Rain Gutter Side Skirts

[Tango Charlie]

Thanks, cfg83. No, I wasn't the first. I was inspired by Xringer. I'm not sure what basjoos used.

Now I need to get that belly paneled in...

[chuckm]

My gutters have been on for over a year now (painted w/black Krylon as well). No problems from the few times I've scrapped them.

[NeilBlanchard]

Hi folks,

Can I ask what is the intended aerodynamic function of these side skirts?

Personally, it feels a bit counterintuitive -- I would think that you want to have air "escape" out from under the car; and not to trap it under the car. And none of the ultra-low Cd cars that I am aware of have anything like this.

[chuckm]

The Loremo has side skirts. Some high performance vehicles extend their bodywork down lower than the lowest point on the suspension.
I think the idea is that air wake generated by the tires does not propagate and further disturb the air flow underneath the car.

[cfg83]

NeilBlanchard -

Originally Posted by NeilBlanchard

Hi folks,

Can I ask what is the intended aerodynamic function of these side skirts?

Personally, it feels a bit counterintuitive -- I would think that you want to have air "escape" out from under the car; and not to trap it under the car. And none of the ultra-low Cd cars that I am aware of have anything like this.

My (ever so flawed?) thinking is that I am separating the "clean airstream" from the "bad airstream", but I don't really know. With this mod I think I should create a "snow-plow" air dam to minimize the amount of air flowing under the car. If nothing else, in tandem with an air dam, I think this could be a form of "virtual lowering".

I did some flow simulation YouTubes and found something interesting. The imaging is a top view and is problematic, because none of the "objects" actually touch the ground, they only interfere with the air stream. I was trying to simulate the engine, transmission, suspension, and exhaust piping :

http://www.youtube.com/watch?v=WcCE7bYvUmE

http://www.youtube.com/watch?v=SQ3uZw-oUgw

If the above is showing a valid result, then the rear ( non-moving!!! - ) tires seem to have less turbulence associated with them.

CarloSW2

[instarx]

Rain gutter material also makes a nice front air dam...

[wagonman76]

I thought about trying side skirts but attaching isn't near as friendly as that Saturn. I'd have to fab something up, and would probably use more lawn edging. I got a bunch of it from spring cleanup piles earlier this year, some of it still brand new.

[cfg83]

instarx -

Originally Posted by instarx

Rain gutter material also makes a nice front air dam...

Oh yeah, I remember yours. Fantastic work because it's so OEM-ish.

CarloSW2

[cfg83]

Hello -

Based on this comment from aerohead :

Originally Posted by aerohead

NASA's research demonstrated an 8.7% drag reduction @ zero crosswind,and 19% drag reduction under a 6 mph wind @ 6-degrees yaw.

I modified my side skirts to taper-in at the front *and* taper-out at the back. It was super-easy to do because there are only 3 wing nuts holding it up. I left the center wing nut the same and drilled new holes in the rain gutter on each end. The new holes were offset 1/2" from the original holes. That leads to this look from below :



And from the side :



I don't think the taper-out at the back matters because the side skirt and rear front mudflap are already sticking out. It's probably a better compromise.

I doubt it will make a measurable difference, but I like the idea of copying the "trucker side skirt" model.

CarloSW2

[jeongyun]

Thanks for bumping up the thread. Ingenious idea.