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Concerned about some corrosion on tubes

G

Globemaster

Registered User
I recently bought this cub and noticed some corrosion on the X brace and a couple other tubes in the cockpit. Everything else looks fairly clean but these spots are showing some clear signs of corrosion. It kind of looks like some of the rust was painted over at one point as well. It's going in for its first annual next week and I'm a little worried about what might come of this. Just trying to budget for the annual bill, anyone have any idea if this is something that can be cleaned and protected or am I looking at a major repair with replacing these tubes?

In one of the pictures you can see I cleaned a small spot of the rust off, it wasn't deep but the tubes definitely have some minor pitting left behind from the rust. :/
 

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That does NOT look like "Minor" rust to me. A little hard to tell for sure from photos, but that would spook me. And, in any case, I'd REALLY want to know what the rest of the frame looks like.

Where was this plane before you bought it? High humidity/coastal area? Do the logs offer insights? Do you know who rebuilt it last? Etc.

MTV
 
When was it built and is there rust showing on the fuselage lower tubes any where?Check the tail group carefully.If you see any brown stains on the fabric inside the fuselage along the longerons then I would say find yourself another plane! That is from personal experience...
 
Rust never sleeps. You own the airplane so keep after it. A little elbow grease, primer and paint goes a long way. The lower longerons are critical to inspect.
 
Hard to tell, but looks like some of the gingerbread also has corrosion.

Not that hard to deal with that area, though you might end up pulling the skylight to really get it Clean.

What I would be concerned with is having that much corrosion up high where it doesn't get wet, and wondering how much corrosion is on the lower part of the plane where it really gets wet?

As your mechanic though. Let him guide you as it is his signature on the line. Also, he can touch it, and inspect it, and make a determination.
 
A prick punch and small hammer spent tapping every, 6/8" up "every one of the lower longeron's"; will tell you awful fast, spend extra time around gear fittings. It ring right out
if it's solid. If they are half rotten thru they will sound flat and punky................ If they are 80% or more corroded from inside the punch will go right thru or dent the tube. This was standard procedure 30 years and NO ONE would have
purchased without doing this test on any rag/tube airplane
Some modern day mechanics will talk about the tiny spot
the prick punch leaves......... Say a .030 spot. Could start coroding after the test. So simply take a small brush and put one tiny drop of paint/dope on the spots. Done.
If it has longeron's that are rusted better plan on $20k to
Replace em in today's market. Your surface rust on the overhead stuff will seam pretty minor if your longeron's are shot!
Good Luck
E
 
Concur with the posts above especially #6, was that aircraft ever a banner tow? Or live outside in Florida? Corrosion up high like that is a tell tale sign it flew in humid salt air.
 
Make sure to check behind the channel on the rear door post.

Everything looked good on this one until the channel was cut off.

436DB555-1791-450C-BC86-43AA4CA07CDB.JPG
 

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To my eye, those pictures show the tubes were repainted over existing rust and other crap. I would hate to see what is back there the fabric wraps the tubes.
 
What does the tail look like? Remove the battery cover or baggage aft panel and look. Seen corrosion on the cockpit tubes from people grabbing the tubes and over time rubbing the paint off.
 
Steve Pierce said:
What does the tail look like? Remove the battery cover or baggage aft panel and look. Seen corrosion on the cockpit tubes from people grabbing the tubes and over time rubbing the paint off.
Click to expand...

Combined with salt from sweat on ones hands.


Sent from my iPad using Tapatalk
 
CharlieN said:
To my eye, those pictures show the tubes were repainted over existing rust and other crap. I would hate to see what is back there the fabric wraps the tubes.
Click to expand...

fortunately it's easy to see the tubes in the back, my cub doesn't have a cargo headliner installed so you can see everything back there. I didn't notice it until after I bought it but the tubes are painted two different colors of grey. This dark grey was the paint put over the corrosion and there's a light gray that was the original. Everything in the back is still the light grey and looks pretty good. I found two small spots of concern but the lower longerons look pretty clean and I've combed every inch of the aft structure with no big issues. Which is why I find it odd that this structure up high is what got corroded.
 
Steve Pierce said:
What does the tail look like? Remove the battery cover or baggage aft panel and look. Seen corrosion on the cockpit tubes from people grabbing the tubes and over time rubbing the paint off.
Click to expand...

Steve, aft looks pretty good. I found two spots where paint had chipped off the tubing and started to corrode, but everything looks pretty clean back there. It's all the tubing in the cockpit including places you could never grab that corroded. Seems very counterintuitive that the tubes up high are corroded but not the tubes down low?
 
heated humid air rises - clouds - until it condenses on something cooler like tubing. If the top of the cockpit is somewhat sealed to venting it gets worse. I've seen it in vehicles and airplanes particularly in winter.

Gary
 
My J3 had pretty good rust on those "handhold" tubes in 1962. Cleaned it up, painted the whole frame in epoxy (cheap back then) and pressed on. No problems since then.
 
jrussl said:
Make sure to check behind the channel on the rear door post.

Everything looked good on this one until the channel was cut off.

View attachment 58154
Click to expand...

how does one check this without cutting the channel off. Mine looks good on the aft side but can't see the front side. Would hate to cut that piece off just to inspect there?

That said, mine is an EAB cub that the builder modified the door so that post slants down and aft to make the door larger. The channel is not welded at the bottom and looks like it allows for moisture to drain out, if I recall from Steve Pierce walking through the annual on the YouTube videos he mentioned this post is a typical corrosion culprit because it's sealed at the bottom and collects moisture?
 
