CTE

[george kennie]

Sorry to disagree here, but it would appear that the conclusion being
drawn by the respondants is that the pushrod expansion and contraction
is the major cause of the problem. Not so, in my experience! Going to
pull-pull cables, whether they be steel or kevlar thread will not get
rid of the elevator trim change under consideration here.The coefficient
of thermal expansion between the cables, which is very small, and the
balsa in the fuse, which is significantly greater(glass too) will
generate a differential of sufficient magnitude that the "devil" will
still attack you when you least expect it.
The best solution that I have observed is to put the servos in the
stabs. Short of this, I have been using servos mounted just at the L.E.
of the stab and using a very short pushrod(approx. 6"). My current
thinking is that I will still mount the servo in the same area and go
with cables.Very light and direct. As regards Kevlar, I currently have a
pattern practise ship that I do almost all of my flying with that has
kevlar on the rudder and it has two years of mucho sequences to it's
credit with no apparent wear or abrasions to the thread. At this point
in time I have still not acquired the necessary intestinal fortitude to
use kevlar on the elevator.
Georgie

Amir Neshati wrote:

> Pull-pull will eliminate the trim change... Amir
>
>      ----- Original Message -----
>      From: Nat Penton
>      To: discussion at nsrca.org
>      Sent: Monday, November 24, 2003 7:24 PM
>      Subject: CTE
>       Gray what is the CTI for balsa ? I have carbon push rods /
>      balsa fuse and my elev trim moves around considerably. I
>      suppose it is because of humidity variation between the shop
>      and outdoors ?? The pushrods are 50" long.      NatPenton
>
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