Door Frame Rust

[Steve Pierce]

I keep finding this same problem time after time. Got some good pictures and hope others will take the time to remove the "U" channel from the rear door frame and look at the tube running up to the right rear wing attach fitting. I suspect water gets in there through the screw holes for the "D" window retaining strip and has nowhere to go. I leave this open on the bottom so I can get paint in there and any water/moisture can drain out.

 

[S2D]

I drill a small hole in the U channel near the bottom of the channel and run an ice pick in. if it withstands a hammer strike I leave it alone. if it goes thru it gets replaced. (that's on flying a/c.)

 

[Darrel Starr]

Jim Richmond warned me of this when I was starting to restore N18SY. Sure enough- closed up water trap just as Steve described. Welded in a new tube and made sure the channel could drain.

 

[NimpoCub]

GULP That looks scary. Didn't look @ mine in there when I had 'er apart. Is there any external "signs"? Mine didn't show any rust externally.

 

[Steve Pierce]

No, It all looks good until you cut the channel off, mine included.

 

[kevin]

The -12s have this channel instead of over the vertical tube in front of the D window, it is over the lower tubes that makes the lower door frame. I checked mine out and it looks good.

 

[Steve Pierce]

This has been an ongoing problem in the Short Wing Pipers as well. Their door frames are all covered with these "U" channels with no primer underneath. I have been using a zinc rich weldable primer underneath to give some protection. It makes a mess when you weld it as it spits a lot but hopefully it will be worth it in the end.

 

[180Marty]

Maybe squirt some ACF-50 in there once in awhile. You could drill a small hole in the channel and use a syringe to inject. It really weeps and would spread.

 

[6 short]

When I looked at my -12 there was rust and pitting, so all of the door frame material came off and rust/pitting was present in places under all of it.

Pat

 

[aktango58]

Mine failed on annual last week. Not where I expected it to. Will take pictures when I get it apart...

Need to get the new fuselage together... then I can fly again. I will be sure to drill some weep holes...

 

[Darrel Starr]

I have never heard of a structural failure as a result of this rust in the Super Cub, but when we found it in my SC, Bob Eckstein and I stood back and visualized the load paths. Not pretty! The tube that rusts out comes down the front of the "D" window and is the main structure that connects the rear wing attach fitting down to the rear gear attach fitting. We made sure this area was plenty robust as we replaced the tube and channel. Just stand back some time and look at how the loads are transmitted -- this tube looks pretty important.

 

[mike mcs repair]

yup,

you can usually plan on having to replace both sides at rebuild..... and sometimes the bottom door tubes that were covered by the U channel too....

 

[kevin]

Steve, I'm not sure what your thoughts/plans are but this might be a good topic to write about in Cub Clues.

 

[Steve Pierce]

Yea, the deadline for the next article is approaching fast. :help I better get busy before Dana is calling me in a panic. 8)

 

[Amy]

Yea, the deadline for the next article is approaching fast. :help I better get busy before Dana is calling me in a panic. 8)

Steve is afraid of making Dana mad . . . Soon you will be familiar enough to her that you will probably be afraid too She runs a tight ship and can always formulate a plan in a hurry if need be!

 

[ag-pilot]

Steve, I have found it just as often on the front tube just above the door latch hole. Same as Brian drill a 1/8" or so hole in the U channel then pick around with something sharp. Most old frames will be rotten to some degree. I think the front tube is maybe even more dangerous with it being the main tube up to the front wing attach fitting.

Dave

 

[Steve Pierce]

and another one.

 

[Skip]

Yall are killing me going to look at mine tonight

 

[Skip]

My 12 dosent have a channel there is it supposed to

 

[supercubdriveroregon]

Good afternoon,

Would a cub with the L-21 glass conversion have the same possible issue?

John

 

[Steve Pierce]

Yes, my LOL had the same thing just not quite as bad.

 

[Larry G]

I will be doing the door jam area on mine soon on my project and I would like to know what I could do to prevent this. Some thoughts would be very helpful. Thank you

 

[Steve Pierce]

I don't weld up the bottom and prime prior to welding. That allows any moisture to run out instead of collecting in the bottom.

 

[skywagon8a]

This is a good area to spray some LPS-3, Corrosion-X, linseed oil, thinned paralketone or some other suitable corrosion proofer in at the top to coat the bare steel section under the channel. It rusts because there was never any protection in there. Even if painted before welding, there will be bare metal at the weld areas.

If the fuselage can be rotated, pour in the corrosion proofer and rotate. Wipe off the excess. It will be messy, but worth it.

 

[Steve Pierce]

Have a 1979 and a 1983 model Super Cub in the shop for rebuild and decided I didn't really want to cut the channel off if I didn't need to so I used a Blair hole saw bit and drilled some inspection holes to inspect the tube behind the "U" channel. Worked pretty well. I will fill the cavity with primer and drill a drain hole on either side.

 

[Steve Pierce]

The previous one was the 1979 model with 1000 hrs. This is the 1983 with 1500 hours.

 

[nightflyer]

You mean 1982? ;-)