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Thread: Tail brace wire installation

  1. #1
    Zac Weidner's Avatar
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    Default Tail brace wire installation

    I sent my tail brace wire hardware off to Memphis Propeller on Monday to have them cadmium plated. When I get them back, I'm going to be installing the wires. It seems like a highly frustrating process for someone who has never done the job (like myself). I'm sure all of you who have done it have some great tips and I'd love to hear 'em. I would think that the aircraft needs to be leveled so that the stabilizers can be leveled at the wires are installed. Also, what should the wire tension end up at?
    Thanks again,
    Zac Weidner

  2. #2
    Administrator Steve Pierce's Avatar
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    Default Re: Tail brace wire installation

    Yes on leveling the airplane and the stabilizers. Use a fish scale to get a 12-15 lb. pull should deflect the wire 1/2".

  3. #3

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    Default Re: Tail brace wire installation

    (This may seem stoopid, but...) You only do this once, when the airplane is being "final assembled", ONLY. You don't do this before you start to cover everything (such as when following "my advice" about "rigging the airplane BEFORE it is covered") because you CANNOT re-install the bolts for the tailbrace wires under the proper "rig tension" again (sorry, don't mean to "talk down"...just trying to help!). You just can't. That requisite met... Once the airframe is leveled using the plumb bob (and for rigging tail surfaces only -not for checking travels of the surfaces as well- side to side is "important" and fore-to-aft is "okay close". That means you luck out by being able to let some air out of a tire to get the lateral level "perfect"!) proceed as follows:

    1) "hang" all four brace wires, pinned in place with the bolts that go there. This means they will be VERY loose when you start. MAKE SURE the little "bushings" are placed in the wires (end brackets) where they are bolted to the horiz stab (top AND bottom) and the "funky washers" are at the top of the vert stab post!!! !!! Properly torque all these tailbrace wire attach bolts BEFORE proceeding. Jam nuts are (there I go again with "the obvious"!) loose. In the "middle", with a decent amount of tension on the wires, make sure the end fittings are attached in place with a "straight pulloff". Loosen and realign, if necessary. Re-torque.

    2) Working BY HAND, shorten all four wires with the goal of not being able to work anymore without tools and so that the aft vert stab post is PLUMB, and the horizontal stabs are "LEVELed". Try to keep the same amount of wire "depth" in both ends of each of "nipples" (on the same wire, not necessarily will "all wires" be the same as all the "other wires". This "is what it is" for each wire) throughout the rig process. You don't have to "be a hero" at this point, just get 'em snugged up, and when you are going to start with tools, START with a plumb and level check and tweak wires as required.

    3) start "wrenching" the wires a little tighter each side-to-side pair, and a little top vs bottom "sides" until they begin to snug up (when you "prang" a wire at about midpoint, they will soon stop going "bzzzzz"/"thump-thump" and begin to go "twang" a little bit.

    (NEVER "force" an adjustment by pulling drastically against the "opposite" wire. You can't do this part "carefully enough", so work in small steps. Be patient and go "around" the tail as many times as you have to...)

    4)confirm plumb and levels, and proceed to tighten each wire against its "opposite", with an eye to "plumb and level (I can't say this enough!).

    5) continue repeating steps 3) and 4) while rechecking plumb and levels, until desired flying wire deflection is attained. Plumb AND level is paramount.

    6) confirm again plumb AND level after each step 5).

    When the deflections measure to your satisfaction, you can "finish the job" by making believe you are a piano tuner. Remember, "Opporknockity only tunes ONCE". A "finished job", when "lightly plucked", should elicit the same musical note on the top two wires and a different "same note" on the bottom two wires (top to bottom, they are different length wires...so they will have different "notes" at the same "tension") AND the vert stab is plumb and the horiz stabs are level. This allows you to "play these harpstrings" on every preflight and any disagreement in an originally "tuned" rig will be quickly evident! If you get a "dead prang" at some later date, you have a problem to correct before next flight. The "same note" thing pays for itself in being able to sleep in flight.

    Just about the time you begin to get with the program with "which way to turn that durn nipple", things will begin to fall into place rather quickly (IF you ever reach that point!). Now, if you find yourself "chasing the last time around" around the airplane, don't hesitate in letting the tension off, evening out your "nipple depth" if required, re-plumbing and leveling, and go at it again. This is where you might "become frustrated". SMALL "adjustments" near the end work best, and "playing piano tuner" is a BUNCH quicker than "fish-scaling" over and over. However, the fish-scale IS the preferred method of setting the tension. Keep re-doing it until the vert is plumb, the horizontals are level AND the tensions are correct (at which point, the "notes" should also be the same. You will probably "hit tune" a couple of times (at least!) only to find you took the vert or horiz out of "plumb", or "level".

