HPP

A 1 trick pony. lol Painted yourself into a corner and now have no way out.

Well, you could just drop it - *if* you really wanted to. Something tells me you don't.

wabmorgan

You don't either.... Do you????

HPP

I've told you. Because you rejected help, because you continue to act like you have any knowledge in the area, and because you proceeded to take a shot at me spurred by your lack of knowledge, you're not getting the "last word". You're wrong about these issues, and you don't understand them and you won't take the time to learn about them, even when people here tried to help. Instead you say they don't know anything and accuse anyone who challenged you, of "attacks" and "spam".

So.... as long as you keep it up, round and round we will go. (That's why I asked you how many pages you wanted to run with this. )

Phoenix 5.7

iTrader: (7)

can yall take this childish bickering to PMs. this isn't a HPP vs. wabmorgan thread, its an aero thread

HPP

Proof right there. You are so dead set in your beleifs that you won't ever take the time to learn the facts. Instead you claim that anyone who corrects you is wrong. Sad. Almost funny, but mostly sad.


The lack of understanding is mind blowing. Part of me is starting to wonder if you're for real, or just taking the ****. People can only be so blind and still manage to survive.


lol Now you've taken to mimicing? A 3rd grade tactic. What's next, raspberries?

LTSpeed

Take a look at just the leading edge of a raindrop. It is not that different from the rear end of an f-body (that T/A spoiler does mess things up a lot backwards though!).

I know I'm the one that brought all this up, but you have to be careful talking about 4th gen f-bodies in a windtunnel backwards. That lower tail sits so high up that a lot of air gets pulled under the car. You actually would need to angle the flow down 2-3* to have lower drag. But the point is not specifically windtunnel testing, it's more about the shape itself. The Camaro is very close to an ideal teardrop in reverse. Take the mirrors off and it's very very slippery. Think of a Cd of 0.29 or less under the conditions I described.

But hey, who tests cars in a windtunnel backwards? (Er, besides NASCAR!) OK, maybe some grad students late on a Friday night with nothing else to do, he he...

wabmorgan

Wouldn't all that air running under the car be a bad ideal??? As in LIFT????

MadBill

For WIW, I know a guy who was part of an attempt at the 300 MPH barrier for a stock bodied sedan at Bonneville. They used a twin turbo BBC-powered Gen II Firebird, and at one point due to a ballasting error, spun the car at 280 plus. They didn't hit anything, but the wind ripped off the deck lid, blew out the windshield, etc... (and the barrier was broken years later by another Gen II FB)

LTSpeed

Yeah, of course. But F-bodies are far more clean underneath than most cars designed up to 1982. (The 3rd gen and 4th gens are nearly aerodynamically identical underneath.) The odd thing about these cars is that they don't get a ton of lift underneath (except the bubble below the radiator previously mentioned). They actually do get a lot from LOW pressure around the roof and rear hatch. For an ideal Bonneville setup, you need to:

1. Convert to a front breather with a mildly vented hood,
2. Lower the car about 2 inches,
3. Extend the air dam and side skirts to the ground,
4. Use "baby moon" style wheel covers,
5. Put a wickerbill on the rear edge of the hood,
6. Add a diffuser under the rear of the car that extends forward of the rear axle,
7. Add vortex generators to the back edge of the roof across the top,
8. Lose the mirrors,
9. Brace the hood so it doesn't distort.
10. Extend the rear spoiler about a foot behind the car horizontally.
11. Add pins to the side windows and rear hatch so they don't try to open up over 150mph.
12. Duct tape every seam.
13. Add HP as needed...

wabmorgan

Good points. Although, I was refering to all the air that would be running under the car in the reverse Areo theory with the rear end being so high in the air.

Btw, I see where you were going with that... Lower the rear end of the car... and the reverse theory makes a little more sense... at least that would get rid of some of the air running under the car.

Of course, losing the mirrors helps.... in either direction.

I remember a few years ago, they were playing around with small cameras to replace the mirrors. They were much smaller than the mirrors to help with Cd.
They cameras would be connected to a video display in the car. I can only guess that the cost made the system impratical from a production stand point and $$$$ it would add to the final system.

Several years ago when Car and Driver was doing their Super Trans Am feature build. One problem they ran into was as the car approched the 200MPH barrier... the side windows started to lift from their sealing surfaces... solution.... DUCT TAPE!!!!!!!

