Ford GT Aerodynamic Stability at 275+MPH


H

HHGT

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First off congrats to all those that have bigger cajones than I do achieving astonishing speeds with an unbelievable piece of American history. Having said that, much has been discussed about the incredible down-force the GT was designed for. However, I can not find any technical reference to the Aerodynamic Stability and speed limits specific to the GTs front end. Is 275 MPH the limit for these cars' front end design? Did Ford ever publish this data? What was the maximum speed testing done in the simulator(s)?
 

Mullet

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First off congrats to all those that have bigger cajones than I do achieving astonishing speeds with an unbelievable piece of American history. Having said that, much has been discussed about the incredible down-force the GT was designed for. However, I can not find any technical reference to the Aerodynamic Stability and speed limits specific to the GTs front end. Is 275 MPH the limit for these cars' front end design? Did Ford ever publish this data? What was the maximum speed testing done in the simulator(s)?

if a 12 year old Camaro can do 253 in the Mile a GT should be able to handle 300 or more. :)
 

B.M.F.

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if a 12 year old Camaro can do 253 in the Mile a GT should be able to handle 300 or more. :)

X2.....As stable as they are @ 266+ I can't imagine them geting all weird a mere 5mph more than Ray has been in his car. Can't wait till someone pushes one alittle farther than a MILE:biggrin Some one with really big BALLSSSSSSSSS:willy
 
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roketman

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The Gt team has tons of data on the aero stuff.Maybe DBK can come up with some info?
 

dbk

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The Gt team has tons of data on the aero stuff.Maybe DBK can come up with some info?

Reichenbach told me the aero was designed for at least 265 mph.
 
H

HHGT

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Where the technical results ever published?

http://www.youtube.com/watch?v=3EjFkPL_H_4
 

dbk

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That's Stormcat's car, not a factory GT.
 

BlackICE

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I think Ray is the formost expert on high speed aerodynmics of the FGT.
 
H

HHGT

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Reichenbach told me the aero was designed for at least 265 mph.

From the July 2003 Automobile Magazine article by Mark Gillies on the new Ford GT, at page 45:
"Close attention has been paid to the aerodynamics. After all, the GT's shape mimics closely the original GT40, and automobile aero has moved on since the 1960s. Tom Reichenbach, vehicle engineering manageer, says that 'lots of time was spent in the wind tunnel. The original car went there, too, and we found that it was good for flow but had bad front-end lift. As the designers wanted to keep the shape faithful, we knew there would be lift problems. What we found was that the guys in the 1960s simply needed to add a proper front-end splitter with clean separation.
"We actually ended up with more front end downforce than we initially wanted,' he continues. 'We balanced that with extra rear downforce.' which is provided by a racing-style venturi tunnel that starts ahead of the rear axle line. There is also a rear wicker spoiler.'"
 

HUBBSTER

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May 9, 2010
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What was the Max speed the GT40s saw at Lemans' Mulsanne straight ?

I think the 7 liter cars probably saw 220 +
 

STORMCAT

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Where the technical results ever published?

http://www.youtube.com/watch?v=3EjFkPL_H_4

Nope .. :secret:

That's Stormcat's car, not a factory GT.

Yep ,,, :biggrin I have more video .. A2 asked if they could make one for their own promo..
 

FBA

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More than I'd ever have the balls to go in a GT... :facepalm:
 

ChipBeck

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Get down.

What was the Max speed the GT40s saw at Le Mans Mulsanne straight? I think the 7 liter cars probably saw 220 +

Gentlemen,

The original GT40 Mark II cars went over 200 on the Mulsanne. They had very poor aero and generated a ton of lift (literally). Modern day wind tunnel tests showed that the cars only weighed about 500 lbs at speeds above 200. Imagine hitting the brakes, in the rain, at night, in traffic, trying to stop 3000+ lbs of momentum, with only 500 lbs of total down force. It's a wonder that any of those drivers lived to talk about it. They were the automotive equivalent of the 1930's pilots who raced the GeeBee aircraft. Jimmy Doolittle is the only man who raced a GeeBee and didn't ultimately die in it.

