Van's Air Force
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Not priming question
- Thread starter BennyC
- Start date
The biggest disadvantage in not priming is in resale. If you have not primed the interior, you have given the potential buyer a lever arm.
I primed but will likely not prime on the next build.
I've primed both my Van's RV14A build and my Zenith 750SD build, but I'm using prekote and sem ezcoat rattle can, so it's not as large a lift as other methods, so I don't see it as a huge downside on my time, a few hours here and there, as I try to bundle as much together for a large session of prekote and prime.
I primed with rattle can only where specifically directed. Goal is to have the plane flying inside of 4 years, and resale is highly unlikely unless major shifts in life occur. There maybe some buyers that insist on a plane with interior prime. Other buyers won’t care. In the words of many car dealers… “there’s an A$$ for every seat!” Someone will buy it at a fair price if you ever have to sell.
I didn’t prime the interior except for the home depot etching primer spray can where the parts are mated. I save a few pounds like this. I doubt a future buyer will care if the primer is used. If they do, I will gladly point out all the Cessna sitting on the ramp with zero primer.
The only people who care about the primer are the builders who are building now. After the airplane has flown, even the RV owners and builders don’t care. They only comment on the expensive paint scheme on the outside.
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I am priming everything on my RV-10 and have considering skipping it many times so that I can move a little quicker, but then I remember this blog post:
https://www.n1017h.com/taking-a-new-stand/
He decided to start priming after the tail cone was finished, so there was no primer on the mating surfaces. I don't know if there were some unusual circumstances that allowed the corrosion to form under the stiffeners but that's enough to keep me priming.
https://www.n1017h.com/taking-a-new-stand/
He decided to start priming after the tail cone was finished, so there was no primer on the mating surfaces. I don't know if there were some unusual circumstances that allowed the corrosion to form under the stiffeners but that's enough to keep me priming.
Carl Froehlich
Well Known Member
What I tell builders, “remember you are building the plane for the next owner, and the ones after that”.
I prime every square inch of the plane using epoxy primer. On the interior I also top coat the exposed areas with single stage urethane that has proven to be very durable. On the first build I waited over a year before final exterior paint. Parked in a T hangar in northern Virginia I found several areas of corrosion on the exterior skin. That was enough to convince me to again prime the next three builds.
If epoxy primer is too hard or expensive, use a rattle can. Any primer is better than no primer.
Carl
I prime every square inch of the plane using epoxy primer. On the interior I also top coat the exposed areas with single stage urethane that has proven to be very durable. On the first build I waited over a year before final exterior paint. Parked in a T hangar in northern Virginia I found several areas of corrosion on the exterior skin. That was enough to convince me to again prime the next three builds.
If epoxy primer is too hard or expensive, use a rattle can. Any primer is better than no primer.
Carl
I am going to post a few photos I took of a Cessna 182 that was recently in the paint shop. All the interior upper skin is corroded, to the standard of VAF. However, to the standard of the FAA, the IA, the A&P, and the series of pilots who used this airplane for the last 40 years, the airplane is 100% airworthy. I posted the pictures before but I think the mod deleted them because they aren't "RV related". If you guys want to see them, I'll repost them here.
Edit: Was checking the aircraft registration, it was borned on 1980. So it's 44 years old and when I last checked today, it is doing the pattern with a CFI and a student pilot like nobody business. Not bad for a corroded out, and non aerobatic wing.
Edit: Was checking the aircraft registration, it was borned on 1980. So it's 44 years old and when I last checked today, it is doing the pattern with a CFI and a student pilot like nobody business. Not bad for a corroded out, and non aerobatic wing.
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wirejock
Well Known Member
Another option. Send parts to a shop to be Alodined. Inside and out protected and zero weight. Probably cost a a few AMUs.
If I did it again, I would prime inside and out at the same time with P60G2. Very little weight. I couldn't measure it.
I do have numbers for 2K primer if anyone is interested. Figure about 3-6 lbs for the inside. Depends on how thick.
If I did it again, I would prime inside and out at the same time with P60G2. Very little weight. I couldn't measure it.
I do have numbers for 2K primer if anyone is interested. Figure about 3-6 lbs for the inside. Depends on how thick.
I just use my accelerator pump without priming. Two full pumps usually does it.
rockyfatcat
Active Member
Aircraft with untreated aluminum are eventually going to corrode. I worked at Robinson Helicopter while going through A&P school. They offered a package that protected the airframe to the same degree as their water based ships. Every part was completely primed before assembly. Every bolt was assembled wet with primer, torqued, and both ends were primed, and then painted.
Normally the inside of most of the ship‘s sheetmetal was raw aluminum. It makes sense that if you encapsulate the aluminum and can keep it as far as you can away from high moisture, it‘s chance of lasting forever goes way up.
Kinda like buying a car with a turbo. If you aren’t going to keep it forever, go ahead and drive the piss out of it and trade it in. A little extra effort and a few pounds of primer will probably make your RV last.
Normally the inside of most of the ship‘s sheetmetal was raw aluminum. It makes sense that if you encapsulate the aluminum and can keep it as far as you can away from high moisture, it‘s chance of lasting forever goes way up.
Kinda like buying a car with a turbo. If you aren’t going to keep it forever, go ahead and drive the piss out of it and trade it in. A little extra effort and a few pounds of primer will probably make your RV last.
