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Observations on Stewarts System

W

wdoubleday

Registered User
Just spent the last week getting my first experience with the Stewarts System by covering the horizontal stabilizers on my Javron cub. To spread out the costs and stage the delivery of materials, they sent me all supplies needed to cover the tail surfaces with manuals and detailed instructions.

From what I can tell from research, the fabric cement Ekobond is neoprene based, very similar to contact cement. Pretty impressive that you can formulate an aqueous solution of a hydrocarbon polymer that is easy to apply with no odors at all. My big learning so far is that the initial bonding of the fabric to a painted tube structure is obviously critical, but requires a thicker coating of Ekobond to the stucture, sufficient drying time, and an iron heated to at least 250 F. I’ve used the blanket method and covered the bottom first. The instructions have you wrap the fabric around the outer perimeter structure and rub the fabric with your hands to get the initial stick, then follow up with the iron to liquify the glue underneath and allow it to permeate into the fabric. You should see the glue discolor the white fabric. This is where I am finding out that if you don’t have a sufficient first coat of glue or not a hot enough iron, this will cause problems when you then apply a brush coat of Ekobond on top of the fabric followed by a paper towel wipe to remove excess and fill he fabric weave. I’ve had several frustrating moments that at this point the fabric loses adhesion underneath and lifts off the structure. I then get into a messy fix by applying the iron to the glue soaked fabric when it’s wet to try and get it to stick.

Sorry for the long post but has anyone else had the same experience with Ekobond?

I’ve attached a picture of this initial glue joint.
 

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I have had zero problems with adhesion by assembling wet. Not absolutely sure the heat improves the bond, although I use heat to smooth the pinked edges. You can probably figure out what is in the glue by comparing it to 3M-30N.

I love the Ekofil, and am not at all sure about my ability with top coats. I should get some experience in 2018.

These expensive coatings have a short shelf life - Ekofil seems to have the longest, but don't let it settle or you will be stirring forever.
 
Just finished covering a set of wings with the Stewart system. I would not put an iron to wet glued fabric. I would just wait for the glue to set on any areas that have lifted. Pressure to the fabric will cause the glue to stick like contact cement. An iron applied to the area helps the adhesion.
 
When I teach a covering class, I show a little different method than in the picture. Before saturating the fabric with Ekobond like in your picture, I instruct to run the iron along the edge to set the fabric and than cut the fabric so it will wrap around the inside of the tube. Like Jim said, only iron after the glue has completely set up or it will not stick properly. I also teach to apply the first layer of glue on the frame below the inside tangent point of the fabric. This way, you can cut the fabric so it will attach inside the frame well below the tangent point. The fabric winds up to be about 270 degrees around the tube and is cut just above the fabric inside the frame. Use the iron than to secure the fabric inside the tube before you apply the second coat to saturate the fabric to the tube. Use the paper towel like you mentioned. The strength of the joint is not where it attaches to the tube. The "certified joint" is the 1" overlap of the fabric from the second side around the tube. On a 1/2" tube this is tangent point to tangent point. On a 3/8" tube, the 1" point is past the tangent point to establish the 1" overlap. After the second side is glued and shrunk around the corners, a final application of glue out to the tape line is applied and wiped with the blue paper towel. Hope this makes sense; sometimes it's difficult to follow without seeing it done.
Marty
 
Sounds like the glue is not quite dry yet, or maybe you don't have enough glue initially applied. I often will do two coats on the frame for just that reason. The temperature in your shop makes a big difference as to how the glue will dry, make sure you're warm enough. Cut those tails off the excess material before your final wipe, will make it easier. If you do get some minor lifting on the inside of the tangent no worries, let it all dry and nail it down with the iron.
 
