Hmmm... it seems I have started an argument, here. Let me clarify a few terms before we all start eating each other.

An airplane wing in cruising flight creates lift by displacing air unevenly over its surface. The air flowing over the top of the wing is forced to travel a longer path, which speeds it up as it goes. According to Bernouli's principle, the faster air goes, the less pressure it exerts. Thus, a low pressure zone is formed over the critical part of the top surface and the high(er) pressure air under the wing pushes it up into that zone.

A Spoiler, in the truest sense of the word, does just what it sounds like it does -- it upsets airflow over the wing, causing turblance that kills lift. You don't need anything really big to do this, a plate just two or three inches high, at the right point, will do the trick.

The first use of a "spoiler" on a race car was done by Richie Ginther on the Ferrari 206SP in about 1961 or so. At speed, the car was all but indrivable, the rear end suffered from severe lift. It was so bad that he could lap Monza faster with the rear bodywork removed. Ginther served as a mechanic with the U.S. Air Force during the Korean War, so he knew about spoilers. Working on a hunch, he told the mechanics to attach an aluminium strip about three inches high along the tail of the car. The lift was destroyed, the car was stable at speed and the problem was solved.

The "spoilers" on race cars -- particularly the Can-Am cars of 1968 or so -- were not just "spoilers" in the sense listed above. They were air deflectors that caused drag and, by virtue of being angled, also forced the car downward. If you doubt this, try walking with a 4' x 8' on a windy day. Or when someone aims a fire hose at it. You will feel plenty of drag and downforce as the result.

Speaking of sheets of material held at an angle to the airflow, that was how Jim Hall's movable wings worked. The airfoil section itself was pretty much symetric and quite thin; the sort of thing you might see on a plane's horizontal stabilizer. This was for low drag on the straights, when the wing was trimmed flat.

In "high downforce" mode, the wing was angled sharply downward, which caused considerable drag and in the process, deflected air upward. The resulting vector produced downforce on the suspension uprights. That, and the fact that it didn't load the springs, why Hall mounted them on the suspension, not on the bodywork. He mounted them on tall stalks because that's where the air was less disturbed by the other cars' wakes.

Flaps on an airplane's wing work in one or both of two ways. One, as in the case of "split" flaps (the kind used on B-17s) are air deflectors. At low angle settings, they increase lift by deflecting air downward. The one vector of the total force is a net upward force.

The second say a flap works is to extend the curve of the airplane's centre line, creating a more pronounced airfoil. In some planes, this is a single element and in others (paritcularly airliners) it can be several elements. Again, the effect is both to increase the curve of the airfoil, increasing lift according to Bernouli, and to deflect air, thus increasing lift as a vector of drag. The multi-element wings you see on some race cars are, essentially, permenently deployed flaps.

Now about "Ground Effects."

As I said before, Bernouli's principle says that the faster you move air, the less pressure it exerts, so long as you don't try to defelct it. If you put this into a tube, you have a "Venturi Tube," or simply a "Venturi," which speeds up airflow at its narrow point and in the process reduces air pressure.

In a carburretter the low pressure draws fuel into the airflow and atomizes it with turbulence. If you put the tube on the side of the race car, with the downward-curved part above and the road as the fourth side of the box, you have a venturi tube that creates a partial vacuum strong enough to pull the car downward.

During the Ground Effects era, this was considered "free" downforce, since cars at the time already had their radiators mounted in side pods; they just weren't aerodynamically shaped.

In the winter of 1977, Mario Andretti mentioned the wing-shaped side pods on the MARCH 701 Formula One car, noting how they affected the car's handling. Colin Chapman got interested in this and starte experimenting. Originally, he put "end plates" on those side pods to control air flow around the "wing tips." Only later did the Lotus engineers discover that they'd created powerful Venturi tubes that produced downforce all out of proportion to their dimensions. By using sliding skirts that dragged on the ground, he sealed off the venturi tubes from high-pressure outside air, making them as efficient as possible.

Speaking of end plates, there's a reason why cars have them, as do an increasing number of aircraft. As I said, a wing moving through the air has a low pressure zone on top. Nature being nature, high pressure air from underneath tries to curl around the wing tips to fill that zone. The result is a "tip vortex" that causes turbulence and drag. It also means that the low pressure zone in the outer third of the wing is compromised. The end plates prevent that from happening by separating the high and low pressure zones. The slots in the end plates let air trapped in the higher-pressure zone (the top of a race car's wing) escape, reducing turbulence at the intersection of the end plate and the trailing edge.

