Metal Mesh Belly Pan?
 

I've heard of some cars (from Mercedes, I think?) that have metal mesh on the underbody, to act as a belly pan of sorts. In a way, it makes sense. Because the mesh is slicing through the air edgeways, instead of hitting it full-face. Thoeretically, that would make it act as a "virtual solid" aerodynamically.

I doubt the mesh would be as effective as a solid surface, though. But it should be better than nothing. And expanded aluminum mesh can be had at the hardware store pretty cheap (and lightweight).

The idea here wouldn't necessarily be to build a complete belly pan from metal mesh, just the parts that are near hot spots, like the exhaust system.

Has anyone tried this yet? A search didn't yield anything.

A bellypan should be rigid. If you don't get the mesh very tight it will sag and flap in the wind.

He mentions expanded metal which is no more flimsy than normal sheet metal. I'd be interested whether this would aid or detriment the aero. I'm sure the mesh itself isn't very good with airflow. Paging Phil! :)

mesh
 

If you go all the way to the back of Hucho's book,in the chapter on Numerical Analysis,he makes mention that air cannot support a load of any kind and will simply deform,attempting to reach equilibrium.
When the Big Dogs do 3-D CFD on cars,they will actually 'panel the wake',setting up the spherical vector coordinates of the wake as if it were a solid body to enable the inviscid flow protocals to function.Quite a challenge when there is no 'a priori' knowledge of how a theoretical cars wake will actually behave.
All this suggests that it requires a solid surface to alter airflow.
********* Here's the caveat for a belly pan though.If the rear valance is low enough to trap and pool dead air below it,for the entire length of the cars underside,a permeable membrane might aid in damping pressure oscillations underneath there.
There may be research published on such a thing.I don't know.So far,automakers are using solid panels,shielding heat sources.
If you have the inclination and want to do some sweat-philanthropy,do the mod and let us know.
You will need an exquisite baseline database for the vehicle for which to compare before and after.

Expanded metal isn't really all that flat though.

you mean somethiong like this?
before

http://i678.photobucket.com/albums/v...nterior028.jpg


http://i678.photobucket.com/albums/v...nterior029.jpg

http://i678.photobucket.com/albums/v...pgq45119-1.jpg

http://i678.photobucket.com/albums/v.../mpgq45117.jpg

http://i678.photobucket.com/albums/v.../mpgq45115.jpg

http://i678.photobucket.com/albums/v.../mpgq45046.jpg

http://i678.photobucket.com/albums/v.../mpgq45057.jpg

http://i678.photobucket.com/albums/v.../mpgq45056.jpg

in one of the middle pics, you see that the belly pan also is under the rear axle so there was no air trapped in the rear bumper.
It helped thsat i am running a IMPUL full body kit which gives me 2 extra inchs lower.

the middle is just screen material. as the air passes next to it it acts as a solid surface.
In the back I used the preformed screen. I had to tilt it down just a hair!

The screen is a good idea for places where you always end up running over tumble weed in the road.

Mesh would resist fluttering in the wind somewhat, due to it being open. Also solves any heat build up problems.

But how much would it shape airflow? Is it really almost as effective as a solid smooth surface? Or is it closer to having nothing at all?

I though about strategically placing holes in a belly pan to try release pressure differential.

Where/why would you have pressure build up around the bellypan?