When to prime a part

[GoN4Broke]

I'm a first time poster and I've just begun the VS for the -12. My plan is to prime the ribs, spars etc. prior to buttoning up the skin. I am very early in the process andI've been working on the spar, I've match drilled the upper and lower spar cap holes and deburred everything. The next step is to countersink some #40 holes on the bottom portion of the spar. What I'm wondering is if I should prime the spar prior to countersinking the holes or wait until after. I'm just thinking that if I paint I will have to scrape out the countersunk holes to make the rivit fit flush. Any advice would be appreciated.

 

[Piotr G]

I did prime after riveting.

have a fun with the building my talilcone in ready, and i am waiting for the wings

 

[Ausflyer]

Jim, one of the principles I followed in my build was to ensure all surfaces that would be clamped together by rivets should be prepped and primed before rivetting. This protects the surfaces against moisture that will get in between.
So wherever possible I did all the dimpling and countersinking before I prepped and primed. I have ended up with unprimed rivet and screw heads that will get primed now at the airframe painting stage.
Rod

 

[panhandler1956]

Jim, one of the principles I followed in my build was to ensure all surfaces that would be clamped together by rivets should be prepped and primed before rivetting. This protects the surfaces against moisture that will get in between.
So wherever possible I did all the dimpling and countersinking before I prepped and primed. I have ended up with unprimed rivet and screw heads that will get primed now at the airframe painting stage.
Rod

I agree and would add that a couple of things that I did. I primed the mating surfaces prior to mating and I did a single coat (dusting) on the other areas- this is totally optional. Also as a tip, I used scrotchbrite to scuff the surfaces to be primed - if you do this do it before dimpling, the dimples tear up the scotchbrite in a hurry....
Good luck and glad to see your 1st post of many!

 

[GoN4Broke]

Thanks everbody for your input. I will go ahead and prime after I do all the countersinking. I was just worried that the paint on the small #40 countersunk holes would cause the rivit to not fit flush. I guess I'll find out

 

[float208]

priming

Scotchbrite everything, prime it just prior to assembly, then I usually run a sprayed coat of primer down the rivet line, if its still accessible, after riviting to cover any scuffs and the also the rivet heads and it looks much cleaner...

 

[flion]

Primer in the countersinks or dimples won't affect anything, unless you apply way too heavily. Most people prime too heavily; it's not a top coat. And, unless the primer you use acts as a moisture barrier (not all do) then a heavy coat really buys you nothing. If you get a chance, check out a quickbuild kit and see the priming job on that. Playing Devil's advocate , if you really want to overkill it, mix up a small amount of primer and put your rivets in that and set them up wet. No, I don't really advocate it but it's a technique that has been used - with bolts as well.