Don't get between a couple of engineers debating the definition of terminology. It can be deadly. Especially beware if they are argueing over the difference between an "engine" and a "motor".

Greywolf, I don't think you started an argument at all. I thought your descriptions were precise and accurate. Likewise Speedsense being the racing Engineer that he is uses all the correct terminology. I enjoy the fact that he does that, as it's always good for me to learn new things. I was just trying to put some layman perspective in.

My heart specialist told me I'd had a Cardiac Infarction in the left anterior descending, which required a stent. He also said I had a heart attack and needed a device put into an artery behind my heart. Both were correct, but the second one made more sense to me since I'm not a doctor nor did I attend Medical school. I don't see an argument, Just because we didn't use the correct terminology doesn't mean we don't have a basic understanding of what is going on. Speedsense understands it in his terms which happen to be the correct ones. AA JMHO

Bill

And I'm looking at this thread as highly informative, and do not feel any bad vibes when being corrected by other, more knowledgeable people on the subject. I get to learn a lot, and some of the misunderstandings I carry with me, because I'm no professional, get corrected. Please don't stop. This is a good thread, and no one is taking offense at anyone...

My god, this is so un-speed-forum like, I think I need to read some fanboy driver-bashing now, or I'll lose feeling "at home" here

Bill,
Call me ant-f*cker (is that term used in english?), but is your point not that the Bernoulli effect is irrelative in the hand-car story, because it's too small, but that it does exist?

I want to see this acknowledged because while I do understand it's irrelevant, I do feel being correct means acknowledging it's existence at the back of the hand. If I'm wrong, and you prove it does not even exist there, my fundamentals on getting Bernoulli will turn out to be false.

speedy_bob - 02 September 2008 04:26 AM

And I'm looking at this thread as highly informative, and do not feel any bad vibes when being corrected by other, more knowledgeable people on the subject. I get to learn a lot, and some of the misunderstandings I carry with me, because I'm no professional, get corrected. Please don't stop. This is a good thread, and no one is taking offense at anyone...

My god, this is so un-speed-forum like, I think I need to read some fanboy driver-bashing now, or I'll lose feeling "at home" here

Bill,
Call me ant-f*cker (is that term used in english?), but is your point not that the Bernoulli effect is irrelative in the hand-car story, because it's too small, but that it does exist?

I want to see this acknowledged because while I do understand it's irrelevant, I do feel being correct means acknowledging it's existence at the back of the hand. If I'm wrong, and you prove it does not even exist there, my fundamentals on getting Bernoulli will turn out to be false.

There was a time when the only moving ground plane windtunnels were quite small and used 1/4 size car models to make it possilbe to have the right wind speed and ground speed relative to size. When this was increased in size to 1/2 sized models (filling three fullsize rooms instead of one) The results were not the same, and the theories and math associated with 1/4 scale had many "different" effects in 1/2 scale went using the same designed and modeled car. The same happened when they went to full size, moving ground plane windtunnels, there were many "fluid" effects that were either too small or unmeasurable in 1/4 scale, that became apparent when they got to full size measuring.. many of the original pieces had to change as their effect was different than calculated and measured with the smaller scales.

hobbymanbill - 01 September 2008 10:29 PM

Greywolf, I don't think you started an argument at all. I thought your descriptions were precise and accurate. Likewise Speedsense being the racing Engineer that he is uses all the correct terminology. I enjoy the fact that he does that, as it's always good for me to learn new things. I was just trying to put some layman perspective in.

My heart specialist told me I'd had a Cardiac Infarction in the left anterior descending, which required a stent. He also said I had a heart attack and needed a device put into an artery behind my heart. Both were correct, but the second one made more sense to me since I'm not a doctor nor did I attend Medical school. I don't see an argument, Just because we didn't use the correct terminology doesn't mean we don't have a basic understanding of what is going on. Speedsense understands it in his terms which happen to be the correct ones. AA JMHO

Bill

Hopefully you're doing well Bill. I guess that makes you a "true" racer at heart. Now that you have same braided hose inside of you. LOL...

speedy_bob - 02 September 2008 04:26 AM

And I'm looking at this thread as highly informative, and do not feel any bad vibes when being corrected by other, more knowledgeable people on the subject. I get to learn a lot, and some of the misunderstandings I carry with me, because I'm no professional, get corrected. Please don't stop. This is a good thread, and no one is taking offense at anyone...