HPP

Air on the bottom does not produce the majority of lift on any design. That is the newtonian principle. If that were the cause of lift (as 90% of the population beleives), symmetrical airfoils would never work. But, we know they do. They are used on all aerobatic planes.

The reason airfoils are shaped like they are, and symmetrical airfoils are possible, is because of the top side. This is also why aircraft sling engines and ordnance on the underside of the wing, it causes almost no interference with lift.

The catch is that another 9% of the population believe the Bernoulli princple. That the shape of the aerofoil speeds are up over the top and since faster air is lower pressure, this causes the underside to press upward.

The boundry layer on top does indeed move faster, and is indeed lower pressure, but that is not sufficient to cause the amount of lift we see aerofoils produce. An aerofoil designed purely on the Bernoulli principle would be ridiculous, basically flat on the bottom and mountain shaped on top, and bloody *huge*. In reality, it would have a hard time moving, let alone producing lift.

The Coanda effect is the major contributor to lift. Newton is the second, and Bernoulli is there, but barely plays a role.

Lift is created almost exclusively on the top side. The shape of the wing pulls air down - as it hits the aerofoil, it sticks to it and follows it's contour and ends up lower than where it started. This in turn pulls more air from above it, down and back. Here's where Newton's 3rd has the biggest role - the equal and opposite reaction is to pull the aerofoil up. The increased pressure of the air hitting the underside contributes, but *very* little.

This could take us into discussion of nürflugels and bell shaped lift distributions and the effects of control reversal (or lack of it), but that gets way outside the scope of this thread.

This is the point behind deffusers. Since a teardrop is symmetrical, the are is pulled the same amount in all directions and has neutral lift. A car (like these) is basically a teardrop shaved in half. This creates an aerofoil aspect that *does* create lift. By adding a diffuser, you pull are up at the back of the car to allow it to better meet the air being pulled down by the rear window, and help to cancel out some of the lift. This is also why you actually *want* air under the car. You just have to work with it properly.

Phoenix 5.7

iTrader: (7)

i was thinking, what would be better, the firehawk hood or the base hood. the firehawk hood does have the inlet, but it takes up the space of the existing opening. seems like it would be the best compromise

LTSpeed

HPP: Some very good reasoning there. I think we tend to get obsessed with low Cd's and such. High speed stability is how well you balance airflow on all sides of the car--including the underside. Diffusers and splitters are a concession to the fact that we can't totally prevent air under the car.

It's kind of funny how it took so long for these concepts, known since the late 1940's, to make it to cars. Oh well, better late than never.

HPP

Not to nitpick, but I'd argue that they were known since the teens. Single digits actually. The amount of scientific development that the Wrights alone did is really phenomenal and far greater than any non-aero-geek would ever suspect.

But cars aren't planes right? They aren't travelling at near the speed either. I suspect that when coming from the grand coach built era of the 20s and 30s (god I love those cars), aerodynamics aren't even a consideration, and all the people with that skill set are in aircraft design. (just a guess)

But, just as it was slow to creep into automotive design, so too has it been slow to creep into general public knowledge (as you can see).

LTSpeed

I don't see your remarks as nitpicking, just giving credit where it's due. I'd agree on giving the Wrights alot of the credit, but it really was a pretty steady climb in terms of aero R&D up through the early 50's. The biggest changes since then (in subsonics) has just been the use of computers to crunch everything so much more quickly. But the use of fluid modeling for car bodies is still in it's infancy compared to aircraft.

The cool thing about cars is that the Cd is relatively static due to the low speeds. It gets more interesting at NASCAR and Bonneville speeds.

AU N EGL

Here is some basic information that may help

High-Lift Systems for Racing Cars
http://aerodyn.org/Annexes/Racing/hlifts.html

Vettish

Under car diffusers are creating more downforce than wings and scoops now.

LTSpeed

Though I don't have numbers on the new C6R, I'd tend to agree with you. The rear spoiler on the C6R (at least the ones at Sebring) looks more for art than function. But then again, that part is adjustable, while diffusers usually aren't.

chuntington101

wings are normaly adjustable so the aro an be st up for each track! so for a high speed curciet you wold let the wing off a bit so you can get higher speeds. oh slower high Gforce tracks you run more wing!

now the reason pople dnt adjust the diffuser is because adjustment would be much harder than that of a wing!

thnaks Chris.

PS. NO wing in motorsport is there to look good!

Phoenix 5.7

iTrader: (7)

except drifting