafzger [mailto:nafzger@vtc.net]
Sent: Friday, January 05, 2001 4:45 PM
To: Glen Barrett; John Beckett
Cc: land-speed@autox.team.net
Subject: Re: Rear mods
Just another amateur opinion but in one of the many aerodynamics books I
purchased from SAE, a comment was made that needle nosed cars tend to move
the center of pressure forward. That was not explained, it was just a
statement made. If that is true and you put the engine in the rear, you are
trying to shoot the arrow backwards with the same results as it turns out.
Howard
----- Original Message -----
From: "Glen Barrett" <speedtimer@earthlink.net>
To: "John Beckett" <landspeedracer@email.msn.com>
Cc: <land-speed@autox.team.net>
Sent: Friday, January 05, 2001 1:04 PM
Subject: Rear mods
> John
> One thing I forgot to mention on the rear engined roadster was we had a
> long throttle throw so it was more controllable appling the power. It
> made a big difference instead of just on and off with the pedal.
> Glen
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