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Thread: HELP! Bent J4A Cub Coupe Front Spar Lift Strut Fittings

  1. #1

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    HELP! Bent J4A Cub Coupe Front Spar Lift Strut Fittings

    Hi All

    I've joined the forum looking for some help with a new to me J4a Cub Coupe. We've done our first annual inspection and found the front spar lift strut attach fitting to be bent, it looks to have been there a while and i'm guessing its come from being tied down in a high wind.

    Ive downloaded the parts manual and the number listed for replacements is either A16 or 0026-63. I've searched online to no avail, does anybody have experience with getting something like this made? I'm guessing its 4130?

    Thanks in advance for any help

    Long time lurker, first time poster!

    Tom
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  2. #2

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    Not good. The shear nut with no washer looks a bit suspicious.

    The current president (owner?) of Univair is a J4 owner. I would start there.
    Thanks J4A thanked for this post

  3. #3
    BC12D-4-85's Avatar
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    Maybe it's similar to other Pipers like the J-3 or J-5? UNIVAIR might know.

    Gary

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    Cub Builder's Avatar
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    Left or right wing? Front or back fitting? I know a guy that has a set of wrecked J-4 wings. PM me and I'll send you his number.

    -Cub builder

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    Quote Originally Posted by Cub Builder View Post
    Left or right wing? Front or back fitting? I know a guy that has a set of wrecked J-4 wings. PM me and I'll send you his number.

    -Cub builder
    It's the front fittings on the left wing, although they are shown as the same part on the left and right wings.

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    Quote Originally Posted by bob turner View Post
    Not good. The shear nut with no washer looks a bit suspicious.

    The current president (owner?) of Univair is a J4 owner. I would start there.
    Just checked the parts manual and you're spot on, those should be AN360 nuts!!

  7. #7
    Steve Pierce's Avatar
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    I would check with Jim Dyer at Univair. Piper was good at sticking with common parts. maybe they can make you a set as owner produced.

    Changed a set on a Tri-Pacer at Oshkosh several years ago.
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    Steve Pierce

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    Hey Steve, it was your original thread with the tripacer that led me to taking a closer look, I'm grateful for the info!
    Likes Steve Pierce liked this post

  9. #9
    nanook's Avatar
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    Dodge makes an insert/doubler for the PA18, to prevent that damage from happening...you could manufacture your own for the J-4. Good idea if you are in a high wind area...
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    Does anyone else have a lead on someone with a wrecked J4 kicking around the back of a hangar? Univair have told me they're made from sheet 4130 so worst case I guess I'm making them. Do any of the scratch built guys have any pointers?

  11. #11
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    Quote Originally Posted by J4A View Post
    Does anyone else have a lead on someone with a wrecked J4 kicking around the back of a hangar? Univair have told me they're made from sheet 4130 so worst case I guess I'm making them. Do any of the scratch built guys have any pointers?
    I have a few "Mystery" wing parts. Send me a pic or print of what you need and I'll take a look....

  12. #12
    Steve Pierce's Avatar
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    These guys have some J4 parts, maybe they have something. I would call them. They have a complete J4 wing and some misc J4 wing parts as well. https://www.ebay.com/str/gtaviationp...p2047675.l2563
    Last edited by Steve Pierce; 08-21-2021 at 07:52 AM.
    Steve Pierce

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  13. #13
    mvivion's Avatar
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    That damage is what’s caused by tying these airplanes down with chains. The chain is impossible to get really perfectly tight, as a result there’s always a bit of slack. In a wind, the plane comes up against the end of the chain with a HARD stop. Which bends things, and those are the parts that bend, and break. This has resulted in fatalities.

    NEVER tie these airplanes down with chains, folks. And carefully inspect these parts on any plane you’re not very familiar with. After a fatal accident in Alaska, these parts on the Cub I was flying were found to be severely bent, and one was cracked. The last guy who flew the plane had tied it down with chains……in Kodiak.

    Take a really good look at these parts.

    MTV

  14. #14
    Hardtailjohn's Avatar
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    I just sent you a PM with an email for a guy that says he can help you.
    John

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    Heres a better pic of the front spar fittings I'm after...

    Click image for larger version. 

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  16. #16

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    Quote Originally Posted by Steve Pierce View Post
    These guys have some J4 parts, maybe they have something. I would call them. They have a complete J4 wing and some misc J4 wing parts as well. https://www.ebay.com/str/gtaviationp...p2047675.l2563
    Cheers Steve, I'll take a look

  17. #17
    skywagon8a's Avatar
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    Quote Originally Posted by J4A View Post
    Heres a better pic of the front spar fittings I'm after...

    Click image for larger version. 

