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Wow what an argument...
All this talk of drag can be broken in to the three sub-categories.
Profile drag is from the shape of the airfoil. this seems to be what most of you are discussing. It seems that some of the points also are really thinking of surface friction.
Parasite drag applies to the original topic if we are not trying to create lift, negative or positive.
Induced drag is caused by angle of attack. This is the part the rest of you are discussing.
You most certainly can have "Real world" negative induced drag. (thrust from drag) Ask any helicopter pilot.
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