My god, this is so un-speed-forum like, I think I need to read some fanboy driver-bashing now, or I'll lose feeling "at home" here

Bill,
Call me ant-f*cker (is that term used in english?), but is your point not that the Bernoulli effect is irrelative in the hand-car story, because it's too small, but that it does exist?

I want to see this acknowledged because while I do understand it's irrelevant, I do feel being correct means acknowledging it's existence at the back of the hand. If I'm wrong, and you prove it does not even exist there, my fundamentals on getting Bernoulli will turn out to be false.

No, you're correct, it's there but it's NOT the force that moved your arm. Speedsense came behind me and quite correctly stated that ANY object moving through a fluid, has those characteristics. The reason I brought up the Jet fighter is that Bernoulli's principle and the experiments which produced it happened at fairly slow speed. The experiments were actually done in water. It's called FLUID DYNAMICS for a reason. The theory had always been seen as the ONLY explanation for how heavier then air craft fly. Since the 50's however there is a debate as to how far and at what speeds the principle governs reality. It isn't that the wing on a 747 has NO LIFT, its that unlike a glider whose glide ratio may be 20:1 (it travels 20 feet for every foot it loses in altitude), it's glide ratio is more like 1:200 or worse. These modern jet aircraft need thrust (or speed) to maintain altitude. Since air isn't visible to us we have a harder time picturing that it really is a fluid and that things happen that we don't "SEE".

Golf ball design changed radically in the last three years as more is understood and the ability to measure these affects is improved. NASA since the 50's has had and designed more LIFTING BODIES, which are just what they sound like, the entire shape is wing-like, but have no ACTUAL wing. AA JMHO

Bill

speedsense - 02 September 2008 05:01 AM

hobbymanbill - 01 September 2008 10:29 PM

Greywolf, I don't think you started an argument at all. I thought your descriptions were precise and accurate. Likewise Speedsense being the racing Engineer that he is uses all the correct terminology. I enjoy the fact that he does that, as it's always good for me to learn new things. I was just trying to put some layman perspective in.

My heart specialist told me I'd had a Cardiac Infarction in the left anterior descending, which required a stent. He also said I had a heart attack and needed a device put into an artery behind my heart. Both were correct, but the second one made more sense to me since I'm not a doctor nor did I attend Medical school. I don't see an argument, Just because we didn't use the correct terminology doesn't mean we don't have a basic understanding of what is going on. Speedsense understands it in his terms which happen to be the correct ones. AA JMHO

Bill

Hopefully you're doing well Bill. I guess that makes you a "true" racer at heart. Now that you have same braided hose inside of you. LOL...

"NICE PUN" Thank you, that was 10 years ago, and I'm fine. That little bit of "BRAID" has really helped the fuel pump be more efficient.

Bill

speedsense - 02 September 2008 04:47 AM

speedy_bob - 02 September 2008 04:26 AM

And I'm looking at this thread as highly informative, and do not feel any bad vibes when being corrected by other, more knowledgeable people on the subject. I get to learn a lot, and some of the misunderstandings I carry with me, because I'm no professional, get corrected. Please don't stop. This is a good thread, and no one is taking offense at anyone...

My god, this is so un-speed-forum like, I think I need to read some fanboy driver-bashing now, or I'll lose feeling "at home" here

Bill,
Call me ant-f*cker (is that term used in english?), but is your point not that the Bernoulli effect is irrelative in the hand-car story, because it's too small, but that it does exist?

I want to see this acknowledged because while I do understand it's irrelevant, I do feel being correct means acknowledging it's existence at the back of the hand. If I'm wrong, and you prove it does not even exist there, my fundamentals on getting Bernoulli will turn out to be false.

