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Old 12-12-2013, 04:50 PM   #7 (permalink)
aerohead
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Kamm's drag figures

Quote:
Originally Posted by Big time View Post
Do you know of some drag (and maybe lift) tables for teardrop shapes cut at various lengths, Kamm style?
*Kamm reproduced Walter Lay's research at the FKFS,along with Baron Reinhard von Koenig-Fachsenfeld in the late 1930s.
The models tested with K-form architecture represented five different lengths as opposed to Lay's four,adding an intermediate length between Lay's #3 and #4 position.
*The model terminated at 77.3% of the Aerodynamic Streamlining Template,with the rear contour terminating at 27-degrees.
*Length #1 was 37.5% AST.and measured Cd 0.25 with zero edge rounding,and zero plan taper.
*Length #2 was 45.5% AST and measured Cd 0.24 under the same conditions.
*Length #3 was 53% AST and measured Cd 0.24.
*Length #4 was 67.5% AST and measured Cd 0.22.
*Length #5 ,77.3% and Cd 0.21.
Here is the table

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*With Buchheim et al.' body side camber the full-tail Cd falls from 0,21,to 0.186.
*With Lay's 0.14% body width radius edge rounding the Cd falls from 0.186,to 0.151.
*With the full tail plan taper escalation the Cd drops from 0.151,to O.12.
I don't have any facility to analyze the intermediate positions but I did a breakdown at the AST Part-C thread.
*Essentially,the body drag varies as with the fuselage truncation,with the wheel/tire drag super-imposed upon that drag to reach the total.
*The fuselage drag doubles in ground reflection and it's half-body carries the entire drag of both 'above' and 'below' ground half-bodies.
*With wheel fairings the drag can go below Cd 0.12,as with the Cambridge University's 2013 CUER solar racer.
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*I don't recall any lift tables for the FKFS work.Kamm wasn't interested in lift so much as with crosswind stability.All the K-cars suffered gust effect stability issues.Koenig-Fachsenfeld patented a split-fin stabilizer as a palliative.
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*Typically,half-bodies do not generate lift in the general sense of how it is used.
*Proper truncated half-bodies produce no separation 'over' the greenhouse area.All the drag is behind the body chop,acting like a drogue-chute.
*Full-tail half-bodies have no separation at all and no wake as generally understood.As with barn doors,with enough horsepower and velocity they can be made to fly,but at 'normal' highway velocity it's not an issue.
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Last edited by aerohead; 04-05-2014 at 04:49 PM.. Reason: add image
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