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Old 02-10-2012, 11:29 AM   #1
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Waterproof Airstream - Impossible?

I was reading "The Shelters of Stone" - one of a series of novels about early modern mankind, which is pretty well researched. There was a paragraph about traveling tents which went straight to my Airstreaming experience.
The walls of the tent were double layered for better insulation, which caused all of the condensation to form on the inside of the outer skin!
Well Duh! American Indians did the same thing with tepees - for the same reason and with the same result.

I recently had to have my floor repaired and I did have leaks around the rear panos and the trim at the bottom and, and and.... BUT I also have the SE - with no mouse fur covering the inner skins. (2011 models up -they've done a better job of welding the window frames rather than using acryl-R in the corners... but those panos still need close watching and periodic re-sealing. Floor rot doesn't happen because the floor GETS wet, it happens because it STAYS wet. The wall insulation bleeds water a drop at a time through the bottom channel and into the wood. If the base channel had holes lined with plastic or metal tubing that went outside and below the lower trim - what would happen?

The inner skins aren't sealed - so when I breathe, shower, wash dishes, there is a certain amount of humidity in the air and on a cool night it SOME of it will condense between the skins. The more I think about it, the more I think the system needs to have some kind of built in drainage holes in the bottom channel between the two layers of skin. You're still going to need to seal the outside to prevent big leaks, but the pinhole leaks you might miss? When I shower I use the exhaust fan, and when I cook the stove fan is on - but neither removes 100% of the moisture in the air - and I'm still going to breathe and do dishes without a fan running.

To support this hypothesis - the question has to be asked of busy repair facilities - do you see more floor damage and mystery "leaks" with the SE Safari/Flying Clouds and the Internationals? I think it's likely that the vinyl wall covering on the classics and to a lesser degree, the mouse fur on the Flying Clouds both insulate and seal the inner skins.

** I wouldn't want the look of Acryl-R on the interior seams of my unit, but it might have been something that could have been used behind the seams before they were pop riveted in place. The pop rivets will also allow moist air to pass through them (put your lips on the wall around a pop rivet and blow if you don't believe it.).

When I thinks, I falls asleep.....zzzzz Paula
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Old 02-10-2012, 11:44 AM   #2
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This could definitely happen, either with continuous occupation during colder months or with high relative humidity and radiative cooling of the outer skin (e.g. clear weather, low wind conditions). Remember, the night time sky is very cold, and surfaces exposed to it will cool below ambient air temperature if there is little wind to convectively heat them back to ambient.

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Old 02-10-2012, 11:53 AM   #3
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I too have often wondered why they dont install a plastic water trough between the skins with a gradual slope from each end towards the center on each side of the trailer. One small drain on each side that bypasses the wood flooring and worries are over!

If I was rebuilding one I would want to add something like that somehow..

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Old 02-10-2012, 11:57 AM   #4
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Or, a true composite floor which would help with the 100's of other ways our floors get wet from the top, and bottom.
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Old 02-10-2012, 12:03 PM   #5
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Or, a true composite floor which would help with the 100's of other ways our floors get wet from the top, and bottom.
I think this is the answer. It's also why, although I want a bigger trailer, keeping my aluminium-floored Argosy Minuet has a certain appeal...

I also wonder if different insulation rather than the pink stuff would reduce the slow drip of water onto the floor. Drains would be good, but that's got to be balanced with the want to keep critters out and trying to maintain a "dead" air space for insulation.

Also, I don't think AS has built any trailers with the mouse fur wall covering for the last two years or so - even the Sport models now have aluminium interior panels.

Tom
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Old 02-10-2012, 12:07 PM   #6
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I've been saying they need drains for a couple of years now. I think that if the belly pan area were vented it would reduce the chance of the frame rusting away.
I have often thought if I were going to do a shell off rebuild I would put 3/4" x 4" aluminum flat stock around the perimeter of the trailer floor and have it be sandwiched in the "c" channel instead of the wood. There would be drains every few feet and. A barrier to prevent the water from getting to the wood. Then the only concern with leaks would be the internal plumbing.
I don't think you can ever stop the floor rot situation with the current design. You can only slow it down.
With all of the advances in composite material. I don't understand why AS still uses wood for flooring. Someone will say cost I'm sure. If I were buying a new trailer and they had an option for a rot proof floor. Even if it were $2k I would certainly consider it.
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Old 02-10-2012, 12:40 PM   #7
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Judging from the 'fairy ring' of mold that grew to twenty-four inches across from a factory hand print on the inside layer of the outside shell (above the bath tub) I'd say this is a valid hypothesize 24/7/365 whether or not the trailer is occupied - dew happens.

Except very dry climates I'd say dew-cycles present themselves no matter what we try - the key is limiting moisture to X finite quantity. Opening free-air vents anywhere near the ground may be a bad idea since earth has a layer of higher humidity air hugging it identical to the vapor pressure displayed above a pot of water, pond or lake. Everyone has seen ground-hugging fog, the moisture is still present even if you can't 'see it'.

We see it especially bad in Minnesota as the frozen ground surface melts-refreezes-remelts daily for six weeks in spring and not having your car or equipment on well drained pavement means a huge boost in condensation and persistence of water slime-coat on the undercarriage - then toss in water-holding ice-melt chemicals and its a royal corrosion city. Forget 'covering' the equipment with a tarp, all it does is allow the moisture to persist longer by being cooler and lower airflow!

So what you're talking about is a predictable drainage system - an example is Masonry construction and stucco walls providing a sump seep wick AT the solid foundation interface that expel liquid water and provide a channel for outside dry air and sunshine to continually carry away higher interior moisture concentrations.

