First EAA Technical Advisor visit

Yesterday I had my first visit from an EAA technical advisor. He checked my Horizontal and vertical stab work. He said that the workmanship was much higher that he expected. And that made me extremely happy however, he made a comment that has me puzzled. He said that the primmer that I am using (NAPA 7220 self etching) or any other primmer not 2 step epoxy are not water resistant and would cause more harm that good if water got inside the parts. He also said that primmer is not used to prevent corrosion but to provide a good surface so paint can adhere. He said I would be better off not using primer at all, that aircraft mechanic (he is one) prefer to sign off aircraft that don?t have primmer inside because it is easier to check for corrosion and primmer hides it too well. Is all this coming from him or is this true amongst the aircraft community? If so, why the unresolved never ending discussions about primers on these forums? Hope this is not one of them.

He is absolutely correct that 7220 and most of the self-etching non-epoxy rattle can primers are not sealers. They don't do 100% of the job when working alone (i.e. without paint). They are intended to take a top coat of paint. A 2-part epoxy primer such as AKZO will seal the material and function standalone.

However...

Take a look at what Van's uses for primer on quickbuild kits. It's a very light coat of a translucent wash primer. That, just like your 7220, is also not a sealer. If it's good enough for Van's (and remember, these kits cross oceans...salt water air abound), is it good enough for us?

In my opinion, the biggest reason to prime is to keep water from contacting two mating surfaces. No, 7220 or GBP988 or Mar-Hyde don't seal the metal, but if water got in between a flange and a skin or spar web, the "half ***" primer would actually do a pretty "whole ***" job of isolating metal-to-water-to-metal, and imho serves the purpose.

If you leave your airplane underwater for long periods of time, all bets are off.

Is that fresh water or salt water?

AX-O said:

aircraft mechanic (he is one) prefer to sign off aircraft that don?t have primmer inside because it is easier to check for corrosion and primmer hides it too well.

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Ummmm... okay...

I had a long response typed up, and was previewing the post to check my spelling & punctuation, when I decided I should take the higher road.
Sooo, I'll just leave it at this: I DISAGREE WITH THAT STATEMENT.

I've been using Sherwin Williams vinyl wash primer (2 part, not rattle can) for over 25 years. I have discussed it at length with Sherwin Williams, and they agree that it is appropriate for our application. The inside or my -6 looks just like it did in 1989 when I started.

Primer

We've been using 7220 as well as other self etching primer in rattle cans for more than 10 years, with no ill efects and with more than ample protection. The 7220 seems to be the better of the lot.
It is, however, as any other finish, subject to failure if the surface is not clean or "burnished". It is not entirely adequate for finish painting, but better suited for interior and particularly where riviting surfaces meet. Another small feature is that in order to become effective, it should stand several hours rather than when "fast dried".
As to priming interiors, it is not necessarily required when using Alclad aluminum, but looking at uneven patches does look like graffiti.
T88

Do you really even need an EAA tech advisor? I talk with 3 guys at the local EAA chapter building RV's and one has completed 2 without any advisor inspecting their work. I think the advisor thing is more for piece of mind than anything. BTW, There are no advisors in my area so I can't use one anyway.

briand said:

Do you really even need an EAA tech advisor? I talk with 3 guys at the local EAA chapter building RV's and one has completed 2 without any advisor inspecting their work. I think the advisor thing is more for piece of mind than anything. BTW, There are no advisors in my area so I can't use one anyway.

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In addition to this question, I have one to ask. I once was told that having each stage of construction signed off by a DAR had some impact on insurance rates. I was receintly told at my local EAA that these early inspections are not honored for lower premiums anymore. Anyone here had first hand experience with this in the last year?

Bret S said:

In addition to this question, I have one to ask. I once was told that having each stage of construction signed off by a DAR had some impact on insurance rates. I was receintly told at my local EAA that these early inspections are not honored for lower premiums anymore. Anyone here had first hand experience with this in the last year?

