On Jun 10, 9:29 am, Tina wrote:
One point about the lift fairy sitting on the tail I'd like to
understand is this -- actually a serious question. As I understand
it, nearly aways the tail is exerting a downward force, since the
center of lift is aft of the center of gravity on general aviation
airplanes (that is true, isn't it -- that the cg is forward of the
center of lift?). If so the tail really is imposing an increased load
on the airplane, adding to its effective weight. The question I have
is, how many pounds of weight is imposed aerodynamically for an
airplane that might be loaded with its CG at the forward limit? I
don't know where the center of lift is on ga airplanes -- a third of
the way aft of the leading edge of the wing is an ok approximation,
but a few inches error on an airplane weighing what ours does at max
could make a huge change in the required force to overcome the nose
heavy moment.

CG range for most typical lightplane airfoils is 25 to 33%
of the chord, while the centre of lift is around the 40% mark. The
load on the stab/elevator isn't all that big, but it's enough that
we'll teach you in groundschool that the aircraft's stall speed is
lower when loaded to the aft limit than when it's loaded to the
forward limit, and that the cruise speed is a little better at the aft
limit.

Dan