There was a time when the only moving ground plane windtunnels were quite small and used 1/4 size car models to make it possilbe to have the right wind speed and ground speed relative to size. When this was increased in size to 1/2 sized models (filling three fullsize rooms instead of one) The results were not the same, and the theories and math associated with 1/4 scale had many "different" effects in 1/2 scale went using the same designed and modeled car. The same happened when they went to full size, moving ground plane windtunnels, there were many "fluid" effects that were either too small or unmeasurable in 1/4 scale, that became apparent when they got to full size measuring.. many of the original pieces had to change as their effect was different than calculated and measured with the smaller scales.

This is EXCELLENT stuff, because in my last life (working, I'm retired now) I owned a hobby shop (hence the screen name), and I build and fly Radio Controlled model aircraft. Many of which are 1/4 to 1/3 scale. The point being that airfoils as well as flight characteristics of our smaller scale models AREN'T THE SAME AS THEIR FULL SIZE KIN. In many examples, the models are EXACT representations, but even so their flight characteristics are often quite different. One big reason is WEIGHT. A full scale EXTRA 300 weights 1200LBS or so with pilot and produces about 300HP. It generally has a thrust to weight ratio of 1.1:1 (it can hang vertical on the prop at full throttle). My 1/3 scale weights 28LBS and has a thrust to weight of something like 3:1 (it will hover at about 1/3 throttle). As Speedsense said, they couldn't get the MASS to the correct ratio and as a result the smaller models gave false readings compared to the full size. It has taken quite a while for the available technology (measuring devices) to get to the point to be able to ACCURATELY measure and record the ACTUAL data and be able to use it. AA JMHO

Bill

hobbymanbill - 02 September 2008 08:58 AM

speedsense - 02 September 2008 04:47 AM

speedy_bob - 02 September 2008 04:26 AM

And I'm looking at this thread as highly informative, and do not feel any bad vibes when being corrected by other, more knowledgeable people on the subject. I get to learn a lot, and some of the misunderstandings I carry with me, because I'm no professional, get corrected. Please don't stop. This is a good thread, and no one is taking offense at anyone...

My god, this is so un-speed-forum like, I think I need to read some fanboy driver-bashing now, or I'll lose feeling "at home" here

Bill,
Call me ant-f*cker (is that term used in english?), but is your point not that the Bernoulli effect is irrelative in the hand-car story, because it's too small, but that it does exist?

I want to see this acknowledged because while I do understand it's irrelevant, I do feel being correct means acknowledging it's existence at the back of the hand. If I'm wrong, and you prove it does not even exist there, my fundamentals on getting Bernoulli will turn out to be false.

There was a time when the only moving ground plane windtunnels were quite small and used 1/4 size car models to make it possilbe to have the right wind speed and ground speed relative to size. When this was increased in size to 1/2 sized models (filling three fullsize rooms instead of one) The results were not the same, and the theories and math associated with 1/4 scale had many "different" effects in 1/2 scale went using the same designed and modeled car. The same happened when they went to full size, moving ground plane windtunnels, there were many "fluid" effects that were either too small or unmeasurable in 1/4 scale, that became apparent when they got to full size measuring.. many of the original pieces had to change as their effect was different than calculated and measured with the smaller scales.

This is EXCELLENT stuff, because in my last life (working, I'm retired now) I owned a hobby shop (hence the screen name), and I build and fly Radio Controlled model aircraft. Many of which are 1/4 to 1/3 scale. The point being that airfoils as well as flight characteristics of our smaller scale models AREN'T THE SAME AS THEIR FULL SIZE KIN. In many examples, the models are EXACT representations, but even so their flight characteristics are often quite different. One big reason is WEIGHT. A full scale EXTRA 300 weights 1200LBS or so with pilot and produces about 300HP. It generally has a thrust to weight ratio of 1.1:1 (it can hang vertical on the prop at full throttle). My 1/3 scale weights 28LBS and has a thrust to weight of something like 3:1 (it will hover at about 1/3 throttle). As Speedsense said, they couldn't get the MASS to the correct ratio and as a result the smaller models gave false readings compared to the full size. It has taken quite a while for the available technology (measuring devices) to get to the point to be able to ACCURATELY measure and record the ACTUAL data and be able to use it. AA JMHO

Bill

Bill, you might find this interesting, I ran across this interesting link sometime ago, data acquisition for RC vehicles:
http://www3.towerhobbies.com/cgi-bin/WTI0001P?&I=LRBE17&P=1

Got to be the worlds smallest and fairly cheap too? Enjoy