Re: [VAL] Sealing seams internally

[Charlie/Betty Burke <cbburke@xxxxxxxxxxxxx>]

Tom,

Besides the torsional loading caused by move down the road, Airstream do stretch
and shrink. You only have to see a winter built coach in a hot summer sun to see
what it does. There can be  quite a wave or ripple effect on the side sheets.

If I did it was not my intention to suggest that Airstream puts Vulkem all over
the inside of the outer skin. In truth they applied it with a putty knife at all
seams and penetrations. Areas like doors and window typically have it lathered
on pretty thick. And again, once Vulkem sets up it is very pliable and does not
deteriorate when applied on the inside. I have seen lots of wrecked ones over
the years. And Vulkem only breaks down when the metal tears. I've not taken
apart as many coaches as Andy but I've seen enough to be comfortable in saying
what I do.

Airstream has been making these things for about 70 years now. As you know
probably better than I do a lot of factors go into the final product. Durability
has always been high the list. A poorly built trailer would not have survived a
Trans Africa or around the World caravan the way these have.

The most common site of a leak is at a seam or joint that has been field
repaired. That is part of the reason why Andy's recommendation to dab some
Vulkem on each rivet before setting is so important. To many folks out there
skip that step. One of the "things to do" when looking at a potential purchase
is to look for replaced panels. If you find one, very carefully inspect the
inside at that location for leaks or a very recently cleaned surface.

The only "redo" of exterior seams is necessary because Vulkem will breakdown
under long term exposure to the sun. But then don't we all. No one that I have
know has or would recommend keeping Vulkem "on hand" to chase leaks. There are
thousands out there that have never leaked.

Another factor that the aircraft industry has to take into consideration is
pressure differentials. Any aircraft that flies above 10,000 feet is usually
pressurized. This cyclic pressure up and pressure down is major factor in
aircraft design I would think. Not a factor at all in Airstreams design.

Charlie