CTE

[Rcmaster199 at aol.com]

In a message dated 11/25/2003 1:12:08 PM Eastern Standard Time, 
geobet at gis.net writes:


> Subj:Re: CTE 
> Date:11/25/2003 1:12:08 PM Eastern Standard Time
> From:<A HREF="mailto:geobet at gis.net">geobet at gis.net</A>
> Reply-to:<A HREF="mailto:discussion at nsrca.org">discussion at nsrca.org</A>
> To:<A HREF="mailto:discussion at nsrca.org">discussion at nsrca.org</A>
> Sent from the Internet 
> 
> 
> 
> 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 
> 

Georgie,

Don't fret it. I have used Kevlar every where in the tail without problems at 
all. 

BTW Kevlar has a negative CTE, that is it gets shorter as temp increases. 
Kevlar cables actually get a little tighter in summer and looser in Winter, or 
opposite what you would expect. I have never had a set-up that retained it's 
trim as well 

All, I still have a quantity of 40 pound test and 80 pound testTeflon coated 
Kevlar for sale. These are  the smallest profiles around, for all you 
discriminating modelers. The teflon coating eliminates the chafe on composite fuse 
sides. Contact me directly please

Matt K
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