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  #11  
Old 08-05-2015, 06:07 PM
Captain Avgas Captain Avgas is offline
 
Join Date: Oct 2005
Location: Melbourne, Australia
Posts: 1,868
Default Building for "life".

Quote:
Originally Posted by David-aviator View Post
How long do you plan to live?
Nothing lasts forever, build the airplane and go fly it. Your body will wear out before it will with or without priming.
I think this quote highlights a significant problem in the Experimental category. When builders' talk about building "for life", what they are often referring to is the builder's flying life, not the aircraft's flying life.

There are plenty of old builders out there who will be struggling to fly for another 10 years....but the aircraft they have built may go on for decades.

If builders keep cutting corners on their priming there are going to be literally thousands of rust bucket RVs out there eventually.

There are some builders who say: "I don't need to prime 'cause I'm living in the desert in Arizona". I say: "Yeh, but when you eventually sell it, it will probably go to some-one who lives in Florida".

There are also some builders who say: "Cessna and Piper didn't prime them for decades and some of them are still OK". I say: "Yeh, but most of them are now suffering from severe corrosion problems that are threatening structural integrity and costing GA hundreds of millions a year in restoration costs and as a result both Cessna and Piper have now learnt their lesson and now use an epoxy primer on all of their singles."

From time to time you read posts on VansAirforce about RV builders who are getting corrosion on their Alclad parts even before the aircraft is finished.

When you take on the building of an Experimental aircraft the product you produce reflects, for good or for bad, on the Experimental category until that aircraft is written off the register. The aircraft becomes your legacy to the Experimental category.
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You’re only as good as your last landing
Bob Barrow
RV7A

Last edited by Captain Avgas : 08-05-2015 at 08:29 PM.
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  #12  
Old 08-05-2015, 06:29 PM
BillL BillL is offline
 
Join Date: Sep 2007
Location: Central IL
Posts: 5,516
Default

Quote:
Originally Posted by Boomer506 View Post
I don't want to start primer wars either, but this is my second airplane and the sponge brush application of VeriPrime on interior surfaces before dimpling and assembly just really seems to pass the easy/cheap/effective tests for me.

A single quart mixed thin will do all the interior surfaces of my RV-8. I mix a thimble full if I need to by drawing out of the can with a tongue depressor and sponge brush on thin. It dries in 15 minutes or less and I can dimple or rivet away almost immediately.

It is self-etching, so if I have any contaminants on the surface, it cuts through them and still adheres. It has chromate in it, so it serves as the sacrificial annode so-to-speak.

It does not seal, you need a top coat to do that. But for interior surfaces, I think it is the bees knees. I have attached a picture of how my skins look when treated this way. Again, the key is to mix thin. So you will need two quarts of activator to go with your one coat of primer. As you can see, I do my exterior surfaces also. It seems to help prevent scratching during the build.

If one was thinking about going out and purchasing primers today, be sure to check the msds first. The older VariPrime contained zinc chromate which was known to be very effective against corrosion for aluminum containing copper (2024). Many good primers of a few years ago have had this material removed. 615S included.

Look to the marine industry which still has primers with this readily available. Aviation is available, but in larger containers. Also, priming and not top coating can lead to different primer solutions. Some very effective ZnCh primers are not 2K (urethane or epoxy) formulations and will lift with many modern (as in current production) 2K topcoats
__________________
Bill

RV-7
Lord Kelvin:
“I often say that when you can measure what you are speaking about,
and express it in numbers, you know something about it; but when you
cannot measure it, when you cannot express it in numbers, your knowledge
is of a meager and unsatisfactory kind.”

Last edited by BillL : 08-05-2015 at 06:32 PM.
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