Last edited:
BC12D-4-85 said:
heated humid air rises - clouds - until it condenses on something cooler like tubing. If the top of the cockpit is somewhat sealed to venting it gets worse. I've seen it in vehicles and airplanes particularly in winter.

Gary
Click to expand...

I discovered the culprit after some more digging in the logs today... can't believe I didn't catch this before I bought it but it did spend six years in Florida on the Gulf coast, and in those six years it was annualed one time. And there were six or seven hurricanes that went through too. God I hope it wasn't just sitting out on the ramp that whole time. Can't believe I never noticed this. :roll:
 
Well unfortunately I found this as well. I've inspected the entirety of the lower longerons and everything else still looks decent. There's no evidence of any corrosion on the bottom side, and I went along the length doing a tap test. It all still seems solid except for this one spot. It looks like I'll have to cut the belly open to get to this spot, which I figure if I'm going to do that, I may as well get the metal belly kit from Univair. Anyone have any experience putting one on an already skinned plane? Is that a worthy investment?
 

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Globemaster said:
Well unfortunately I found this as well. I've inspected the entirety of the lower longerons and everything else still looks decent. There's no evidence of any corrosion on the bottom side, and I went along the length doing a tap test. It all still seems solid except for this one spot. It looks like I'll have to cut the belly open to get to this spot, which I figure if I'm going to do that, I may as well get the metal belly kit from Univair. Anyone have any experience putting one on an already skinned plane? Is that a worthy investment?
Click to expand...


My guess would be: Hands on the windshield area cabanes leads to minor corrosion. You almost always see that. Upper cockpit, probably had water seep in under the skylight after sitting in the rain. Plane not flown,not dried out. Lower fuselage, water settled in.

Chances are you can deal with this, but I'd strongly recommend you stay on top of it. It's not just a one time fix. You better have a darn good look at the struts and fork fittings. We used to weld in bushings to add Bradley safety straps between the fuselage fork fitting and the strut before sealed struts became available. On one occasion, we drilled the strut for the bushing near the fork and a quart of water came out. The fuselage probably won't fall apart but if a strut fails, it's all over - and it has happened more times than people generally know about. You should also check the lower tail brace wire fittings at the fuselage. Best of luck, Be careful.
 
WhiskeyMike said:
My guess would be: Hands on the windshield area cabanes leads to minor corrosion. You almost always see that. Upper cockpit, probably had water seep in under the skylight after sitting in the rain. Plane not flown,not dried out. Lower fuselage, water settled in.

Chances are you can deal with this, but I'd strongly recommend you stay on top of it. It's not just a one time fix. You better have a darn good look at the struts and fork fittings. We used to weld in bushings to add Bradley safety straps between the fuselage fork fitting and the strut before sealed struts became available. On one occasion, we drilled the strut for the bushing near the fork and a quart of water came out. The fuselage probably won't fall apart but if a strut fails, it's all over - and it has happened more times than people generally know about. You should also check the lower tail brace wire fittings at the fuselage. Best of luck, Be careful.
Click to expand...


Yeah I figured I have some consistent work ahead of me. I'll be moving to Alaska in a couple years and when I finally get it up there my plan is to tear it down and build a new so it just has to last me until then haha. I already ordered new sealed struts for it, should be finished up at Airframes this week and I'm planning to buy all four new tailbrace wires as well. They weren't pretty and I noticed someone painted them with silver paint to hide the corrosion. :x
 
Steve,
After reading through post #25 and seeing what the channel looks like on other cubs I'm going to remain hopeful. It looks like mine was built to allow it to drain any moisture inside it. (Will post a picture later.) That said I'll probably still have them drill in to it like you did. It's a '98 so hopefully it hasn't had long enough to look as bad as some of the ones you found! :Gdrool:
 
Hate to be a party pooper, and it is probably just me, but I would tear it down and start over. Not worth the grief, and you "will" find other problems. Sorry, just my 2 cents.
 
supercrow said:
Hate to be a party pooper, and it is probably just me, but I would tear it down and start over. Not worth the grief, and you "will" find other problems. Sorry, just my 2 cents.
Click to expand...


That is the plan, but at the moment I can't afford that, and I'm getting ready to head off to a year and a half of USAF pilot training so I wont have time to work on it that much. After training I'll be moving up to the Anchorage area, once I get there my plan was to tear it down and start over. I just need it to last a couple more years. *fingers crossed*
 
Globemaster said:
Yeah I figured I have some consistent work ahead of me. I'll be moving to Alaska in a couple years and when I finally get it up there my plan is to tear it down and build a new so it just has to last me until then haha. I already ordered new sealed struts for it, should be finished up at Airframes this week and I'm planning to buy all four new tailbrace wires as well. They weren't pretty and I noticed someone painted them with silver paint to hide the corrosion. :x
Click to expand...

Not to toss even more cold water on your parade, but when you get to Alaska is precisely when you're going to want a flyable airplane, NOT a project. I understand your constraints, as you've explained, but I'd sure try to figure out how to get the thing ready to rock as soon as you arrive in AK. "Project" airplanes can take FOREVER to complete, and while Alaska winters are long, there's still a lot of flying to be done. Trust me, THAT's when you'll want a toy to go play with, as opposed to a "project" to go work on!

MTV
 
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