REFLECTOR: Elevator Trim Spring

Alex Balic alex157 at pwhome.com
Tue Jan 31 08:57:41 CST 2006


I definitely agree with you there Pat- although I remember over the years
several discussions where folks would comment that the position of their
elevator in cruise was abnormally deflected up- just thought that would be
the first place to check- you can of course fly that way by adjusting the
spring position (which I agree should be more accurately indicated in the
plans) but flying with the elevator reflexed more than a few degrees in
cruise is an indication of an out of rig aircraft. As for the incidence
gauges- mine were pretty basic, and the one for the wing was slightly
warped, (although I corrected that) so if all errors went in the same
direction, the canard incidence on any one aircraft could vary by a few
degrees, and on that stubby little airfoil, that would create a big change
in lift. Of course if the actual position of the elevator in cruise is fine,
and you are just out of trim, then of course, they would need to adjust the
spring position.

-----Original Message-----
From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On
Behalf Of Pat Shea
Sent: Tuesday, January 31, 2006 12:37 AM
To: Velocity Aircraft Owners and Builders list
Subject: RE: REFLECTOR: Elevator Trim Spring

Alex,

The relationship between the wing and canard is
relatively accurately set by the incidence gauges. On
the other hand, the neutral position of the elevator
trim system is very roughly set by the TLAR method
(That Looks About Right). If I recall correctly, the
directions read something like "Remember, you'll need
more up trim (elevator trailing edge down) than down
trim." Consequently, I suspect most builders end up w/
too much up trim and run out of down trim at high
speeds. This is by no means any indication that the
wing to canard configuration isn't correct.

It's been my experience that the standard elevator
trim system has enough throw to cover both the high
and low speed ends of the envelope - you just need to
fine tune the neutral position.

Pat XLRG

--- Alex Balic <alex157 at pwhome.com> wrote:

> I was under the impression that the starship used
> variable sweep on the
> canard, not variable incidence- this increased the
> lift authority at slow
> speed (extended)  and reduced drag at high speed
> (swept) I agree that there
> is a fundamental design feature to keep the canard
> stalling before the main
> wing, but the particular aircraft that we are
> discussing might need an
> adjustment of canard incidence to correct the pitch
> authority problem
> without going so far as to allow the wing to stall
> before the canard-
> really, a close and precise gauge of the incidences
> relative to each other
> will determine if adjustment is needed.. 


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