In a message dated 9/16/2005 8:51:10 P.M. Central Standard Time,
marv@lancaironline.net writes:
Excessive wear is the very nature of aluminum in a hinge
environment. The
wear is not on the pin, but rather on the
inside diameter of the hinge
itself. Aluminum is a relatively
soft material and it corrodes easily.
Logically as the aluminum
wears away on the inside diameter that houses the
pin, you would
conclude that the slop would increase over time. Flutter is
caused by unbalanced control surfaces. I don't think loose pins
would
necessarily lead to flutter, but perhaps, if there is a minor
imbalance,
movement allowed between the control surface and airframe
via a sloppy
fitting hinge could move you closer to destructive
flutter.
John,
The issue of hinge looseness is not about flutter per se. It doesn't
take much looseness in the LNC2 aileron hinges to be reflected in the
"lash" in what should be a very tight system. With tight hinges, if one
clamps one aileron and moves the other, one would see 1/8 to 1/4 inch of
movement, a measure of the lash inherent in any system consisting of 2 times
several push-rods with bearing rod ends, bell cranks with bearing pivots and
hinges that are another pivot point. With loose hinges alone (my airplane,
prior pins) that lash could be 1/2" to 5/8", depending on how much force is
applied. One compensation for any lash is to rig the ailerons a bit high
so as to put a wee air load on both, thus eliminating sloppy movement that
could be potentially excited by airframe vibration. For me, another assist
is the use of a servo driven spring trim system which also places a small
tension on the aileron control system.
I am not experiencing "flutter" at the outboard elevator hinges, but a
peculiar movement that excites the horizontal stab.
If carbhinges would have been available when I was building the wings (Um,
1991-92) I would have considered them although my education took flight only
after flight. I would not consider installing them now, after the paint
has dried. I would rather like to investigate my minor "problem."
Scott Krueger
AKA Grayhawk
Lancair N92EX IO320 SB 89/96
Aurora, IL
(KARR)