Stewart Systems Alternates/substitutes

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Mohawk750

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Hi All,

I've been reading here for a while on fabric covering systems. I used the Stewart System 20 years ago to recover my Taylorcraft (since sold) and the fabric and finish has held up spectacularly well as the aircraft has been hangared it's entire life. I used the Ekobond and Ekofill and top coated with Sikkens polyurethane.

I suspected at the time that Stewart didn't formulate its own coatings and just rebranded some existing products. It seems common knowledge now on this board that the Ekobond fabric cement is in fact 3M 30-NF Fastbond Contact Adhesive.

I'm wondering if anyone has cracked the code on the carbon black Ekofill product and the water based top coat systems they are using?

Thanks for your input, Mark
 

Built2Fly

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That's very interesting.

I looked up 3M 30-NF. It says that it is best for wood, formed plastics, veneer, and canvas. This means that the fabric to frame tube gluing is not what's holding it up. The wrap up fabric-to-fabric overlap is what gives it the strength.

Also it does not say anything about heat activation with 3M 30-NF. How certain are we about that EkoBond is 30-NF? Or is heat activation just another gimmick marketing?

Thanks for the information.
 

rv7charlie

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MSDS for the two products are very similar, though not identical. They do seem close enough to me to wonder if the differences could be explained by Stewart rewording the ingredients list.
https://multimedia.3m.com/mws/mediawebserver?mwsId=SSSSSuUn_zu8l00x4xtvPYtSlv70k17zHvu9lxtD7SSSSSS--
https://www.aircraftspruce.com/catalog/pdf/09-41200msds.pdf

On the question of the carbon black, are you talking about UV protection? If so, are you familiar with the widespread use of 'latex' (actually acrylic) house paint on fabric? I recovered a Kolb Twinstar using the brand name Stewart glue, but all finishing techniques were based on the very helpful Weinerdogaero web site.
That gentleman presents forums at OSH every year, and has covered/finished multiple a/c using the technique. As a heads-up, the guys who have done real 'homework' on the issue say that white exterior 'latex' primer actually has superior UV blocking ability to black. I was very impressed with the technique. I hate painting, but got what I consider very good results as a 1st time fabric finisher. I didn't go nearly as far in polishing as the site details, and I got a finish that at least equals typical fabric finishing techniques. My covering is only 3 years old, but many others are flying planes with many more years on their finishes. Our own Ron Wanttaja has done it:
ISON Tandem AirBike Builder's Log -- Latex Paint Pt. 1
Painting a Fly Baby With Latex Paint - Fidoe

Charlie
 

Mohawk750

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Well yes, I am familiar with the wienerdogaero site, At least I read the whole thing last night. I did read that white apparently has more UV block than black but then I also read of others using aluminum pigment latex paint as base coat as well. I found a product like this with 14% aluminum content.

But really I'd still like to know what Stewart is using for UV blocker. They call it Carbon Black and it may be as simple as carbon powder added to clear 3M N30 because I think it may be.
 

Built2Fly

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I just went through the wienerdogaero presentation video at EAA this afternoon. It is very interesting. Here (PDF from EAA Chapter 54) is the newsletter of the gentleman who did the UV study which found that white blocks more UV than black.

Another finding is that on Aircraft Spruce, in the answers for EkoBond, it is clearly stated that the glue is not temperature activated, but just being melted a bit for the fabric to tack on. That answered some of my questions above. It is just a glue that attaches fabric to fabric, not fabric to tube.
 

TFF

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The question is do you want to absorb or reflect UV? The next question is how good does it need to be for you? A FAA STC covering system is technically good forever. That is how the FAA looks at it. Drive out of the Anchorage airport terminal and there are 500 tied down fabric airplanes. Looks like a mall parking lot at Christmas They are not in hangars. Every day for 20 years probably if not more.

Is your homebuilt going to live that life? No. It’s going to be in a garage, hangar or covered up. A homebuilt that flew 1000 hours and stored inside has been in the sun the same as a plane on the ramp for about 83 days if a day was 12 hours long of sun. Yes that’s taking it far, but if you stop 80% UV with something, it’s going to last a long time.