Thanks everyone for your suggestions and advice. Much appreciated. Marty, I will try your suggstion on the elevators. I ended up not trying to iron down the wet glue and let it dry to the touch, then hit it with the iron. I finally got one of my stabilizers done. Used the modified Staggering knot at 2.5 inch spacing. Looking at the big parts like wings and fuselage with much trepidation, but it’s one step at a time, one skill at a time to build an airplane, and lots of coffee!
 
wdoubleday said:
Thanks everyone for your suggestions and advice. Much appreciated. Marty, I will try your suggstion on the elevators. I ended up not trying to iron down the wet glue and let it dry to the touch, then hit it with the iron. I finally got one of my stabilizers done. Used the modified Staggering knot at 2.5 inch spacing. Looking at the big parts like wings and fuselage with much trepidation, but it’s one step at a time, one skill at a time to build an airplane, and lots of coffee!
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Best way to cover with Stewarts is to do two pieces at a time. Apply the glue to one and move on to the next. After glue is applied to second piece the first is dry and ready to apply the fabric. Fabric is always applied after the glue is dry. If you find an area where you didn't apply enough glue, apply more and move back to the second piece you are covering. The back and forth process ensures that you give the glue time to dry before applying heat to any glue joint.
Marty
 
I really like the Stewart System and use it all the time. After a while it will all make sense as to what step to take when and your speed will pick up. Kinda sounds like your rushing the glue, also if your tacking the fabric down on metal you may need to turn the iron up . Remember that your not trying to get the fabric to stick all around the tube at first just a 1/8"-1/4" line that shows thru and the fabric is stuck.
Most important if you don't have the DVD's buy them before you do anything else. You'll save the cost in wasted materials, time and frustration. Also you'll get a much better job. Watch the one that applies to where you are.
 
They key to good looking fabric is the same as flying IFR. The farther ahead you are thinking the better. I routinely have 2 or even 3 irons running, and one is always a monokote style iron that heats all the way up the tip and on the topside of the shoe. That iron gets the inside of the tubes rickety split.
On pieces like the tail feathers I tack it down all the way around the outside of the tube (just a pass) and then take a compass or dividers to scribe an even line around the fabric that's running long. A quick slide of the shears and you now have an even line cut all the way around the inside of the frame. I too run it a 270 around the tube. Don't get it under the first panel or it will show. Don't make squirrelly cuts thinking the next piece (or a tape) will hide that, because it will still show under those, unless you are using bondo for paint. After you have it trimmed, Iron the piece down all the way around, including everything inside the tubes.
A couple more pieces, and I think you will find Stewarts to be the easiest thing out there. At least maybe short of Oratex. Also, I agree with the post above, tacking pieces down the tube acts as a heat sink and routinely takes more oomph than you'd think

Take care, Rob
 
OK this covering system is starting to make sense. I made sure to brush on a sufficient coat of Ekobond and let it dry for 20 min before I stick on the fabric. Also jacked up the heat a bit on my irons. When I welded up the stabs and elevators, i did not do them together to ensure alignment of the ribs, so a couple are off-set a bit and one not parallel. I compensated with the tapes that cover the rib stitching so at least the tapes are aligned. Thanks again for your help. This is great website.
 

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Very nice looking job. Now the ekcofill , the brush coats should go on thin and worked into the fabric. Not trying to build up the layers at this point, just trying to work into the fabric.
 
algonquin said:
Very nice looking job. Now the ekcofill , the brush coats should go on thin and worked into the fabric. Not trying to build up the layers at this point, just trying to work into the fabric.
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i thought the new manual says the whole piece must be brushed with ecobond? before the ekofill?
 
