[NSRCA-discussion] Elevator trim change

[rcmaster199 at aol.com]

Bob, originally I had my Temptress' elevator set-up on pull-pull (K-Kord, my stuff) and experienced practically no drift in elevator trim. One day, one of crimps I was using pulled apart. It really wasn't a big deal to land on one elevator half. The other half only allowed down command so it wasn't really trivial matter but wasn't terribly serious either. Note Temptress uses a Temptation fuse.
 
Rather than replacing the K-Kord, I decided at that time to try the carbon pushrod arrangement that CST sells that is similar to a DEPS. I have been experiencing exactly what you describe ever since. Not exactly the identical set-up you have but the materials used are very similar.
 
Usually, once the plane is trimmed at the start of the flying session, it doesn't drift the rest of the day but still I don't care much for that arrangement and will replace the carbon with pull-pull again. I will probably never use full length carbon rods again unless the fuse is carbon also.
 
FWIW
 
Matt
 
-----Original Message-----
From: Bob Kane <getterflash at yahoo.com>
To: nsrca-discussion at lists.nsrca.org
Sent: Mon, 8 May 2006 08:04:04 -0700 (PDT)
Subject: [NSRCA-discussion] Elevator trim change


My new Temptation is using a carbon pushrod system for
the elevator. The length is roughly 30" and it is all
carbon from the servo to the elevator horns except for
the titanium ends.

I have been experiencing significant (more on what I
consider significant later) trim changes in elevator
from one flight to another. I did some searching in
the RCU forums and found a two year old thread, the
conclusion (if there is such a thing in online forums)
is the expansion/contraction of the composite fuselage
is large relative to the change of a carbon pushrod
system if both are subjected to the same change in
temperature.

What I mean by significant is two or three clicks as
measured by my Stylus trim levers. My three previous
pattern planes all featured rear mounted elevator
servos with short (< 12") pushrod systems. These
planes exhibited little trim change (1 click) with
temperature swings.

I changed servos last night and will be test flying
this evening to see if the servo was contributing to
the trim change. 

What are other experiences with carbon
pushrod/composite fuselage combinations?

Bob Kane
getterflash at yahoo.com

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