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Another neat trim idea

7 posts in this topic

Posted

Hi all, it's not my idea, but I like it.  I think I will do it on my next plane.  The elevator is covered and it doesn't have a trim tab built in.  I really like the adjustment feature.  Lot of these vernier cables laying around to.  JImChuk

Kitfox - Trim Tab Update - YouTube

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Posted

Be careful, I have read of issues of flutter in some such applications of the Vernier cables.

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Posted

I wonder why it would be any different from other methods, like the lever Avid used for trim?

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Posted

I think it gets into play and flex in the system. I'd say if you grabbed a hold of the trim flap and try to move it, as long as it would hold firm against you it would likely be okay.

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Posted

I posted this same video on Team Kitfox, and mentioned the flutter comment.  One guy said he had this same system on a different type plane and flew it to 150 MPH and had no problems with flutter.  He said he actually used a throttle cable from a road grader that was 14' long, it used the same mechanism as the vernier.  That reminded me, I have a long new one that came from a big truck.  Maybe it will be long enough by itself as well.  I'm sure that if the tab is to wobbly, flutter could happen.  JImChuk

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Posted

The concern for flutter comes from the engineering of that cable is such that it's designed to pull, not push.  

So that being a given, putting a spring around the cable to assist in pushing  on the trim tab rather than relying solely on the cable would be very advisable.

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Posted

On my Avid Flyer, I had a factory supplied bowden cable going back to the trim tab.  A short lever in front of the seat truss moved the cable back and forth.  Friction on a leather washer on the lever keeps the lever where you set it.  Only time I had flutter of the trim tab is when the cable broke.  That got my attention I'll tell you.   I'll have to double check, but I think the vernier throttle would lock the cable from moving back or forth when the button is not pushed in.  In my digging around, I found this longer throttle cable for a pretty good price.  It would be nicer perhaps to have it mounted up next to the throttle so you can see better what you are doing when you adjust it.  JImChuk

Vernier H.D. Adjustable Throttle Locking Control Cables (truckntow.com)

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