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Thread: New tail brace wires = new play in tail

  1. #1
    Kodiakmack's Avatar
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    New tail brace wires = new play in tail

    https://youtube.com/shorts/0IgosPyH5HE?feature=shareSo I had my shop replace my streamlined wires with a new set from dakota. New wires rigged per spec and square and where once was a nice tight tail there is now a frightening amount of play. The play seems to center around the junction in the rear vertical stabilizer post, but is most visually apparent at the rear liner tube as shown in the video. This has everyone scratching their heads and me seeing dollar signs. Any input appreciated.
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  2. #2

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    looks like the rear liner tube wasn't drilled correctly when the horizontals were installed.

    in other words, the horizontals were not snug against the fuselage when the rear liner tube was drilled.

  3. #3
    Kodiakmack's Avatar
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    Quote Originally Posted by akwing View Post
    looks like the rear liner tube wasn't drilled correctly when the horizontals were installed.

    in other words, the horizontals were not snug against the fuselage when the rear liner tube was drilled.
    that doesn’t explain why the big difference with the change in wires. The previous wires were even somewhat loose, however the tops and bottoms were tuned to each other. So I don’t suspect that one side was torqued down to pull everything to one side.
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    Tighten one, you tighten them all. The trick is to tighten them so the surfaces are orthogonal.

    But your problem is clearly that liner tube. A new tube, properly drilled, is the cure - but if you have a lathe you can make a spacer. I have "seen" safety wire wrapped in there to stop the lateral motion.

    Your mechanic may have taken the time to free up the rotating tubes, it is possible that you had corrosion on the rear tube, inhibiting the side to side motion before the work was done. Or maybe he just put some Mouse Milk in the lube holes - either way, it now rotates, but is too loose laterally.
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    Quote Originally Posted by Kodiakmack View Post
    that doesn’t explain why the big difference with the change in wires. The previous wires were even somewhat loose, however the tops and bottoms were tuned to each other. So I don’t suspect that one side was torqued down to pull everything to one side.
    i'd rather speculate why this problem, with such an obvious solution, has everyone at your shop scratching their head.

    with that much slop, anything less than a properly drilled liner tube is unacceptable.

  6. #6
    frequent_flyer's Avatar
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    Quote Originally Posted by akwing View Post
    with that much slop, anything less than a properly drilled liner tube is unacceptable.
    What lateral float is acceptable in the front and rear stab location, and where is that specified? I have more freedom than I would like in an FX-3 Carbon Cub.

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    BC12D-4-85's Avatar
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    How to do it with instructions: https://www.supercub.org/forum/showt...ear-liner-tube

    Gary

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    Steve Pierce's Avatar
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    How much slop is in the front liner tube? I would order at least the rear liner tube and if there is any slope in the front it as well. With a couple of people you can push the stabs together as someone else drills the liner tubes.
    Steve Pierce

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    stewartb's Avatar
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    If the tail wires are tight there’s no way that horizontal moves like that. I don’t get why your mechanic is scratching his head.
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    The vertical fin can wiggle, allowing what is shown in the video no matter how tight.

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    Grant's Avatar
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    Think of it this way...

    The fuselage has a rear horizontal stab support that is FIXED. The liner tube should be drilled to have a very minimal lateral movement (Only enough required to allow for the rotation of the trim movement)

    Because the fuselage support is FIXED, regardless of ALL OTHER variables, it is CLEAR that the liner tube needs to be replaced and redrilled with little to no lateral play.

    Until you do that, there is no way to PROPERLY rig the tail.

    I have no idea why it was tight and now its not. I think Bob's thoughts about it being "gummed up" or corroded is the most likely.

    HOWEVER, I have seen people drill another set of holes perpendicular to the originals in the liner tube. It is possible that could be the problem too. Regardless, that liner tube needs to be replaced. I have never seen safety wire used on the rear liner tube, only the front.


    The vertical fin can wiggle, allowing what is shown in the video no matter how tight.
    I disagree. Even without the wires installed the stab should not move like that if the liner tube is properly located and drilled.
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    No you don't. The verical fin will not wiggle if there is no lateral motion in the stab mount.

