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Electric trim threaded rod length

dbaflyer

dbaflyer

Well Known Member
I changed to electric trim late in the game and ordered most of the parts from RayAllen. It came with a seven inch thread rod to connect the servo motor to the trim tab. Does anyone have a known length this should be? Or do I adjust to give the proper travel?
 
I hooked up the assembly with a temporary on/off switch and 9VDC battery and played with the length until it met the specs.
 
Use a 9-volt battery or a cordless drill battery to run servo back and forth to its center position. Install the servo in the elevator and use tape to hold the trim tab in the neutral (center) position on the elevator, just line up the trailing edges. You can then mark and cut the threaded rod to the desired length to fit the horn on the trim tab.
 
ok, sounds like there is not a known length. Is there any truth to some posts suggesting we should set it up to allow more nose up trim than nose down? Maybe center the servo and have the tab slightly down?
 
dbaflyer said:
Is there any truth to some posts suggesting we should set it up to allow more nose up trim than nose down?
Click to expand...

Yes.


An RV requires way more nose up trim (especial one like the 9 with huge slotted flaps) than nose down trim.

I would suggest you adjust for a 2:1 ratio (nose up to nose down) this will use pretty much all of the nose up travel available in the tab.
 
rvbuilder2002 said:
Yes.
An RV requires way more nose up trim (especial one like the 9 with huge slotted flaps) than nose down trim.
I would suggest you adjust for a 2:1 ratio (nose up to nose down) this will use pretty much all of the nose up travel available in the tab.
Click to expand...

Please remember that nose-up trim requires the trim tab to go down and vice versa.
I feel the need to comment here because about 1/2 the airplanes I inspect have the trim tab, the trim indicator, or both reversed.
 
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