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My understanding as well, fwiw. At the same time, definitely get someone who knows more than you to take a look at your work from time to time. Always a good practice.

Not required but reccommended

This is what the FAA says in AC 20-27E...

8. DESIGN AND CONSTRUCTION.

a. Many individuals who wish to build their own aircraft have little or no experience with respect to
aeronautical practices, workmanship, or design. One source for advice in such matters is the EAA (see
appendix 1 of this AC). The EAA is an organization established for the purpose of promoting
aviation safety, construction of amateur-built aircraft, and providing technical advice and assistance to its
members. The EAA has implemented the Technical Counselors Program to assist in ensuring the safety and
dependability of amateur-built aircraft. EAA Technical Counselors are sometimes available to visit an amateurbuilt
aircraft project and offer constructive advice regarding workmanship to EAA members. The EAA has
advised the FAA that it will not provide technical assistance to the builder in designing an aircraft.

b. Amateur builders have adopted a practice of calling upon persons having expertise with aircraft
construction techniques to inspect particular components (e.g., wing assemblies, fuselages, etc.) prior to
covering, and to conduct other inspections as necessary. Those persons include EAA Technical Counselors,
persons with aviation design and/or engineering experience, mechanics with aircraft, airframe, and powerplant
experience, and other aircraft builders. This practice has proven to be an effective means of ensuring
construction integrity and an acceptable level of safety.

I recommend it, and it's free - but pizza and drinks are always appreciated...
But I'm also biased, being a TC....

If no TCs are in your area, a friendly A&P can provide a second set of eyes before you close up assemblies.

A DAR, technical advisor, or any other inspector should not sign anything untill the airworthiness inspection. When you have someone look at your work, YOU should note in your builder's log that "Joe Blow, technical advisor, A&P, experienced builder, or whatever, inspected my project on this date and had the following suggestions......." This is what the airworthiness inspector wants to see. The standard is a minimum of 3 progress inspections. Personally I like to see at least 5. These progress inspections are not required but, they will give the inspector a "warmer" feeling.

The EAA TC program is free to EAA members. As a member, why wouldn't you take advantage of it, even if it has no bearing on insurance or certification? The more experienced eyes looking at your project, the safer it will be. Besides, you are not required to do anything in response to anything the TC tells you. That is, if he or she "recommends" that you change something or improve something, there's no rule saying you have to do it.

On the flip side, I just did a TC visit last weekend where the builder told me he had a local A&P check his work. The A&P had no comments, didn't find anything that needed attention. I found a whole handful of things -- nothing major, but still.

I've heard the same thing about some other TCs, not just A&Ps. The EAA provides a "visit report form" that the TC and builder fill out, and there's a big comments field at the bottom. I hear some TCs just leave that blank. I usually fill it out with all the little stuff that came up. That way the builder has a record (for his or her builder's log) of the visit and what came out of it.

There's definitely some variation in the level of attention you get from TC to TC. Some are nit-picky, and others gloss over things and give you a pat on the back -- don't get me wrong, there's something to be said for that. If you don't agree with what one TC tells you, or if you feel the TC hasn't paid close enough attention, get a second opinion!

As a TC I fall on the "nit picky" side of the fence. While trying to be tactful, my goal is to help the builder produce an airplane that is as safe and reliable as humanly possible. I don't focus on rivets as much as I do on items that will create maintenance or reliability issues. I try to keep up with what the top quality DARs are looking for, and I try to uphold their standards...so that when the DAR shows up, it's wham-bam-thank-you-maam.

In any case, the TC service is just that: a service to you that costs you nothing if you're a paid EAA member. The EAA kindly doesn't place any limits on the number of visits you can have. Take advantage of this!

dan said:

I try to keep up with what the top quality DARs are looking for, and I try to uphold their standards...so that when the DAR shows up, it's wham-bam-thank-you-maam.

