Today, I spent the day prepping the vertical stabilizer spars, ribs, and rudder stiffeners.  I am not going to go into great detail here on my priming technique.

Long story short, clean and etch parts with Alumiprep, dip in Alodine, and prime...

The first couple of times I pressed the trigger on the paint gun, primer just trickled out (of course that was all over the parts to be primed).  I finally got the gun to work fairly well (at least it would atomize the primer and spit it out).  I set the pressure at the gun (or more accurately at the regulator on the bench) to around 35 Ibs.  I had to play with the two adjustment knobs on the gun for the fluid needle and the spray pattern.  The only way to set this us is to just spray on some scrap cardboard or wood until you get a nice pattern.

My first couple of parts look really poor...  They are well covered (and that includes primer runs).  Good thing these will be enclosed inside the stabilizer and rudder.  When I got done, I had some extra primer left and practiced with the paint gun (now in hindsight, it would only seem logical that I would have practiced 1st and then primed parts).  I primed two ribs from the horizontal stabilizer that I screwed up.  They turned out the nicest of all the parts I primed today.  It figures that they were the last parts I did.