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Date: Wed, 28 Feb 2007 21:32:41 -0500
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Subject: Re: aileron reflex on LNC2
From: "bob mackey" <n103md@yahoo.com>
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>>>What does the group think about reflexing both ailerons up a degree or
so?<<<

Adjusting the ailerons upward has roughly the same effect as increasing
the washout. Typically, that would slow the progression of a stall
from inboard to outboard, and improve aileron authority near minimum
controllable airspeed.

Another way to get a similar effect is to lower your flaps
a degree or so. That's not quite the same because it also
affects the incidence angle of the tail and the fuselage.
There was already quite a bit of effort expended in figuring
out what was the right airfoil, twist distribution, planform,
tail incidence, flap settings and such. The result is a compromise
between many factors. By raising the ailerons, you are basically
choosing a different compromise from the one chosen by the designer.

If you want your compromise to favor
low speed roll authority over other factors like cruise speed,
then go go ahead and try your experiment and see if you like
the results.  My guess is that without careful measurement,
you will not be able to perceive the difference.

>>>My ailerons are indeed rigged so that both are slightly above
the wingtip faired in position. The purpose was to provide a
very slight air load in order to reduce the dead band around
the system lash and any "flutter" induced by the no-load situation. <<<

Hmmm... is there any reason to expect that the ailerons are unloaded
in level flight? I would have expected that they are carrying a
slightly higher pressure below than above, and are pressed upward
in cruise flight. Raising them from their stock position puts
them closer to the no-load condition by shifting lift inboard.

PS - if the ailerons are much displaced by cruise flight loads,
there is too much slop in the hinges and/or bearings. Any more than
about 1/8" at the trailing edge is an excuse to reread the thread
on hinge slop and then do something about it.

BTW, sailplane designers worry a lot about flap and aileron settings.
Some go so far as to design flaperon mixers that change the
aileron rates and twist distribution to minimize drag over
a wide range of flap settings. I designed the controls for
one sailplane that had three mixed flaperon segments on each
wing. Full 3D CFD models were done including maneuvering flight
for all flap settings. In the end the glider had excellent
control feel, good performance over a wide speed range,
and extremely good maeuverability at very low airspeeds.
One part of that reflexing the ailerons (outboard flaperons)
upward when the flaps (inboard flaperons) were all the way down.
This made the wing very forgiving in the landing configuration.