    Another poster said you get the wires tight enough and the side-to-side motion cannot occur. I was just stating where you can get from side to side even with very tight wires.
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    BC12D-4-85's Avatar
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    If it were mine I'd first wrap wire around both sides to take up slack (not for flying) then see how much wiggle remains. New tube best.

    Watch one at takeoff some wiggle under power. Crosswinds has a fix. http://crosswindsstol.com/stc.html

    Gary

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    Grant's Avatar
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    Quote Originally Posted by bob turner View Post
    No you don't. The verical fin will not wiggle if there is no lateral motion in the stab mount.

    Another poster said you get the wires tight enough and the side-to-side motion cannot occur. I was just stating where you can get from side to side even with very tight wires.
    Let me clarify... The HORIZONTAL stab should not have that movement even without the vertical stab in the tailpost. The problem is VERY clear. The vertical stab, or the brace wires have nothing to do with the problem that is demonstrated in the video. full stop.

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    That is true.

    It is also true that if you have space in the rear tube as in the video, with tight wires, when you move the stab back and forth, the vertical fin will move to accommodate - in the same direction.

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    Quote Originally Posted by bob turner View Post
    That is true.

    It is also true that if you have space in the rear tube as in the video, with tight wires, when you move the stab back and forth, the vertical fin will move to accommodate - in the same direction.
    Bob - Sure that's possible but dont forget there are also bottom wires. Regardless, to suggest that the vertical stab movement is part of the problem is wrong. The root of the problem is very clear, but you proved your point. Good job sir.

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    I’ll bite.

    The inner lining tube is drilled wrong, too far apart.

    With the wires properly tensioned (twang) it shouldn’t move side to side like that.

    Can you video us the whole tail including the tail wires and do that?
    Last edited by AKjurnees; 10-01-2022 at 08:55 AM.

  18. #18
    Grant's Avatar
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    Did the liner tube come out when the wires were replaced? This is the kind of stuff I've seen before with an extra hole. It would actually be kind of hard to get it that far out without the front being pretty far out as well. Also it would be good to see a more comprehensive video. Regardless, please let us know what you find. Another possiblity is that the liner tube is completelty broken in the middle somewhere.

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  19. #19

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    ive heard of bad things happening with twice drilled liner tubes.
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    Kodiakmack's Avatar
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    All the input appreciated and I understand the system and the issue more now. We are turning the liner 90 and re-drilling, and going back through the wire process. Sometime soon a new liner will go in. This is just to get me through to annual this winter. Probably 20 hours.
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    stewartb's Avatar
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    I’d carefully check the front tube installation, too. I can’t imagine that’s correct given the movement you have at the rear.
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  22. #22
    Kodiakmack's Avatar
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    Quote Originally Posted by stewartb View Post
    I’d carefully check the front tube installation, too. I can’t imagine that’s correct given the movement you have at the rear.
    the front is actually fine. There’s zero lateral play and the liner rotates freely in the tube.
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    Quote Originally Posted by Kodiakmack View Post
    All the input appreciated and I understand the system and the issue more now. We are turning the liner 90 and re-drilling, and going back through the wire process. Sometime soon a new liner will go in. This is just to get me through to annual this winter. Probably 20 hours.
    thats dumb

    a new liner tube is only $90.

    fix it right the first time, it'll be cheaper.

    it'll cost more in labor to replace it later on

  24. #24
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    Quote Originally Posted by Kodiakmack View Post
    All the input appreciated and I understand the system and the issue more now. We are turning the liner 90 and re-drilling, and going back through the wire process. Sometime soon a new liner will go in. This is just to get me through to annual this winter. Probably 20 hours.
    If the tube is bad, replace it! Don't EVER take a chance on being 'that guy'.

    Web
    Life's tough . . . wear a cup.

  25. #25
    Kodiakmack's Avatar
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    Caution noted.
    HAVE FUN. DON'T DIE.

