Mystery of frame rust revealed by "boatdoc"

[markdoane]

Originally Posted by TomR

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.

[TomR]

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

[TomR]

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

[Wabbiteer]

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!

[Jim & Susan]

Originally Posted by Wabbiteer

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.

Jim

[LI Pets]

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.

[boatdoc]

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"

[markdoane]

. . . . 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.

[wahoonc]

Originally Posted by Lipets

Here's another issue, we're all talking about draining and ventilating the belly pan. What about draining and ventilating the bannana skin areas?

I would think that the banana skins would pretty much drain themselves. As far as venting if you leave a few of the rivets out.... I suppose you could install the lower edge of the banana skin over the belly pan that would help it drain.

Aaron

[Pahaska]

Originally Posted by TomR

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

My late, but not lamented TrailManor had a laminated foam floor at least 3 inches thick. It was probably the best feature of that trailer. You can see this construction featured on the TrailManor web site.

The foam was sandwiched between aluminum sheets and an additional this (1/8", I think) sheet of plywood laminated on top to spread out point loads and prevent deformation of the aluminum.

The floor was quiet, always warm in winter and cool in summer. Where the battery resided, there was a square hole in all but the bottom aluminum layer and the battery box sat securely in that opening.

I would love to see that floor construction in my squeaky-floored Classic.

[Wabbiteer]

Originally Posted by Jim & Susan

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.

Jim

Just a ridge of silver silicone caulk about 3/8 inch tall and 5/8" wide formed to induce the water to shed easily from the lowest point...

[LI Pets]

Great idea, but it depends on the amount of rainfall, if it's heavy nothing will stop it!

Also when you're driving in rain the spray will go all over that area, so not sure if it's worth the effort?

[Wabbiteer]

This is a completly passive measure aimed at stalling damage from normal exposure to daily weather. We are so well protected in our homes that we forget everything gets soaked twice a day many days out of the year.

Water has a propensity for attraction to itself via surface tension, etc. so the active drip edge with water flowing down the outside can & will siphon water back and down that has found its way beyond the edge on the inside to some extent. Study a pinhole leak in a rain gutter sometime, gravity usually wins on the flat metal surface.

Not looking to stop deluge floods, just the twice daily dew and multi-day drizzles that refresh moisture content of underbelly seams and rivets - but even moderate amounts of sheeting water will be stopped by the 3/8" lip located where the horizontal plain starts using only gravity as energy.

And remember silicone beads water for a long long time while being exposed to dirt & dust so it's using the material to its best advantage. For the shape to form the caulk bead into I think a "V" style thats more like an inverted Mt. Fuji shape than a right angle would be best...

[Aerowood]

I plan on drilling 1/2 " holes in the bottom of the belly pans that will hold moisture (low spots) and then install small scopes (NACA Vents) with the openings facing aft. This should create a very small negitive pressure in the cavity helping with moisture removel while the trailer is in tow. Its just another small way to remove moisture. The best method is preventing large quanities of water to enter by proper sealing from the start, followed with proper ventilation.

[2airishuman]

hi boatdoc and others

good effort on the reduce the rust analysis...

i posted a pic of the bubble foil in the floor back in this thread...

http://www.airforums.com/forum...lts-13953.html

post 14 or so...click on the pic for a larger view...

the frames unfortunately start rusting even before trailer assembly...

i'll post some pics here later today of naked frames as currently used in j/c.

cheers
2air'

[boatdoc]

Hi Aerowood: You sure are not sleeping at the switch. Contact Tempo Marine Products. Get yourself few replacement bladders for Tem#370030 ADP. [automatic drain plug] Cut 3/4" holes just in the front of each crossmember. Using a generous amount of 3M-4200 glue them over the holes. Allow proper time for the 4200 to cure before taking it on the road.
Good luck, "Boatdoc"

[LI Pets]

No make that 5200 they need to be there 30 years

[Mr.InsideOut]

One solution might be to pack the space beneath the floor with these:

http://www.desiccantpackets.com/

[TomW]

Silica gel will only absorb so much water. After that, the packets must be either replaced or regenerated.

Tom

[boatdoc]

Hi Aerowood: Do not forget SS screens over the holes. Wasps do not like to travel. Thanks, " Boatdoc