MGC (MAC)?

when you guys figure out mean geometric chord (MGC) or mean aerodynamic chord, do you include the flaps?

Yes

>Yes
A typically succinct and to the point response from Howard.

A two minute blurb on why follows.

There seems to be an uncontrollable urge on the part of modelers to want to separate the parts of aerodynamic sufaces. Talking about wings AND flaps and/or stabs AND elevators as though they are independent entities. Such a distinction should be avoided.

The facts are that flaps and elevators are nothing more than parts of the fixed surface to which they are hinged. The only difference is that they are movable and by virtue of that movement can alter the camber of the entire lifting surface. When deployed the moving surfaces alter both the camber and the angle of attack of the total surface and modify the lift which is produced as a result.

We like to think of the "flippers" as the devices which "flip" the airplane into a new attitude. The reality is that by doing their "lift enhancing thing" to the surface to which they are attached they produce more or less lift and, in the case of the tail that lift drives the pitch attitude of the aircraft "about" the center of gravity. In the case of the wing the lift thus produced not only allow the aircraft to climb by virtue of the increased lift but also produces a "moment about" the center of gravity of the acft by virtue of the distance from the CG the lift produced acts ... called the aerodynamic center of the total wing.

Thus, if the CG and the AC are at roughly the same location longitudinally (from front to back) the lift will cause little or no moment but, if significantly far apart, will produce a moment in the obvious direction consistent with the amount of lift and the distance between it and the CG.

Thus the modern approach to CGs to get them roughly in line with the AC of the wing (about 25% of the MAC +/- a bit depending on camber and angle of attack and other esoteric bits of trivia). There will still be some opposing pitching moment due to the fact the airfoil is now cambered and a pitching moment in the direction of the deflected surface is a fundamental part of the forces at play with a cambered surface.

The above is a large part of the reason for the discussion by Gary Weaver of the fact that is airplane turned less quickly with flap deflection than without.

OK, may five minutes. Don't be a clockwatcher!