If we place wicks from the lowest frame channel downwards perhaps liquid water percolates down - but it has to be 'air tight' to stop the convection chimney effect lift of the shell sun heating (or maintaining a heated trailer interior) that would draw in as much or more 'new' moisture during morning and evening dew cycles than the few CC's that might be expelled. And who wants possibly rotten belly air from outboard of the main ladder frame mixing with the interior air?

So - an airtight wick to dump or minimize/equalize liquid water - but the drainage plane has to be defined (where the water IS) and rapidly routed to a lower point. And the material can't 'hold' more water than it will rapidly expel - and it should be shielded from rain contact or road spray when traveling.

There are masonry & stucco systems that use flat wafer board to poke out from the first course of bricks that might be worth looking into - say a 1/4" wide strip (to not hold more moisture than an otherwise average) leading to a down-drain tube, maybe more of the same material rolled up with the 1/4" strips leading to them like a firecracker fuse - and the downwards end having the rolled material cut and fluffed up like a pom-pom.

I've been yelled at here before suggesting open venting the belly pan area is a bad idea (if it were a good idea all our RV's would have it already) mostly by people living in drier climates. Our 'mental' picture of the belly pan is from when we are in attendance, usually nice or nicer weather and not when the dampest cold drafts are roaming around like blobs of mercury or week-long tropical depressions will provide unlimited water vapor, or the twenty minutes every morning and evening that (air temperature : humidity levels : surface temperatures) guarantee a film of liquid water condensing out. Keeping water to a limited finite amount is better than opening up to infinite replenished moisture...
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Old 02-10-2012, 12:40 PM   #8
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barts (post #2) is exactly right. If you LIVE in it, in the winter, eventually you'll see this. In my case, I will notice condensation dripping from between the shells, around screws on the top of the rear window frame, onto the screen below. It can amount to quite alot...this is despite the fact that my dehumidifier is right next to the bed, pumping its little a$$ off the entire time...
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Old 02-10-2012, 01:12 PM   #9
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Floor rot doesn't happen because the floor GETS wet, it happens because it STAYS wet.
Dumb question time (and remember, there really are no dumb questions, just dumb people asking them)

How exactly is the wood treated? Paint? Polyurethane? Varnish? Nothing? If it has been coated, were ALL the surfaces coated, or just the visible surfaces? Wood that has been kiln-dried is like a sponge, and will soak up water to replace the sap that was cooked out of it, but wood that has been sealed on all surfaces, especially the end grain, will be more resistant (though not necessarily immune) to rot.
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Old 02-10-2012, 01:43 PM   #10
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It's plain old plywood, and they paint the edges with water based paint on a roller. THEN they start drilling holes in it, and putting screws into it to attach the shell, run wiring and plumbing, etc. End grains protected NOT.

Paula
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Old 02-10-2012, 02:07 PM   #11
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It's plain old plywood, and they paint the edges with water based paint on a roller. THEN they start drilling holes in it, and putting screws into it to attach the shell, run wiring and plumbing, etc. End grains protected NOT.
I see. Plain old plywood, not even marine-grade plywood. Not sealed on all surfaces to prevent water intrusion. They are ASKING for rot to set in.

There are all manner of techniques that boatbuilders use to ensure that the wood they use doesn't rot. If people can build plywood boats that last decades, they ought to make trailer floors that can stand up to condensation, but I guess not many boatbuilders assemble trailers.
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Old 02-10-2012, 02:13 PM   #12
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I have been saying that they need drains in the bottom of the C-channel. I am going to add some while I have the skins off. I am also going to plug the gaps at the corners where the curved sections meet the straight sections. Unfortunately, RV's are designed with the mindset that they are temporary luxury items that you don't really need so if they rot and fall apart who cares. It is part of our disposable American mindset. SOB trailers are even worse.

Perry
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Old 02-10-2012, 03:37 PM   #13
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There are better ways to insulate and to protect from water, but Airstream is way behind the times.

Spray foam can seal spaces where air comes in and out—one source of condensation. It provides better R value than fiberglass. Spraying around windows will seal them much better. Modern methods of home construction create air tight houses and better insulation. Wall interiors need to be vented on one side or the other to prevent condensation. This allows water to evaporate. The outside walls can be made watertight—house wrap was a step toward that, but better things are now available. Once the ribs are assembled, impervious sheeting could be put over them before the skin is attached. Everything that goes through the walls can be sealed with waterproof tape, spray foam and a more flexible sealant that will move with stresses to the trailer. That would create a vapor barrier on the outside wall. The foam also acts an insulator. Ventilation on the interior side would be fairly simple.

Car companies can make doors that don't leak, but Airstream exterior doors to storage compartments have a long history of leaks which also destroy floors. And the company is tone deaf to using marine plywood and sealing all cuts and holes on the edges.

The various items on the roof leak, but flashing can be and is designed to prevent leaks on houses from chimneys, soil stacks and skylights.

Airstream is disconnected from the world of home construction and auto assembly and we all suffer from that. The workers are not experts at all the things they do and the supervisors and executives do not know how to change or adopt new methods. It is also cheaper to do the same things and be content in the knowledge that they are making a marginally better trailer than most others.

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Old 02-10-2012, 05:00 PM   #14
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Question So then what do you replace it with?

So it's looking like I'll be replacing all the flooring in our '73 Tradewind.

If you were going to replace all your flooring, what would you use? Is there some sort of alternative like green board that's available and would be more water-resistant than plywood?

-Alana
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