The test if you have enough of silver with Polyfiber is you put a flashlight on the outside of the silver. If you can’t see the light , you are good. Not saying you can’t have UV transparent paint, but I doubt you grabbed some. The question comes is how thick does it need to be to get where you want? That decides if it’s worth going cheap or not.

Fabric glued to a tube usually has to wrap around an inch from first contact, so you have to glue to a tube somewhere. Leading edges are between 2 and 3 inches. It creates a bag of sorts, but the bag can’t blow away either. That is of course unless you want to sew it together instead of glue.
 

Dan Thomas

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I used the black latex for UV on my Jodel, with white latex over it as a base for the yellow. Yellow doesn't cover darks well at all. Topcoated with DuPont automotive urethane with a flexant added. I wouldn't do it again, it was cracking after ten years and was shot after 20, and only the last five of those years was it parked outside. And the job was considerably heavier than if I had just bought Poly-Fiber and done it right. Wouldn't have cost much more. Would have lasted much, much longer.
 

rv7charlie

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It's worth noting that virtually all paint mfgrs warn against using other systems either under, or over, their products. Dan, did you have anyone else on record saying they'd had good luck putting automotive urethane over latex primer, on fabric? I'm surprised that automotive urethane wasn't *more* expensive than even Polyfiber.

Others using latex over latex (actually acrylic over acrylic) exterior house paint are reporting far better results. I don't have my numbers handy, but I found the weight gain in my Kolb using latex was at least as good, if not better, than traditional dope products.

Charlie
 

Kyle Boatright

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Others using latex over latex (actually acrylic over acrylic) exterior house paint are reporting far better results. I don't have my numbers handy, but I found the weight gain in my Kolb using latex was at least as good, if not better, than traditional dope products.

Charlie
The difference is that certified coatings have been tested and those tests should be a good indicator that the coverings will stand up on the ramp for 20 years. Latex paint or whatever non-certified process we use may work as well, heck it may work better. But there is little or no testing to tell us that. We're left to anecdotes on message boards and in presentations at Oshkosh. As another poster noted, if an airplane is hangared, its non-certified coating will get a fraction of the abuse an aircraft sitting on the ramp will see. So, latex may be a 20 year solution for a hangared aircraft, which is great. But would it last 20 years on the ramp? Probably not. I know the paint on my house is good for ~8 years and it doesn't suffer the flex and other abuse the fabric covering on an airplane will. I seriously doubt that paint would hold up well on an aircraft tied down on the ramp.

I'd have no problem using latex paint on an aircraft that's hangared. Otherwise, I'd probably go with a certified process.
 

rv7charlie

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The acrylic latex on my house has been there since I applied the siding, about 20 years ago, and it's still in good shape. I doubt that I'll ever need to repaint it. But...the siding isn't wood. It's fiber-cement, which doesn't have any of the issues that cause paints to release from wood substrate. I'd concede to 'maybe' it isn't a 20 year ramp solution, but are traditional a/c finishes 20 year ramp solutions? Most would say no, even on metal a/c. Most are chalky and thin or flaking off well shy of 20 years.
 

Dan Thomas

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The acrylic latex on my house has been there since I applied the siding, about 20 years ago, and it's still in good shape. I doubt that I'll ever need to repaint it. But...the siding isn't wood. It's fiber-cement, which doesn't have any of the issues that cause paints to release from wood substrate. I'd concede to 'maybe' it isn't a 20 year ramp solution, but are traditional a/c finishes 20 year ramp solutions? Most would say no, even on metal a/c. Most are chalky and thin or flaking off well shy of 20 years.
Your siding also isn't laid horizontally. It doesn't get the most intense heating and UV at noon. It doesn't have snow and water and hail and pollutants landing and laying on it. Birds don't poop on it. It doesn't get 100+ MPH winds hammering at it. It doesn't flex much.

