Just a random idea.

[freebeard]

I second the ball peen hammer suggetion.

Reynolds Number
If the dimples are correctly sized for a golf ball, logically, either bigger or smaller dimples would work on a car. I wonder which it is.

Rather than dimples, I'm more currious about faceted panels, like the F-117 jet pane. Here is a body based on a 6v octahedral-symmetry sphere. Obviously it is more aerodynamic than the prolated octahedron it is based on. One could test 2v and 4v versions as well to see if there is a drag minima at less than a smooth compound curved surface.

[RedDevil]

Originally Posted by Frank Lee

Cortex generators are what the world really needs.

Wow. I thought it would be cool to have a VW Beetle covered with golf ball dimples - and a Golf badge.
But a Beetle with a cortex pattern, that would beat it never mind the badge.

"Does it really reduce drag?"
"It thinks so..."

[freebeard]

Dimples? I'd heat a spot the size of a dime cherry red and hit it once with the ball peen. Save concaving the surrounding metal

I wasn't going to post this. But you made me, OK?

from: The Bubble Monster Strikes Again | Art Car Central

[oldtamiyaphile]

Originally Posted by freebeard

Rather than dimples, I'm more currious about faceted panels, like the F-117 jet pane.

I believe the F-117 is the least aerodynamic aircraft ever to fly sucessfully.

[freebeard]

Further to my point. The edge angles on the F-117 are equivalent to a 2v octahedron, the 6v version I showed is within percentage points of a smooth compound curve as the angles approach 180°.

I suggest there may be a drag minima somewhere in between, where the edges encourage reattachment of the airflow.

[aerohead]

Originally Posted by freebeard

Further to my point. The edge angles on the F-117 are equivalent to a 2v octahedron, the 6v version I showed is within percentage points of a smooth compound curve as the angles approach 180°.

I suggest there may be a drag minima somewhere in between, where the edges encourage reattachment of the airflow.

The box cavity performs according to this principle.The sharp trailing edge precipitate separation,but the trailing edge of the cavities step lies along the 'Template' line,if you will.This trailing edge allows reattachment and capture of a locked vortex which allows the inviscid outer flow to close,decelerating and building pressure to cut pressure drag.
We'd pay for the circulation of all the vorticity,but I suspect we'd see an overall drag reduction.
And we wouldn't have to do the compound curves which are the most difficult to pull off.
This would be a great graduate research project for scale testing at a university wind tunnel.

[aerohead]

Originally Posted by backpacker3

Hey guys sorry if this gets posted a lot I had just seen some things that said that adding dimples works and just thought I would post this.
Xist the I saw the mythbusters episode too that's where the idea came from I didn't realize the general consensus here was that it didn't work. I figured that it might be useful for someone who maybe had removed roof rails or something
Ike that as an option to cover the roof of the car with something that might help a little bit for fuel economy. But hey if this end up corralled or closed it was just a though so no big deal

Not that it really matters at this point but if you put some masking or painters tape on the outside of the balls they would come out easy.

I want to say that it was Slowmover who shared a link to an Ethiopian gentleman's Masters Thesis on pickup truck aerodynamics.I've looked back and can't find the post.Sorry!
Anyway,within the thesis,the author reported that the pickup maintained 30 millimeters of Laminar Boundary Layer (LBL) at the nose before transition to full Turbulent Boundary Layer (TBL).Which means that without any 'dimpling',the truck was behaving as fully-dimpled within just over 1-inch distance from its nose.
The TBL would create a constant drag coefficient and the separation line would be fixed.
If any benefit came to the Mythbusters' car it would not have been from the Reynolds number effect,but rather from the dimpling along the roof /C-pillars acting as vortex generators.
The second drive of the car would also have been conducted under a 'warmer' condition which always improves mpg.
Only full instrumentation of the car would have revealed a full and accurate account of all the variables at play during 'testing.'

[Superfuelgero]

Originally Posted by oldtamiyaphile

I believe the F-117 is the least aerodynamic aircraft ever to fly sucessfully.

True, it actually wants to backwards and upside down. If it wasn't for fly-by-wire systems, it wouldn't fly.

I do like the idea of trying to change the surface. When I painted my car, I had to break up the paint work. With the rough fill primer on, it was noticeably quieter. Probably had to do with a separation layer.

[TheManVan]

Wouldn't you be increasing the frontal area by adding enough material to indent with said dimples? just askin!

[gone-ot]

Used-car salesman to customer: "...those aren't hail damage dimples, they're aero-divets..."