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Old 04-16-2012, 07:54 PM   #329 (permalink)
aerohead
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'Template'

Quote:
Originally Posted by kach22i View Post
Guilty as charged, but in my own defense the deviations were rather symmetrical which was something I was trying to point out.

Proper alignment:
Automobile 2 - Odds and Ends pictures by kach22i - Photobucket


Compare to first overlay:
Automobile 2 - Odds and Ends pictures by kach22i - Photobucket
For the 'Template' to function,nothing can be altered except where the truncation is made.The shape IS the premise for its performance.And the shape is chosen with great care in mind.
The curvelinear contour of the aft-body behind the position of max. body camber cannot be altered(*) in any way or you assassinate the boundary layer,the flow will separate and you're inviting a low base pressure and strong vacuum in the wake turbulence.
(*)The exception would be to 'relax' the contour,extending the rear even further back,but you must understand that the extra length is adding wetted area and the drag will begin to climb again do to the additional surface friction.
The same will happen with streamline sections.The drag minimum will occur at a length/width ratio of 3.92:1.Any shorter,or any longer and drag goes up.
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