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What Parts to Prime

H

hjd3021

Member
New to the forum. Will be picking up my empennage kit on Friday and am very excited to be starting an RV-12 build. You guys have provided a wealth of information here which is extremely helpful for us first time builders. I have studied the threads related to priming and understand the differences of opinion. What I am curious about is for those that have decided to prime what items are you priming. Is it only the no alclad parts, assemblies, specific areas such as the exposed hinge lines, entire internals? I am assuming that priming is done at parts level prior to assembly. Any suggestions would be much appreciated.

John
 
I ran a brief survey on VAF when I was at about the same stage. Apart from the parts you are required to prime, about 50% of RV-12 builders didn't prime anything else, 25% primed rivet lines and other surfaces in contact, and the other 25% primed all the internals. Priming is generally done as you go.
 
John,

The decision of which parts to prime, or not, is yours to make, based on your own situation. Here are some of the factors that go into the decision:

Your location: Anywhere near salt water, or in a humid locality?
Resale value: Do you think a prospective buyer would be impressed by more primer?
Time considerations: It will take longer to prime everything.
Cost considerations: Primer costs $.
Weight considerations: Are you wiling to pay the weight penalty?
Your personality (no kidding): How much of a perfectionist are you?

Then there is the question of what kind of primer to use. Do you have work space and spray equipment to apply a two-part primer, or would rattle can primer be good enough?

I can tell you what my decisions were regarding "to prime or not to prime", but my decision factors probably won't be the same as yours. I used a NAPA 7220 rattle can primer on all internal structures, EXCEPT the inside surfaces of the skins. A comprimise, based on my situation.

Hope this helps, rather than confusing you further!
 
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BigJohn said:
John,

<snip>
I can tell you what my decisions were regarding "to prime or not to prime", but my decision factors probably won't be the same as yours. I used a NAPA 7220 rattle can primer on all internal structures, EXCEPT the inside surfaces of the skins. A comprimise, based on my situation.

Hope this helps, rather than confusing you further!
Click to expand...

BigJohn,

How did you prepare the aluminum before spraying? Also, did you prime the center section channel this way?

Jerre
 
Scuff the aluminum with scotchbrite pad. Clean off with acetone. Spray the primer. I used an acid-etch aluminum primer (rattle can) with a matching formulation color finish paint from Home Depot for the interior. Worked great. Painted all the interior parts that show. Paint the fuse interior before you put the side skins on. Paint those skins (inside) before riveting them on.
 
Priming/interior paint suggestion.

Just to add to that, I studied photos of other finished RV-12's to see what interior surfaces are still visible after the carpeting and side panels are installed. Turns out, most of the interior is covered so while I am priming the whole interior, you only need to use interior finish paint on a limited number of additional surfaces (i.e. inside top/side skins in baggage and fuel tank areas, the central channel and front side of fuel tank are a few of them)
 
Bill_H said:
Scuff the aluminum with scotchbrite pad. Clean off with acetone. Spray the primer. I used an acid-etch aluminum primer (rattle can) with a matching formulation color finish paint from Home Depot for the interior. Worked great. Painted all the interior parts that show. Paint the fuse interior before you put the side skins on. Paint those skins (inside) before riveting them on.
Click to expand...

Found this thread while researching for my RV-8A... lol, really glad to hear someone say this. It didn't make sense to me all of the people advocating using really expensive cleaners, preps, etc. on brand new aluminum. Certainly a scuffed, cleaned, and primed kit is better than nothing.
 
I was flying a Cessna 140, circa 1946 before the RV-12 and it had no evidence of corrosion. Yes, it was based for its life in the midwest. On the 12, I primed a minimal amount. Rib flanges with a small roller, but, did not prime the wing walk.

Is priming necessary? Nope! The plane will outlive just about all of us. If I build another, will not waste my time.

Ask Dick what he did near the factory in Oregon.
 
My View

Marty I agree with you 99% of the time.
Three things have to be considered
Where the plane will live, how old you are and resale.
I live in Florida and the airport in Clearwater is on the water's edge.
I think priming if you are near salt air is a good idea, otherwise not so much
My view

One more link

http://www.corrosion-doctors.org/Aircraft/aircraft-design.htm


MartySantic said:
I was flying a Cessna 140, circa 1946 before the RV-12 and it had no evidence of corrosion. Yes, it was based for its life in the midwest. On the 12, I primed a minimal amount. Rib flanges with a small roller, but, did not prime the wing walk.

Is priming necessary? Nope! The plane will outlive just about all of us. If I build another, will not waste my time.

Ask Dick what he did near the factory in Oregon.
Click to expand...
 
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I asked this in another thread but thought I could get more opinions here. For those of you who used primer whether everywhere or just the rivet lines, did you have any issues getting the blind rivets into the holes? I'm having a difficult time getting rivets through thicker material like the HS spars. If you guys had no trouble, could you please explain your technique. I'm at the point of skinning the HS and don't want to damage anything.
 
You can use an icepick to line up the holes but also to clear the holes of primer. Just turn it a couple of times and you should have no problems with inserting the blind rivets. Or take another rivet, some rivets are just a little bigger and hard to get in some holes.
 
I live in the panhandle of Florida and will keep my RV-12 in a hangar about 25 miles North of the Gulf of Mexico. I decided to prime all the internal RV-12 parts because of the high humidity in the summer, and because (in a few years) I want to be able to sell my RV-12 to a buyer in Florida who may be near salt water.

I used the Sherwin Williams P60-G2 wash primer recommended by Van's Aircraft. Bought one gallon of P60-G2 and two gallons of S-W Catalyst Reducer R7K44. I mixed these one part P60-G2 and two parts R7K44. Just wiped down the parts with lacquer thinner, then sprayed a thin coat of the mix using a Harbor Freight 66871 touch-up spray gun, while wearing a 07193 3M dual cartridge respirator and Harbor Freight nitrile gloves.

Cost two years ago for everything (primer, catalyst, lacquer thinner, spray gun, respirator, and gloves) was about $250 and the 1 gal primer plus 2 gal catalyst quantities was adequate to do all the internal parts and other external parts needed (such as brackets). I would go this route again because the P60-G2 is easy to use and cures/dries in just a few minutes adding very little weight to the parts, and it does not plug up any of the rivet holes.

I used T-pins from a fabric shop to pin the parts to cardboard from the kit boxes. Spray a thin coat on one side, wait about 5 minutes, turn parts over and spray other side. Do a "batch" of several parts at one time.

Be sure to clean up the spray gun parts with lacquer thinner after each use or it will "stick" itself together--and you will wish you had cleaned it up!

Cordially,
Fred Carnes
 
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