Rag and tube structure

What guys really do? They look for weak
spots in the normal places like lower longerons using a hammer and a punch.
 
Tom-D said:
I asked the question to raise the awareness that these aircraft are subject to this problem.

I know of several old Stinsons being restored at home by owners that are not A&Ps.

when buying -- be aware, the only way to really know is to cut a section out and measure it.. sellers probably won't allow that.
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Tom, leave the Stinsons alone ;)


If your concern is with "garage restorations" wouldn't it be far more common, easier, cleaner, and waaaay more likley for a non AP to have access, and use, a stripper then have a giant media blaster in, and use in it their home garage?
 
GlennAB1 said:
Yes. Can't imagine a GA owner wanting to pay for a UT inspection of an entire tube frame. Usually UT is mapped in 1/4 inch increments.
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I wouldn't do the entire frame, but IF you were genuinely concerned, you could select some samples of suspect areas. I would think that would be preferable to cutting out sections and re-welding.

Even the Beech SB doesn't call for UT'ng the entire spar.
 
Stewartb said:
What guys really do? They look for weak
spots in the normal places like lower longerons using a hammer and a punch.
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Pretty much. And when they find a problem area, then they cut it out and weld a new splice.
 
Fearless Tower said:
Exactly. This is what the recent SB on the Beech 18 spar suggests. Ultrasonic testing to gauge the thickness of the tube spar. In that case, the question being addressed is more a matter of how much erosion has occurred inside the tube rather than on the outside.
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That would be "corrosion loss" not erosion.
 
James331 said:
Tom, leave the Stinsons alone ;)


If your concern is with "garage restorations" wouldn't it be far more common, easier, cleaner, and waaaay more likley for a non AP to have access, and use, a stripper then have a giant media blaster in, and use in it their home garage?
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Any tube structure is subject to this, Stinsons are no exception. most home restorers take their fuselages to a large facility to have it striped. these facilities use rough media to get the job done quick.
 
Who can tell me what the little screw in the side of the tube means?
 

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Tom-D said:
Who can tell me what the little screw in the side of the tube means?
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It means that someone filled a hole in the tube with a screw. Now why are there holes in the tubes? Mabe to allow hot air to escape,
or for corrosion proofing, or mabe both?
 
Fearless Tower said:
I wouldn't do the entire frame, but IF you were genuinely concerned, you could select some samples of suspect areas. I would think that would be preferable to cutting out sections and re-welding.

Even the Beech SB doesn't call for UT'ng the entire spar.
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It's always nice to have something like an SB for guidance.
 
No one has asked do I guess I will-
What media are you using yo blast it with?
Why are you worried about thus I the first place?

Most fuselages are so overbuilt that you could lose quite a few tubes before you would have to start worrying. Unless there is a size able hole in the tube somewhere, internal corrosion is a useless thing yo worry about, after the o2 inside the tube is used up,then it is a non event. In all honesty, you should be more worried about the blasting putting dents in your tubing that material loss. Try not to start worrying about these things, just remind yourself that they are built very well. Piper has planes still flying along after seventy plus years and when was the last time any airplane just fell apart? On the ground or in the air?
 
Shine a bright light down the tube length and look for variable heights, measure the thickness of the high and low areas. If you have more than 10% difference, you might be concerned.
 
Tom-D said:
It's easier to simply strip a short section of tube, measure, then subtract that number from the tubes original size, to see how much material has been lost.
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If you are doing this post sandblasting to determine loss why would you need to strip it?
 
Stewartb said:
What guys really do? They look for weak
spots in the normal places like lower longerons using a hammer and a punch.
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Common sense, as well as a specified method for ADs applying to some lift struts on airplanes such as Champs and Maules. Even a very small metal hammer tapping the metal will reveal bad spots; they don't sound right.
 
SkyDog58 said:
If you are doing this post sandblasting to determine loss why would you need to strip it?
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When you are buying, or doing the first annual after the restoration will it be protected?
 
In Alaska we get our tube structures sand blasted and powdercoated. The powder coaters up here phosphatize (Parkerize) the blasted frames before priming.
 

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Stewartb said:
In Alaska we get our tube structures sand blasted and powdercoated. The powder coaters up here phosphatize (Parkerize) the blasted frames before priming.
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That looks good. You can drop that off at my house once you finish putting it all together....

I was talking to an AP that inspected a tub/fabric plane for a customer to determine if it needed a recover. He didn't even get that far, after feeling along the edges of the stabilizer and wing. They felt rough, so he gave the edges a squeeze. He could feel the frame crumble inside the fabric. The owner, who flew the plane in told him to stop, but he just couldn't help himself... lol

So yeah, cut out and replace.
 
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