Frame Separation: Airstream Service Bulletins, 1971

[PA BAMBI II]

“Frame separation at the rear of the trailer is indicated by the chassis of the trailer dropping away from the shell or body” (Airstream Service Bulletins, Volume 2, Bulletin #146).



The topic of rear end separation in Airstreams of late 1960’s-early 1970’s vintage often comes up in conversations among Airstream owners, both sitting around campfires and chatting on virtual forum discussions. A quick Google search recently turned up over 73,000 pages of information on this most dreaded topic. Not surprisingly, the first post (at least at the time of this writing) was connected to the AirForums.

Many blame rear end separation on a poor structural design among this generation of silver bullets. Apparently, the way the outer skins do not properly overlap the banana wrap/belly pan material creates a literal funnel into which rain water runs, eventually rotting the plywood subfloor, then rusting the rear crossmember and attaching hardware, thusly allowing the rear main frame rails and bumper to noticeably sag from the separation of these strategic structural parts.

Others blame the malady not only on the above, but also on the addition of extra weight on the rear bumper…say in the form of a loaded spare tire or bicycle rack…which only makes the problem worse. I have a personal connection to this as my Dad had installed a custom-made bike rack on the rear of the family’s 1972 31’ Sovereign. He used it for a few seasons, then abandoned it as it was cumbersome and he felt it was easier to just put the bikes inside the trailer. That trailer definitely suffered from rear end separation, but he used it for another 25 years and enjoyed it anyway. The Airstream Company officially addressed the issue in Service Bulletin #166, drafted December 5, 1972, by restating an existing policy: “Structural damage or towing problems resulting from additional weight being placed on the rear of an Airstream will not be Airstream’s responsibility. The results of additional weight placed on the bumper of an Airstream is not just actual weight; but the leverage it has from the axle is referred to as ‘foot pounds.’”

One thing I didn’t mention is that it is often also believed that this damage occurs over years or even decades of time. The water leaks into the structure, weakens critical parts, and any added weight hastens the process.

I recently acquired a 2-volume set of vintage Airstream Service Bulletins which have documentation proving that not only was Airstream aware of the design deficiency and the probable weakening of the structure that would occur, but that time wasn’t necessarily a factor. The second volume, dated April 16, 1971, includes a very detailedbulletin (#146), on“Shell to Chassis Separation,” its causes, and technical details on exactly how to repair the problem in factory certified service stations across the country.

The process to repair the malady, seemingly common on Airstream trailers even then, is fairly straightforward. The service bulletin lists different processes for repair of frame separation on 1969-1972 trailers and for 1968-prior trailers. Regardless of the generation of Airstream discussed, repair involved opening up the damaged area by removing rub rails and accessing the area between the inner and outer skins and directly above the main frame rails (on 1969-1972 models this could be achieved by cutting 3” square holes in the outer skin directly above the main frame rails; on 1968-prior models, this involved removing rivets from the entire panel under the rear window and the bottom rear wraps…literally getting into the belly of the beast!). After jacking the frame up into proper position, holes needed to be drilled through the main frame rails to accept heavy duty 3/8” bolts, washers, and nuts, and sometimes ¼” thick steel plates to strengthen the damaged structure, then everything needed to be snugged up before closing the campers up again with standard and Olympic rivets and a generous dose of Vulkem.

All-in-all, even to a shade tree Airstream repair hobbyist, the processes described in Bulletin #146 are straightforward and understandable. Luckily for all who own an Airstream of this vintage, even frame separation can be repaired with enough time and patience. Fortunately, though the problem is documented to still exist in later model years, it was never as prevalent as it was for the model years addressed in Airstream Service Bulletins Volume 2.

[Jcondon]

The biggest offenders for this issue were the rear bath models. In order to put the drain valve in the rear trunk area the last crossmember that sat directly under the rear channel was a flimsy 1" x 2" by 1/8" formed channel that was laid sideways. The rear tiedown angle was connected to this with a few bolts. This channel could not support the load of the frame, subfloor, tank, and furnishings and it failed quickly. This opened up a gap between the lower trim and the flat aluminum sheet that directed any water that landed on the trunk lid straight into the trailer. This rots the floor, channel, and tie down angle. On top of all this the tie down angle was steel against aluminum with plenty of water flowing in. The repair placed two bolts through the channel into the frame like the aluminum channel had enough strength. This only destroyed the channel. We open the back skin and replace the channel with a full size crossmember then an aluminum tiedown riveted to the hatch or skin and gussets installed on both sides from the frame to the vertical supports for the window. This spreads the load out to a wider area. Then we install a counter flashing for the rear so no water can run forward. From the outside it looks original.