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Old 05-11-2012, 11:47 AM   #1
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Default Under car Aero improvements

Without question a full coverage under tray would yield the best results. The reality is most will not go to that length. What if anything should be done to improve the under car aero?

Rear bumper area looks to be a problem. Would paneling the rear sub frame to bumper make any difference?
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Old 05-11-2012, 02:53 PM   #2
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The center section isn't really that bad. I would run a splitter back to the front subframe and then paneling under the rear sub-frame leading into a diffuser, with something done to keep the diff cool. If you have nice smooth transitions between the center section and these two pieces I'd be you would have pretty good laminar flow... but the rules for SSM don't allow a diffuser or under car aero behind the center line of the front wheels, so I'm maxed out with just my splitter

For reference (ignore the yellow crap):

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Old 05-11-2012, 05:18 PM   #3
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In a fully covered bottom, where does the radiator air typically end up?
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Old 05-11-2012, 06:33 PM   #4
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Out the hood from the vents you should be cutting.
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Old 05-11-2012, 07:23 PM   #5
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Have you considered trying to limit the amount of air that gets under the car? I'm considering using some ABS to skirt the front edge of my splitter and along the rocker panels. Just needs to be flexible enough to not get torn off on curbing or loading on the trailer, but stiff enough to hold its shape against the wind. Skirting is legal in SSM, which is the main reason I'm considering it.
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Old 05-12-2012, 01:14 AM   #6
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Do you mean skirting that drags along/skims the surface or just a bit lower than standard bodywork?

You could research 1978 - 84 (ish) F1 cars for the touch the ground stuff. I spent ages studying this stuff years ago, they had major problems with it tearing off even on the smooth F1 level tracks, though the tracks probably weren't that great back then. Not like we see now...fascinating subject anyway, love to see where you get too.
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Old 05-12-2012, 12:55 PM   #7
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Bunch of Racecar Engineering articles on aero:
http://www.rightwheeldrive.com/Aero_articles.zip
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Old 05-12-2012, 01:10 PM   #8
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Quote:
Originally Posted by njn63 View Post
Bunch of Racecar Engineering articles on aero:
http://www.rightwheeldrive.com/Aero_articles.zip
I'm nominating this post for "post of the year".
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Old 05-12-2012, 02:33 PM   #9
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Quote:
Originally Posted by mx5-kiwi View Post
Do you mean skirting that drags along/skims the surface or just a bit lower than standard bodywork?

You could research 1978 - 84 (ish) F1 cars for the touch the ground stuff. I spent ages studying this stuff years ago, they had major problems with it tearing off even on the smooth F1 level tracks, though the tracks probably weren't that great back then. Not like we see now...fascinating subject anyway, love to see where you get too.
Something like that. I was thinking of mounting it like 1/2" off the ground. It tearing off is definitely a concern, and the last thing I want is to leave debris in the track... maybe its not such a good idea.
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Old 05-12-2012, 04:25 PM   #10
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Quote:
Originally Posted by njn63 View Post
Bunch of Racecar Engineering articles on aero:
http://www.rightwheeldrive.com/Aero_articles.zip

GREAT info in there! Some nuggets I've gathered so far:

1. The angle of a rear diffuser should be the highest possible without cavitating, and should be mounted in such a way as to create the longest flat under tray as possible.
3. Big end plates make serious improvements on a wings effects.
2. A front splitter that ends under the engine bay will increase the engine bay pressure, making hood venting even more critical.
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Old 05-12-2012, 06:14 PM   #11
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NOTE: If music is not for you, mute it.


0.39 for front underpanels
1.05 for rear under panels


I've since added another 30x36" panel after the front subframe-- it ends halfway through the catalytic converter, is inline with the frame rails.

The biggest improvement was covering everything after the rear shelf (about halfway through the driveshaft, covering everything there)... without this, air at diffuser was showing turbulence.

I've also since covered up the RLCAs. The rear outside corner is hanging by loose ziptie to the bumper to note any up/down movement (if any) to hopefully see any signs. This is on street and highway driving.

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