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Old 06-12-2012, 10:19 PM   #1
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Why not all Aluminum?

Seems like if Airstream had made the frame out of aluminum as well, that a lot of the issues being dealt with (frame rusting out and causing many other problems) would have never happened. Has anyone replaced a rotting out frame with a newly built aluminum frame? Is there a place to get these from for specific models?
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Old 06-12-2012, 10:43 PM   #2
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I'm not an engineer (nor do I play one on TV), but two reasons occur to me:

1. Without a complete change of design, the strength of aluminum can't equal steel, especially in places like the frame.

2. It would cost more. Yikes! That's enough all by itself!
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Old 06-12-2012, 10:55 PM   #3
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I am a mechanical engineer by degree. Steel has three times the young's modulus of Aluminum (30 million PSI vs 10 Million). You would need to have an aluminum frame cross section with 3 times the moment of inertia to come out equal in rigidity. It could be done. The thing that seems to fail the first on Airstreams is the wood floor and the rubber axles, so those are the area I would work on first, if I were to redesign an Airstream.
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Old 06-12-2012, 10:56 PM   #4
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There was a thread in the past regarding trucks that had cracked aluminum frames, etc. It's just too brittle under load and moving stress.

Many people think it should be galvanized though. The ones that go to Europe ARE galvanized, but they are also bolted together, not welded. And one weakness with galvanized metal is that a small gap in the coating can let in rust - and then it rusts behind the galvanized layer where it can't be seen until the part fails.

Didn't Uwe built a Stainless Steel frame for an Argosy he restored?

Paula
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Old 06-12-2012, 11:00 PM   #5
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Quote:
Originally Posted by dwightdi View Post
The thing that seems to fail the first on Airstreams is the wood floor and the rubber axles, so those are the area I would work on first, if I were to redesign an Airstream.
Good point. In fact, Airstream built a number of Argosy models with an aluminum sub-floor, years ago.

I have no idea why the idea didn't stick. It would seem to be an ideal answer to that old problem...
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Old 06-12-2012, 11:06 PM   #6
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I agree with Paula, hot dip the whole damn thing. An aluminum frame could be designed. Pernaps an I beam with with a 1" web and 6" flanges. I'd have to do the calculations. I'd feel comfortable with the material but not the welds. Machine welding might work under some very controlled conditions. Welding aluminum is difficult and I know people who can do it and have a nice looking bead, but how strong is it? A cold joint will snap like a toothpick if flexed under load.

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Old 06-12-2012, 11:07 PM   #7
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Stainless steel frame and floor would be so super sweet. It would last and last.
Has anyone used a hardy plank material for the floor? That seems like a good idea.
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Old 06-12-2012, 11:13 PM   #8
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Steel is more fatigue resistant that Aluminum. They make aluminum airplane frames, but they have a predicted useful life. Proper galvanizing is a sacraficial material for the steel frames. If properly done, even scratched galvanize will protect the steel from corroding until all the zinc is gone. Depending on how much salt they use of the streets the trailer is used on it will last a good long time. A great paint job over the galvanized steel is even better. Boat trailers, intended for salt water use, are hot dip galvanized.

Fiberglass foam core floors would stop the rotten wood floor issue.
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Old 06-12-2012, 11:21 PM   #9
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dwight, I like the foam core idea, even ABS foam core would work well. It's been used in pipe for years, it's durable, quite flexible and the skin on the outside could actually be the floor surface.Aluminum is much more mallable than steel but depending on the carbon content of the steel it can be quite soft as well. It's been a long time since I've seen young's modulus referenced.

Eric,Hardiplank is a cementus material and would not withstand the flex the floor encounters as it travels.It's also heavy as hell.

Dan

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Old 06-12-2012, 11:23 PM   #10
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Don't want an aluminum frame around here ...
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Old 06-12-2012, 11:29 PM   #11
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Quote:
Originally Posted by Foiled Again View Post
There was a thread in the past regarding trucks that had cracked aluminum frames, etc. It's just too brittle under load and moving stress.

Many people think it should be galvanized though. The ones that go to Europe ARE galvanized, but they are also bolted together, not welded. And one weakness with galvanized metal is that a small gap in the coating can let in rust - and then it rusts behind the galvanized layer where it can't be seen until the part fails.

Didn't Uwe built a Stainless Steel frame for an Argosy he restored?

Paula
Hi, Paula; That was BoatDoc who made that stainless steel frame.
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Old 06-13-2012, 12:29 AM   #12
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Are cracks in aluminum frames repairable thru welding/doublers etc. in a practical manner?
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Old 06-13-2012, 02:42 AM   #13
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Ye you can with a specialized welding called TIG tungsten inert gas welding. The toughest to master in my opinion an expensive machines, but possible. Side note the skin in my mind is way to thin to TIG weld comfortably.
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Old 06-13-2012, 07:11 AM   #14
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Programmed life...

If any company built its' products so they would have an infinate life, they would eventually run out of need to sell and close shop as the market dried up!

Ironically, the current Euro spec Airstreams come standard with a galvanized chassis.... why are our US spec AS not built this way?

Anything zinc plated will certainly outlast something painted.
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