Sealing an Airstream

They all leak.  If it doesn't leak now, it will leak in the future.  Airstream restoration and ownership involves lots of sealing and re-sealing to prevent leaks.

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Rivets

I highly recommend checking every single rivet on your Airstream, one by one, and sealing or replacing the bad ones.  This is a job you can finish in a day, and you will almost certainly find an alarming number of leaks you didn't know about.

To check a rivet, stick a suction cup over the rivet.  If the suction cup sticks, the rivet is good.  If it doesn't, the rivet needs to be resealed.  When you find a bad rivet, the suction cup will often pull a bunch of water out of the hole.  Fun!  Disconcerting!

If you have the skins off, you can often rebuck bad rivets to seal them back up, but the approach I prefer is to remove the rivet and replace it with a wet bucked rivet.  It's a good idea to remove every Olympic rivet you find and replace it with a wet bucked rivet, since Olympics tend to leak over time.  The buck rivet kit from Vintage Trailer Supply is a good investment if you're doing any major work on your Airstream.  To wet buck a rivet, put a dab of Sikaflex 221 on the hole before you insert the rivet, then buck as normal.  Once it's bucked, use a clean rag with a bit of carburetor cleaner to remove the excess sealant. 

If you don't have access to the back side of the shell, you can use Captain Tolley's Creeping Crack Cure to seal up bad bucked rivets.  Add the sealant and let it dry, then test it with the suction cup again.  Repeat until the suction cup sticks.  For bad Olympics, it's better to drill out and reinstall with a new Olympic than try to reseal.  Use the Olympic Rivet without the neoprene washer, and install it wet.

Window and Door Gaskets

After decades of use, the window and door gaskets on vintage Airstreams need to be replaced.  Check Vintage Trailer Supply for correct window and door gaskets for your model.   To remove the old gasket from aluminum door and window frames, I suggest using a sharp razor blade to remove the bulk of the gasket material.  Then soak what's left in goo-gone, scrub with a soft-bristled stainless brush, and repeat until clean.  The brush will scratch the aluminum to a "brushed" look, but since the area is behind a gasket anyway, you'll never see it.  Be sure to clean the goo-gone off with carburetor cleaner before trying to apply the new gasket material.  Don't use this method anywhere other than behind gaskets, since it will scratch the aluminum.

If your Airstream has cast aluminum plumbing vents, the vent pipe gaskets need to be replaced as well, and I'd suggest adding a little sikaflex under the gasket as added insurance.

Window, Door, and Vent Frames

The sealant around the window and door frames should also be removed and replaced periodically.  Old Vulkem sealant is easiest to remove without damaging the aluminum using carb cleaner, a bunch of rags, and this 3m radial bristle disc.  Run the disc over the sealant to break the surface, soak it with carburetor cleaner, then run the disc over the sealant again.  Repeat until you've removed most of the old sealant, wiping up with your rag as needed.

Use a caulking syringe to inject a nice clean bead of Sikaflex 221 into the channel you just created.  I prefer Sikaflex over Vulkem 116 or its successor, Trempro635, because Sikaflex isn't sticky when it's cured. Sikaflex stays where you put it, so it’s good for vertical surfaces and areas where you want the sealant to hold its shape. Dicor Self-Leveling sealant works well on the roof, since its thin consistency naturally flattens out. Dicor is available in Gray and White, depending on if you have bare aluminum or white roof.

I am not a fan of the aluminum tinted gutterseal, since I didn't find that it "wicked" into seams like it's supposed to, and it's impossible to tool once applied. 

Never, ever use silicone caulk on an RV.  It’s impossible to maintain. Nothing sticks to cured silicone except dirt, including more silicone. So cured silicone needs to be thoroughly removed before reapplying (nearly impossible), or you have to apply ever-wider beads to reach fresh substrate.  If the previous owner used silicone on the shell, you'll want to remove it with several applications of silicone caulk remover.

Lots of folks recommend using painter's tape to mask off clean lines around your caulk lines.  I've never had much success with this method.  Instead, I wipe any excess off with a finger, then repeatedly wipe with a carb cleaner soaked rag until all that's left is a perfect line.  The caulking syringe helps a lot with ensuring you don't add way too much sealant.

If you're adding a new vent or other item to the Airstream shell, it's a good idea to use butyl tape between the item and the shell, then seal with Sikaflex around the perimeter. Urethane sealant like Sikaflex is a pretty strong glue, so if you use it in the wrong area, it can make it very difficult or impossible to remove whatever you glued down in the future. Butyl tape is removable, so it’s used under vent and window flanges, behind clearance lights, etc.