Originally Posted by Excellin
Hello all, Looking for the newest year airstream that will take a mirror shine.
Welcome to the forums!
The short answer to your question is 1982.
The long answer is a lot longer. I'll tell you what I can remember off the top of my head.
Airstreams have always been made of high-strength aircraft aluminum alloys, typically 2024-T3 (and I think) 6061-T6. If you remove the interior skins from the shell you will see the alloy designation roll-stamped on the inner surface of the outer shell.
Prior to 1982--and this is the important part--they were made of Alclad sheet, which consists of a core of the high-strength alloy faced with a cladding of .005" of pure aluminum. The reason for Alclad is that the alloys do not have the corrosion resistance that pure aluminum does. Early in the days of aluminum aircraft, the aluminum industry figured out that the corrosion problem could be largely eliminated with the thin coating of pure aluminum.
So far as I know the same alloy is used for the single-curved skins and the stretch-formed end shells. The reason that they weather and polish differently is that the stresses from the stretch forming affect the hardness of the aluminum.
The guy who can tell you all about this, Dale "PeeWee" Schwamborn, is an active member of the forums. (User name PeeWee) Among his other jobs at Airstream over the years was purchasing the aluminum. I don't remember whether his dissertation on the subject is on the internet or whether I heard it one of the times I heard him speak.
The gist of it is that when he was buying the aluminum that went into Airstreams, they bought the material for the single-curved skins from Alcoa but the stuff for the end shells from Kaiser. The Kaiser aluminum stretch formed better. They didn't know why, just that it did. (There's a lot of art to metal forming.)
The really neat secret that PeeWee revealed is that they bought a special grade of aluminum from Alcoa. The quality of the finish depended on how new the rollers were in the rolling mill. Right after Alcoa would replace the rollers they would make special "Boeing grade" aluminum sheet for Boeing. But they did make a little sheet aluminum for one other customer even before they made Boeing's--and that customer was Airstream!