Careful of those dark lines on the edges of your tapes. If it's not all wiped through the fabric it will show through the top coats
 
Didnt see that in my stuff. Hope not did three airplanes with ekofill straight on the fabric. I'll look it up tonight. Thanks, Tom
 
algonquin said:
Didnt see that in my stuff. Hope not did three airplanes with ekofill straight on the fabric. I'll look it up tonight. Thanks, Tom
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When I became involved with this system in the mid 90's ( I wound up being part owner) the procedure was to seal the weave with diluted Ekobond. When Stewarts finished the STC process, they went to just brushing Ekofill into the weave. The current owner of the system has gone back to diluted Ekobond as a weave filler, yet retained the option to use Ekofill. So you're both right...it can be done either way.
John
 
Just read the new manual, so I'm OK but would also like to know the reason, thanks Tempdoug I hadn't seen the new manual. I have the whole set of tail feathers and controls covered ready to prime and will hold off until this is cleared up.
 
tempdoug said:
and the reason is???
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The manual says the first coat of Ekofill is to be applied to damp fabric so it will penetrate down into the weave and then the subsequent coats adhere. Apparently for some people, it is hard to define "damp", and they applied the first coat to dry fabric, it didn't penetrate into the weave and the coats of Ekofill and Ekoprime and the top coat would separate from the fabric. It is easy to define diluted Ekobond. I still apply the Ekofill to damp fabric and have been getting good results. With the diluted Exobond, my understanding is that if you happen to iron the fabric with the diluted Ecobond applied and you pass the iron over an underlying structure, it may attach. I don't know if that is a real problem, but according to my wife, I never change anything anyway.
 
I may just stick with the Ekofill , it's working very good for me. Also I've been shooting top coats right on the Ekofill without the ekoprime. What's you feelings on that. I like the system but am concerned that I put out first rate work.
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algonquin said:
Didnt see that in my stuff. Hope not did three airplanes with ekofill straight on the fabric. I'll look it up tonight. Thanks, Tom
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You will be fine. The change was in response to concerns from builders in Alaska. They has some problems that turned out to be related to colder than optimal shop temperatures. The ekobond step eliminates the first fill of the weave and gives a better surface for the Ekofill to stick to. As long as fabric is damp, Ekobond will work just fine on bare fabric. The Washcoat of Ekobond to fill the weave eliminates a couple steps. Ekofill with a foam brush is still acceptable. If you are doing a certified aircraft and using the STC, it would be advisable to follow the current manual to keep the FAA happy.
Marty
 
algonquin said:
I may just stick with the Ekofill , it's working very good for me. Also I've been shooting top coats right on the Ekofill without the ekoprime. What's you feelings on that. I like the system but am concerned that I put out first rate work.
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The Ekoprime on top of Ekofiull is only needed with some colors for contrast and ease of color saturation. I had some difficulty with metallic yellow over ekofill. Getting to color saturation took additional fog coats before I was ready to shoot the semi and than the wet coat. By shooting a coat of white ekoprime first over the ekofill I was able to get to color saturation with less of the yellow for a lighter weight overall paint covering. Another example was on my fuselage. I shot white ekoprime than Ivory top coat. It was tough to see where I had enough top coat as there wasn't a good contrast. With ivory, a light coat of charcoal gray ekoprime would give better contrast. The last seminar I did we shot Ivory right over ekofill and we had good contrast, fast color saturation with fog coats, and good coverage. Whatever colors you shoot, practice on a test frame first to make sure you have everything down first. Make a 24" x 24" wood frame and staple the fabric to the wood. Do the three shrinks followed by all applicable finish steps. See how your color covers the ekofill to decide if you need a coat of ekoprime before the top coat.
Marty
 
Good to know stuff, thanks. The white under yellow and red have been a standard practice in the other systems. Without it a friend of mine had to shoot 9 coats of Cub Yellow and there was still a little shading.
I'll give it a try on the tail feathers this week and see how it works. I guess it can't hurt.
 
algonquin said:
Good to know stuff, thanks. The white under yellow and red have been a standard practice in the other systems. Without it a friend of mine had to shoot 9 coats of Cub Yellow and there was still a little shading.
I'll give it a try on the tail feathers this week and see how it works. I guess it can't hurt.
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Never mind tail feathers, get Matt going ��
 
I'm done with Matt's , finished his fabric before Christmas, I hate waiting on other people to get things done though.
 
