CTE

[Keith Black]

> At this point in time I have still not acquired the necessary intestinal fortitude to use kevlar on the elevator.

If you do use pull-pull on the elevator just use completely independent cables to each elevator half. That way if one breaks the other elevator half will still work. I've done this by connecting a ball link clevis to each side of the servo control arm and running one elevator half from one clevis and the other elevator half from the other clevis. If one cable breaks it does not effect the other cable. Of course if your servo goes south you're SOL, that's what's nice about two servos in the stab.

Keith
  ----- Original Message ----- 
  From: george kennie 
  To: discussion at nsrca.org 
  Sent: Tuesday, November 25, 2003 11:57 AM
  Subject: Re: CTE


  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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