Cc: "Terence Teer" <terry.tee...@yahoo.com> Subject: KR> Trim Looking for direction on adding a manual or electric trim tab on my -2. How to size and such. I would like to make it manually adjustable in flight, but may have to go the electric trim route. I’m adding a autopilot and will need trim availability. I’m thinking Bowden cable and trim lever. Any help?
Terry /) ---------------------------------------- I would avoid trying to control a trim tab with a single bowden cable. I did that on my SuperCub Clone per the Wag Aero plans. When I trimmed nose down, the cable was pushing the trim tab up. The bowden cable started flexing, then broke, leaving the trim tab flapping free in the breeze which brought on quite a case of tale flutter. Slowing to minimum controllable air speed did not moderate the flutter, which was quite violent. The Cub has a braced tail structure, but even with the bracing, the tips of the elevator were moving roughly 6" vertically while the trim tab was in flutter. You could both feel and see the shock from each flutter cycle propagate through the air frame and out the wings. You could quite literally see the shock waves moving out the length of the wing from the violent shaking in the tail. Pulling in full flaps changed the air flow over the tail enough to moderate the flutter enough that I was able to make my way into the nearest airport where I made temporary repairs. After I returned home, I stripped the tail and installed a Ray Allen trim servo. I also found a few cracks in the elevator, likely a result of having flown for several minutes with the trim tab in full blown flutter. I know of numerous other failures of a single bowden cable on the trim tab with similar results. I recommend avoiding that type of configuration. -Jeff Scott Cherokee Village, AR _______________________________________________ Search the KRnet Archives at https://www.mail-archive.com/krnet@list.krnet.org/. Please see LIST RULES and KRnet info at http://www.krnet.org/info.html. see http://list.krnet.org/mailman/listinfo/krnet_list.krnet.org to change options. To UNsubscribe from KRnet, send a message to krnet-le...@list.krnet.org
