REFLECTOR: Elevator balance

["Al Gietzen" <alventures@email.msn.com>]

When balancing elevators you might like to keep in mind that counterweight
is more effective at the outboard end than at the inboard end.  Of course
you can get "static" balance either way, but "dynamic balance" is what
really counts.  There was a recent article in Sport Plane or Kitplanes on
the subject.

The gist of it is that flutter is an occurrence involving the flight surface
and the control surface; a resonant flexing in the flight surface driven by
a flexing in the control surface.  The idea of the counter weight is to have
its inertia working against the movement the dampen it out.  Since the
amount of (potential) flex increases as you go out from the fuselage; you'd
ideally like to have the counterweight distributed proportionally along the
length of the control surface (less toward the inside and more toward the
outside.

If you are going to lump the counterweight; it's more effective to put a
bigger lump on the outboard end.

In the Velocity, I'd guess wing/aileron flutter is quite unlikely since the
wing (especially with the tip sail; a.k.a. "winglet") has a very different
resonant frequency than the aileron, and the aileron has distributed
counterweight.  Not so with the canard/elevator.  So do the static balance
on the elevator carefully, and if you have to take off weight, take it off
the inside weights.  Or on the 173's where it's more likely to need added
weight; add to the outboard weight.

Of course, when you can, it's always nicer to reduce trailing weight rather
than increasing counter weight.

Well; at least that's my take on the subject.

Al Gietzen  RGE

-----Original Message-----
From: R. Wayne Owens <wamowens@bellsouth.net>
To: reflector@awpi.com <reflector@awpi.com>; MTETER@aol.com <MTETER@aol.com>
Date: Tuesday, May 04, 1999 5:48 AM
Subject: Re: REFLECTOR: elevator balance


>Thanks
>Wayne
>