I found this facinating and scary posting while stumbling thru Tom's archive
pages looking for something else.
Anyway I was surprised and wonder when Airstream changed this practice. (I
trust they did ??) i.e. what model years do we need to worry about not
trusting the rivet lines up top to stand on..?
~~~~~~~~~~~~~QUOTE
"Subject: [airstream] Working the roof
Date: Thu, 28 Jan 99
From: Roy Lashway
Forgot to mention on my comments of ladder useage wen getting to top of
trailer. I recently removed some inside paneling on the '56 I"m rebuilding
and noted a interior structure system I was somewhat surprised at. When you
look at rivet lines on outside of trailer you tend to think the skin is
riveted to a series of structural ribs runing vertically and horizontally.
Not exactly the case. I learned that the major structural ribs are mostly
vertical and have rivets spaced about an inch or less apart. You can note
other rivet lines with rivets about 2 inches apart. These wide rivet patterns
go into both vertical and horizontal bracing pieces that do not connect to an
solid structual member. The serve as bridging across an expanse of aluminum
skin just to give it some rigidety and not permit the skin to bend or flex to
much. I found the inside skin is not riveted to these braces and have seen
the inside skin with bracing of its own, at least around the vent area. You
may have wondered, as I have in the past, why the outside side panels seem
overly flexible when you push against them when they appear
to riveted to a brace. There is only bridging behind the panel.
The point of all this is to remind one to be careful when placing a ladder
against or standing on a wide rivet line as there is not much strength there.
Roy "
END QUOTE ~~~~~~~~~~~~