Boatdoc prepared a very interesting and informative response on a new thread...I have included below with my comments to keep the flow of the discussion.
In my opinion, Boatdocs comments apply mostly to older and coaches under restoration...and likely do not represent the types of "fixes" a buyer of a new Airstream expects
to have to do (or have done) to their newly purchased, premium priced AS. Maybe I am wrong...and many expect to add new insulation in the belly pan, cut multiple drainage holes and install air dry fans in the brand new $100K AS? Or maybe have a new frame built that will not rust?
It seems to me that there is very little interest or understanding of the moisture/frame rust issues...as it applys to NEW ASs
. When some of your members with 2000 and newer year ASs post to discuss the frame rust on there near new AS...very little discussion of what the factory could/should do to prevent this
. My goal was to determine if a new AS is a good purchase...I seem to be nearly the only one with this question. If I learn anything helpful I will post...otherwise I will just go back to my corner...and wait for the snow to fall. Tom R in Two Harbors, MN
Boatdoc Reply...from other thread
Mystery of frame rust revealed.
First, I need to assure everyone that I am not connected to AS manufacture in any way. Therefore, no favoritism will play a role in this article. First of all I am tired of hearing all this belly aching about AS, without a proper understanding how complicated moisture control can be. For those who do not believe this statement, they should buy a better product and not AS. Since this is a subject that affects all, I may get the “most crap” award contained in one article, but for your benefit just bear with me. Today in the field of global economy all manufacturers are facing number of economical issues, not to mention [why should I care] attitude in regards to workmanship. Since further discussion on this subject is not the goal of this article, let’s address the causes to which some remedies may not be economically possible to institute by the manufacturer.
#1 is Condensation [most difficult to control] and not easily avoidable unless complicated measures are instituted.
#2 is Road salt.
#3 is exposure to adverse effects of towing on wet roads.
]#4 is placement of the trailer [your parking spot.
Since the condensation is the biggest and most difficult subject, I like to save it for last.
Unavoidable road salt is avoidable if you do not tow your AS in the snow. Let’s look at this realistically. YES, you should rise off the salt Tom, after towing on salted road. This is not the Factory’s responsibility, it is yours. You take a shower daily or when you get dirty? You cannot compare automobile to AS. AS does not expel lot of engine heat which can dry up quickly open and exposed to heat metal, thus minimizing the salt effect on metals while it is in a dry state. Just wash and blow dry the AS and it will be fine too.
Exposure to adverse effects while towing, is to some degree avoidable if you maintain the integrity of the belly skins. While towing your AS at 65 miles per hour, fighting a strong head wind, the water will be forced in to the low pressure area inside the belly skin through most minute gaps. Unless your belly skin is maintained and totally sealed [which is just about impossible] water will enter it. Solution for that is to provide a clam shell effect drains, in back of each compartment within the frame. The exit end must face rear or you will create a ram effect for water to enter.
Where, your AS spends its life is equally important. We all park our cars in a driveway don’t we? Does your AS sit in the grass or unpaved lot where the condensation process occurs twice a day? Have you ever noticed a dew on the grass on days when the temperature changes drastically once at the evening and then on the morning? Where do you suppose that moisture goes on the morning? Pavement acts as barrier, preventing the moisture from being raised up at night by the warm air from warmer than air and moist ground.
Instead of parking your AS in the weeds, park it on large tarp if you cannot park it in the driveway. Tarp will provide a moisture barrier.
Now let’s get into the meat and potatoes of CONDENSATION mystery.
Whenever you enclose airspace, condensation becomes very hard to eliminate or to control. Condensation occurs when two opposing temperatures collide against, on a temperature transferring barrier such as the belly pan. This process was very helpful in the prohibition time to those who had homemade stills, it is however detrimental to AS. To be able to remedy this condition one must understand what takes place between the belly pan and the floor. If there were no temperature changes such as in a controlled environment, rust would not take place. Since the reason for having RV is to be in elements we must try to some extend control causes of condensation. While manufacturer can take additional steps to limit it, this can be very expensive to implement, and that can place them out of competitive pricing in today’s market.
There are some relatively inexpensive measures which can be implemented at rather low cost to the consumer wanting the best. However this is where custom options come in.
