[quote]ORIGINAL: banktoturn


Not being a golpher (?) I am surprised that velocity is restricted.
I suspeck that limit exceeds the practical ability of human golfers .
The wind tunnel inquiry was in jest.
Just pokin at the nest.

Mention has been made a couple of times about the race car the Petty's ran that had a vinyl top.

Both Richard and Kyle have told the story of that car in detail. It was at a time when the teams were acid dipping the car bodies to reduce the weight above the CG of the car and that was part of the whole story. It was also at a time when nobody had much understanding of aero.

They did not do the top that way for aerodynamic reasons. Their "punch line" is that in fact the vinyl came loose and blew open in front. They chuckle about the irony of that.

Didn't remember the vinyl top, but the rear fin and nose piece that followed on the Super Bird was an aerodynamic attempt that was right on track, but a little ahead of its time! Sure was odd looking compared to anything else at the time, but I'd love to have one!

Not very definitive. One car, with wackey people, doing a show for entertainment. They get almost as much wrong as right.

I gather the vinyl was holding the steel foil roof together?

When it came out many people hated the car. It was geared for race at Daytona and did not accelerate well, and not many people wanted to go 200MPH on the interstate!

A lot of people still hate the look of it! But anything with a 426 hemi has my attention!

It may be that those morons pretending to be engineers used three different cars. They probably had three different drivers who accelerated from stop at a rate that varied with their temperament. I have worked around some of those Show Biz Special FX guys, and some are real sharp, with some real engineering savvy. Others just think they are. Those Myth Buster Schmoes are the latter type.

The third response, about separation of laminar flow, is correct.

(I admit, I have an attitude about it. I worked on a major theme park that shall not be named, where designs of mine did not work properly because they were altered during manufacture by some of those latter types, who thought they knew more than I did. For this reason I no longer put my name on designs that I do not have total control over. I will own my screw ups, NOT those of others.)

Shmows they are. There was an episode where they said a car wouldn't pole vault if the front drive shaft U joint broke. I've seen it happen numerous times with street cars at the drag strip. That's why NHRA requires drive shaft loops on all cars but stock streeters.

asumbing the mythbusters data is correct (i believe it is)

im betting their are two main reasons that car manufactures dont put dimples on a car.
one reason...looks
their have been a lot of cars out their that look really weird but perform well, they never sold because they were so strange.
reason 2....cost
it would cost a lot to dimple a car, parts would have to be moved, new machines to make the dimples, some space would be lost, ect.
the manufactures dont care how much we have to pay for gas, if the retail price of the car increased by a few grand that may be enough to scare people away from the design.

and thats just the main reasons,
how much fun would it be to clean a car with dimples? or what happens when it rains and the dimples are full of water or snow or leaves or mold, ect? how fragail would the design be?
the argument, if it worked so well we would all have dimples on our car, is not valid. their is a lot more to it.

"We moved that pivot point 6 inches 'cause we cuddn't get our hands in there to bolt it. Are you saying it makes a difference?" [:@]

Actually, a piece of debris hit the top edge of the roof and caused it to buckle, then the air got under it and made it worse...it wasn't just the vinyl...nor was it the fact (? ) that the sheet metal was thinner than stock. I have the race on video...Richard gets up on the hood with a hammer and beats the #$%@ out of it...then takes an awl and punches holes, then wires the metal back down to the roll bar hoop at the top of the windshield
It's been on "The Glory Days" with Dave Despain on Speed Channel and whatever the name of that channel was before they changed it to "Speed"...might have been ESPN, back in the 80's.

I remember reading an article in (I think it was ) Hot Rod magazine written at the time, by the Chrysler engineers about the theory of the surface roughness and boundry layer, etc. trying for some kind of edge to help get them more competitive on the faster tracks.
Ya gotta remember that they (Chrysler ) had dominated in '66 and '67 but when Ford and Mercury introduced the fastback Torino and Cyclone, they (F & M ) slaughtered everyone in '68 and '69, setting speed records, and winning the NASCAR championship both years.
Richard Petty left Plymouth for Ford in '69 because the '68 cars were so uncompetitive on superspeedways. That's why Chrysler came out with the Plymouth Superbird and Dodge Daytona with the pointy beaks and 2' high wings in 1970.



The Mythbusters used the same car for the entire series of tests...
Check out the Discovery channel web site...you can visit the Mythbusters forum and ask them yourself if you want.

Oh really! What do you base your findings on? I would like to read up on the dimples on the skin of a sub.

I am kind of interested in the way actual occurrence is fashioned to fit formula but I am more interested in the way things really work in the real world as opposed to the way things work in the artificial world of formula based text. I just cannot bring my self to believe what I read when it totally contradicts what I can see with my own eyes in the real world that I live in.

It may serve a pilot well to define drag as a force that opposes the motion of an aircraft through the air. But it does not serve me well at all because it only represents a fraction of what drag is about, but most of all its an inaccurate definition. When I read the faster the aircraft goes the more drag it produces I am aware of the fact that some aircraft have a completely opposite dynamic.

I would rather win an argument by citing real world occurrences than by citing popular opinion. I would advise anybody not to believe what they read about aerodynamics without applying it to what they can see and feel in the real world where they are a solid object being influenced by a relative airflow 24-7 from the day they started the process of respiration at the very least.

By the way I was up in your very beautiful part of N.C. you are from a week ago riding my sport-touring bike. I am from the boring flat lands of F.L.

All they really needed to do was to leave their car out in a hail storm to get some effective dimpling! Next time someone has a hail storm let us know and we'll come over for some improved MPG.

they could park the cars on the driving range

[quote]ORIGINAL: mike31

Oh really! What do you base your findings on? I would like to read up on the dimples on the skin of a sub.
[/quote
to reduce sonar reflection.http://wings.avkids.com/Book/Sports/...r/golf-01.html

If dimples are so helpful aerodynamically, why are golf balls the only dimpled projectiles?

Submarines reduce drag by having a nice pointy tail. Something that will not work on a golf ball.

feathers and rifling came before golf.

I couldn't find anything. Except that dimples on a Russian sub, put there for a special missle, caused it to be easier to track by sonar.

Maybe if you point the tail to the rear, and it is made to fall off when it hits the ground?

lnewqban,

Dimples aren't helpful in every situation. The drag of a sphere is strongly affected by the location of the flow separation. Dimples force the boundary layer to be turbulent, which moves the separation location rearward, which reduces drag. For some projectiles, the drag may not be strongly dependent on the separation location, or their shape may result in a fixed separation location. In cases like this, forcing a turbulent boundary layer doesn't help, and probably increases drag. For example, a classic bullet shape, with a squared-off rear end, will experience flow separation at the square corners, whether the boundary layer is laminar or turbulent, so dimples can't shift the separation location, and wouldn't reduce drag. Some wings do have the equivalent of dimples, used to tailor which part of the wing experiences separation first, or to prevent a laminar separation bubble. The drag on a submarine is significantly higher for turbulent flow, so dimples would not be used to reduce drag on a submarine.

banktoturn

The range on some artillery shells is increased with base bleed systems to cut the drag.

That's really interesting. Does that mean that some air is vented from a high-pressure area to the base?