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Old 10-16-2006, 05:45 AM   #15
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Hi Lipets: While you are correct in your statement you have missed my point. The reason for that is that the basement usually stays much cooler or much warmer than outside air. Venting the basement, brings in air of different temperature to collide with opposing temperatures inside to condensate. As you can see that statement reinforces my theory. In the basement you can control the temp's, in the bellypan you cannot. Air will warm up or cool down and will stay trapped. For as long as it takes for the temperature inside the bellypan to equalize with the temperature outside of the bellypan, condensation will occur. Thanks for your input Lipets, "Boatdoc"
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Old 10-16-2006, 06:02 AM   #16
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Hi Aaron: You are right, lapped joint are not sealed. However, the cross members on older units have a bend up wards which creates a pool with no provision to drain it. Collected water is there to evaporate again when temp's change. And yes, the insulation sponges that that water as it evaporates. The second issue is the small amounts of water trapped between the bellypan skins and the frame which is hard to dry. This is where the rust starts. The lapped joints can be plugged with road dust and may contribute to collection of water the sooner you drain it the better you off. Thanks for your input Aaron. "Boatdoc"
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Old 10-16-2006, 06:26 AM   #17
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Hi Jim & Susan; Your thinking is on the right track. It is important to seal the banana wrap behind the molding. I have found out that a silicone sealers often separate with time allowing the rainwater to enter the bellypan. For that I recommend small but uniform bead of 3M #4200. As for the small drains pick the lowest spot in the belly skin near the back, which most likely be in the center of the frame. Thanks. "Boatdoc"
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Old 10-16-2006, 08:09 AM   #18
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Boatdoc, only a sailor would recommend 3M #4200
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Old 10-16-2006, 08:35 AM   #19
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Originally Posted by boatdoc
Hi TomR; While your suggestion is excellent, there are some cases where the fiberglass insulation may lay on top of the belly pan. The insulation along with the paper vapor barrier will considerably slow down the air movement throughout the underbelly. This condition would make the idea useless. Wet fiberglass insulation is very difficult to dry for that reason. Try to understand that reversed clam shell is not going to force the air in. Something like a small exhaust fan mounted in the rear must pull the air from the front of the air intake. Some water ingestion in front intake pending location may be unavoidable during towing, but it can be drained easily. Than again the drying process with the help of the fan while trailer is parked would be shortened considerably. So as you can see that idea will work for some and others will see no benefit if the air is not free to move in the underbelly. As for the idea of the clam shell production we are speaking only about cents for the material. There is a solution to every problem but every problem is not the same, and must be considered individually in order to resolve it. The one more thing I need you to understand that the enclosed bellypan traps the hot or cold air [pending time of the day] and encapsulates it, then when temperatures change drastically it acts as a condensing chamber by allowing the varying temperatures to collide at the skin. Unless provision is made to balance the temperature inside the bellypan with the falling or rising temperature outside as quickly as possible while providing a good vapor barrier to the floor, nothing will change. Thanks for your reply TomR. "Boatdoc"
Boatdoc...I think we need to divide our discussion into "new or newer" vs "older"...I am not sure where the break point between the two is. The reason I say that is that it "appears" that the factory is no longer using the "bat" type insulation that is so likely to absorb water and drop to the bottom of the belly plan...as you discuss. See quote below:

"found a recent Jackson Center visit report that may be good news for you, confirming that the fiberglass under-floor insulation is now replaced with bubble foil insulation."

1) Question for Boatdoc and all??? If you installed Boatdocs "reverse clamshell" drains (say three or four?) and a very small exhaust fan (with appropriate protection from incoming moisture and bugs, etc) in a new AS with a clean belly pan...might that allow any water that gets in to drain...AND to allow the exhaust fan to pull air through the belly pan to cpmpletely dry it out...maybe after you return from a trip...or while camped????? Seems like this could? work with some type of pre-designed and fabricated parts and "fix" kit. Many products have aftermarket "fixes" that work and often are adopted by the manufacturer at some point. Maybe Andy will join the discussion.

2) My other thread on this topic drew the following response:

"You could import an Airstream from Europe. There they have galvanised frames . And aluminum sheathed foam floors . It appears they are having the entire chassis built by BPW in Germany."

Does anyone know that this is true??? If so...there is NO! reason Airstrem should not do this here. Maybe someone can confirm the above claim. BTW...I am NOT planning on importing one from, Europe.

Seems like Boatdoc has got something good going here...but I think we need to label our comments as "new or newer" vs "vintage" or pre-bubble insulation...assuming the factory is now using a non (or less) water absorbing under floor insulation.

Thanks All...Tom R in Two Harbors, Minnesota
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Old 10-16-2006, 08:51 AM   #20
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Here's another issue, we're all talking about draining and ventilating the belly pan. What about draining and ventilating the bannana skin areas?
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Old 10-16-2006, 09:32 AM   #21
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2) My other thread on this topic drew the following response:

"You could import an Airstream from Europe. There they have galvanised frames . And aluminum sheathed foam floors . It appears they are having the entire chassis built by BPW in Germany."

