Originally Posted by OZPAF
While no expert I would have to disagree with this common misconception that profile or form drag increases with AR for the same WING AREA. By definition form drag is only related to the area and the operating Cd of the airfoil in question, thus the actual span has no effect(on form drag). Frontal area is misleading and its the actual Cd of the airfoil that is important not the actual thickness.
There are numerous aerodynamics texts that would disagree with your assessment. Hoerner would be a start. My previous post on the subject is right on the money. Nobody said that AR was driving the frontal area increase, just the fact that you are adding span.
We are talking about flying a plane at zero lift, so the minimum drag of the aircraft is mostly related to the frontal area..all other things being equal (both planes with V-tails, similar fuselages...etc).
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.