I used the latex process because I was on a severely restricted budget at the time and others had used it, but they were recent users. There was no long history of it to evaluate longevity. And yes, the DuPont urethane was more expensive than Poly-Fiber topcoats, and I had to use a lot since it was yellow. Yellows don't cover well and haven't done so since the lead was taken out of them. Poly-Fiber recommends white between the silver and yellow topcoat to avoid having to apply too many coats of yellow.
 

rv7charlie

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I thought you were talking about urethane over latex primer (instead of latex over latex, as recommended in the links I offered). Apples vs kumquats. Yellow latex covered grey primer (on the metal parts) for me without any issues at all; I can't address coverage with urethane.

Kolb complete.jpg
 

proppastie

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If its hangered do you need to finish it? The original Carbon Dragon was un finished to save weight....Of course it is no longer with us. Read somewhere it deteriorated.
 

rv7charlie

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If its hangered do you need to finish it? The original Carbon Dragon was un finished to save weight....Of course it is no longer with us. Read somewhere it deteriorated.
Well, there's your answer. ;-)

Seriously, very few hangars shield their contents from UV well enough to expect any protection, and deterioration will happen pretty fast even with limited flight time, anyway.
 

Kyle Boatright

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Seriously, very few hangars shield their contents from UV well enough to expect any protection, and deterioration will happen pretty fast even with limited flight time, anyway.
I don't know what your hangar is made out of, but mine is made of steel and excludes 99.9% of UV and ambient light if the doors are closed. ;-)
 

rv7charlie

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GA's climate isn't that different from MS. I suspect that you have windows, and I'm pretty confident that you have at least one really big door, as well. Maybe yours is air conditioned and you only open the door long enough to get the plane in/out, but I'm poor (and cheap); my hangar door is open most of the day, almost every day, in all but winter months. I haven't yet found a filter that stops UV and freely admits air flow. ;-)
 

Kyle Boatright

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GA's climate isn't that different from MS. I suspect that you have windows, and I'm pretty confident that you have at least one really big door, as well. Maybe yours is air conditioned and you only open the door long enough to get the plane in/out, but I'm poor (and cheap); my hangar door is open most of the day, almost every day, in all but winter months. I haven't yet found a filter that stops UV and freely admits air flow. ;-)
It is just a big steel box. I *wish* it had skylights or windows. The only time the airplane sees sunlight, UV, or any of that is between when the hangar doors open as I'm pulling it out to fly until I put it away afterwards.
 

proppastie

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I think UV is direct sunlight. ...in shadow no UV?
And perhaps the wood of the original Carbon Dragon was not varnished to save weight and moisture got to the wood/glue
 

rv7charlie

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Convenient link:
The shady truth about shade - Health & Wellbeing

"It turns out not all shade is equal, and even if you spend long hours out of direct sunlight, you can still receive quite a lot of UV. This is because ultraviolet radiation reaches your skin in two ways:

  • directly, as radiation from the sun,
  • indirectly, as radiation that's been reflected from the atmosphere above, and/or bounced back from surfaces such as sand, concrete or even grass."
 

WarpedWing

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In planning for the finish work on our Ridge Runner 3, my brother in-law and I have been doing quite a lot of research on the use of latex. We wanted to get away from the toxic, hazardous and expensive spate of systems currently used (our pocket are not bottomless). During our research I made a call to Sherwin Williams and spoke to a gentleman in their product development team.

It turned out that the gods of fortune seemed to be smiling down upon me that day. The guy was himself a builder. He had a Kitfox and understood what questions I was going to ask. He was very helpful. The main takeaway I got from him, was to use the best premium latex product I could find (of any mfr) with the highest concentration of "Titanium Dioxide". It is TiO that is the main source of UV protection. He further stated that in the primer coat, we should add TiO to further increase its effectiveness on fabric protection. It is not expensive at all and I have a small package ready to mix and use when we get to that point in our build. I will post here our experience in using it.

just an fyi ...
 
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