Section 6 - Vertical Stabilizer (priming)

I'm now at the stage of cleaning/prepping and PRIMING the metal - a topic that has been the subject of many highly opinionated forum posts.  It seems there are as many ways to prep and prime as there are people who have completed RVs.  From reading WAY too many of those posts, I'll summarize what I feel to be the best balance of quality, durability, weight, cost, ease and efficiency.

After all metalwork has been accomplished, including dimpling and countersinking (but, of course, BEFORE riveting anything), I cleaned the surface of all pieces to be primed with 100% acetone, using blue nitrile gloves to prevent oils from my skin to contact the surface and prevent the primer from sticking.  I decided to prime the following: all 4 ribs, both spars, the two doublers, and the internal rivet lines in the skin (not the outside, and NOT the entire internal surface skin - it already has a nice protection from the pure-aluminum alclad coating). I am NOT priming the 6 steel hinge brackets, since they came from Van's powdercoated (but, after match- and final-drilling, I did add a little 3-in-1 protective oil to any exposed steel surface, to prevent rust).

After acetone cleaning the surface, I used a Scotchbrite maroon pad to scuff any surface to be primed - for the ribs, spars, and doublers, I scuffed every surface. For the skins, I scuffed only the internal rivet lines. I then cleaned the surfaces well with Kleenstrip Prep-ALL, let dry, and primed with SEM #39683 self-etching gray primer (aerosol can) - it is expensive (about $21 per 15.5oz. can), but it is easy to apply (no HVLP gun needed!), dries quickly, and is tough after it has cured.  I bought a little spray can trigger handle to ease application of the primer, and primed until I couldn't see metal (~3 light passes or so), waited 5 minutes, flipped the pieces and primed the other side (the skin was primed standing vertically). I plan on letting the primer cure at least 2 days before riveting.  Here are most of the pieces, drying/curing after priming the second side:

And here is the skin:

Note that I am not worried about how the lines look, since it won't be visible once riveted.  It was just important to ensure all "mating" surfaces, which touch parts of the substructure (e.g. ribs and spars), were covered with primer. Make sure to use a P100 respirator (I used a 3M half-mask) and safety glasses ... SEM is an industrial product that has a number of carcinogenic VOCs.  Even with a mask, if I didn't breathe in correctly (e.g. the seal on my face "broke" a little, b/c the mask was too loose at first), I could smell the vapors.  Even after pulling all the pieces into the workshop, the smell lingers.  I just left the workshop for a few hours to ensure all the vapors have dissipated.