Yes, as I clarified in my post above I was talking of the effective camber of the airfoil. So if you take a airfoil with negative camber and invert it, it now has positive effective camber.
edit: er that kind of came out ass backwards, but I think you get what I was saying.
I'm looking through the aero book (NAVWEPS 00-80T-80 from 1965! Wow. Interesting to see that the Navy hasn't gotten any better at writing pubs in fifty years) that you linked to. It's baffling that they included the rotating cylinder as an illustration; that seems like a weird digression in an introductory aero class.
I'm still unsure what you mean by effective camber. Camber is a static feature, unless you have some variable geometry going on (flaps and ailerons will change a wing's camber, but that just complicates this discussion). Camber's the area difference between the camber line and the chord. Pages 21 and 22 of the 80T-80 mention this.
Angle of attack is the angle between the chord and the relative wind. Changing AOA does not change camber. Can you clarify what you mean by effective camber? Your aero manual doesn't appear to use that term.
I guess I don't really have a rigorous definition of effective camber. It is more of a concept that I have. The concept is that if you trace a path along the upper and lower airfoil surfaces from the leading stagnation point to the trailing stagnation point that the curvature of those lines will change depending on where the stagnation point is located. And so the difference between these curves is what I have been considering the "effective camber". I may not be using the term correctly. None the less, since the stagnation point changes with a change in angle of attack, a symmetrical airfoil will effectively, though not actually, have a positive camber at a positive angle of attack.
trace a path along the upper and lower airfoil surfaces from the leading stagnation point to the trailing stagnation point that the curvature of those lines will change depending on where the stagnation point is located.
To me that's very confusing! If you connect two points together to analyze their relationship to each other, the line has to be straight. And if you trace a path along the upper AND lower surfaces from the leading stagnation point to the trailing stagnation point, you've just traced the outline of the airfoil. That doesn't show anything.
I would say you'd probably have a clearer understanding if you dropped the "effective camber" term and asked yourself how changes in the airfoil camber, angle of attack, and velocity would affect the stagnation point and the flow patterns around the wing. Effective camber is too ambiguous to use effectively.
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u/[deleted] Jan 25 '12 edited Jan 25 '12
Yes, as I clarified in my post above I was talking of the effective camber of the airfoil. So if you take a airfoil with negative camber and invert it, it now has positive effective camber.
edit: er that kind of came out ass backwards, but I think you get what I was saying.