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Comment by Chris Boultinghouse on November 1, 2016 at 10:43am

I saw that video too. My concern would be getting all of the Alumiprep rinsed off, or it getting between the surfaces, since it's a diluted phosphoric acid solution. In reality, 6061 is really corrosion resistant, so unless you live in a salt water environment it's probably massive overkill to do much (if any) priming. 

Comment by Greg Harris on November 1, 2016 at 10:39am

I was thinking the same thing about the skins, both on the inside mating surfaces and the exterior. But then I saw one of Jon's tips, and he was spray-bottling it right on the outsides of the skins after assembly. Not sure I'd want Alodine on the outside, but that method he was using seemed pretty easy for the insides of skins. Still...heck of a mess when doing skins or large pieces.

Comment by Chris Boultinghouse on November 1, 2016 at 10:30am

I did the aluminprep / alodine on all the ribs for my Sonex. They were a really pretty gold color, but of course that's not really practical on skins. "Primer wars" is always a fun topic on any metal airplane discussion forum. :)

Comment by Greg Harris on November 1, 2016 at 10:28am

If I ever get around to building the CH 640 someday, I'm almost certain I'll go with Alumi-prep/Alodine.

Comment by Greg Harris on November 1, 2016 at 10:27am

PTI Zinc Chromate Yellow in a rattle can for now. I may switch to the brush-on so I can prime during winter in the garage. I have no way to vent the fumes if I use spray in winter, so I've been doing all my priming outside. Though the brush-on is also toxic, it's way less vapor than the spray. I'm not a fan of the Zenith-recommended Cortec. I have some, but I didn't like the results when I did the rudder. Another builder had similar results...peeling in spots, really hard to clean off where it doesn't peel. If I had to do it all over again (and if i had more space), I'd probably go with Alumi-prep and Alodine. Very consistent results and no added weight.

Comment by Chris Boultinghouse on November 1, 2016 at 10:21am

Looks great! Very smooth.  What kind of primer are you using? On my Sonex I used a NAPA-sourced self-etching gray primer on the mating surfaces, but I'm not sure what (if anything) I'm going to use this time.

Comment by Greg Harris on November 1, 2016 at 8:52am

Top of the skin final riveted! Woohoo! You have to leave the bottom surface un-riveted/clecoed until you've finished rigging the elevator hinges. But I think it turned out great!