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Old 02-20-2012, 07:19 AM   #71
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The floors tend to rot in the end cap areas. On my 81 the straight sections have a different extrusion. The ends of the plywood are cradeled in a channel. This helps protect the wood from leaks that would soak the end grain of the wood. Plywood will suck up water like mad through the end grain. On the end caps that channel is missing and they go back to using regular C-channel and the edges of the wood are right underneath that belly band. The banana wraps cover that area but I have seen places where the wrap was on the outside of the skin which would funnel water right into the sub floor. The floor in my 30 yr old trailer is in decent shape accept for these end cap areas and a problem area to the right of the door. Anyway it is a really good idea to cover the exposed ends on the plywood with Vulkem to help protect from end grain water intrusion. There are gaps where the straight section meets the end cap C-channel. Any water in the C-channel will end up on the floor in these areas.

Perry
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Old 02-20-2012, 09:46 AM   #72
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So, aluminum tape and duct tape don't work, but I'll have to find something. I have to check what temps are ok for the exterior sealant too. Sealing and not sealing the plywood each have fans. My thinking is that plywood can get wet on occasion and dry out, but chronic dampness and water over time will eventually cause it to deteriorate no matter how much ventilation there is. Vinyl will create a vapor barrier, but the planks I will use will have a 1/4" gap around the edges and can be lifted up from time to time to check the floor. Carpet lets the subfloor breathe, but also wicks water down to the subfloor. Laminates often require a vapor barrier underneath because they deteriorate if the substrate gets wet.

The best floor solution would be to leave the subfloor exposed, or replace it with something that can't absorb water, paint it and use that as the floor. I doubt anyone is going to do the first, and few will do the second.

I'm not going to remove every penetration of the body and install rubber gaskets before I put them back, but that would be the way to go I think. If I ever start my own RV company, that's what I would try, but the chances of me starting an RV company are pretty low. And I'm not going to remove and replace my subfloor with an impervious product, at least not as long as the OEM one is ok. By the time it fails I will probably be too old to fix it so I'd better make sure it doesn't fail.

Once the snow melts, I'll probably use duct tape on one side of the door trim because it will take take a couple of months before it starts to fall apart and reseal that area when it is warm enough to do so (unless I can do it at 35˚ or 40˚). I'll use a couple of coats of exterior polyurethane on the floor and thin it enough so it will flow under the inner skin—I'm not sure that will work, but I'll try it. I'll have to be more careful about keeping up with re-sealing all the penetrations. The nature of the new floor means I can check the subfloor from time to time. I'm sure my approach isn't perfect, but I don't know what else to do. Now I'm glad Airstream uses the cheapest vinyl they can find, because if I hadn't decided to replace it, I wouldn't have known about the leak and the damp spot.

I never thought I'd have to think about all this when we started looking at Airstreams—I thought it was like a car or truck—made of metal and sealed properly. So many surprises in life….

Gene
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Old 02-20-2012, 10:23 AM   #73
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As all of you may or may not know I have been using my GT as an aluminum tent for several years now. Not because I'm lazy but my flying schedule seems to be in the warmer maintenance months. Anyway I can honestly say that I am "LEAK" free at this time, it has been a long road fixing all the leaks, and that I am almost done with just 3 more window frames to do. I do believe I have identified all the previous leak sources and it has been a long list that can be attributed to a short list of causes. Airstream construction techniques is the main cause. Not a single lap seam had a faying surface seal but just a fillet seal. Nothing was installed wet with sealant. The window frames are installed with a foam seal that wicks water as it gets old. The access doors and cavities behind them is an open invitation for moisture intrusion.
So what have I done differently? I have opened all the lap seams and injected a very high quality sealant in between the the skins and shot it back together. I have decreased the rivet spacing to give a better sealing contact between the underlying structure. I have tied the internal framework together for a more unified structure that does not twist or flex as much as it used to. No matter how you seal everything up, if the structure moves around to much it matters not a bit how well it is sealed as the seal will fail. I have removed the windows (almost all) and removed the foam seals. I have replaced all the sheet metal screws that penetrated the exterior shell and replaced with sealed anchor nuts. One of the biggest leaks fixed was to install the banana wraps and side wraps under the exterior skins instead as they are installed now acting as a water inlet scupper.
So have I gone a little over the top with everything I have done so far, most likely. Is my approach for the average Joe, most likely not. The point I.m trying to make is that of all the issues I have run into, is that 99% could have been accomplished at construction with a minimal cost increase by the manufacture, if they would just have recognized a deficiency in their construction processes years ago.

Is condensation for me still an issue, you bet it is, but if you give a path for any moisture accumulation to exit then you are ahead of the game. I do like Perry's idea for the drain tubes in the lower C channel to exit the water into the belly pan so it can drain out, I will do just this. It is also my opinion that the condensation is only caused when we are using our silver bullets and has no way to exit and dry when parked, so allowing for drain paths and a minimal amount of airflow would be of a great benefit. By the way, every Aircraft I have ever worked on has drain holes in the belly for just this purpose, but they do have the added benefit of having differential pressure to ventilate and help the condensation drain the airframe, but the drain paths are all over the inside of the fuselage and is part if the inspection procedure to keep them open.

The access doors are going to leak no matter how good of a seal is on the door, that's just the way it is and should be accepted. The issue here in my opinion is to concentrate on sealing up the cavity behind the access doors and allow a path for the moisture to exit. The cavity itself should be completely sealed off from the inside of the trailer and waterproofed, then it doesn't matter if it gets some water in there as long as there is a water exit path and minimal ventilation.
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Old 02-20-2012, 10:36 AM   #74
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I'd like to see a picture of these drain paths in the c channel and a detailed explanation of materials and whether u attempted a slope or ? Any one care to link?
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Old 02-20-2012, 10:51 AM   #75
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Perryg114 I hope you don't mind but I copyied your idea and picture and posted below.

