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Old 03-25-2015, 05:39 PM   #15 (permalink)
aerohead
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length

Quote:
Originally Posted by serialk11r View Post
Hmmm that reminds me, some cars have much longer (in the sense that you used the word "length") mirrors than usual but some lowish drag cars have your typical flat brick shape mirror, does adding extra length help a lot? I'm guessing it's not more common because you have to pay attention to interference drag if the mirror is near the A pillar.
I don't have a pictorial to share,but here's some data to think about.
*Kach22i's prop spinner is about Cd 0.30 in a free stream of air.
*If you put 1-soup can(same outside diameter) behind it,it drops to Cd 0.233
*If you add a second soup can ,Cd 0.225
*Adding a 3rd can,Cd 0.215.
*Mair's boat tail wind tunnel model,with prolate ellipsoid nose and 3-soup cans was Cd 0.204.
*The 'GAVRE',Aberdeen,5-degree boat-tailed artillery projectile is Cd 0.16 in subsonic flight.

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So length does matter,aerodynamically.
The 1996 Porsche 911 GT race car has very 'long' elliptical mirrors,far from the body.My opinion is that Porsche spent a lot of tunnel time developing these LeMans mirrors.
Only full-scale testing or DNS CFD is going to show us the way.
The A2 or DARKO tunnels would be perfect for us.They're both capable of 1-count accuracy and perfect repeatability.
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