Only priming fraying surfaces.

[Roy25101]

I?m leaning in the direction of priming only faying surfaces but cannot seem to find much information on it. I ran across an EAA video with the owner of Zenith aircraft and another fellow painting primer only on the flanges of wing ribs with a paint brush but they mentioned little about the full process. A few years back I ran across a video of a guy building what I believe was a -12 and he was doing the same thing but with a roller brush. I was just curious if anyone else who has gone this route could share some insight into the process. I have decided on and purchased AKZO two part epoxy. My understanding is to only prime one of the mating surfaces so this could be a simple and effective way to protect.

As always, thanks to all for your time.

[kentlik]

That is what I have done on my build. Taped off the area and prepped and self etch primed it. I believe you can save much time doing this.

[wirejock]

If you're only priming fay surfaces, you want to paint both.

[Kyle Boatright]

Originally Posted by wirejock

If you're only priming fay surfaces, you want to paint both.

Yep. Faying surfaces trap water. That's why you need primer on both sides of the joint.

[JonJay]

I did this on the RV3B empennage and control surfaces. I didn?t mask off anything. I used one of the common self etch primers out of a rattle can. I didn?t care about overspray on the inside of the surfaces. They get closed up and can?t be seen.

It is much faster than priming the entire skin and rib. It is also completely reliant on the 2024 Alclad for corrosion protection on those surfaces.
On my 6, I did not prime my baffles. After 12 years, always hangared, in a good environment, there is nothing more than some slight oxidation of the Alclad surface that wipes off with little aggression.

Will know in a 100 years how it holds up. Right now, and for the lasts several years, the RV3B has been buzzing around somewhere in Montana I believe.