Here is Perryg114's idea
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Old 02-20-2012, 10:55 AM   #76
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Has anyone tried treating the perimeter top (approx 6 - 10") of the subfloor with CPES penetrating epoxy as a rot prevention measure? It seems that this could be done fairly easily with the shell on and the floor covering removed.
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Old 02-20-2012, 10:55 AM   #77
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One of the reasons Airstreams leak through even a pinhole opening is the air pressure is lower inside than outside when the wind is blowing rain, or it is moving down the road in wet weather. Its like water being sucked through a straw.

Auto's don't leak in this manner because there are forced air vents and fans keeping relative interior air pressure higher than outside.

In addition to sealing, which can be quite futile because you'll never maintain the necessary perfection, what can be done to create a positive air pressure inside the trailer?

doug k
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Old 02-20-2012, 11:04 AM   #78
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Has anyone tried treating the perimeter top (approx 6 - 10") of the subfloor with CPES penetrating epoxy as a rot prevention measure? It seems that this could be done fairly easily with the shell on and the floor covering removed.
Yes I have done just as you said but I used thinned poly first before installing the new subfloor then used thinned epoxy later on. The thinned epoxy found its way under everything and really wicked in. I used 3 coats and the wood absorbed it like a sponge.
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Old 02-20-2012, 11:20 AM   #79
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In addition to sealing, which can be quite futile because you'll never maintain the necessary perfection, what can be done to create a positive air pressure inside the trailer?

doug k
Our trailer came with two Fantastic Fans only set to exhaust. I rewired one of them to make it an intake fan. Running it alone, or at a higher speed than the exhaust fan should create a little higher pressure. It is supposed to be ok according to FF to leave the vent door open while traveling, but we've never done that. I don't know if this would create enough air pressure to keep water from entering at the penetrations of the exterior skin.

Since there are three places where there are doors—fridge, water heater, and furnace—there's a source of outside air. I would not want to do anything with the last two, but the fridge compartment is pretty big and propane fumes may not be a problem. A vent with a fan that pushes air into the trailer might be possible if it can be kept away from the chimney. I'm not too excited about this idea because of the propane issue.

Another way to get air in is behind the rock guards ("segment protectors"). They protect from rain and splash pretty well and a vent with downward facing fins could let air into the trailer when traveling. A smaller vent in the rear could provide flow-through venting and some positive air pressure.

Gene
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Old 02-20-2012, 07:12 PM   #80
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No I don't mind at all. I have installed these drains already in the section between the door and the nose. I used 3/8" thinwall stainless steel tubing and flared the end of it. I used a wood countersink bit to flare and clean up the hole a bit. I coated the inside of the hole with parbond and then put Parbond around the outside of the pipe flare and stuck it into the floor. It sticks up a little bit but it is pretty close to flush. I also made a little gutter to the right of the door to funnel water below the skins. Anything that comes down the right side of the door frame ends up under the floor. I have sealed all screws with Vulkem so they are not a leak path. I am going to wet test by pouring water into the C-channel just to see where it goes. The biggest problem is some rivets are drilled a little too close to the bottom of the C-channel. This provides a leak path. I may Vulkem those low rivet holes and drill new ones higher on the channel. I am in the process of painting the floor under the battery boxes. They are not there right now. I am just using Latex right now. It is not as good as Epoxie but it is better than nothing. Last fall, I painted the whole subfloor with latex to seal off the stains and other nasties that were under the carpet. I would have used polyurathane but that stuff takes a long time to dry and for the smell to go away and I did not have time before we were going to use the trailer. The gray floor paint looks pretty good compared to the stained and nasty sub floor. I did use urathane on the section of floor I replaced but it could dry outside in the sun.

Perry

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Perryg114 I hope you don't mind but I copyied your idea and picture and posted below.

Here is Perryg114's idea
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Old 02-20-2012, 07:17 PM   #81
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You know we have always said to stay away from treated plywood but if you coated it first and used stainless steel fasteners would it matter? I looked at some 1/2" thick composite aluminum the other day. That would be sweet for a sub floor but you would have a lot of money tied up in it. I may still replace the section in front of the door with some of that stuff.

Perry
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Old 02-20-2012, 10:43 PM   #82
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Second Trip in new trailer

Well we just got back from a very wet cool trip to the southwest Washington state coast. There were three of us travelling and I really paid attention to inside humidity, condensation etc. Several weeks ago I bought a cheap digital humidity/Temp recorder at Home Depot and used that as my guide.
Inside temps were always between 68-70 and the humidity varied. I found that about 65 percent humidity I got window sweat and anything above 70 percent the walls began to sweat as well. Slightly opening both Fantastic Fans seems to keep the problem at bay. The weather was rainy and windy with outside temps in the 40-45 degree range. Positive inside air pressure may be a good solution. I have to think about this. Where would be a good air draw point? A minimal inside positive pressure differental would push water and moisture out. But think about this. Combustion from the cooktop would need outside air thereby creating a negative pressure and the combustion process itself creates moisture. So cooking is bad on two counts. I have to stop now. My head is starting to hurt.
All I know is I am to old to go back to the tent.
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Old 02-21-2012, 12:43 AM   #83
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Marine Grade Plywood.

The Airstream rep assured me that marine gradw plywood is used. Is this a recent development?
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Old 02-21-2012, 05:41 AM   #84
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I think Airstream has used OSB off and on. Someone on here said they have not used it since 2006 but other have said they have it in newer trailers. If I was buying a new one I would say SHOW ME. If customers start demanding plywood then maybe they will use plywood. My 81 has regular plywood not marine grade. As much as these things cost they should make the floor out of something that won't rot at all.

Perry
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