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HELP! Bent J4A Cub Coupe Front Spar Lift Strut Fittings

J

J4A

Registered User
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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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.
 
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
 
Cub Builder said:
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
Click to expand...

It's the front fittings on the left wing, although they are shown as the same part on the left and right wings.
 
bob turner said:
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.
Click to expand...

Just checked the parts manual and you're spot on, those should be AN360 nuts!!
 
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.
IMG_20180726_181945_1.jpg

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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!
 
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...
 
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?
 
J4A said:
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?
Click to expand...

I have a few "Mystery" wing parts. Send me a pic or print of what you need and I'll take a look....
 
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
 
Heres a better pic of the front spar fittings I'm after...

1CBE6732-4E1B-4B39-B32C-EC28C0B84B00.jpg
 

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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.
 
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
 
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?
 
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
 
Probably these Atlee reinforce strips, should be first mod on any Cub left outside, makes the attachment brackets 4X stronger.Screenshot_20210915-024956~2.png
Had yours had these installed none of that
Damage would happened.
Good luck
E
 

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J4A said:
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?
Click to expand...
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.
 
J4A said:
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?
Click to expand...

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.
 
CharlieN said:
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.
Click to expand...
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.
 
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