BravoAlphaRomeo
Active Member
Don’t forget the other alternative, which is to treat periodically with ACF-50, or any other equivalent corrosion
inhibitor. I know they can be a little bit messy, but that’s normally because it’s put on too heavy. I’ve been using this stuff for years and think that it works pretty well.
inhibitor. I know they can be a little bit messy, but that’s normally because it’s put on too heavy. I’ve been using this stuff for years and think that it works pretty well.
Do not EVER use CorrosionX or ACF-50 before you paint the exterior as it will weep for a long time and cause major issues with paint adhesion. Once the aircraft is painted, they are great products.
Prime if you want, it will add significant build time, effort, some weight, and cost.
Either way, the aircraft will likely outlast the builder. Do you want to build an aircraft to last 100 years or 150 years?
RV7 To Go
Well Known Member
I primed my 3 builds for the resale. Not because it increases the value but because it increases the market. I don't think a person will pass on a buying a plane they like because it was primed but many will pass on one that isn't primed. Sooner or later we all must sell our plane....unless we just scrap it.
Thanks for the photos
If I cut up the wing skin of the C182 above, and perform a coupon test to measure the remaining ultimate strength, I am willing to bet it will be very close to the published strength of the original metal in 1980. I also surmise the cyclic loading of this airplane is no where close to the fatigue limit of the metal. The unpressurized GA fleet, spending most of the life under 10,000ft MSL at 1G, does not experience the amount of cyclic loading compare to the airline fleet where the operational enrivoment ranges from sea level to the flight level multiple times per day.
This is the key. The alclad will outlast most of us. Also in order to prime the metal correctly per aerospace standard, the metal must be pre-treated using the Alodine method prior to the application of primer. I know many builders skipped the Alodine step. I also know the the Alodine process is laborious, including scuffing the aluminum, cleaning, rinse, apply acid etching, rinse off, then alodine, and rinse. It is a messy process before you apply a 2mil layer of epoxy primer. You can Alodine a wing rib but do you have a facility to Alodine a large wing skin, a large fuselage panel, etc?
Personally, I Alodined every piece of aluminum in my RV8. This process took days and days and days. I wore out at least two bundles of the purple Scotchbrite pads doing this. The accidental acid splashing corroded a few pairs of jeans. I tried to forget the toxic chromate exposure on my body too. Just want to put things into perspective.
Thanks, this perspective helps a lot.
I didn't prime my first build but primed the last two with Akzo epoxy primer and if I build again, I surely will prime. It adds a little extra work and money but it gives a ease of mind plus better resale value.
If your concern is the time it takes, if you plan it right it will not be nearly as bad as some make it to be. For a reference, my last SB 14A took me 13 months from ordering to airworthy inspection and the only thing that was outsourced was the seats.
If your concern is the time it takes, if you plan it right it will not be nearly as bad as some make it to be. For a reference, my last SB 14A took me 13 months from ordering to airworthy inspection and the only thing that was outsourced was the seats.
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Im still building but so far have scuffed, etched with EkoEtch and primed with EkoPrime. I do it in batches to save time. Basically I prime all parts for a subassembly at the same time. No nasty chemicals and the finish is very tough. The additional time to prime is such a small fraction of the total build time and I’m glad I will have corrosion protection and better resale.
This has not been my experience. Once I have enough parts prepped and ready for priming it only takes me maybe 90 minutes to scuff the parts with PreKote, hang them on my priming rack, spray them with Akzo and clean up afterwards. For me, priming has been less than 1% of my build time.
Now if I was priming parts every couple of days rather than gathering all the parts I need for an assembly before priming them, then yes, it would add significant time to the build. Maybe that's what everybody else does and why it takes so much time for them to prime? I dunno. I'm a new builder so maybe I'm doing it wrong.
I've primed virtually everything (live near the coast - even with that, on the next plane I will only prime mating surfaces). I haven't tracked how much time it's taken, but it's really pretty minimal relative to other build activities. For me, the biggest annoyance of priming is the fact that waiting to prime batches sometimes requires you to juggle the order you do final assembly in. In the winter when it was harder to prime due to the temperature, I'd have to just move from one major assembly to another, even though my preference would have been to completely finish one before the other. It's not a huge deal, but it did cause me to lose motivation at times because I didn't see assemblies go together, only the parts pile grow for priming.
Personally, I think that a lot of builders don’t like to say that they aren’t priming due to feeling like they’re being perceived as sloppy, lazy, etc.
There are merits to each approach, and I’m fine with my decision that was based on education and acceptance of the pro/con and risk assessment of my choice. “Prime if/as desired.”
There are merits to each approach, and I’m fine with my decision that was based on education and acceptance of the pro/con and risk assessment of my choice. “Prime if/as desired.”
I watched build videos of a guy building a 14A in San Fransisco. I think he primed this way. I think this is what I will do too.
Walt
Well Known Member
Worked on GA in Florida for a number of years, EVERY airplane that came in for annual had corrosion repairs. We sprayed them with corrosion inhibitor every year, it probably helped but didn't prevent it. Needless to say, my airplane is totally primed with Akzco 2 part epoxy.
Corrosion pits are stress risers and a likely source of stress cracks.
Corrosion pits are stress risers and a likely source of stress cracks.
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