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Thread: Improving on Tail Wires

  1. #1

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    Improving on Tail Wires

    Big Cub, big tail, big engine making for noticeable tail shake. My tail wires ate typical Cub. I pitched my D&E triangle tabs and went with the certified versions after a couple of guys here had them fail. I’m wondering if there’s merit to improving on the wires and ends. Perhaps use Brunton flying wires with turnbuckle fork ends and replace the triangle tabs with bent stainless tabs like ski tabs. I can make the wire support system stronger. Have these monster Cubs reached the limit for standard wires? Thoughts?

  2. #2

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    I know of a gentleman who did just what you describe, and it was the common method of construction for most interesting biplanes.

    Paging Ted Waltman...

  3. #3

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    I recall Ted’s wire failure. I’ve thought about running a second set of wires but that would make 2 attach points and I’m not sure how that would work with vibration and flex of the horizontal.

  4. #4

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    Quote Originally Posted by stewartb View Post
    Have these monster Cubs reached the limit for standard wires? Thoughts?
    Are there any "monster Cubs", except Scrappy, using more powerful engines than the IO-390 used in the XCub?

    Are the tail brace wires of the XCub any different from the much lower powered Carbon Cubs?

  5. #5

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    Quote Originally Posted by frequent_flyer View Post
    Are there any "monster Cubs", except Scrappy, using more powerful engines than the IO-390 used in the XCub?
    Yes. Bigger, bigger tail, longer airframe, higher gross, more power. Becoming more common all the time.

  6. #6
    cubdriver2's Avatar
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    Maybe a Heim joint going thru the stabilizer back tube with a wire on each side?

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    Glenn
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  7. #7

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    I’m thinking simple angled tabs and streamlined flying wires. I hope to have the wires order placed tomorrow. Today’s a travel day. Lots of airport time to daydream.
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  8. #8
    mvivion's Avatar
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    How about streamline tubing....

    MTV
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    Quote Originally Posted by mvivion View Post
    How about streamline tubing....

    MTV
    That's what I would do If I had a "Monster Cub", Like the way Aviat does on the Husky, except with the moveable stab you have to attach to the rear spar of the stab and it has to move.

    Brunton wires take a LOOOOOOOOOOOOONG time to get.

    Mr. Piper Had a lot of this figured out... but we keep "improving" where we can.

  10. #10
    TurboBeaver's Avatar
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    Why try to reinvent the wheel.................Piper fixed it 50 years ago. Pawnee 4 wire system. Problem solved.
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  11. #11
    wireweinie's Avatar
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    I was thinking about the brace wires on floats. Strong and with a stream lined cross section. What did the Pawnee use?

    Web
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  12. #12
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    Quote Originally Posted by TurboBeaver View Post
    Why try to reinvent the wheel.................Piper fixed it 50 years ago. Pawnee 4 wire system. Problem solved.
    Pawnee has a different trim system.

    Sent from my SM-G965U1 using SuperCub.Org mobile app
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  13. #13

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    The wire isn’t the weak point. The attach is. If I can use a simple angle tab I can get 1/4” rod cut and threads rolled for AN486 or AN665 terminal ends. That should make a much tougher assembly than what I have while maintaining adjustability.
    Last edited by stewartb; 08-23-2021 at 09:51 PM.

  14. #14

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    Quote Originally Posted by mvivion View Post
    How about streamline tubing....

    MTV
    Can't imagine doing that.
    https://www.supercub.org/forum/showt...l=1#post775152
    Regards, Charlie
    Super Coupe E-AB build in process
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  15. #15

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    What about the Crosswinds STOL streamlined tubing tail brace system? Cal & Charlie Center figured this out a long time ago when they started hanging big engines on PA-12s etc. It works in harmony with the current trim system and takes the wiggle and stress off the tail wires. Only downside is it requires some welding, better done on a build but with TIG it’s doable. Wet towels are marvelous fabric protection. Don’t see why it wouldn’t work on an -18. Certified may be more hassle but Charlie can probably line you out on that. He typically has the parts and pieces in stock.

