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Dimple and prime, or prime then dimple?

Everwild

Well Known Member
Hi. New RV10 builder here. Working on figuring out my process to maximize efficiency without sacrificing quality and have a question about the order of the prime and dimple process.

Looks like some folks drill, deburr, dimple then prime before riveting assemblies together. Others drill, deburr, prime then dimple.

I plan on using Prekote and AKZO 2 part epoxy primer.

Looking for pros and cons for each process.

Dimple then prime

Pros
Seems like a more logical order when following the plans

Cons
I read that it's harder to Scotchbrite the parts with the dimples and tears up the Scotchbrite faster

Harder to get even primer coverage in all of the dimples

Prime then dimple


Pros
Easier to prep and prime without dimples

Cons
Guessing parts can get scuffed up more during the dimpling process?


Finally, if I prime will I have to re-drill the holes before final assembly to get the rivets and bolts to fit? Or even the dimple dies for that matter?

Just wrapping up my practice kits and ready to start the VS.

Thanks!
 
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I prime when I have a sunny day to assist drying. If the parts are already dimpled, countersunk, etc, great, if not, oh well. I don't think it makes much of a difference. I sometimes end up having to gently scoop primer out of countersinks and dimples anyway to ensure the rivets fit well. I think I read on VAF somewhere about a builder who primes (or alodines) every part right after they unbox it so there seem to be many ways.
 
You could scuff, dimple then clean and prime. I etch and alodine everything ahead of prime but my steps are this: drill, debur, scuff, dimple, etch and alodine, prime. I am OK to leave parts scuffed for long durations (month or so) since etching cleans everything up nice and I do a light scuff in the solution too. I try to keep it to under two weeks between alodine and prime because I dont like to wipe things down and clean up again before prime. I use Akzo 2 part epoxy and things are holding up well during my build.
 
Some steps on the RV-10 have you prime, then countersink (the spars on the Horizontal Stabilizer get primed and assembled w/ doublers etc first, then countersunk later). So, I think it is generally an ok practice to prime first then dimple/countersink later. That being said, typically the plans specify priming after the parts are finished (deburred, dimpled, countersunk) and I typically follow the plans. Once you have a few sections done, there's enough stuff to do (back ordered parts, assembly, fiberglass) that you can jump around a bit.

You should not have to re-drill holes if you are applying the primer correctly. It should be a fairly thin coat and shouldn't materially effect either the size of the hole or the seat for the rivet head in the dimple/counter sink. But, sometimes you get a stubborn drip or something in there -- for those cases, I use a #40 or #30 reamer in an electric drill to slowly clean up the edges of the hole.

Edit: I prime with EkoPrime, and use Scotchbrite/EkoEtch for prep. The instructions state to prime within 24 hours of etching, so my typically process is to do parts in batches all the way through, from etching to priming in one sitting. If you look ahead in the plans and batch appropriately, you can have a nice set of parts to rivet and a set of parts to prime if your priming booth is weather dependent (like mine).
 
Prime procedure

You could scuff, dimple then clean and prime. I etch and alodine everything ahead of prime but my steps are this: drill, debur, scuff, dimple, etch and alodine, prime. I am OK to leave parts scuffed for long durations (month or so) since etching cleans everything up nice and I do a light scuff in the solution too. I try to keep it to under two weeks between alodine and prime because I dont like to wipe things down and clean up again before prime. I use Akzo 2 part epoxy and things are holding up well during my build.

Same here. Match drill, scuff, dimple, scrub, dry, prime. I didn't Alodine inside. I did Alodine the exterior.
 
I started with dimpling before priming but after a while I switched the order and found that prep for priming was quite a bit easier when the parts didn't have dimples.

If you want to try dimpling after priming then I would recommend trying it on some scrap first to make sure that your primer is able to withstand the dimpling process. I use an epoxy primer that needs about 48 hours before its cured enough to be really durable. If I dimple sooner than that I'll probably loose all the primer on the dimples.

You also may have issues with rivets/bolts fitting into holes after priming depending on the primer you use and how heavy you spray the primer on. With the first primer I used I had to ream a lot of the non-dimpled holes to get a rivet to fit. Since switching to a different primer and working on spraying a lighter coat I don't really have that problem anymore.
 
I do a mix of everything, depends on the order of assembly. Some of the fuselage bulkheads get primed and partially built before drilled to the skins. In that case, you have to prime before dimples.

In a perfect world, I scuff as part of the hole deburring then dimple. Use a scotchbrite pad to apply the alumiprep or otherwise. Then spray primer on the dimpled skins/structure.

As stated earlier, sometimes deviations are required due to build sequence.

If countersinking is required on already primed parts, a Q-tip dipped in primer is a great way to touch up the bare metal.
 
With epoxy primer you might be OK with prime-then-dimple. I'm using rattlecans, it is not as tough so I've been dimple-then-prime, faying surfaces only, scuff before dimpling. At some point I messed up my order of operations and shot primer before dimpling, and a non-trivial amount of it ended up stuck to my dimple dies instead of the skin. Which probably says something important about my process, but it's a data point nonetheless.
 
Hi. New RV10 builder here. Working on figuring out my process to maximize efficiency without sacrificing quality and have a question about the order of the prime and dimple process.

Looks like some folks drill, deburr, dimple then prime before riveting assemblies together. Others drill, deburr, prime then dimple.

I plan on using Prekote and AKZO 2 part epoxy primer.

Looking for pros and cons for each process.

Dimple then prime

Pros
Seems like a more logical order when following the plans

Cons
I read that it's harder to Scotchbrite the parts with the dimples and tears up the Scotchbrite faster

Harder to get even primer coverage in all of the dimples

Prime then dimple


Pros
Easier to prep and prime without dimples

Cons
Guessing parts can get scuffed up more during the dimpling process?


Finally, if I prime will I have to re-drill the holes before final assembly to get the rivets and bolts to fit? Or even the dimple dies for that matter?

Just wrapping up my practice kits and ready to start the VS.

Thanks!

Welcome to the building world. I would say you're gonna get 50 different answers. But for what I did on my -7A (mostly the wings since my fuse was QB) was: Cleco, final drill, disassemble, dimple, prime, re-assemble, and rivet.

For me it was using this logic: Once I re-assemble a structure, that's the last time I'm putting it together and I wanted to minimize my chances of scratching my freshly primed parts.

FWIW - I used the two part AZKO epoxy primer and waited until I had a decent sized batch of parts to prime, then I would set aside an entire weekend to alumiprep and prime on Saturday, then re-assemble and final rivet on Sunday. Most of my weekday time was spent with the final drill and dimple. Your mileage may vary depending on when you can get out to the shop and work on your project.

I would say either way works. But this is just what I did.
 
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