  26. #26
    Gordon Misch's Avatar
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    If the front fits correctly and the back is too wide, something else is wrong. Maybe there was a sleeve between stabilizer and fuselage that was not reinstalled with the stabs?
    Gordon

    N4328M KTDO
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    Grant's Avatar
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    Quote Originally Posted by Kodiakmack View Post
    ...... We are turning the liner 90 and re-drilling......

    In the nicest possible way, that's a bad idea but your choice. If your mechanic is onboard with this solution then I completely understand why they were "scratching their head".... Good Luck. I hope you find the solution.
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    BC12D-4-85's Avatar
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    Ask your A&P to review this and then have a conversation> https://www.cubclub.org/samples/web_cubdoctor.pdf

    As owners/operators airworthiness is our responsibility not others.

    Gary
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    I am waiting for the Paul Harvey moment. That is when we find out the rest of the story. I suspect the play was there all along just not noticed. Perhaps a second set of holes already was drilled but not noticed or used on reassembly. If the tail feathers came completely off lots of things could have changed. You will figure it out down the road, let us know when you do. It is cheaper to overnight a new tube than pay for disassembly/reassembly/rigging twice just saying.
    DENNY

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    Steve Pierce's Avatar
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    I seem to remember an accident with a liner tube with multiple holes that cracked and broke, Charlie Center's Dad?
    Steve Pierce

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    Kodiakmack's Avatar
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    Liner is ordered and won’t fly until the new one is in. I thought I remembered seeing the turn and drill as a popular fix on here and was confused with all the discouragement in this case. Read through a lot of threads and see that’s not the case. Will get it replaced. ����*✈️������
    HAVE FUN. DON'T DIE.

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    bushwacker air, i believe, which i put in my exp, 20 years ago, use to make a little thicker walled liner tube, which i dont think is neccessary, especially for the lower hp planes like mine, but ive had it out a couple times and still looks good , no cracks. if i had a 160, 180 or up i would look into it again if i was going to do it again.

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    way at the bottom of the article clyde wrote some dont dos. something to read. https://www.cubclub.org/samples/web_cubdoctor.pdf

  34. #34
    stewartb's Avatar
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    Quote Originally Posted by Steve Pierce View Post
    I seem to remember an accident with a liner tube with multiple holes that cracked and broke, Charlie Center's Dad?
    I was told it was Cal’s yoke that broke. He attributed it to the 180hp tail shake. That led to his jackscrew mod to stabilize the tail. If I had a jackscrew I’d have that mod.

    I don’t get how turning and redrilling the liner would be a problem. I wouldn’t expect a liner tube to break at the bolt holes. That’s not where the stress is.

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    While a new liner is a good thing, I agree with Stewart - the bolts in the rear liner serve only two purposes - one, to keep a teeny bit of space between the stab and fuselage to aid in rotation, and two, to keep the tube from sliding sideways.

    Airplanes with trim tabs don't even have bolts back there - check out your local Decathlon.

    The front is a different story - If you want to re-drill the front, the new holes need to be laterally displaced from the old ones, not just drilled at 90 degrees. The front does have some stress, but again, as Stewart says, it isn't mostly on those bolts.

    What happens is when you change tailfeathers, the holes never line up. You need the liner tubes that go with the stabs.

  36. #36
    Gordon Misch's Avatar
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    the bolts in the rear liner serve only two purposes - one, to keep a teeny bit of space between the stab and fuselage to aid in rotation, and two, to keep the tube from sliding sideways.
    Disagree, Bob.
    That liner tube is also in shear from stabilizer air load.
    Gordon

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  37. #37
    stewartb's Avatar
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    The stab is, and the liner tube is. The bolts are not.

  38. #38
    Gordon Misch's Avatar
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    Yes they are, resisting the tail wires. But that's not a big stress.
    Gordon

    N4328M KTDO

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  40. #40
    stewartb's Avatar
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    Resisting the tail wires? My horizontal and elevator butt to the tubes the liners go through. Any clearance the wires may try to close would be measured in thousandths of an inch. My own tubes are TIGHT. Removing the horizontals is very difficult. I’m 99.9% sure my tail would be fine without bolts.

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