September 14: Got all the parts for the vertical stabilizer and rudder prepped and ready for primer. I’ve waded through the primer wars for the four years I’ve been on Vansairforce.com, and I had primed my earlier RV-7 project with SEM self etching, which I discovered was not solvent resistant. So I decided to go with AKZO two-part epoxy primer. But I did choose to forego the etch and alodine steps that many others have promoted. I did like the idea of dipping clean parts into prep solutions, with minimal elbow grease required. But I wasn’t too keen on the logistics of disposal of acidic and hex chrome waste.
I prepped the parts of the RV-7 with Bon Ami and red Scotchbrite. But I found through the VAF forums and other builder’s logs that Prekote was an option to prep for primer. It seems to be just a glorified soap, at $40 per gallon, but it was non-hazardous and one step instead of multiple steps.
I chose a perfect late summer day to set up a plastic table in the driveway and get to work on all the parts. You have to spray the Prekote on, scrub with the Scotchbrite until you get a lather, spray again then scrub at 90 degrees to the first pass. Then you should get a water break free surface when you rinse. This indicates that the aluminum oxide layer has been broken. I had already built a spray platform from 1x6s and chicken wire, which I laid on a workbench and arranged all the parts on it.
For priming, I bought a cheap purple HVLP gun from Harbor Freight, which so far has done a great job.
And I know this will get gasps of horror from some builders, but I did research it on VAF, and decided to prime both sides of the skins with the AKZO. Other builders have gotten input from aircraft painters at some major airframe manufacturers, and they are fine with receiving an AKZO primed aircraft to finish paint. They wet-sand it then shoot their own primer that is compatible with the top coat. True, I will incur a weight penalty, but prefer having things protected inside and out, and especially at faying surfaces and lap joints.