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How about a TC that is also a DAR? Periodic checks, TC reports included with your log, so that at inspection time, he's already familiar with your project and see's his own signature on the TC visits! Talk about a slam dunk...hopefully. Hi Mel!

IMO, if you're an EAA member, this program is really a no brainer.

Joe

I am new at this and have had little training. That is why I wanted someone to look over my work. Working in flight testing for our military has shown me that the more eyes that look at things, the safer and less of a probability of failure you will have. So I will take advantage of it, but as someone said, if I don't agree I don't have to comply and can always ask for a second opinion.

The TC has an option too....

AX-O said:

So I will take advantage of it, but as someone said, if I don't agree I don't have to comply and can always ask for a second opinion.

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I'm not sure about Dan, but remember that the TC also has the option of not coming back... we are unpaid volunteers after all.

If you don't want to comply with what a TC might consider a safety or workmanship item, don't expect a return visit.

I can thankfully say that this has never happened to me, and the things I find while inspecting (I'm a nit-pick like Dan) are welcomed by the builder and are corrected pretty quickly....

gil in Tucson

az_gila said:

I'm not sure about Dan, but remember that the TC also has the option of not coming back... we are unpaid volunteers after all.

If you don't want to comply with what a TC might consider a safety or workmanship item, don't expect a return visit.

I can thankfully say that this has never happened to me, and the things I find while inspecting (I'm a nit-pick like Dan) are welcomed by the builder and are corrected pretty quickly....

gil in Tucson

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Thank you for the advice. I would comply without a question if it was a safety issue.

dan said:

He is absolutely correct that 7220 and most of the self-etching non-epoxy rattle can primers are not sealers. They don't do 100% of the job when working alone (i.e. without paint). They are intended to take a top coat of paint. A 2-part epoxy primer such as AKZO will seal the material and function standalone.

However...

Take a look at what Van's uses for primer on quickbuild kits. It's a very light coat of a translucent wash primer. That, just like your 7220, is also not a sealer. If it's good enough for Van's (and remember, these kits cross oceans...salt water air abound), is it good enough for us?

In my opinion, the biggest reason to prime is to keep water from contacting two mating surfaces. No, 7220 or GBP988 or Mar-Hyde don't seal the metal, but if water got in between a flange and a skin or spar web, the "half ***" primer would actually do a pretty "whole ***" job of isolating metal-to-water-to-metal, and imho serves the purpose.

If you leave your airplane underwater for long periods of time, all bets are off.

Click to expand...

Dan:

(This is in response to your input about primer--back in March '05)

Regarding the AKZO 2-part primer---

(1) How did you prep the parts before spraying the AKZO primer? Alumaprep and then alodine; something else?

(2) How would you describe the thickness (i.e. viscosity) of the mixed AKZO primer? I ask because I'm considering buying an inexpensive Wagner HVLP sprayer at Lowes (the FineSpray 2400, for $98) to do spraying of primer. It's only rated for lacquers, varnishes, oil-based enamels that can be thinned, etc. Any recommendations here?

Thanks!

22Tango said:

Dan:

(This is in response to your input about primer--back in March '05)

Regarding the AKZO 2-part primer---

(1) How did you prep the parts before spraying the AKZO primer? Alumaprep and then alodine; something else?

(2) How would you describe the thickness (i.e. viscosity) of the mixed AKZO primer? I ask because I'm considering buying an inexpensive Wagner HVLP sprayer at Lowes (the FineSpray 2400, for $98) to do spraying of primer. It's only rated for lacquers, varnishes, oil-based enamels that can be thinned, etc. Any recommendations here?

Thanks!

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See here: http://www.rvproject.com/primer.html Everybody has a different method...that was just my personal method. And it's a method I'll never use again.

Sprayer-wise, AKZO is fairly thin when properly mixed. FWIW, I just used a cheapo $19 touch-up spray gun from Harbor Freight (pictured on that link above).

