priming tail feathers

[airman]

Do I need to prime and paint my 4130 tail feathers and fuselage. I am building a double eagle.

[Jeff Point]

Yes, the bare 4130 will rust under the eventual fabric covering. Not only can this weaken the structure but will show through the fabric and paint.

There are a million opinions on which primer is best to use. My vote is Stewart Systems Ecoprime, top coated with Ecocrylic prior to fabric covering. That's what I used on my 4130 tail feathers prior to fabric.

[airman]

I am planning on painting with poly fiber. Is stewart system easy to apply? I have used the fabric glue and that was easy.

[Jeff Point]

If you are going to use Polyfiber then I would start with their epoxy primer. Unless you really, really know what you are doing it is important to stick with one system all the way through from primer to top coat. I prefer Stewarts based on ease of use and less noxious odor.

[Matt Gonitzke]

+1 for Jeff's advice...the chemicals in Poly-Fiber will likely readily dissolve the Stewart Systems paint.

[airman]

I have used polyfiber several times with no issues. Have herd stewart system is hard to get perfect. Air temp and mixing the paint has to be right on. Also thanks for the help.

[Tom Downey]

IMHO the Eco-Prime is their best product. it is thinned with water, what you don't use goes back into the can, and the equipment cleans up with soap and water. After it is applied and dried nothing effects it. Epoxy stripper won't remove it.

When the Eco fill is on, and dried you can use any top coat you desire. it will not lift the eco-fill.
Amateur Home built aircraft builders are not required to adhere to the STC instructions.
I have 1 aircraft that has Stewarts system up thru the Eco-Fill and top coated with Randolph Ura-? from Aircraft Spruce. It has sat outside for the last 5 years, and still looks new.

[Tom Downey]

+1 for Jeff's advice...the chemicals in Poly-Fiber will likely readily dissolve the Stewart Systems paint.
Not true.

[crusty old aviator]

Eco-prime's good stuff, but you have to lightly fog on the first few coats or it may form an alligator hide texture, even after cleaning it as instructed. Polyfiber is vinyl based and uses MEK as it's main solvent, which dissolves almost everything it's sprayed on, so I can see how Matt jumped to that conclusion. However, Stewart's uses lacquer thinner to clean up their system with, once it's dried, so maybe the MEK in the Polyfiber topcoat won't affect it. However, Stewart's, being water borne, relies on mechanical attachment of one coat to another. Polyfiber relies on chemical attachment, using the MEK as the solvent to facilitate that bonding. So I would recommend using Polywollydoodlefiber all the way, even though Stewart's is an awesome primer.

[Matt Gonitzke]

Clarification: By paint, I meant "Topcoat". My friend had to do a repair on his bird that is finished with Stewart Systems, and I'm 99% sure he used MEK to strip the topcoat off. Unless they changed something in the 3 years since I painted my glider, there was no mention of cleaning anything up with lacquer thinner.

[Jeff Point]

Not true.
Yes it is true, although not quite well stated. I think what Matt meant, and certainly what it true, is that the MEK in Polyfiber will not work with some components of Stewarts. While it might not dissolve a cured top coat, for example if one were to apply Polybrush over fabric that had been glued with Stewarts, you would certainly have problems. That is what I meant when I said "unless you know what you are doing..." I know of at least one certificated aircraft manufacturer that uses Stewarts glue (actually just the 3M product) and uses DuPont products over it through top coat- so it can be done.

To the OP- I see you are in Illinois. I'm in Wisconsin- Milwaukee specifically, and I'm painting an aircraft with Stewarts right now if you want to visit and see it in action. PM me for contact info.

[turtle]

I have used polyfiber several times with no issues. Have herd stewart system is hard to get perfect. Air temp and mixing the paint has to be right on. Also thanks for the help.

You have heard correct.

I've had the displeasure to repair a few planes done by the book with Stewarts. Ringworm, peeling, cracking, blisters full of water, etc.. The most disturbing part was the amount of rust on the tubing for having been recovered a few years prior. Unfortunately, with Stewarts, it can look perfect in the beginning but fail within a year or two.

[crusty old aviator]

Well, that's disappointing! I just covered a set of Champ tail feathers with Stewart (and they do specify using lacquer thinner for cleaning up anything dried and cured, especially in the spray gun, but no mention of MEK), so hopefully it will still be looking good when my warranty expires! This was such a humid summer, I used Stewart, at the owner's suggestion, instead of nitrate & butyrate dope.