The new Ford GT has the opposite problem at speeds above 200. It has too much downforce and it slows the car down. At 200 the front suspension is completely bottomed out. As the rake increases so does the drag. Mark McGowan told me the car has the least drag when the belly pan is parallel to the ground, but it's impossible to keep it that way as speed increases and front downforce causes the nose to dive.

Matech was working on a lower downforce front end for the Ford GT to use at high speed events.

The stock aero has been taken to 270 MPH by Ray and he reports that it's rock solid at that speed. Many of us have taken our cars above 220 and everybody says they are very stable at those speeds. Cheers.

Chip
 
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Fubar

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Frankly, I am more concerned with the GT tearing itself apart (literally) because of it's ability to shift headwind into downforce. If the front end bottoms out at 200mph, imagine the amount of force trying to rip the front splitter off the GT at 250mph or more. I requested my fabricator, Shawn, reinforce the rear edge of the front splitter as much as could reasonably be done without dedicated design work.

I wonder what speed the back suspension begins to bottom out, and does the GT become "flat" at that point? It is very possible that the front and back have different traveling distances. These are questions that can only be answered by someone with a brain that can leap tall buildings with a single bound calculative logarithm, and calculate the half-life of uranium isotopes in a speeding locomotive in ancient Sanskrit and do it all with a slide rule in one hand and a crown and seven in the other. Bill? Tell your wife that Marky Mark, and the funky bunch need you again.

Cheers.
 
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twobjshelbys

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Jul 26, 2010
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The search for best performance at high speeds will be the same dilemma that Kelly Johnson faced with the SR71. Until the SR71 got to altitude and "warmed up" it leaked like a sieve. To get the best downforce at 200+, there will have to be some compromise at less than that. The question will be how much.

Remember it was the light front end on the J-car that went airborne that killed Ken Miles.
 

BlackICE

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Since the front end bottoms out the suspension would it be advisable to up the spring rates for the miles runs?
 
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Fubar

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The search for best performance at high speeds will be the same dilemma that Kelly Johnson faced with the SR71. Until the SR71 got to altitude and "warmed up" it leaked like a sieve. To get the best downforce at 200+, there will have to be some compromise at less than that. The question will be how much.

Remember it was the light front end on the J-car that went airborne that killed Ken Miles.
MoTeC could open up some vents at speeds to sessen the affect for these devices but it would require wind tunnel testing for sure.
 

twobjshelbys

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Jul 26, 2010
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MoTeC could open up some vents at speeds to sessen the affect for these devices but it would require wind tunnel testing for sure.

I was looking at their system a couple of weeks ago. It's a very sophisticated system. Can they manage vents based on sensors (e.g., air speed (pitot tube like) or down pressure) vs just a speedometer reading?
 

Fast Freddy

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Since the front end bottoms out the suspension would it be advisable to up the spring rates for the miles runs?

if i were to make runs in excess of 250 mph i would want stiffer spring rates both front and rear....
 

ChipBeck

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Frankly, I am more concerned with the GT tearing itself apart (literally) because of it's ability to shift headwind into downforce. If the front end bottoms out at 200mph, imagine the amount of force trying to rip the front splitter off the GT at 250mph or more.
I wonder what speed the back suspension begins to bottom out.

Mark,

Only a fraction of the front end downforce is generated by that splitter. I don't know what the % is though. Photos of my car at 220 show the outside edges of the splitter bent downward quite a bit. I have stiffer front springs (about 35%) and I still get a lot of front end dive above 200. At 260+ Ray's GT (also with higher rate springs) shows that the rear of the car does not level out by catching up with the front even at those speeds.

Here's what I do know from some members of the FGT build team. When the GT is level it has less drag and.... when a GT is lower it has less drag.

You brought up a good point Mark, if the front splitter came off at 200+, it might cause a loss of control.

Chip
 
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