    THEN, you are "done". If this is your "FIRST TAIL RIG", you are already "going at it" with the "I don't really know what I am doing" attitude. This works FOR you. Your third or fourth airplane (when you start to believe that you know what you are doing) usually are the most frustrating. Take your time, and just as soon as you realize you seem to be beating your head against the wall, back off take a break. You WILL appreciate that your tailbrace wires are really pretty darn snug when you get all done. But you will ALSO know that if the "note on the top" and the "note on the bottom" stay in tune, you are "good to go". If you strip anything, it WON'T "be all right like that", and you'd better seek "professional help" from have somebosy else do it for you , NEXT TIME (with new parts!). Finally...lock down the jam nuts and go PLAY!

    Howsat? More than you wanted???

  4. #4

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    Default Re: Tail brace wire installation

    JW - When you finally hop off the twig (and I hope that will be in the distant future) heaps of experience and knowledge like your last article, will go with you, unless we can convince you to sit down now with a tape recorder or something and put all your tips, tricks and information in a book or on a CD.

    I will place my order now - don't care what it costs - it will be worth it.

    Do it as a present for your grandkids or donate it to charity or whatever (the "JW Retirement Fund" would be a great charity) just don't take it with you - the rest of us haven't got enough time left to learn it all.

    Curly

  5. #5

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    Default Re: Tail brace wire installation

    That really was a "watershed" story by John, wasn't it. If you don't know how to rig the tail after that, you never will. But , Holy Crap - "Opporknockity only tunes once"! He may have been born on Mars, but it's good for us he landed here!

  6. #6
    Zac Weidner's Avatar
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    Default Re: Tail brace wire installation

    Quote Originally Posted by JohnW
    (This may seem stoopid, but...) You only do this once, when the airplane is being "final assembled", ONLY. You don't do this before you start to cover everything (such as when following "my advice" about "rigging the airplane BEFORE it is covered") because you CANNOT re-install the bolts for the tailbrace wires under the proper "rig tension" again (sorry, don't mean to "talk down"...just trying to help!). You just can't. That requisite met... Once the airframe is leveled using the plumb bob (and for rigging tail surfaces only -not for checking travels of the surfaces as well- side to side is "important" and fore-to-aft is "okay close". That means you luck out by being able to let some air out of a tire to get the lateral level "perfect"!) proceed as follows:

    1) "hang" all four brace wires, pinned in place with the bolts that go there. This means they will be VERY loose when you start. MAKE SURE the little "bushings" are placed in the wires (end brackets) where they are bolted to the horiz stab (top AND bottom) and the "funky washers" are at the top of the vert stab post!!! !!! Properly torque all these tailbrace wire attach bolts BEFORE proceeding. Jam nuts are (there I go again with "the obvious"!) loose. In the "middle", with a decent amount of tension on the wires, make sure the end fittings are attached in place with a "straight pulloff". Loosen and realign, if necessary. Re-torque.

    2) Working BY HAND, shorten all four wires with the goal of not being able to work anymore without tools and so that the aft vert stab post is PLUMB, and the horizontal stabs are "LEVELed". Try to keep the same amount of wire "depth" in both ends of each of "nipples" (on the same wire, not necessarily will "all wires" be the same as all the "other wires". This "is what it is" for each wire) throughout the rig process. You don't have to "be a hero" at this point, just get 'em snugged up, and when you are going to start with tools, START with a plumb and level check and tweak wires as required.

    3) start "wrenching" the wires a little tighter each side-to-side pair, and a little top vs bottom "sides" until they begin to snug up (when you "prang" a wire at about midpoint, they will soon stop going "bzzzzz"/"thump-thump" and begin to go "twang" a little bit.

    (NEVER "force" an adjustment by pulling drastically against the "opposite" wire. You can't do this part "carefully enough", so work in small steps. Be patient and go "around" the tail as many times as you have to...)

    4)confirm plumb and levels, and proceed to tighten each wire against its "opposite", with an eye to "plumb and level (I can't say this enough!).

    5) continue repeating steps 3) and 4) while rechecking plumb and levels, until desired flying wire deflection is attained. Plumb AND level is paramount.

    6) confirm again plumb AND level after each step 5).

