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Old 06-15-2013, 02:44 PM   #27 (permalink)
aerohead
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Originally Posted by Xist View Post
I tried searching for that, but did not come up with anything.
*The GM Optimum tail made the cover of the Winter 1995 magazine which Texas Tech publishes.It's in their article about the Aero Lab's Project Tailwind (in which they tape over GM,leaving only 'Optimum Tail.')
The GM tail is only shown in side elevation.It's 20-degrees on top,10-degrees on bottom,and is as long as the trailer is tall.
*My boat tail was also 20-degrees in 1980,with a length equal to 75% of body height,bending gently into the slope.
*NASA's 1981 boat tail was also 20-degrees,bending gradually into the slope.
*Walter Korff (Lockheed Aeronautical) also used 20-degrees,with gentle transition into the slope,with length equal to 70% of body height.
*W.A.Mair,who specialized in boat tail research recommended no more than 22-degrees.He used 1.8X body height to reach the 22-degree slope.
*Ahmed et. al. used 25-degrees at top with hard corner,10-degrees on bottom,10-degrees on sides.It was 62.5% of body height.It lowered the models Cd from 0.25,to 0.214,a 14.4% drag reduction.
*An ideal boat tail,on that same model would have returned a 52% drag reduction.
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