Priming question...

[danielhv]

I really haven't looked too much into priming, but im kinda considering it since im still early in the project... my question is: Do you prime after match drilling, dimpling, etc... and if so, does it change the size of the holes you drilled to the point where it has to be re-drilled to get the rivet through?

[SvingenB]

I found it much easier to dimple after priming. The other way will make your scotch brite pad shread on the dimple when matting the surface.

[jsharkey]

For what it's worth I generally primed after all drilling, deburring, counter sinking and dimpling. Occasionally I had to run a tapered awl or drill through a stack of holes to get them aligned and the rivet in.

I prepped for DuPont Variprime with their etching system, usually after scuffing with Scotchbrite. I gave up on Alodining before the prime coat early on. Some of the HS parts were Alodined only.

I have also used Marhyde grey rattle can primer on small parts, some times with just a scuff and acetone clean before hand.

A few alclad parts I left bare - empenage skins, shims, tip-up canopy seal angle, etc. I primed the canopy frame after assembly - it is already partially assembled with welds when received.

I used to keep a few ounces of left over Variprime in a jar to touch up any cut edges or holes drilled after priming using a cotton bud. The Variprime seems to last for ever - if you keep it shaken, or poshibly even shtirred Mish Moneypenny.

I guess I was experimenting and learning. Perhaps next time I'll do it differently and more methodically. I like to keep things simple, light and economical so will probably go with only priming non alclad parts.

Jim Sharkey
RV6 Tip-up - getting there!

[Phil]

I'm in agreement with both posts above.

1) Prime before dimple, otherwise it tears up the scotchbrite pads. It also is much easier to keep your spray from going through the holes and getting on the outside of the skin. Just give it 24 hrs to cure.

2) I gave up on Alodine. It just wasn't worth the hassle.

3) I did use the Dupont (912S - If I remember correctly) Cleaner to prep for Aluminum parts. But it requires a rinse with water. I was too lazy to use distilled water and nervous about using tap water for rinse. So I canned the DuPont 912S in favor of PPG DX-330. The DX330 is very simple to use and doesn't require a rinse. You just put some on a paper towel and wipe your part until the towel comes up clean.

4) I have primed every internal surface with Dupont Variprime up to this point. I don't expect that to change. (Including the interior of skins, etc).

5) I keep a little airbrush handy (From the aviation dept at Hobby Lobby) and use it to touch up scratched areas..

6) The Rattle Can Primer is also a good thing to keep close. If I'm working in an area that no one will ever see, I don't mind shooting the gray over the top of the mustard-colored variprime.

[panhandler1956]

I dimple before I prime so I don't unnecessarily scratch the surface any more than possible. I am using NAPA 7220 and it's good, but it isn't as durable as 2 part epoxy primer. I too don't like destroying my scotchbrite pads so I scuff them before I dimple and then I clean (acetone) and then prime.

Just a slight variation on some of the ideas listed above - not saying I'm right or wrong.

Good luck!

[Michael Burbidge]

I alumiprep, alodine, and prime internal parts using rattle can Zinc Chromate. I don't prime the inside of the skins. Most of the parts on the empennage are alclad. I don't do the inside of the skins because they are alclad and I don't find that I scuff or scratch them while working with them. My understanding is that alclad is the best corrosion protection. So why scuff it and then prime it?

I prime the internal parts, ribs, spars, etc. because I find that they get pretty scuffed up drilling, deburring, etc.

[docrick]

I prime AFTER I dimple. I don't use the scotchbrite pad real aggressively. I use the water based Aircraft Finishing Systems primer with the etching done with their "ecoetch" product.

Incidentally, when I built the HS I washed each part in soapy water, cleaned with MEK, etched with ecoetch and primed. Took ALOT of time.

Now I simply use ecoetch without cleaning first in soapy water and MEK and then prime. The primer "holds" everybit as good and I've saved ALOT of time.

[FlyerJumper]

Originally Posted by SvingenB

I found it much easier to dimple after priming. The other way will make your scotch brite pad shread on the dimple when matting the surface.

Originally Posted by Phil

1) Prime before dimple, otherwise it tears up the scotchbrite pads.

Another alternative is to scuff your surface & clean it, then dimple it, then prime it. Solves the shreaded pad problem and you don't have to wait for the primer to cure before dimpling.

[allbee]

or you can do the alternative and not do it at all.

[danielhv]

Originally Posted by allbee

or you can do the alternative and not do it at all.

That was definately a thought.. but after consideration... I will probably only build one plane my entire life and I want it to last as long as possible!