First, if you intend to stay in the Ridgecrest area, 40 miles from Death Valley, you probably can do just fine with no primer at all--after all, where there is no water, there is no corrosion.

Secondly, a couple issues back in the RVator, they reported the results of a little experiment they did, putting 3 pieces of aluminum outside under a stairway for about a year, if I remember correctly. Also, if my memory is right, one had no primer, a second had a wash primer(?) and I think the 3rd had an epoxy. Anyway, the result after being putside for an extended time exposed to Oregon weather (40-50 inches of rain, mostly between October 1 and June 30) was that the unprotected piece had some slight corrosion and the 2 primed pieces showed none, suggesting that a minimal level of protection should do fine in most environments. Don't anybody apply these results to salty areas, however.

See, here's where all those "left outside for X months" experiments go painfully wrong. They leave out single sheets or pieces of aluminum, but I haven't heard of a test where MATED SURFACES are left in moisture or moist environments. Imho, it's the mated areas where corrosion is most likely to appear.

I'm not saying you need to use primer. Just making an observation.

Thanks, Dan.

Appreciate the link to the info on your website, and the input on the AKZO.

OK, I'll bite: WHY is the prep method you used one you'll never use again? Seems like you're saying after all was said and done, you don't feel it was really necessary to use the alumaprep and alodine before spraying AKZO primer; just the alumaprep?

I'm just getting started and am cleaning out & setting up shop; ordering a -9A empennage in February. I really appreciate your website.

Kevin
N4822T (reserved)

Mel, You mentioned you like no less than 5 inspections. Can you tell me what are the best stages to request these visits? I'm sure one would be before the empennage sections are closed but when are the best times to conduct the next 4?

I appreciate any advice you can share.

22Tango said:

OK, I'll bite: WHY is the prep method you used one you'll never use again? Seems like you're saying after all was said and done, you don't feel it was really necessary to use the alumaprep and alodine before spraying AKZO primer; just the alumaprep?

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No, I still think the etch+alodine is the best treatment prior to shooting AKZO. It's just that you'll never again see me etch+alodine+AKZO anything. I use self-etching primers now...and I'll only prime mating surfaces. Self-etching primers such as GBP-988 or SEM are definitely inferior to e+a+A, but they're good enough for my needs!

praterdj said:

Mel, You mentioned you like no less than 5 inspections. Can you tell me what are the best stages to request these visits? I'm sure one would be before the empennage sections are closed but when are the best times to conduct the next 4?

I appreciate any advice you can share.

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I like to get one inspection in when the project is first started. That way we can catch any initial problems before they get too far along. After that the tech counselor can judge when the next inspection should be. If your workmanship looks good, he may say, "Call me before you close the wing." Some builders need a little closer guidance than others. But, regardless, always feel free to call him if you have a question or problem. That's what we're here for. The last TC inspection should be during weight & balance and just before the airworthiness inspection.

How do you seal 7220?

I moved from dry California to wet humid Florida. I am using the NAPA 7220 self-etching primer. What can be used to seal this primer. I would be doing the sealing on surfaces that are mating.

Thanks

Jonathan

Noooooooo, not the primer wars...

Anyway, on both topics. I usually use zinc chromate (WEAR A MASK or Respirator!) on ribs, and stiffiners, and go bear on the skins and other alclad parts that haven't had the snot bent out of them.

As for the inspections... Mel/Dan any idea on what would be a good point for a first visit? I've got my HS and VS done, working on the elevators since I messed up the Rudder stiffiners (cut the wrong sides... darn prepunched kits). Obviously i'm an A&P, but still would like another opinion.

osxuser said:

As for the inspections... Mel/Dan any idea on what would be a good point for a first visit? I've got my HS and VS done, working on the elevators since I messed up the Rudder stiffiners (cut the wrong sides... darn prepunched kits). Obviously i'm an A&P, but still would like another opinion.

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Oops, too late. Just kidding. But right before you close up your HS is the best time for your first visit. That way if anything needs attention, you have full access.