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Thread: Stabilizer/Elevator rigging

  1. #1
    giangab's Avatar
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    Stabilizer/Elevator rigging

    Hello friends.
    The restoration of my PA18-95 is short from being completed.
    I need help again.
    I could not find the rigging instructions relevant to the cable/spring connecting the elevator upper horn to the stabilizer joke.
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    The spring pulls the elevator up, more when the trim is full nose down, and less when the trim is full nose up.
    I understand this device is for two purposes:
    1. Center the joke in level flight with trim somewhat neutral
    2. Allow controlling the elevator in case of elevator control cable failure
    Thanks for helping.
    Ciao
    Gian


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  2. #2

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    I know absolutely nothing about that, except if it was mine I would figure out a way to get that spring to mess with my elevators less. I was told its only purpose was to certify the aircraft in a hands-off terminal velocity dive. I occasionally fly a Cub with a really loose spring, and it is a delight! I don't have to trim in the pattern.

  3. #3
    cubdriver2's Avatar
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    Quote Originally Posted by bob turner View Post
    I know absolutely nothing about that, except if it was mine I would figure out a way to get that spring to mess with my elevators less. I was told its only purpose was to certify the aircraft in a hands-off terminal velocity dive. I occasionally fly a Cub with a really loose spring, and it is a delight! I don't have to trim in the pattern.
    I fly one without a spring and trim 11 turns ( double pully , no flaps ) between cruise and landing. I'm hoping a spring will help me to trim less, like my Pa11 was.
    Most guys who cut there teeth on a J3 don't like the spring

    Glenn
    Last edited by cubdriver2; 11-08-2018 at 11:16 PM.
    "Optimism is going after Moby Dick in a rowboat and taking the tartar sauce with you!"

  4. #4
    www.SkupTech.com mike mcs repair's Avatar
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    that cable and spring were only relevant to the plane as it weighed when it left the factory.... you can play with cable length and spring size to get the personality of your plane to be nice... heavy cubs just remove it....

  5. #5
    giangab's Avatar
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    Hi all, thanks for taking your time and replying to my question.
    So for it is understood, but I nelieve there should be a “basic” or standard calibration of the spring,or possibly a range.
    Surely the cable-spring device should never be loose and be in tension along the full trim excursuon.


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  6. #6
    Steve Pierce's Avatar
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    The cable length and spring tension need no adjusting. Install it and go. There is nothing to adjust. It is there to meet the pitch stability tests for certification. Yes it gets loose and tight depending on the trim setting.
    Steve Pierce

    Everybody is ignorant, only on different subjects.
    Will Rogers

  7. #7
    giangab's Avatar
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    Thanks.
    I have installed the one that was on the plane before restoration, but it appears (to me) to be very tight, I mean with trim neutral on the ground the stabilizer stays up some 10 degrees and the stick is quite hard to push forward. Possibly someone has changed the original spring with a tough one.
    Any suggestion to check this to reflect the design - factory condition?
    Thanks.


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  8. #8
    Steve Pierce's Avatar
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    Can you post a picture?
    Steve Pierce

    Everybody is ignorant, only on different subjects.
    Will Rogers
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  9. #9
    giangab's Avatar
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    Click image for larger version. 

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  10. #10
    Steve Pierce's Avatar
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    Do you have a picture of the cable and spring?
    Steve Pierce

    Everybody is ignorant, only on different subjects.
    Will Rogers

  11. #11
    giangab's Avatar
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    Click image for larger version. 

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  12. #12
    giangab's Avatar
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    This is the device


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  13. #13
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    Click image for larger version. 

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  14. #14
    giangab's Avatar
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    Ful down trim


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  15. #15
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    Click image for larger version. 

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  16. #16
    cubdriver2's Avatar
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    Pretty sure there are 2 different springs. One for Pa11 and Pa18-95 and one for Lyc powered 18s?

    Glenn
    "Optimism is going after Moby Dick in a rowboat and taking the tartar sauce with you!"

  17. #17
    giangab's Avatar
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    Full up trim


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  18. #18
    giangab's Avatar
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    Then ther should be a specification for each of them: anyone knows?
    Grazie


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  19. #19
    cubdriver2's Avatar
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    Quote Originally Posted by giangab View Post
    Then ther should be a specification for each of them: anyone knows?
    Grazie


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    Both listed in Univair

    Glenn
    "Optimism is going after Moby Dick in a rowboat and taking the tartar sauce with you!"

  20. #20

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    The spring is part number 10940-02 and the cable number is 40123-78. The cable is 21 3/4 inches in length from end to end.
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  21. #21
    Steve Pierce's Avatar
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    That is a home made cable. My parts catalog calls out calls out 40123-66 for the "95".
    Attached Files Attached Files
    Steve Pierce

    Everybody is ignorant, only on different subjects.
    Will Rogers
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  22. #22
    www.SkupTech.com mike mcs repair's Avatar
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    Quote Originally Posted by Steve Pierce View Post
    That is a home made cable. My parts catalog calls out calls out 40123-66 for the "95".
    that's not readable, maybe SJ can upload it without it degrading it??

  23. #23

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    40123-78 is for the lycomings. spring used is the same for all.

  24. #24

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  25. #25

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    Your jack screw yoke is mounted upside down from the one in your picture. Might make a difference in spring tension at up or down trim if spring cable is not in center of yoke travel.

  26. #26

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    Sorry looking at it wrong, it is the same as the picture

  27. #27
    giangab's Avatar
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    Thanks to all. I have checked the drawing suggested by Steve 40123/66 and Cubdriver2 40123/78, but I can't figure the discussed "elevator spring for PA18/95".
    Thanks for furthwer help (I am ready for test flying and wish "no problems".

    Thanks again, Gian
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  28. #28

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    Spring takes the pressure off the stick as you add nose up trim.Made my cub much nicer to fly when slow.

  29. #29
    giangab's Avatar
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    The function of the spring (also called bungee) is clear.

    I also understand that pilots have differen “tastes” regarding the strength of the spring: in this respect I would be pleased to know what would be the strength or force to pull the originally designed spring.

    I cannot find such info in the mentioned drawing.

    Thanks again.
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  30. #30
    Steve Pierce's Avatar
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    Why not just purchase the spring from Univair and that way you know you will have the correct tension and length?
    Steve Pierce

    Everybody is ignorant, only on different subjects.
    Will Rogers

  31. #31
    giangab's Avatar
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    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

  32. #32
    Steve Pierce's Avatar
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    I don't have the parts manual in front of me but item 30.
    Steve Pierce

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    Will Rogers

  33. #33
    cubdriver2's Avatar
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    Picture of spring on my old Pa11



    Glenn
    "Optimism is going after Moby Dick in a rowboat and taking the tartar sauce with you!"

  34. #34

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    Quote Originally Posted by giangab View Post
    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.

  35. #35
    giangab's Avatar
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    Thanks for the clarification


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  36. #36
    giangab's Avatar
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    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. Click image for larger version. 

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  37. #37
    giangab's Avatar
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    The “elevator sprng” thread discussion was very useful. Thanks to all.


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