Factory Fuselage Assembly

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Nathan K. Hammond
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Factory Fuselage Assembly

Post by Nathan K. Hammond »

Those that have cut open frames; did Aeronca drill holes in the longerons at the clusters? In other words, if I flood the frame with ACF-50 or linseed oil, will it creep everywhere, or do need to drill every tube?

nkh
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Aerco
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Re: Factory Fuselage Assembly

Post by Aerco »

I never understood why this kind of thing was done in the first place. When you weld a tube to the longerons, it can't possibly have any trace of moisture left in it. The weld seals it shut forever and unless it cracks it will never corrode from the inside out. Drilling holes however, means that if moisture gets in somewhere, it has the opportunity to reach every single tube. I don't know what Aeronca did at the factory, but on my homebuilt I would never do this.

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hangerash
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Re: Factory Fuselage Assembly

Post by hangerash »

Peter,

The short tubes are not the issue as much as the long ones, which have a propensity to condense what atmosphere is sealed in the tube when subjected to temperature changes. Albeit small and slow, the process eventually weakens the tube and it fails. The linseed oil or ACF-50 serves to displace any moisture that might attempt to form on the inner surface of the tube.

You could skip the coating process if you evacuated each tube before you welded it shut, but I'm bot sure this would be practical.

Richard @ vnw
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clipperfixer
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Re: Factory Fuselage Assembly

Post by clipperfixer »

When I cut mine open to replace the longerons there were no holes drilled into the clusters. If you put put sealer in the longeron tube it will only go into the longeron and it won't go into the cluster.

Bo Grave
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Re: Factory Fuselage Assembly

Post by Bo Grave »

Guys,

The bottom line is to deny it one of two thing (moisture or oxygen) remove one and it will never rust. It takes both for corrosion to start.

regards,

Bo Grave
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Eugene ( Bo ) Grave
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Nathan K. Hammond
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Re: Factory Fuselage Assembly

Post by Nathan K. Hammond »

Well bummer, but I figured that was the case. Thanks for the help!

The idea of keeping out moisture and oxygen is great, but unless your welder is high class with a purge function, or you have access to a vacumme chamber; both will make it into the frame. Especially after a field repair.... of which my frame has many...

Next question then, where have you guys injected preservative?

nkh
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MikeB
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Re: Factory Fuselage Assembly

Post by MikeB »

Nathan,
I remember Bill Pancake saying he made some kind of an adapter and puts low pressure air into the longerons (at least) and uses soap bubbles to look for leaks. For whatever it's worth, I've drilled a small hole into the longerons, heated lindseed oil (I'm cheap) and shot into the longerons with a cattle syringe with a big needle and rolled the air frame over and over to make sure it's well coated. I sealed the hole with a PK screw coated with sealer. I guess a person could do it with all the tubes but unsure where one draws the line. The stuff that Poly-Fiber sells is supposed to 'crawl' and I think they seal the hole with a pop rivet of some sort. I've also read that the spine tube can get moisture in it and rust out back by the vertical fin for whatever it's worth. I do know that the lindseed oil does a good job of coating the tubes.

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Re: Factory Fuselage Assembly

Post by Aerco »

I'll allow that longerons are different matter, but all the crossmembers should be left isolated in my opinion. As stated above, it takes oxygen and moisture to start corrosion and the welding process itself heats the tube enough to drive out all the moisture on a short length of tubing. No moisture - no rust. And there is no need to purge anything; as you finish the weld, the tube is hermetically sealed with only dry air inside. But no moisture.

I have seen 1940s Auster fuselage frames in Britain with rusted tubing on the outside, but clean insides, and they were not drilled anywhere. And that is about as wet (and miserable) a climate as you can imagine.

With longerons, I have in the past poured oil into them from the firewall end and let it drain out of a small hole at the rear before sealing it shut.

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Re: Factory Fuselage Assembly

Post by brink »

That’s interesting reading, on my new Project it was in a sea land container for about 30 years, when I cleaned the tubing by hand I found some small holes, around the interior, cockpit area, I guess used or drilled for mounting interior panels. Praketone, thinned with mineral spirts, I guess I better inject those tubes, and seal up those small holes. Has anybody used fogging oil, comes in a spray can, designed to fog Cylinders on engines. I did pour a quart of prakitone in my struts, mixed with mineral spirts, hopefully it will coat the inside, one of my forward struts was full of dirt and sand, but no metal, might have been left over from a sand blasting, I used a magnet, but no metal filings were their, very interesting reading,

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