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<DIV><FONT face=Arial size=2>Both sides of a the cable will expand or contract
the same, so the trim will still not change due to different CTEs</FONT></DIV>
<DIV><FONT face=Arial size=2>They may </FONT><FONT face=Arial size=2>get tighter
or looser, but still no trim change.....I flew a few hundred flights on a glass
fuse. with a carbon</FONT></DIV>
<DIV><FONT face=Arial size=2>pushrod, had the trim sensitivity set to 20% and
would take as much as 6 of these little clicks to trim each
flight.</FONT></DIV>
<DIV><FONT face=Arial size=2>As it got warmer, the problem I encountered was
that I would take off, on the trim pass the plane would head for the
ground,</FONT></DIV>
<DIV><FONT face=Arial size=2>so I would start adding the up trims....about a
minute in the flight the fuselage would cool and now the fuselage
would</FONT></DIV>
<DIV><FONT face=Arial size=2>contract a bit, so comes in a click or two of down
trim now, but noticed the rudder pull-pull would never change trim
with</FONT></DIV>
<DIV><FONT face=Arial size=2>any changes in temps ..so, I gave pull-pull a
try on the elev. and after 400 flights in temps. ranging from 50 to 100
degrees</FONT></DIV>
<DIV><FONT face=Arial size=2>it still worked great. I tightened the cables only
one time after the first day or two of flying and didn't touch them
again.</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>The only thing I can see here is that due changes
in air density (the CTE for those tiny molecules of air)</FONT></DIV>
<DIV><FONT face=Arial size=2>a tiny bit of elevator change may be experienced,
and one may change the trim by a tiny click and be done.</FONT></DIV>
<DIV><FONT face=Arial size=2>Where as with a pushrod, I had to change elev. trim
by 4~6 clicks at first, then after a minute or so into the flight</FONT></DIV>
<DIV><FONT face=Arial size=2>as the fuselage temps. stabilized due to the
cooling air flowing over it, would have to re-trim again...</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>I weighed a carbon pushrod once that was ready to
install and weighed around 1.5 ounces and I believe the </FONT></DIV>
<DIV><FONT face=Arial size=2>40 lbs. coated fishing line stuff weighed only
a few grams...Kevlar would probably weigh only a couple of grams.</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>Have fun,</FONT></DIV>
<DIV><FONT face=Arial size=2>Amir</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
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<DIV><FONT face=Arial size=2></FONT><BR></DIV>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:
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<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 title=natpenton@centurytel.net
href="mailto:natpenton@centurytel.net">Nat Penton</A></DIV>
<DIV style="FONT: 10pt arial"><B>To:</B> <A title=discussion@nsrca.org
href="mailto: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></BLOCKQUOTE></BODY></HTML>