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Stabilizer/Elevator rigging

Steve, you are right!
univair has two elevator bungee/springs: which one is the rifht one?

[h=1]U10940-002 UNIVAIR BUNGEE SPRING - FITS PIPE
or[/h][h=1]U81411-002 UNIVAIR BUNGEE CONTROL CABLE SPRING - FITS PIPER[/h]Similar but different.
Thanks
 
Steve, you are right!
univair has two elevator bungee/springs: which one is the rifht one?

U10940-002 UNIVAIR BUNGEE SPRING - FITS PIPE
or


U81411-002 UNIVAIR BUNGEE CONTROL CABLE SPRING - FITS PIPER

Similar but different.
Thanks


10940-002 is the top spring. 81411-002 is the trim cable idler pulley spring.
 
I have checked my spring and found that with trim netral would keep the elevator up about 10 deg and the stick was very heavy to move forward. With trim full up the spring was loose.
I measured the spring to be 2.1 mm wire and 1/2” coil and abot six inch long. Surely too heavy. The univair spring is about 1.3 mm wire and 1/2” coil and about the same length.
I have changed to a light spring 1.2 mm wire 1/2” coil and avout 5 “ long to keep the cable straight when full trim up: the stick is light and the elevator drops slightly when trim is neutral: this appears to be the condition recommended by most of you. I will follow comments when I will test fly. IMG_6869.JPG


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The “elevator sprng” thread discussion was very useful. Thanks to all.


Inviato dal mio iPhone utilizzando SuperCub.Org
 
I just went through this issue with my super cub, had to muscle stick for pitch and it took a lot of trimming after flap inputs. Turns out the bungee cable was twisted and kinked, causing it to be too short with constant tension on cable; this same condition is caused by too short of a cable.
 
I'm going through this exercise for the EAB-12 I'm working on.

The spring callout in my PA-12 parts book is 81411-00. The Univair catalog says their U81411-002 supersedes the -00 part number. Says it is for J-5, PA-12, PA-18, PA-20 and PA-22 https://www.univair.com/piper/piper-j-5/view-all/u81411-002-piper-bungee-control-cable-spring/

It's unclear what length cable to use for connecting the trim yoke to the spring. The PA-12 length is 20 5/16", and the PA-18 length is shown as 21 1/4". I assume the longer length is due to balanced elevators. In our build we are using extended chord elevators, which would suggest the shorter (20 5/16") length.
PA-12 https://www.univair.com/piper/piper-pa-12/view-all/u40123-035-piper-bungee-cable/
PA-18 https://www.univair.com/piper/parts/u40123-078-piper-bungee-cable/

I'd sure appreciate any applicable thoughts? Thanks.
 
Umm, I think that’s why they call it EXPERIMENTAL. I suspect that during your Phase 1 testing you may end up making several in different lengths and pick the one that works best through your entire flight envelope. There is a reason for that Phase 1 testing.


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I'm going through this exercise for the EAB-12 I'm working on.

The spring callout in my PA-12 parts book is 81411-00. The Univair catalog says their U81411-002 supersedes the -00 part number. Says it is for J-5, PA-12, PA-18, PA-20 and PA-22 https://www.univair.com/piper/piper-j-5/view-all/u81411-002-piper-bungee-control-cable-spring/

It's unclear what length cable to use for connecting the trim yoke to the spring. The PA-12 length is 20 5/16", and the PA-18 length is shown as 21 1/4". I assume the longer length is due to balanced elevators. In our build we are using extended chord elevators, which would suggest the shorter (20 5/16") length.
PA-12 https://www.univair.com/piper/piper-pa-12/view-all/u40123-035-piper-bungee-cable/
PA-18 https://www.univair.com/piper/parts/u40123-078-piper-bungee-cable/

I'd sure appreciate any applicable thoughts? Thanks.

Univair is wrong. Different stiffer spring on -18


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