As I understand it, the original formulations when the product was called Blue River weren't that good. The product has evolved to what we know as Stewart Systems but what has changed along the way to make it a better covering system?

Can anyone here vouch for a plane they've personally covered or saw through the covering process and which has many years on it that is still looking great with no covering system issues?

I'm about to make a decision for a set of Citabria 7ECA wings. The plane was done with Poly Fiber and Aerothane but the water based Stewart product would make life here at home a lot easier and I can eventually top coat the fuselage and tail with the Stewart product when I have time.

First hand experiences would be appreciated and thank you!

Bart

Hope this isn't a thread hijacking. :)
 
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Gordon Misch did a nice job on his PA-12. I think his has been done for a decade. He is a participant here.

My experience is small repairs. We had a 7ECA here. I am not going to tell you who repaired it, even though it is now dead and the statute of limitations is up - but the heavy coat of catalyzed auto enamel was seriously cracking along all ribs and around all rib "stitches".

New tapes were applied with Stewarts glue after quickly roughing up the surface. Not going to spend time on a dirtbag!
Ironed the pinked edges when dry, then three brush coats of Ekofill, then outside storage for six months. Survived, although ugly. Finally a cosmetic coat of sort of matching old expired white butyrate. Back outside for another year.

Absolutely no problem with it, even though down and dirty. Sold to a guy who thought he could fly the thing. Crashed on takeoff. Wing patches were all that was left. Still good.
 
bob turner said:
Gordon Misch did a nice job on his PA-12. I think his has been done for a decade. He is a participant here.

My experience is small repairs. We had a 7ECA here. I am not going to tell you who repaired it, even though it is now dead and the statute of limitations is up - but the heavy coat of catalyzed auto enamel was seriously cracking along all ribs and around all rib "stitches".

New tapes were applied with Stewarts glue after quickly roughing up the surface. Not going to spend time on a dirtbag!
Ironed the pinked edges when dry, then three brush coats of Ekofill, then outside storage for six months. Survived, although ugly. Finally a cosmetic coat of sort of matching old expired white butyrate. Back outside for another year.

Absolutely no problem with it, even though down and dirty. Sold to a guy who thought he could fly the thing. Crashed on takeoff. Wing patches were all that was left. Still good.
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Thanks for the feedback Bob, really appreciate it. I thought we were good to go and was about to order materials until I ran the idea past my IA. His experiences some time ago were bad enough that he suggested I not use it. It was also long enough ago that the product today is probably/hopefully very different so I'm still interested in it for my 7ECA.

Would love to hear whatever else is out there in the way of pros or cons from people that have done the work or who personally know how it is after years have passed. Thanks!
 
Bart23Sept said:
As I understand it, the original formulations when the product was called Blue River weren't that good. The product has evolved to what we know as Stewart Systems but what has changed along the way to make it a better covering system? There are no products that were in the Blue River system that are still in this system. The only part that is remotely related is the Ecofill, which is based on the old Eonex system (if you've been around long enough to remember that one). Blue River's glue was a disaster, the pre-preg fabric was a disaster, the topcoat was a disaster....none of that is in this system.

Can anyone here vouch for a plane they've personally covered or saw through the covering process and which has many years on it that is still looking great with no covering system issues? I've been using it since the mid 90's. Covered a few, and they're all fine. In fact, they look great. I think there are a few that are members here that have used it with great results.

I'm about to make a decision for a set of Citabria 7ECA wings. The plane was done with Poly Fiber and Aerothane but the water based Stewart product would make life here at home a lot easier and I can eventually top coat the fuselage and tail with the Stewart product when I have time. I have a friend that did his Stinson wings in the living room and his wife didn't mind at all. haha

First hand experiences would be appreciated and thank you!

Bart

Hope this isn't a thread hijacking. :)
Click to expand...

John
 
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