Coefficient of drag as a function of vehicle profile

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alignman88

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Low frontal area like the car was too skinny? And thus not stable?
Yes but… Roadsters go fast there exactly because that, but the trade off is low downforce (coupled with low traction) skinny=fast so it’s the deep end of the talent pool to drive them at high speeds. Pretty sure that car is well under 2,800 lbs. My 29 Ford roadster all steel with small block is only 2,500 lbs.
 

Erik the Awful

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I read once about how over 200 mph the steering is backward. Not as right is left, left is right, but rather that the car steers you and you have to convince it where to go. Scary stuff. I think I'll stick to road courses with lots of traffic in sketchy cars.
 

Orpedcrow

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I read once about how over 200 mph the steering is backward. Not as right is left, left is right, but rather that the car steers you and you have to convince it where to go. Scary stuff. I think I'll stick to road courses with lots of traffic in sketchy cars.
I heard that too… and that it’s like driving through shaving cream or something.

I wonder if land speed guys claybar, polish and wax their vehicles. I wonder if that makes enough of a difference at those speeds.

Or if the golf ball dynamics would be scalable…
 

RichLo

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The reverse steering is for motorcycles. A lot of bike riders dont even realize it unless they actually try it. Push on the right handlbar and the bike will lean right and turn right. Once you realize it you can really start to throw the bike around and become a much better defensive rider.

Below 15mph (Parking lots) steering is normal, 15mph to 120ish (speed depending on the geometry) steering is backwards, above that it goes back to normal because the bike doesnt react to leaning like it does in that sweet spot.
 

Spareparts

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Close to 30 years ago i had a 1992 Ford Probe GT that had been "worked on" before i got it.
I can tell you without a doubt above about 130mph the small cracks in the road will try to steer your car for you. Im not sure but i believe the down force at speed would make the care want to fallow the cracks. The steering would become stiff as in it took both hands firmly gripping the wheel to steer it where you wanted to go not where the cracks wanted to take you.
In reality i don't know how fast that car went. If i remember right the speedo went to 120mph and i could bury it to about what would be the 160mph mark had there been numbers and the engine tack reading 7K rpm. Fastest car i ever had.
 

alignman88

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I read once about how over 200 mph the steering is backward. Not as right is left, left is right, but rather that the car steers you and you have to convince it where to go. Scary stuff. I think I'll stick to road courses with lots of traffic in sketchy cars.
Yup that’s kinda what I heard from people that had done it, it’s about driving it out of a spin constantly in a counter steer. That’s mainly on dry lakes like Muroc and the salt flats. At a certain point you become a passenger only reacting to what the vehicle does. That’s why the saying about land speed racing is not about how fast you go, it’s how you go fast. That’s why it’s so much engineering and cubic dollars at the big speeds. The world becomes a different place especially in a door slammer.

It’s what people don’t realize about the NASCAR, F1, Indy cars drivers etc they make it look “easy” but they’re at the edge, they’re special humans. One of my dads friends tested for Goodyear and ran in a bunch of Indy 500’s his stories he told laughing would make ya poop a lil just hearing them LOL. Had a dirt late model with a buddy for a couple seasons, and I swear it was like driving into your neighborhood with all the other neighbors and tryna pull into your driveway…at 90 mph.
 

kenh

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I used to race radio control airplanes. The engines were .15 CI and the sweet spot was around 23,500 rpm on the ground. Didn't have a positive way to measure in the air RPM but was generally accepted the engine would unload to about 30K in the air. The only thing we were supposed to modify was the prop... Well anyway, we found out that a very sharp (knife) edge on the prop trailing edge was good for about 50 RPM on the ground. Other than that the prop had the typically wing shaped airfoil. Same for the wing and tail of the airframe. The trailing edges seemed to have much more effect on speed than the leading edges.

Ken
 

618 Syndicate

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I read once about how over 200 mph the steering is backward. Not as right is left, left is right, but rather that the car steers you and you have to convince it where to go. Scary stuff. I think I'll stick to road courses with lots of traffic in sketchy cars.
Some cars will exhibit this at less than 200. Once the front end starts to lift because air is going under rather than around or over, things get real sketchy real fast.
 

Pinger

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I used to race radio control airplanes. The engines were .15 CI and the sweet spot was around 23,500 rpm on the ground. Didn't have a positive way to measure in the air RPM but was generally accepted the engine would unload to about 30K in the air. The only thing we were supposed to modify was the prop... Well anyway, we found out that a very sharp (knife) edge on the prop trailing edge was good for about 50 RPM on the ground. Other than that the prop had the typically wing shaped airfoil. Same for the wing and tail of the airframe. The trailing edges seemed to have much more effect on speed than the leading edges.

Ken
The art of aerodynamics is to create as little as possible turbulence at the front of the object - then convert what turbulence there is back to laminar flow before it departs the vehicle at the rear. Hence the importance of a clean trailing edge.
IIRC air will detach from a surface when the angle between the two exceeds 8 degrees. Thus, length allows a more moderate angle and a better chance of recombining the flows that are above, below, and around the object. A 'teardrop' knows this.
 

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