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Old 8th Jan 2011, 06:46
  #12 (permalink)  
CliveL
 
Join Date: Dec 2010
Location: Europe
Age: 84
Posts: 286
Hmm, I'm afraid that is not universally correct.
That would be the Center of Pressure.
The Aerodynamic Center is the Point at which the moment is constant, independent of AoA, but not necessarily Null.
Sorry guys, but that is not what I said. If you take moments about the point where the lift due to incidence acts then you will get a constant pitching moment as incidence varies and this point is generally close to 25% chord. So the aerodynamic centre is the location where the lift due to incidence acts and is independent of incidence (more or less).

Centre of pressure on the other hand varies with incidence. At zero lift the centre of pressure is at plus/minus infinity if there is any wing camber, because the pitching moment at zero lift is produced by a couple. As you increase incidence (and lift) the centre of pressure will move towards the 25% chord point but it will never get there.
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