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    I hope for your sake, the wood is in better condition than that which is shown by that picture.
    N1PA

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    I just sent you an email with a pic showing the pressing tool I used to make my strut fittings. I’ll send you another photo tomorrow of the finished product, so you can decide to go this way or not.
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    Quote Originally Posted by J4A View Post
    Heres a better pic of the front spar fittings I'm after...

    Click image for larger version. 

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    I think I have some of those fittings, NOS.

    But...I think you need a rebuild.

    Tim
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  20. #20

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    Just for clarification those aren't my wings, just a picture someone sent me of a wrecked J4. Tim, if you have a lead on some NOS fittings I'd be forever grateful!

    Cheers
    Tom
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  21. #21

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    No luck finding a set of strut attach brackets yet, I'm going to look into getting a set made. Any scratch builders out there have any hot tips other than stick to the drawings?

  22. #22

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    Take measurements of yours and compare with a J-5 or J-3, might be the same dimensions?

  23. #23
    skywagon8a's Avatar
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    Quote Originally Posted by AKjurnees View Post
    Take measurements of yours and compare with a J-5 or J-3, might be the same dimensions?
    Very likely true since Piper was known for mixing common parts between models in order to conserve costs.
    N1PA

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  25. #25
    TurboBeaver's Avatar
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    Those pic's of Steve's showing the attachment brackets horriblely bent and twisted show the flaw in the design of them. ( Distance between the end and first attachment hole is to great) About one more 60kt gust and the wing would have separated from the fuselage! Take Nanook's advice and add the Atlee Dodge filler strips while your replacing the brackets! Cheap insurance for next big wind storm......... Your call.
    Good Luck
    E

  26. #26
    TurboBeaver's Avatar
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    Probably these Atlee reinforce strips, should be first mod on any Cub left outside, makes the attachment brackets 4X stronger.Click image for larger version. 

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    Had yours had these installed none of that
    Damage would happened.
    Good luck
    E
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  27. #27

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    Quote Originally Posted by J4A View Post
    No luck finding a set of strut attach brackets yet, I'm going to look into getting a set made. Any scratch builders out there have any hot tips other than stick to the drawings?
    As a scratch builder, measure the width and wall thickness and look into what is available in 4130 box tube. You can then build them with taller flanges in the middle and equal or next dimension thicker.
    Going at it this way you have no metal forming to do, just cut, edge finish and drill/ream holes.
    Regards, Charlie
    Super Coupe E-AB build in process

  28. #28
    RVBottomly's Avatar
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    Quote Originally Posted by J4A View Post
    No luck finding a set of strut attach brackets yet, I'm going to look into getting a set made. Any scratch builders out there have any hot tips other than stick to the drawings?
    I like Charlie's idea of looking for box tubing--thinking out of the box for sure.

    My guess is that those are .090, at least that is the size for Wag-Aero wings. I bent some .090 4130 into a similar fitting, but mine also had a compound curve. Spent a lot of time trying different methods, presses, custom dies, hammering freehand over an anvil, etc. I finally got some done with custom milled dies. The freehand hammering over an anvil with heat was just about as good.

    I recall Wag Aero had something similar, but no longer. The radius of the bend was apparently too tight--that is not good.

  29. #29
    BC12D-4-85's Avatar
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    It's hard to believe the brackets are unique to the J-4 among all the contemporaneous Pipers.

    Gary
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  30. #30
    Gordon Misch's Avatar
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    Quote Originally Posted by CharlieN View Post
    As a scratch builder, measure the width and wall thickness and look into what is available in 4130 box tube. You can then build them with taller flanges in the middle and equal or next dimension thicker.
    Going at it this way you have no metal forming to do, just cut, edge finish and drill/ream holes.
    Maybe. The 4130 box tube I've seen has sharp corners, not radiused. That may or may not be a stress concentration issue. Sounds like an Owner Produced Part candidate though. Get some 4130 sheet of the proper thickness (Aircraft Spruce or similar) and find a local shop that can replicate the parts to spec.
    Gordon

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  31. #31
    RVBottomly's Avatar
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    I just reread the thread. Go with Farmer Hank’s approach on the dies. Gordon’s suggestion on a local shop is good. Those look pretty easy to make.


    Sent from my iPhone using SuperCub.Org

  32. #32

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    J4A, did you ever find up your parts? Have you checked EBay?

    Maybe put a free ad in Barnstormers.

    I’m surprised that Univair doesn’t have what you need, the owner is restoring a J-4.

  33. #33
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    I would also use a sling girth hitched (or better yet clove hitched with a section of rope) around the upper strut rather than through that tie down eye. This is common damage. I would never use chain to tie down if you can avoid it.

