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Old 03-06-2010, 04:04 PM   #30 (permalink)
aerohead
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8-degrees

Quote:
Originally Posted by Otto View Post
NASA guy told me ~8 degrees was max slope on aft body, to avoid undue separation and turbulence. German sailplane research showed essentially that, as seen in oil smear tests in wind tunnel.
Remember,they're talking about sections or bodies of revolution with very low thickness and high fineness,and they're operating in turbulent free air,trimmed for max efficiency,at altitude.
Also,during landing and take-off the wings can survive angles of attack close to stall,and with turbulators ( vortex generators ) they can push that angle another 6-degrees.
With suction slots,wings can maintain attached flow up to around 40-degrees.
Mairs research ascertained that for automobiles,22-degrees would be the limit.
You'll see this angle with Klemperer's Cd 0.16 'minivan',Walter E. Lay's Cd 0.12 'pumpkin seed'.It's also the terminal angle for the L/D 2.5 streamline body which Hucho references as the drag-minimum in ground-reflection,developed by Ludwig Prandtl under inspiration from Edmund Rumpler.
And before you say it,some of the exotic fancy laminar sections with remarkable low drag can suffer up to 300% drag increases when used as 'cars'.
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