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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.
<br>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.
<br>Georgie
<p>Amir Neshati wrote:
<blockquote TYPE=CITE><style></style>
<font face="Arial"><font size=-1>Pull-pull
will eliminate the trim change...</font></font> <font face="Arial"><font size=-1>Amir</font></font>
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<div style="FONT: 10pt arial">----- Original Message -----</div>
<div
style="BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color: black"><b>From:</b>
<a href="mailto:natpenton@centurytel.net" title="natpenton@centurytel.net">Nat
Penton</a></div>
<div style="FONT: 10pt arial"><b>To:</b> <a href="mailto:discussion@nsrca.org" title="discussion@nsrca.org">discussion@nsrca.org</a></div>
<div style="FONT: 10pt arial"><b>Sent:</b> Monday, November 24, 2003 7:24
PM</div>
<div style="FONT: 10pt arial"><b>Subject:</b> CTE</div>
<font face="Arial"><font size=-1>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</font></font> </blockquote>
</blockquote>
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