How about meet half way?
Now that we've made the plunge into all-out primer\anticorrosion protection on our 7-A, it's got me thinking.I know that we are adding weight, and I know that we are adding alot of time to the build and that's the price we pay for security and confidence in our airframe. But what about the added value I keep hearing about if we ever sell our plane? Does anybody have first hand experience in this matter?Are the man-hours spent on primer really calculated into additional dollar\value at time of sale?And if so,how much? I hate the idea of ever selling my plane,[heck if I do it right my GRANDKIDS could be flying it in 60 years ,heritage man!], but I am curious.
Seems like you are looking at it the right way. Two things about the primer wars, Brands and Weight: One is brand or "paint system". I'm not going to get into that. Van suggest some products in the manuals and they are great. There are dozens of dozens of good products out there. I'll say follow the manufactures recommendation and contact them if in doubt about the application. I use a German brand called Sikkens. (I'm not recommending, just that the nearby paint wholesaler is a dealer.) Sherwin Williams has the JetGlo products or commercial equiv. You want something made for aluminum. There is everything from rattle can to sealing two part epoxy primer, wash primers, self etching primers and so on. Nuff said.
You can't prime and not add any
weight, but you can prime and not add a lot of weight, with care by putting on MIN thickness (basically transparent) or being selective. Van uses a WASH primer in the QB kits. It's not very satisfying from a coverage standpoint, because you can still see the metal. It does seal a little (or a lot depending on who you talk to) and provides more protection over the clad. DO NOT USE WASH PRIMER ON BARE ALUMINUM PARTS LIKE THE HORZ STAB STAPS (made from bar stock). For that you need a sealing primer that will be opaque and colored either yellow, green or any color now a days.
PREP is a key process. The corrosion protection package starts with a perfectly clean, abraded, etched and alodine surface, before the primer gets applied. This is time consuming stuff. There are "self etching" primers that you supposedly can just shoot on shinny clad aluminum and it sticks. It probably does work OK. Personally I do the full prep if I prime.
The big player is TIME. What happens during the building process, you do the same thing over and over: fit, cleco, drill, un-cleco, deburr, dimple, fit, cleco again & rivet. This process might need more iterations. Now if you want to prime, JUST WHEN YOU ARE READY TO MAKE A PART, STOP, prep the parts, clean, etch, alodine, mix primer, get gun ready, set up your "spray booth" or area, prime, wait-dry, prime the other side, wait-dry, clean paint gun...........than you can make an assembly. This is the issue of dong little batches.
One trick if do want to prime, and it makes a lot of sense, PRIME YOUR WHOLE KIT AT ONE TIME. Or at least prime the parts you want to prime all at one time before any construction. Than if you mess up the primer drilling, cutting fitting, than just rattle-can touch-up before assembly. This will save a lot of time.
Consider the
environment. You will have old etching, alodine and clean up solvent solutions running off into the drain? If the environment police caught you not collecting and hauling off barrels of waste water to the Haz Mat dump it could be illegal. ASK a local paint shop what they do. Some just jump crud down the drain. I'm guilty of that in the past. Just saying consider getting the big barrel and saving your waste. I believe solvents and paints can just be left out and open to evaporate and solidify. Than they can go in the trash.
Also if using two part epoxy its a
health hazard. You really need to have fresh air and keep it off your skin. Some chemicals get into your body and stay. Ask some early composite builders that became sick and allergic to the epoxy goop they used. Just be careful.
Think about what you want and
NEED to prime.
Prime just those parts or just specific areas of a part. Often I prime important (in my opinion) structural parts, areas hard to see or inspect, like where ribs and spar flanges mate, lap joints or anywhere it turns me on. If there's a deep scratch on a clad part, I'll prime that area not the whole part. Clad is what provides the protection. If you scratch it off its gone, so you should prime those scratches, even if its a light rattle-can or self etching wash primer. You are just trying to keep the air/mosture off the material.
My personal preference is NOT wholesale priming of every internal surface. Do I need the back of the instrument panel primed? No; I want to use Classic Aero's side panels, so why prime behind those part? Besides if I remove the panel, I can see corrosion starting. If needed (ever) I can deal with it in 40 years (if I care by than). If I can get to and inspect an area, I usually don't prime. Exposed parts of the cockpit get the full meal deal, cleaned, scotch brite, etched, alodine and primed with two part epoxy, than painted. I want areas I see and use to be durable. If done properly its almost like armor.
So the answer might be in between prime it all & none......priming some. May be the answer is not using all "high build" (heaver) sealing primer everywhere but using a mix of sealing and wash primers in different areas? Many RV's have been build and flown for decades without ANY primer, except on the bare aluminum parts. Choosing to prime will add TIME, cost and weight, but it will have more corrosion protection. Its your choice.