What manufacturer is using 3M Fastbond?

[Jeff Point]

I won't argue with your observations but I dispute the "by the book part." If those kinds of problems resulted, clearly something wasn't done properly.

[1600vw]

I won't argue with your observations but I dispute the "by the book part." If those kinds of problems resulted, clearly something wasn't done properly.

I have to agree. I did some repairs 5 years ago on my airplane using the steward system. I also used a rattle can to repaint the repair. Jump to 1:15 mark on this short video and I show this repair that was made 5 years ago. You will see I beat on this repair. No cracks or ringworm in 5 years and around 200 hrs of flying time.

This repair was so simple it was funny. I did a few repairs but this was the only one I showed. i could show another under the horizontal on the rear. She had a hole on her when I purchased the airplane. Someone crawled under the airplane with a screw driver in their pocket and ripped the fabric. I put a 4x4 patch over this and then repainted. I used the steward system on this and all repairs on this airplane. Amazing how it has held up. i repainted with auto paint put into a rattle can that was a two part mix. Meaning it needed hardener mix with the paint to work. This is done with a button on the bottom of the can.

If you watch this from the beginning I repaint parts of this airplane using this rattle can. I am very pleased with the results and others have told me she looks much better. I must agree.

https://www.youtube.com/watch?v=tDWqJn_x4e4

In order to remove the tape without damage to the paint. I sprayed the tape and paper with water. Let it sit for about 5 mins then it came right off. Almost fell off. There was a couple area's I used a vinyl tape and water would not soften this. In these area's I did have problems with the paint wanting to lift. But I used this in such small amounts around really sharp curves it was not a problem. But if I do this again I will not use this vinyl tape.

[turtle]

I won't argue with your observations but I dispute the "by the book part." If those kinds of problems resulted, clearly something wasn't done properly.

That's something the typical Stewart apologists say. "You had a failure? You must have used a different revision of the exact spray gun than the one in the videos / humidity wasn't exactly 72.521579% / painted on a Thursday / worn the wrong color shirt / etc."

Nothing changes the fact that you are spraying water on a bare metal part and hoping it evaporates before the paint / primer skins over and entraps it. Then you are encasing it in a polyester bag, brushing more water through it and hoping the back side somehow evaporates through your tiny little drain holes.

In less than ten years, the Stewarts have had to revise the manual many times, change how it's applied and change the product formulas. All due to very few customers having any success. You'd buy all the materials, follow the instructions, have some weird failure during application, then a new "fix" would come out and you'd have to recover the part from scratch at your own cost. When confronted with blisters and water bubbles appearing years later, they admitted themselves that the product was hydrophilic.

No wonder the Stewarts sold it off to some other sucker. I bet they wish they could remove their name from it as well. The last few years at their booths they looked like they were getting worn down answering support questions.

[Kyle Boatright]

Nothing changes the fact that you are spraying water on a bare metal part and hoping it evaporates before the paint / primer skins over and entraps it. Then you are encasing it in a polyester bag, brushing more water through it and hoping the back side somehow evaporates through your tiny little drain holes.

How is that different from any of the solvent based systems? Isn't the only difference the carrier or solvent?

[crusty old aviator]

I won't argue with your observations but I dispute the "by the book part." If those kinds of problems resulted, clearly something wasn't done properly.

I assumed I had strayed from the book, too, but the nice folks at Stewart said that it happens when the first couple of coats are fogged too heavily or when the primer is too thin. It had nothing to do with my prep work. You have to barely fog on the first cross coat, just enough so you change the shade of what you're spraying. I fogged along the lines of what the goomer in the video does: way too heavy! I also thinned it so it drained out of the Zahn #2 cup per the video and instruction sheet. The whole exercise is just another reminder that with airplanes: it's never easy!

[DaleB]

How is that different from any of the solvent based systems? Isn't the only difference the carrier or solvent?
The difference is that the carrier in the Stewart products is water, which will rust steel, versus other solvents which won't. That's just my observation. I used Ekoprime on the RV-7 I was building, but only on the aluminum parts. Steel parts got a shot of rattle can SEM self-etching primer. The Ekoprime took a while to reach its full cured hardness. It was pretty soft for the first few days but toughened up after a while. It was easily removed with MEK, acetone, or reducer for acrylic enamel.