[rebel-builders] Moose: Elevator trim (crush tube)...was: Ra

[Eric Fogelin]

My experience as an Elite on floats, is that there is no need for an
electric trim tab. I am tempted to remove the entire MAC servo and make the
tab fixed. I've only used the servo a few times. When CG moves aft when full
of camping gear, it is nice, but not necessary, to bump the servo a little
(change from full forward to full aft CG is about a 1/3" change in the
trailing edge of the trim tab).

It is very close to being in-line with the elevator (up slightly lightly
loaded, down slightly aft CG). So, I don't think it is getting much load. I
am most concerned with the MAC servo getting water on it during takeoff and
landing and shorting out causing a trim runaway. The MAC servo is not
watertight. I have a circuit breaker right next to the panel trim adjust
switch.

I will take the plane off the floats this winter and fly for the first time
as a tail dragger. The airspeed envelope will be much larger and possibly
the need for trim will be necessary, but that is not what I have heard from
other Elite/Rebel builders. Same trim works for takeoff, climb, cruise,
descent and landing. Electric trim is nice but not necessary.

If so, I will remove the MAC servo and use a fixed but adjustable (bendable)
trim. Then I won't need to worry about runaway electric servo. So, I think
the bending threaded rod on Rebels and Elites is less a risk than a runaway
servo.

The Moose may have different air loads and elevator trim requirements. My
experience is with my Elite.

Eric

-----Original Message-----
From: mike.davis@dcsol.com [mailto:mike.davis@dcsol.com] On Behalf Of Ken
Sent: Monday, August 24, 2009 6:51 PM
To: rebel-builders@dcsol.com
Subject: Re: [rebel-builders] Moose: Elevator trim (crush tube)...was: Ray
Allen Servo

I think the Rebel part is short enough that it is not a problem John.
I'm not familiar with the Elite. Don't remember hearing of any problems
on Rebels although there is a bulletin to double the horn on the trim
tab for those of us with the older kits.
Ken

gleeso1 wrote:

G'Day All, I guess that it applies to the Rebel as well?
Re Oshkosh,
Thanks to Ted and Dick for organising the Murphy mob get together at
Ted's Moose, got a few piccies if anyone's interested.
Including one of Bob P. looking for the beer in the Esky ;-)
Regards to all
John Gleeson
Rebel 804 Down under



N.Smith wrote:

Hi All
It's in Elite's as well. The threaded rod will try to bend under

compression

from the wind loads on the trim tab, and it has weak spots all along it's
length due to the thread on it. The tube prevents the rod bending and
therefore prevents fatigue cracks setting in. (so I was once told

anyway!)

Nig
745E

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