Does anyone know that this is true??? If so...there is NO! reason Airstrem should not do this here. Maybe someone can confirm the above claim. BTW...I am NOT planning on importing one from, Europe.
Don't know if it is true or not. I'm just quoting what is on the Airstream website, specifications for the 532 model. Didn't expect you to buy one.

As with many components, Airstream outsourced the chassis, coupling, brakes and wheels to a well known European manufacturer. That's why they don't do it here.

I guess my reason for mentioning it was to show the Airstream is at least aware of the problem, and chose to use galvanizing in a new model.
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Old 10-16-2006, 10:08 AM   #22
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Hi Mark...hope you didn't read my post wrong...I was just trying to add your info to the discussion since I think it is critical that AS has recognized at some level that galvanizing is appropriate. To me that is an important part of AS maintaining their "premium" position in the market.

Do you have an AS? What year/model/length?? Do you participate in the WBCCI (?) locally?

Thanks...Tom R in Eden Prairie...soon back to Two Harbors
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Old 10-16-2006, 10:25 AM   #23
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Hi All...Here is what Mark found on the AS Euro web site:

CHASSIS & SUB STRUCTURE
48mm thick sandwich floor -styrofoam insulation Std Std
BPW galvanised steel chassis, with outriggers Std Std

I truly don't understand why the current US frames are not galvanized????

Also, what do you think about "sandwich" styrofoam floors vs plywood???

Seems like we are getting some where with this issue... Tom R
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Old 10-16-2006, 11:11 AM   #24
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I am planning on a drip edge at the bottom of the bananna wraps' curve to keep live water drips from reaching the belly skins - planning probably just a fat bead of silver silicone caulk, but I know there needs to be some type of drip edge to keep water from reaching the flat seams and rivets...

Something "overlooked" is the acid rain & dew everyone gets up here in the snow belt states. I've had the knees burnt out of a couple of pair of Levi's from kneeling on the driveway after a spring drizzle & throwing them into the hamper to be washed later! Carbolic acids from natural gas or sulphuric acids from power plants never sleep, even if they are condensed out as our morning frost! The power plants and millions of furnace flues upwind of me here in the Twin Cities turn every morning dew into etching fluid complete w/ a tackifyer film of home heating oil residues that over weeks buildi up as channel edges that guide beading condensation down the same paths morning and evening.

I am thinking even with belly band seams well caulked the daily dew cycles will run down the bananna wrap and then wick into every horizontal crevice - I had many rivets corroded into white smears or the sheet perforated around the rivet without damage to the spar above it, my Airstream had lived the last 10 years in New England...

I am in the middle of a 1973 belly rehab. The number one corrosion problem I've found is long term seepage & resulting galvanic corrosion, ie: trunk hinge plate at the shell seam or gapped belly band. The fine surface rusts from condensation are worrisome but having it feed mildew and keeping plywood beasties from ever going truly dormant is a valid concern. I have a 175' roll of the Prodex foil-foam-foil insulation I will be stitching into a vapor barrier - found 1/2 price 3M automotive spray adhesive for foam I will be using to glove spars etc with using roughly the same plan as posted above....

Thanks for adding to the myraid swarm of uncertainty I'm feeling about closing this Airstream up!
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Old 10-16-2006, 11:32 AM   #25
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I am planning on a drip edge at the bottom of the bananna wraps' curve to keep live water drips from reaching the belly skins - planning probably just a fat bead of silver silicone caulk, but I know there needs to be some type of drip edge to keep water from reaching the flat seams and rivets...
Wabbiteer, I'd love to see a drawing of how you will do this. I'm about 3/4 of the way complete replacing my belly pan. A drip edge never occured to me.

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Old 10-16-2006, 12:21 PM   #26
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What I plan on doing is putting the main belly pan on first, then the bannana wrap on next that way water coming into the bannana skin from the moulding or condensation should not go in the belly area (I think)

The other thing I noticed is the edges do have some corossion, I'm painting 2-3" inside and outside of all the edges with POR.
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Old 10-16-2006, 12:33 PM   #27
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Hi again TomR; Truthfully I was not aware that AS now installs bubble foam. This is a sign of things going in the proper direction. Galvanized frames would solve majority of problems, however not all. The closed space in the belly pan will still sweat and it needs to be vented in used or new. There is no need to place more intake clam shells than the exhaust fan can handle moving the air out. This issue applies to new and old AS. As for the outrigger area, unless the factory changes outrigger design to an open instead of solid plate, there are too many compartments to vent. If the banana wrap is sealed well at top, condensation will not be so bad because it is a smaller compartment. Mass of locked air has to do with the amount of condensation produced. The outrigger on my Stainless frame consist of 1x2" rectangular tubing on the top and 1/2"x 2" coming from bottom of frame curved on outside to the top piece. This allows for having one compartment at full length of frame. Thanks, "Boatdoc"
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Old 10-16-2006, 02:08 PM   #28
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. . . . Do you have an AS? What year/model/length?? Do you participate in the WBCCI (?) locally?
Tom,

I'm at the tail end of a three year shell-off, frame out, new axle, new floor, all new appliances, grey tank addition, new skin resoration of my '59 Tradewind. Hope to be on the road to Grand Marais by springtime.

I love your tugboat, the Edna G.

Don't belong to the Wallyites, but my trailer still has the original number, 3430.
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