[NSRCA-discussion] Composite expansion/contraction

[Pat Hewitt]

I know from experience that a 2.6 Composite ARF that is Dark in color will
change by as much as 4 clicks on a hot Kansas day.

Pat Hewitt




------ Original Message ------
Received: 10:18 AM CDT, 05/08/2006
From: Bob Kane <getterflash at yahoo.com>
To: nsrca-discussion at lists.nsrca.org
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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