In order to minimize effects of condensation [which cannot be eliminated] in the belly pan, a temperature barrier of good “R” value must be in place. Ideally this barrier must provide a solid moisture barrier on both sides of it. On one side of this barrier, we must provide a dead air space for it to have a full effect. This means that we must prevent the cold and the hot air from coming in contact with each other. Let’s take a look at fiberglass insulation used in a house. Inside and outside walls form a sort of a temp barrier along with dead air space between them. One side of the insulation has treated paper which is your moisture barrier. The double thick edges of paper are stacked on top of the studs pinched by the sheetrock thus creating a good seal. In AS frame a good seal is almost impossible to create or maintain. Once the moisture barrier is compromised, plywood floor will get wet and eventually rot. Let us look at places where rot starts. It is always in the edges where the barrier seal is compromised and hard to maintain. Sealing the moisture barrier to the frame is a very difficult task, with the weak paper barrier used in fiberglass insulation. There is no easy way to seal the joints, and after time it may get torn up for number of reasons. When it does, it stops to function as what it was meant to do. While the frame coating can be improved at the factory, stopping the condensation is another story.
To minimize its effects we must provide a temp barrier, ventilation and drainage of the belly pan. This must include moisture barrier insulation such as Prodex, which provides an excellent double moisture barrier. This should be attached to the frame and cross members with dead airspace between it and the plywood floor. This dead air space can be obtained by cutting a closed cell urethane foam ¾” thick to 2” strips glued to the floor at about 18” apart to which you can glue the Prodex. The second area of dead air space will be below Prodex and the belly skin. This area however will require drainage and nominal ventilation. Each section between cross members should have a drain. The cross members at the bottom edge are bent up providing perfect spot for pooling of water. Factory should provide a small horizontal drainage at the belly pan level to eliminate this condition. Drainage from the belly pan can be achieved by making a ¼ “ cuts in the center of belly pan facing across, just in the front of each cross member which may stop the water from draining into next section. By placing a small flat screwdriver pull the front side of the cut, thus creating a small clamshell drain. Be sure that the opening is less than 1/8” in height to keep yellow jackets from entering. My AS will also include a small screen protected computer fan in the belly skin in the rear of underbelly. They operate on 12 or 24 Volt DC and draw only about 0.17 Amp which is no threat to any battery. In the front in the underbelly I will cut a 2”x 8”opening for intake air, sealed with SS screen.
To keep water from entering, a small clam shell with the opening facing rear will prevent water entry when towing. This will create air exchange, preventing the dead air from condensing and speed up the drying process in the underbelly below the insulation. Instead of complaining, there are things you can do to considerably slow down the decay process. Nothing made by us lasts forever. We are the throw away society and are used to it. While all the complaints are valid they do not resolve any issues unless someone does something about it. I did not wanted any rust in my frame I have made new one from Stainless Steel without complaining, because it would accomplish nothing. This article does not represent views other than my personal research in the boating industry for past forty years, where cold water and hot sun create ideal climate for condensation. We to had to come up with a solution to the problem, you can to.
Tom R response
Boatdoc...Thanks for the interesting discussion. I wish I too had the ability and desire to create my own new frame and restore 30+ year old ASs
...but I concluded awhile ago that I do not have the time, skill or desire to go to such lengths...thus my change in focus to the new or "near" new ASs.
I don't think Airstream wants to sell their trailers with a limitation of not using in the snowbelt...or near either coasts...to prevent frame rust. I doubt many owners have facilities to wash off the belly and dry off if/when they use their AS during or after a snow...or after every trip to the beach...and I assume some will park on grass. Yes, moisture, salt and the elements are going to impact your trailer and should be considered by the manufacturer when designing their product..
Your insulation/drainage and airflow ideas may indeed be a great start...but why doesn't AS take these steps to protect their $100K trailers? I am sure some who read your ideas will be appalled that they, as new purchasers of an expensive AS, are expected to be able to make the modifications you have suggested. One thing as you restore a 33 year old AS...another if you spend $100K to buy a NEW one.
Auto makers have worked hard to make there products much more rust resistant than say 20-30 years ago and have been quite successful. I am sure they are still trying to do better...never had an auto company tell me to spray off the salt each day and dry off the underside...gets pretty cold up here when the salt is on the road!
Boatdoc...I am envious of the skills you have to perform such "deep" level restoration and fixes...but I don't think most/many new AS buyers feel they should NEED to make such modifications on such an expensive new product.
I hope others have some further insite regarding new(er) AS moisture/rust prevention factory fixes. Thanks...Tom R in cold and "salty" Two Harbors, MN.
P.S. Please don't resort to the "just buy SOB if you don't like it"...meant to be a positive discussion.
BTW...maybe the lack of a belly pan on the SOBs is actually an advantage?...the frame and underneath can "air dry"?...TomR