    When the deflections measure to your satisfaction, you can "finish the job" by making believe you are a piano tuner. Remember, "Opporknockity only tunes ONCE". A "finished job", when "lightly plucked", should elicit the same musical note on the top two wires and a different "same note" on the bottom two wires (top to bottom, they are different length wires...so they will have different "notes" at the same "tension") AND the vert stab is plumb and the horiz stabs are level. This allows you to "play these harpstrings" on every preflight and any disagreement in an originally "tuned" rig will be quickly evident! If you get a "dead prang" at some later date, you have a problem to correct before next flight. The "same note" thing pays for itself in being able to sleep in flight.

    Just about the time you begin to get with the program with "which way to turn that durn nipple", things will begin to fall into place rather quickly (IF you ever reach that point!). Now, if you find yourself "chasing the last time around" around the airplane, don't hesitate in letting the tension off, evening out your "nipple depth" if required, re-plumbing and leveling, and go at it again. This is where you might "become frustrated". SMALL "adjustments" near the end work best, and "playing piano tuner" is a BUNCH quicker than "fish-scaling" over and over. However, the fish-scale IS the preferred method of setting the tension. Keep re-doing it until the vert is plumb, the horizontals are level AND the tensions are correct (at which point, the "notes" should also be the same. You will probably "hit tune" a couple of times (at least!) only to find you took the vert or horiz out of "plumb", or "level".

    THEN, you are "done". If this is your "FIRST TAIL RIG", you are already "going at it" with the "I don't really know what I am doing" attitude. This works FOR you. Your third or fourth airplane (when you start to believe that you know what you are doing) usually are the most frustrating. Take your time, and just as soon as you realize you seem to be beating your head against the wall, back off take a break. You WILL appreciate that your tailbrace wires are really pretty darn snug when you get all done. But you will ALSO know that if the "note on the top" and the "note on the bottom" stay in tune, you are "good to go". If you strip anything, it WON'T "be all right like that", and you'd better seek "professional help" from have somebosy else do it for you , NEXT TIME (with new parts!). Finally...lock down the jam nuts and go PLAY!

    Howsat? More than you wanted???
    JW, your posts never cease to amaze me. Thanks for the WEALTH of information! How important is it that the side-to-side tension be equal like you say? If it's really critical, I might be able to use my brother's guitar tuner to get them equal in such respect. I was kinda' figuring that I was going to have to do it just like you said, but I didn't know if there was some "secret" that would help me. Again, thank you tremendously for the "instruction manual".

  7. #7

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    Default Re: Tail brace wire installation

    Naw, really. A guitar tuner would surely get 'em equal...but that would be overkill. The real proof is in the "other pudding". When you have the vert stab post plumb, you have the "side-to-side" tensions equal. You CAN have all the wires properly tensioned but still have the surfaces pulled out of "square"...but if your surfaces "repose" were they are supposed to, you either have REALLY LOOSE tailbrace wires, or correctly tensioned ones. There is why I "can't stress the rechecking for plumb/level" enough. Then it becomes an issue of the tension actually being "enough" to support the airloads, yet not "too much" so as to deform structure. Right there is where the fish-scale/deflection "standard" came in. This is simpler than it looks, and its hard enough to locate the 12-15 lb pull for @ .5 1nch deflection. I don't have a CLUE were you would locate the frequency the wire should vibrate at!!! 'Bout all you could do is go "tune" a few -20s or -22s out and about, but I bet you'd get as many different "notes" as there were airplanes in your "samples".

    Uhhh, it just occurred to me that you may be questioning the "side-to-side being important and the fore and aft not so much" statement that I made before listing "steps". Errr, that is in reference only to the LEVELING PROCEDURE before you get into the rigging steps, not as applied to the finish rig itself. That is why the 12-15 lbs per 1/2" deflection becomes the "numbers" you are shooting for when the rig is complete [and how do I make this NOT confusing???] and yet "plumb and square" is as (or more) important than "how tight the wires are." The, ummm... its BOTH...take my meaning???

  8. #8
    Zac Weidner's Avatar
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    Default Re: Tail brace wire installation

    Okay, I am adjusting the wires today and I have the stabilizers leveled and fin plumbed, but the problem comes with the tension. The bottom is ~17 lb. at 1/2" deflection and the top is ~10 lb. I can see that there should be a different deflection required between top and bottom wires. I have checked each wire 2 or 3 times each in the middle of the wires and the numbers are right.

  9. #9
    Lownslow's Avatar
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    Default

    Just installed mine the way John so superbly described. Sweet!

    Lou S.

  10. #10
    Rotormech's Avatar
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    Default Re: Tail brace wire installation

    Zac - did you ever get the top and bottom wires in the 12-15lb range with 1/2 inch deflection?


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