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Old 08-14-2006, 10:15 AM   #1
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dimple tape?

along the same lines as VG tabs, I stumbled across a "dimple tape" for use on gliders:

*photo courtesy of wingsandwheels.com

It's cheap enough that I'm considering buying a roll and experimenting. Where's the best place to install it - the rear roof or decklid?


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Old 08-14-2006, 10:22 AM   #2
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I would guess only the high impact sites on the vehicle since the dimples are so small, unlike airtab-like devices. Bumper and front of mirrors...

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Old 08-14-2006, 10:31 AM   #3
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Saw this on the EV digest ala google.
Its refered to as the Magnus effect. You can buy dimpled tape and sheetswith this on it. Skin friction on autos has a small effect compared tofrontal area because of the speeds. The single largest drag item on a car isactually the road - under body interface. That's the highest pressure and normally byfar the dirtiest place aerodynamically on a vehicle.
About the only effects you could expect to see with the dimple tape on a caris having a nifty conversation starter and making the guy who sold you thestuff a wee bit richer. ;-]
If they did work, you'd need a lot of them. I remember seeing some lexus commercial about how dimpled underbody panels reduced drag, but I can't find anything on it. Here's some more. VGs supposedly work because the drag they induce in order to fill in low pressure areas in the rear with air (and have the flow seperate farther down stream) is less than having the flow seperate immediately at the rear of the vehicle. Ideally uinderbody panels should smooth flow enough to where these aren't needed, of course the ground may not be as smooth as the underbody of your car, so who knows?

Another quote
If your car had the same profile as a golf ball dimples would help, but cars don't. If the golf ball was smooth the air flow would separate at around 0 and 180 degrees and then cause "pressure drag" which is suction. The dimples disrupt the boudary layer, causing the flow separation to happen over a smaller area, thus reducing drag.

Laminar flow is a good thing, flow separation is a bad thing. Eventhough laminar flow is "sticky" the boundary layer acts like an air bearing, reducing overall drag. Zero flow separation would get you close to zero drag, but there will alway be some drag due to the air "sticking" to the surface. Well unless you are in a vacuum.

For a very nice, low drag, shape, look at a dolphin or a shark. They have it made, low drag in a fluid much more vicous than air (yes, air is a fluid aerodynamically speaking).

Anyway, that is the way I remember it from my sub-sonic aerodynamics class.
Originally Posted by FormulaTwo
I think if i could get that type of FE i would have no problem driving a dildo shaped car.
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Old 08-14-2006, 10:35 AM   #4
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Originally Posted by lindermant
Don't want to be off topic, but where did you buy the smooth hubcaps?
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Old 08-14-2006, 11:27 AM   #5
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omgwtfbyobbq - I remember that Lexus commercial (vaguely), and you're right - the entire underside of the car was covered... guess the single strip of tape wouldn't do much then

matt - I got the hubcaps from moon eyes:
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Old 09-09-2006, 10:36 PM   #6
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How about self-adhering rubber bumpers from electronics supply stores?


I would only consider the "hemisphere" shapes.

Cheap, easy to apply, and removable. But where to put? Probably needs spares if/when they start flying off. UV exposure would probably melt the adhesive. If they don't stay adhered, then maybe go with epoxy installation.


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