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  #1  
Old 07-30-2017, 10:29 PM
Eztroller Eztroller is offline
 
Join Date: Dec 2012
Location: West Linn,Or
Posts: 20
Default When to prime

I am on page one step 7 of the emp, and was wondering when/what I should prime. If I just follow the directions, will that be sufficient? I plan on priming. I read ahead several pages and they state, to prime parts but arent specific as to what to prime.

Little confused already....
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  #2  
Old 07-31-2017, 03:45 AM
mturnerb mturnerb is offline
 
Join Date: Apr 2015
Location: Ponte Vedra, FL
Posts: 390
Default

Get ready for a very long discussion. You may want to look through some of the "primer wars" threads.

A few points:

1. Vans QB wings/fuse use "wash primer" that seems to hold up well in the area where you live. I have a set of QB wings on order and will be depending on their experience in this area.

2. Some people elect to prime only where plans specify - mostly steel and non-alclad parts. Many of these airframes are flying pretty much corrosion-free after 1-2 decades or more. Advantages - build time, weight

3. Some folks prime everything. Even though I live in Florida (humid and potential salt air exposure), my approach is to prime internal parts like ribs, skins where they meet other parts like ribs/stiffeners, and bottom skins fully since water might collect there. (I want primer to cover any area where water/salt/gunk might collect). I also prime any part that's not alclad (and of course I prime any part called out in plans - most recently gear braces in Section 29). Most Florida airplanes from certified companies are doing OK after decades with very little internal priming from the factory - my approach is to try to balance weight/time/airframe longevity.

4. Primers vary from the "wash primer" used by Van's to self-etching "rattle can" primers (I use SEM mostly, with some Eastwood epoxy primer in certain areas like bottom skin overlap), to spray-on two part epoxy primers (AKZO seems to be most popular).

One more suggestion - look at build sites/blogs ("Carl and Rafael", Tim Olson for example) for ideas on priming and parts prep as well as general guidance when you can't figure out what the plans are trying to tell you...
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Last edited by mturnerb : 07-31-2017 at 04:47 AM.
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  #3  
Old 07-31-2017, 05:21 AM
Reflex Reflex is offline
 
Join Date: Jan 2015
Location: Baldwin City, Kansas
Posts: 60
Default

EZ,

Good question, I got a little confused there too. On one hand it tells you to rivet, on the other you know you've got to prime first....if you're priming.

I cleco'd the entire assembly up to page 06-04. After Step 3 on that page, the plans say to "Disassemble all parts and deburr". The next line says "Prime parts as applicable if desired". I deburred and primed everything that I had assembled at this point.

Regarding what to prime, it's up to you, but pretty much the inside of the entire structure is going to get primed. The hinges are powder coated so some builders scuff and prime, others leave as is.

As I recall, I primed in two sections 1) The assembly described above 2) The skin after final drilling and deburring.

As you progress, you'll be surprised how much of the structure can be cleco'd together before disassembly and priming.

Hope that helps.

Fred
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  #4  
Old 07-31-2017, 06:22 AM
BillL BillL is offline
 
Join Date: Sep 2007
Location: Central IL
Posts: 3,869
Default

Here are some questions (as I understand them) to ponder regarding primers:

Will the there be a top coat?
Will the top coat lift the primer?
What primers are proven effective with all the RV aluminum alloys?
Does my selected primer pass the salt spray, and weather exposure testing?
How do I want to apply the primer?
Is my selected primer available for the method I want?
Is only one primer required for the whole plane?

Answer these questions and you can select a good primer.

Now - as a community - what corrosion problems have been seen in the RV fleet? Cessna? If there are no issues, then, is a primer needed? Can an inappropriate primer accelerate filiform corrosion?

The answers are a lot longer than the questions, thus primer wars. All is within VAF.
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  #5  
Old 07-31-2017, 08:58 PM
Eztroller Eztroller is offline
 
Join Date: Dec 2012
Location: West Linn,Or
Posts: 20
Default

Wow! Thanks for the clarification and very thorough responses. Hopefully i can return the favor someday.
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  #6  
Old 07-31-2017, 10:22 PM
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wirejock wirejock is offline
 
Join Date: Oct 2005
Location: Estes Park, CO
Posts: 2,647
Default Prep

Quote:
Originally Posted by Eztroller View Post
Wow! Thanks for the clarification and very thorough responses. Hopefully i can return the favor someday.
Don't stop you're research on primer alone. Preparation is as or more important than the primer choice.
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Donated 12/01/2016. Plus a little extra.
RV-7A #73391, N511RV reserved (1,800+ hours)
HS SB, empennage, tanks, wings, fuse, working finishing kit
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I cannot be, nor will I be, held responsible if you try to do the same things I do and it does not work and/or causes you loss, injury, or even death in the process.
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  #7  
Old 08-01-2017, 11:42 AM
unitink72 unitink72 is offline
 
Join Date: Oct 2014
Location: Cedar Rapids, IA
Posts: 78
Default prime before/after dimpling

Only thing I might add. On the RV-10 the instructions tell you when to prime, but they always say to do it after dimpling. My prep process includes maroon scotch-brite. Scrubbing down around and in all those dimples is a big PITA, so I always dimple after priming.

Should mention that i use AKZO, and it sticks just fine even in/on the dimple.
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