My Know-it-all teenage son says the dimples help as the golf ball "spins", probably not helpful in a Bonneville car, or anything thats not supposed to "spin"
That looks like the contraption I was talking about seeing earlier. They have the answer as to why they only did the back side, no weather they would say why...
Flat Paint does not reflect sunlight. Makes it more difficult to spot the aircraft. Also the bottom of the planes are usually white or a lighter color whereas the tops are usually a darker color like a gray. Reasoning is that the lighter color makes it more difficult to spot from the ground as it will blend in with the surrounding sky and the darker color makes it more difficult to spot from above because it will blend in with the ground or water below. Of course the stealth fighter and bomber are a different breed and not painted this way.
the reason scaling makes a difference is something called the "reynolds number" basically what it means is that the scale of the object being pushed through the air may change, but the size of the air molecules it's pushing don't change. This changes the way the molecules react to the shape of the object going through the air. their are many specific airfoils that have been made for low reynolds applications (usually model airplanes or small UAV's) an example of this is a flat airfoil with a blunt leading edge. this can be a fairly efficient at small scales but if you scaled it up to say the size of a piece of plywood, it creates huge drag.
I disagree. They did almost nothing in terms of control of the unknown. They also did not run a statistically significant number of tests. They also did no error propagation, nor did they calculate a meaningful confidence interval. http://en.wikipedia.org/wiki/Similitude_(model) The very good example on the wikipedia page talks about modeling a 1/40 scale submarine in a water tank. Simple enough, set the speed at 1/40 of the real submarine, and the force is 1/40 of the real sub, right? No. To do it right you need the model speed to be about 22 times the speed of the real sub. The force on the model is about 1/3 times the force on the real sub. So you can test models for aerodynamics. But you need to some math to get the conditions right. It does not agree with common sense but so much of the real world does not. Common sense is pretty much worthless when it comes to investigating the real world. If it got 11% better fuel economy, then a lot of people would want one. 18 wheelers could save a lot of money with that one.
I thought, that on a golf ball it was referred to as "passive boundary layer control", or something like that............... They tried it on some early fighter jets, ( not passive), on the F-4 Phantom to name one...... "Blown leading edges" and "blown flaps"....................Yes, it accellerated the airflow over the surfaces, 'cause the surfaces did not lift worth a shit at low speeds. That's how it was 'splained to me, as "boundary layer control" to decrease drag, increase lift.
This thread makes me want to dimple a geo metro to see if it helps...if it doesn't, at least you can say you commuted a golf ball.
Actually the tires were filled with helium. Problem was the helium molecule is so small it leaks out of the tires VERY quickly. Pretty much a kilometer (a bit over a minute) was all it was good for.
This dipshit I work with has a Geo Metro that's been through atleast 1.5 million Central Texas hailstorms and has never been repaired. It is literally a golf ball. I guarantee you that piece of shit doesn't go any faster than it did new. Mythbusters be damned. haha
Seem to remember an article on one of the big racing sailboats skinning the hull with some sort of (maybe vinyl) skin to increase speed.
Anyone remember Kenny Bernstein's Ford Tempo F/C back in the '80's? It had "vortex generators" on the backsides of all the bodysurfaces such as the rear window area designed to de-laminate the airflow and make it hug the roofline, thus feeding air to the rear spoiler so a smaller spoier could be used to the same effect as a big one. Wonder why they don't today?
Well, there you have it. At least the Tempo "kinda" looked like a real car. Not like his goofy-looking Reatta-bodied "Batmobile".
---------------------- Actually, that was a myth. Richard Petty ran a car with a vinyl roof and *claimed* that the dimples in the vinyl 'helped to stabilize the car at speed. The trutfh of the matter was that the vinyl roof was there soley to cover up and hide some illegal 'massaging' they had done to the roof. Mart3406 =========================
Something about that was in either Petty's or Smokey Yunick's book. They were either trying to disguise the slightly chopped roof, or the roof skin had been thinned out so much from being acid-dipped it would "oil-can" at speed. Depends on which story you want to believe, or maybe it was both.
Well, ya might say it was the "acid dipping" that did it..... See, they were trying to lighten the body a bit...... but they left it in the dip a bit too long...... anyways the roof, she was a touch thin..... like patato chip thin..... couldn't paint that so what to do...... Hey how about a vinyl top...... the rest is history....
------------------------ The stories that I've heard was the the roof had either had been chopped slightly and/or had a section taken out to increase the taper of the roof, in order to improve the aerodynamics - and the vinyl top was added both to cover up the area were the cuts had been made and also to make everything less noticeable by visually drawing attention away from the fact that the roofline had been altered. When questioned about the reasons for vinyl top, the Petty team top resorted to further obfuscation of the facts, by claiming that the dimpled texture of the vinyl replicated the dimples on a golf ball and increased the stability of the car at speed. While completely untrue, and not the real reason for the vinyl top at all, the explanation sounded plausible enough to some people that a myth was created that still persists. Mart3406 =====================
The myth busters also did the test on the pickup with the gate up and down, mlieage was better with the gate up, thus making the bed interior into a large dimple. The bed area is square would it work better if it was round? Airplane wings i think would be off limits for sure as it would mess with lift / high and low presures, but the main body? maybe dimples there would mess with the integety during presurization up and down. Someone else here mentioned jet skis, i had a friend who ran a team and he used 80 grit on the bottom and the differance was huge, especially in colder water that was more dense. Going by this would dimples on a salt flat car work better in colder or warmer air, warmer air is less dense to start with?
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