Quote:
Originally Posted by Cd
Whoa ! I am just now seeing this. I just posted a similar question Aerohead. Sorry 'bout that
Since you bring up ThinkFlight's design, you might notice that it falls out of the Template curve. ( Have a look at his second video )
This got my attention, because despite having too steep a curve at the rear, the design had great attached flow all the way to the tip of the tail, and even along the centerline.
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1) The V1 tail follows the 1935 FKFS, 5-configuration, 'Kamm' test model, and W,A. Mair boat-tail contour. It's upper slope, for it's 'length, never exceeds 19-degrees, while the diffuser goes off reservation, @ 20.5-degrees ( impossible for flow attachment).
I estimate Cd 0.214 for the 40.528-mpg performance.
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2) The V2 tail, with airdam & rocker panel extensions, conforms to W. A. Mair's initial contour, and evolves into the 1981 Cd 0.14, VW Flow-Body( long-tail ) contour, 'peaking' @ Buchheim et al.'s 23-degrees at top ( classical limit for flow attachment ), and the diffuser has been relaxed down to 5-degrees.
This #4-configuration is estimated at Cd 0.1764, to explain the 43.097-mpg ( a 20.99% mpg increase).