OK, brace yourself.  This post is going to get detailed, forensic, and possibly scary to the faint hearted.  We’re going to do surgery on the Airstream.

Let me start with a little about how a modern Airstream is put together.  The aluminum body rests on a steel frame (or chassis) and is fastened down around the perimeter to that chassis. This is “semi-monocoque” construction, which is normally pretty strong.  The body and the chassis work to support each other, and as long as they are well tied together everything goes well.

Now think of the Airstream’s body as a teeter-totter, with the axles being the fulcrum.  In normal towing the rear of the trailer is bouncing up and down on the road a little. With every bump, as the rear goes down, the front end is being pulled upward from the chassis. Since the chassis of the trailer is held down at the front by the tow vehicle, there’s a lot of strain on the chassis-body connection.

The longer the trailer, the more force is put on the front end. When the attachment between chassis and the front of the body loosens, that’s “front end separation.” Essentially the body is now banging on the chassis rather than being firmly tied to it. As separate units, the body and chassis are now both weaker and they start to beat each other up. The visual symptoms are things like broken rivets, stress cracks in the body, mangled aluminum and gaps around the lower edge, and other things.

Now before you panic, let me point out emphatically that all Airstreams (and for that matter, all RVs of any type) will normally flex some as they travel.  They can even flex a little when they are parked if you crank the stabilizer jacks too much.  So some movement is good–it’s a way to distribute stress across the body structure.  Airstreams are not designed to be rigid, just like a bridge or the wing of a jet.  If the wing of a jet couldn’t flex in turbulence, it would just break off.

But separate movement of the body and chassis means problems. Longer trailers are particularly likely to have this problem, and they often have a particular symptom when they are flexing too much at the front end: they develop a fatigue crack in the skin just above and forward of the entry door.  On 30-foot bunkhouses like ours, the cracks first seem to appear at the corners of the front compartment hatch–and other places, as we discovered.

The 2004-2006 bunkhouses had what I consider to be a design flaw: a large square-edged front compartment.  The hatch for this compartment created a weak spot in the body, and it also eliminated the possibility of designing a structural attachment in the front center of the body where stresses are high.  (The shape of the opening is also relevant. Airstream has since gone back to rounded corners on exterior hatches and my guess is that this is part of the reason. Square corners are weak points.)

For years Colin Hyde, of Colin Hyde Trailer Restorations, has been pointing at our trailer and two tiny cracks by our front hatch, saying “You have front end separation.”  This became a sort of game.  I would deny it, and then he’d say, “You just don’t know it yet.”  Although I could not admit this to Colin, I knew he was right and that someday we’d have to go in there and find out how bad it was.  This week became “someday.”

Here’s a photo at the beginning of the project.  The front wrap protectors have been removed along with the lower beltline trim and the hatch door.  With the door removed, it’s more clear how little structure existed to spread out stresses that are transferred from the main frame members (A-frame) through the body.  The circles show the approximate locations of cracks that appeared, and the red lines show theoretical lines of stress.

The front is a high stress area, so in older Airstreams there’s sometimes a steel plate installed that extends upward from the chassis to the front panel of the aluminum body, connected by two or three rows of rivets.  Obviously that wasn’t possible with this front hatch design.  We struggled with leaks through this compartment because the door fit differently depending on whether the trailer was hitched up or not, and also the door would jam shut when the weight bars were tightened.

These two photos show cracks we didn’t know about until the front wrap protectors were removed.  This is the mounting point for the wrap protectors. Both mounting points (on opposite sides of the trailer) had the same cracks because they were weak points. The cracks are the result of metal fatigue from repeated flexing.

These cracks were definitely letting rainwater in, which is of course the cause of floor rot, so it was yet another reminder of how serious the side effects of front end separation can be.  The cracked spots were fixed with a new aluminum plate and sealant, as shown in the third image.  But this was only treating a symptom.  The real problem was down where the body and chassis were joined.

The photo above shows a reinforcement that was installed in 2008 by a dealer’s service center. They basically slipped some cut aluminum behind the existing exterior skin around the hatch in the hope of adding strength to the corners of the door.  You can see how well that worked: completely cracked through. This patch basically replaced a weak spot with another weak spot—and again, it was only treating the symptom.  It didn’t do anything to strengthen the body-chassis connection.