    You also might try Dakota or Jay at Javron to see if they can fab one for you as owner produced as well.

    Good luck.


    Quote Originally Posted by mvivion View Post
    That damage is what’s caused by tying these airplanes down with chains. The chain is impossible to get really perfectly tight, as a result there’s always a bit of slack. In a wind, the plane comes up against the end of the chain with a HARD stop. Which bends things, and those are the parts that bend, and break. This has resulted in fatalities.

    NEVER tie these airplanes down with chains, folks. And carefully inspect these parts on any plane you’re not very familiar with. After a fatal accident in Alaska, these parts on the Cub I was flying were found to be severely bent, and one was cracked. The last guy who flew the plane had tied it down with chains……in Kodiak.

    Take a really good look at these parts.

    MTV

  34. #34

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    Nothing yet on eBay, i got in touch with univair and they were unable to manufacture another set. I've emailed cub club to try and get some drawings but not had any reply, in the UK I'm able to manufacture my own parts however there's no way it would get approval without an original spec to go from. I might put an Ad on Barnstormers and will get in touch with Javron. Does anyone else have a lead on where I might get some construction drawings for the J4?

  35. #35
    soyAnarchisto's Avatar
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    Dakota makes wings for J3 - surely they can do J4 as well or at least have access to the drawings:

    https://dakotacub.com/index.php?rout...ategory&path=5

    Quote Originally Posted by J4A View Post
    Nothing yet on eBay, i got in touch with univair and they were unable to manufacture another set. I've emailed cub club to try and get some drawings but not had any reply, in the UK I'm able to manufacture my own parts however there's no way it would get approval without an original spec to go from. I might put an Ad on Barnstormers and will get in touch with Javron. Does anyone else have a lead on where I might get some construction drawings for the J4?

  36. #36
    Marty57's Avatar
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    Here's a picture of my wood wing Wag 2+2. It's very similar to the J4 (with flaps hardware from SC). Not sure why you couldn't use it; it's a PMA's part but not for the J4. Main difference is how the drag wires fit; they are J3 wires.

    Marty57

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  37. #37
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    Quote Originally Posted by Marty57 View Post
    Here's a picture of my wood wing Wag 2+2. It's very similar to the J4 (with flaps hardware from SC). Not sure why you couldn't use it; it's a PMA's part but not for the J4. Main difference is how the drag wires fit; they are J3 wires.

    Marty57

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    That’s the part I fabricated. A member here found me three and I ended up making the 4th. Good luck trying to find that these days. Wag discontinued it.



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  38. #38
    skywagon8a's Avatar
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    Quote Originally Posted by soyAnarchisto View Post
    You also might try Dakota or Jay at Javron to see if they can fab one for you as owner produced as well.
    Be careful of the use of "owner produced". If you take advantage of "owner produced", the parts must be made in accordance to the original approved part specifications.


    Quote Originally Posted by J4A View Post
    Nothing yet on eBay, i got in touch with univair and they were unable to manufacture another set. I've emailed cub club to try and get some drawings but not had any reply, in the UK I'm able to manufacture my own parts however there's no way it would get approval without an original spec to go from. I might put an Ad on Barnstormers and will get in touch with Javron. Does anyone else have a lead on where I might get some construction drawings for the J4?
    If you can locate a drawing for this same part as used on another Piper model, look in the title box in the lower right corner. It should state there to which models that particular part is applicable. Perhaps J-3, J-5 or any other model would be the same as the J-4?
    http://www.supercubproject.com/drawi...s/A3310097.pdf
    http://www.supercubproject.com/drawi...s/A3290625.pdf
    http://www.supercubproject.com/drawi...s/A3290623.pdf This calls out the material spec.
    http://www.supercubproject.com/drawi...s/A3290054.pdf
    This is a collection of drawings for the PA-18. http://www.supercubproject.com/drawings/main.aspx Some of them give reference to the J-4. You should be able to gather what you need for your plane. It appears in viewing the title box in several of these drawings, while not specifically stating so, the fitting for the J-4 is likely identical to the other early high wing Pipers.
    N1PA

  39. #39
    cubdriver2's Avatar
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    If you contact Kerri Ann ( fifinella) on the J3 site she might help you. She made some for her L4 clone that were very nice.

    https://www.j3-cub.com/

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

  40. #40
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    Quote Originally Posted by cubdriver2 View Post
    If you contact Kerri Ann on the J3 site she might help you. She made some for her L4 clone that were very nice.

    https://www.j3-cub.com/

    Glenn
    Glenn, You should know, is this fitting the same on the J-3 as it is on the J-4? Knowing Piper, my guess is Yes.
    N1PA

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