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  16. #16

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    No jackscrew in my tail. I have it figured out with some validation from Ted Waltman. I’ll gather the parts tomorrow. Mine isn’t a 9-1-1 project.
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  17. #17

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    Bent tabs.....Consider using 1/8" thick 4130 steel for your tab material. The designer of the the Bearhawk keeps things light, but he used that material in that same application. If you want to save some money on flying wires, the Bearhawk five builder used steel cable for the wires and had Spruce swage the fork ends to the cable. I'm unsure of the cable diameter. It was larger wire than 1/8" (2000 lb 7x19 galvanized) maybe 5/32 (about 3000 pounds) or 1/4" (7000 lb) That decision could save $800. The wire in the print was 4130 turned down to .250" between the threaded ends.

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  18. #18

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    Ted confirmed that he converted the standard Piper assembly to a Husky-like AN665 terminal fork to a bent tab using the same wires. Sourcing rolled thread wires isn’t the easiest thing I’ve ever done so skipping that step is a relief. Parts ordered. Making tabs will be simple. I enjoy making things better than they were.
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  19. #19

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    I can attest Ted's look much better, and are obviously way stronger. The only gotcha is the installation is a little less forgiving.

    This winter I will be plasma cutting myself a set and converting my little Cub over to the same.
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  20. #20
    Steve Pierce's Avatar
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    Quote Originally Posted by bcone1381 View Post
    Bent tabs.....Consider using 1/8" thick 4130 steel for your tab material. The designer of the the Bearhawk keeps things light, but he used that material in that same application. If you want to save some money on flying wires, the Bearhawk five builder used steel cable for the wires and had Spruce swage the fork ends to the cable. I'm unsure of the cable diameter. It was larger wire than 1/8" (2000 lb 7x19 galvanized) maybe 5/32 (about 3000 pounds) or 1/4" (7000 lb) That decision could save $800. The wire in the print was 4130 turned down to .250" between the threaded ends.

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    Piper did the same thing. On the same Piper drawing as the more common tail brace wires.
    Steve Pierce

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  21. #21
    tedwaltman1's Avatar
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    Here is a link to document detailing initial wire break: https://fly2ak.com/PDF/TailClevisBreak.pdf

    And a picture of my new tail brace wire attachments: Click image for larger version. 

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  22. #22
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    Quote Originally Posted by tedwaltman1 View Post
    Here is a link to document detailing initial wire break: https://fly2ak.com/PDF/TailClevisBreak.pdf
    Thanks for this Ted. It appears the part was made with a press brake using too tight a die and not enough bend radius. Thus the bend was prestressed and subject to cracking. The knife edge on the square washer only exacerbated the issue. I'll have to double check my wires. So far no issues.
    N1PA

  23. #23

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    AN665-21 terminal forks are rated at 2400#. I don't believe the stock Piper assembly would match that. Probably moot for a typical Cub and back when Ted's broken part happened it was identified that the problem was related to D&E tabs, so limited to EXP airplanes. Mine had the D&E and the press tracks so I replaced them with approved parts from Univair. Still, with the way my own tail shakes? I'll feel better with a more robust attachment. If a guy wants to go one better he could use 1/4-28 rods and forks. That nearly doubles the pull strength over the 10-32 wires we use now. One point I'll share, in talking to Burl Rodgers about this he advised that at least half the rod threads need to be engaged in the fork to maintain the strength. If anyone else is making tabs and ordering forks keep that in mind.

    FWIW, I'm still considering using 1/4" wires and 1/4-28 forks. Burl can produce the wires with rolled threads and stocks the forks. Apparently Aeronca Sedans use a similar wire system.
    Last edited by stewartb; 08-26-2021 at 12:57 PM.
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  24. #24
    Gordon Misch's Avatar
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    "use 10-28 rods and forks"

    Did you mean 1/4-28?
    Gordon

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  25. #25

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    Quote Originally Posted by Gordon Misch View Post
    "use 10-28 rods and forks"

    Did you mean 1/4-28?
    Yes. Thanks for the catch.

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