To fix this right, we made the tough decision to eliminate the hatch entirely.  This would allow Colin’s guys to fabricate and install two additional ribs, and attach those ribs to the existing ribs plus the new steel frame plate and a single sheet of aluminum on the inside and outside.  In other words, we were replacing a big hole and 16 rivets with a battleship-like sandwich of aluminum, steel, and 160 new rivets.

I pitched in a little by removing the front bed and frame, lower curtain track, and all our personal stuff.  This left only the big Lifeline 8D AGM battery and the Xantrex Freedom HFS converter/charger/inverter that we installed in January, plus some wiring.

The different colored floor tiles at the front end were installed way back in March 2006 when the front compartment first began leaking. Since we now had everything out, this was a good chance to remove those tiles and finish the floor with walnut (vinyl) flooring to match the rest, so I ran out to Lowe’s and bought a box of planks and installed them.

Now, compare that photo above with the one below.  Notice the two new ribs coming all the way down to the floor where the compartment used to be, and the black steel plate with three rows of rivets firmly attaching it to the body and ribs.  That plate is welded to the steel frame below.  It takes the stress between the body and chassis and distributes it, rather than concentrating it on a few weak spots. That’s the key: you can’t eliminate the stress, so you spread it out instead.

The photo below was taken a little earlier in the process.  It shows how the steel frame plate was welded to the frame.  Notice that in our case we chose to remove the old battery box that hung between the frame members.  We weren’t using it, and it was in the way.

The next photo shows the exterior work nearly done.  Joe is bucking rivets with Chris (inside).  Buck riveting is a two-man job and it requires access to both sides, which is why Olympic-style rivets are often used for exterior repairs.  But buck rivets are far stronger.  Notice five rows of rivets horizontally (four on the steel frame plate and one at the aluminum panel joint above) and four vertical rows added to the ribs (plus two vertical rows that were pre-existing and two rows for the vertical aluminum panel joint).  Seriously strong.

The blurry photo at right shows the interior when done.  We didn’t put the white fuzzy Ozite fabric back, as we aren’t really in love with the stuff, and opted instead for a single sheet of aluminum.  The new flooring is in place also.

By this point I had been living in Colin’s parking lot for three nights, and we still had a lot of problems left to solve.  For one thing, we no longer had access to the storage space under the head of the bed.  Also, I wanted to muffle the fan on the Xantrex, since it’s right under Eleanor’s head and it runs when the converter is bulk charging the battery.

The solution was a pair of new hatches.  We divided the compartment with a 1/2″ plywood bulkhead.  The left hatch contains the battery and Xantrex; the right side is “dead storage”.

The battery is now secured with two big straps.  If we have a catastrophic accident, it won’t go flying and possibly short against something (which could cause a fire).  Also, since the battery no longer shares space with any stored items, we’ve eliminated the chance that some metallic object might accidentally contact the positive lead on the battery (which would cause a huge spark at the very least).

To soundproof the compartment, I lined it with acoustical foam used in recording studios.  On the underside of the bed platform (the hatch) I layered the foam over heavy automotive sound-deadening material.  We will have to pull the mattress out entirely to access this compartment, but since there are no routine maintenance items in there, it shouldn’t need to be opened very often.

You can see in an earlier photo that the right side hatch is much smaller.  We designed this so that we could simply slide the mattress toward the bedroom door to expose this hatch.  There’s a piano hinge at the very front edge. Lying on the bed, it’s easy to put things into the compartment below.  We will continue to use this as dead storage for things we need only rarely.  Funny thing is, it’s easier to access now than it was through the old front hatch, and so I was able to pack everything we were carrying before into a space half the size!

Obviously this was a big job.  But we got a ton of benefits from it:

• eliminated leaks at the front hatch and at cracks on the body
• eliminated possibility of future stress-related problems stemming from front end weakness
• quieted the inverter fan
• front storage is more usable and accessible
• battery is much better secured
• eliminated potential electrical risks at battery
• cosmetics: got rid of stained Ozite, finished flooring, eliminated cracks at exterior hatch
• much more stable bed platform

There’s even more that we did in this service visit at Colin Hyde Trailer Restorations, but I’ll wait for the next blog to talk about that.  Just a hint: it’s a really cool improvement that I don’t think anyone else has.