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Old 08-12-2010, 07:37 PM   #2 (permalink)
aerohead
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equation for 2.5:1 teardrop

My template is based on a Zeppelin airship,teardrop form,with a length to diameter ratio of 2.5:1.
Teardrops as short as 2.1:1 have the same Cd,but if you use them for a template,out at 80% aft-body they violate Mair's maximum boat tail tangent angle of 22-degrees.
The 2.5:1 'body-of-revolution was the 'shortest' teardrop I could come up with that maintained the 22-degree angle limit at 80% of potentially useful length.Teardrops with greater fineness ratios will begin to accrue additional drag due to increased skin-friction from the additional wetted area.
Someone with a calculus background could probably help write the equation for the curvature.
'Apology for the rough graphic of the template.At larger scale,a french curve could be used for curve smoothing to take the 'bumps' out.
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