Thread: New Product Baudis Fosa F3B/F3F
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Old Nov 11, 2010, 11:53 PM
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PS- I should probably be more specific. The "operating CD" you mentioned is a translation of the force placed on the airplane to the reference area of the wing. What I have stated is that the frontal area has a direct effect on that force, and will have an inherently different "operating CD" because of that.[/QUOTE]

Hi Aaron,

Apologies to Reto if this is straying off his original thread, but I think this is an important design issue.

I think we are both a little guilty of not being specific , so I would like to explain myself a little better.

What has been labelled wing "form drag" in this thread would more correctly be called "wing zero lift drag" and includes both pressure drag of the foil and 'skin" or "friction drag" as I understand it.

If we compare wings of equal area and of similar airfoils (every thing else being equal) then the wing zero lift drags will be same for low and high AR, providing the airfoil performance is the same with the change in Re No's(assuming the same flight speed). Both wings will have similar pressure drag(airfoil characteristic) and the same wetted area(skin area).

I feel that what has held these low AR models back has been stuctural limitations and maintaining airfoil perfcormance(at the lower Re's) as others have mentioned.

However it appears that the Fosa may have overcome these limitations with a very stiff wing and competitive airfoils of a slightly higher thickness ratio.

Again apologies to Reto for the drift off the thread.
Cheers
John
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