Cc: "Mike Sylvester" <shagste...@hotmail.com>
Subject: KR> Flew yesterday.
I've been working on an internal trim system and I think I finished it
yesterday. The weather warmed up enough for me to test fly it and I was happy
with the results. My original thinking was that I didn't want the drag of two
surfaces working against each other like the trim tab does. I was looking for
every MPH I could get. If I could go back in time, I would just do the Ray
Allen trim tab system and be done with it. To all you builders out there, Keep
working and stay with what you know works, All the guys that went before us
have done all the testing.
When I cut the tail off my KR and built a larger tail, I decided to use a
spring biasing trim system, also in an attempt to keep the tail as
aerodynamically clean as possible. I flew with it like that several hundred
hours from 2005 - 2013, but would consider it to be a miserable failure. As
the plane speeds up, the elevator control pressures load up and pull on the
springs. It would never reach an equilibrium, regardless of the speed, so the
plane was constantly pitching up and down and wouldn't ever hold an altitude.
I could have improved it, but I don't believe I could have ever cured it with
that configuration. I finally removed the spring biasing system and put a trim
tab on the elevator with a Ray Allen trim servo. Details of both installations
are on <http://jeffsplanes.com>
On the SuperCub Clone I had a single bowden cable control to the trim tab as
per Wag Aero plans. That cable started flexing and failed in flight creating a
high speed and violent flutter that shearedmost of the rivets attaching the
trim tab and caused some cracks in the elevator that had to be repaired. (Also
scared the crap out of me!) The Cub was also modified so it now has a Ray
Allen trim servo.
Cherokee Village, AR
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