Quote:
Originally Posted by HydroJim
Freebeard-
Based on your chart, a shape with a height/length ratio of 1:4 is better than the template's ratio 1:2.5. Why then is the template only 1:2.5?
If I remember correctly, I think it has to do something with the 1:4 template being too impractical because it's so long. But I was wondering if there was another reason.
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The 2D flow drag minimum for struts or symmetrical wing sections is 1:4.
The 3D flow drag minimum for a streamline body of revolution which also respects W.A.Mair's 22-degree max.boat tail tangent angle is around 1:2.5.
1:2.1 is shown as the drag minimum for free flight in Hoerner's report but it violates the rear contour for flow attachment in a bluff body.
Some use the 1:4 contour in plan-view.
If you were doing something like Aptera or the Edison car,the 1:4 strut might be the way to go,as this would be pretty much 2D flow around the wheels.