Fabric Cover

[Kamcoman77]

Since Stewart's is waterbased, I decided to use Varathane waterbased urethane spar varnish on my wood so there would be no chance of any oily residue interfering with the Fastbond adhesion. I'm sure oil-based is fine if the dried surface is oil-free.

[Mark Kramer]

I think you are making a valid point. A waterborne product it will be.
Now I think I will search the forum for a wing strut topic. Got a few questions there.
Thanks

[scottiniowa]

  I like two specific things about the Stewart's over the Poly-Fiber. One, there are no dangerous to breath or flammable fumes, and two, you can paint the glue on complete portions of your airframe and come back later that day or the next day and put the fabric on. With Poly-Fiber, you put the glue on in short applications and immediately place the fabric down because the Poly-Tak (glue) dries quickly and should be wet to bond fabric.

I might add, and this may be true of the other NON Stewart products, but the "certified" method of being able to count on max sheer strength of a glued overlap of only 1" is really worth something.   Even having a 1" cap strip or anything 1" or more, could/can allow NO rib stitching    That and the assurance of how a simple tube wrap will hold for the duration of the fabric life. 

[Mark Kramer]

Hi Scott, I think I may have missed your point. I know next to nothing about this subject, when you say the certified method, are you referring to the poly fiber system?

[scottiniowa]

I might add, and this may be true of the other NON Stewart products, but the "certified" method of being able to count on max sheer strength of a glued overlap of only 1" is really worth something.  Even having a 1" cap strip or anything 1" or more, could/can allow NO rib stitching    That and the assurance of how a simple tube wrap will hold for the duration of the fabric life. 

I probably worded that a bit incorrectly, what I meant was, I think their (stewart) system was certified using 1" overlap joint.  If I am still saying that wrong, I don't mind being corrected.

[Mark Kramer]

Hey fellow builders,
If I was to use the water based system, how would you suggest the gluing to the rib tops would be accomplished? I talked to the boss yesterday, I hope it’s not unethical to repeat what he said. He suggested I use poly tack to glue the fabric on and then go straight to latex primer and paint. Backing up a second ,he said coat the rib tops with poly tack and let dry before covering. After cover and shrinking, apply I think  reduced poly tack to the rib tops to soak thru and activate a good glue bond to the ribs.
My wife and I live on the second floor over top of my shop, so creating noxious fumes is to be avoided. The water based system seems to be the way to go, except the rib gluing thing still leaves me with questions.
Again I hope I am not stepping on any toes here.

[Kamcoman77]

I'm not sure how others have done it, but I will coat the rib upper & lower surfaces with Fastbond (Stewarts EkoBond?). After it dries lay down the fabric and use a small heating iron to press the fabric onto the rib. The heat activates the glue to make a fairly strong bond. Next, a coating of Fastbond painted along the rib and rubbed into the fabric with a blue paper towel (shown in many Stewart's videos) to lock the fabric down. This should be as strong as Poly-Tak rubbed through the fabric like Leonard does in his video. I plan on making a few test pieces to check this bond. If the fabric pulls loose from my test rib easily, I will rib stitch the upper wing surface in the area affected by prop blast.

[Mark Kramer]

Good deal. I will be very interested in hearing about those tests. I hope it works good, so I can put this issue to bed. Decided to go ahead and fit the wings to the fuselage anyway. Got some time before cover now.

[Kamcoman77]

It's going to be a few months before I cover my wings. No tests til then.

[okdonn]

The polyfiber process is fairly easy to patch/repair. Can you do the same with Stewarts or latex house paint?

[Dan_]

... I plan on making a few test pieces to check this bond. If the fabric pulls loose from my test rib easily, I will rib stitch the upper wing surface in the area affected by prop blast.

I saw a "test" at the Oshkosh Poly Fiber workshop many years ago.  I enjoyed the workshop so much I wanted to do it again but dint.

If memory serves, the lady doing the test had 2 strips of dacron fabric glued together about a foot long and about and inch wide.  I'd say about an inch overlapped where the glue was.  She had 2 people pull on one sample, they could not pull them apart.  She then took the other sample in her hands and peeled it back over itself like one would do removing masking tape...

So the glue was great in sheer but not when being peeled off.  However I submit that neither of these scenarios is what a wing is subjected to in flight.  I would tend to believe it is more like suction (tension) on top of the wing and pushing (compression) on the bottom.

The absolute strongest fabric attachment to rib cap strips is the Hipec system.  Below is a pic of Chuck Slusarzcyk standing in a test box showing the strength of the fabric glue. 

See here: https://hipec-aircraft-coatings.squarespace.com/about/ and here:http://musclebiplane.org/htmlfile/hipec.html

I read somewhere that Hipec glue is good for 120 pounds per square inch.  Below is a pic of Chuck Slusarzcyk in his more svelte days giving the glue the "empirical test"...

[scottiniowa]

 

The absolute strongest fabric attachment to rib cap strips is the Hipec system.  Below is a pic of Chuck Slusarzcyk standing in a test box showing the strength of the fabric glue. 

See here: https://hipec-aircraft-coatings.squarespace.com/about/ and here:http://musclebiplane.org/htmlfile/hipec.html

I read somewhere that Hipec glue is good for 120 pounds per square inch.  Below is a pic of Chuck Slusarzcyk in his more svelte days giving the glue the "empirical test"...

I don't disagree with a word said here or on the website....but when I asked the company, "how do I do a recover?" or "start over"  it got pretty quiet...I would love to hear the answer to this, but presently they just say you have to grind (and not a light easy grind) it off?  is that true?

[Dan_]

I don't disagree with a word said here or on the website....but when I asked the company, "how do I do a recover?" or "start over"  it got pretty quiet...I would love to hear the answer to this, but presently they just say you have to grind (and not a light easy grind) it off?  is that true?

Ran across this...

November 16th 03, 09:57 PM

Ray Toews external usenet poster Posts: n/a

What about a recovering job or repairs in general... I have used Hipec on several ULTRALITE designs and found it very easy  to use.  I have used most systems, Randolph, Stits, Ceconite 7600 (what  happened to it?) and prefer the Hipec method.  It is easy, quick and rugged, stinks to high heaven but ventilate or  use respirator and you can get a nice finish with a foam roller in a  clean room. It is a bit tricky to spray, I had a friend with a body  shop spray it and made a mess which I cleaned up very nicely with a  roller.  I dismantled an aircraft which had 1/2 inch aluminum ribs that had  been Hipeced and the fabric was a real bi hatch to pull off the ribs.  On Sat, 15 Nov 2003 01:06:15 GMT, "Blueskies" wrote:

And this from a Lazair group:

Postby bdiedenhofen » Mon May 12, 2008 8:22 am
I did do a final shrink, and it was fine. There is some minor scalloping on the trailing edge, not bad though.
The underside was slightly shrunk, and then weights were placed between the ribs, and the sunbarrier was brushed through to hold the cloth to the ribs. When dry, the weights were removed, and a final shrink was done. It has held to the camber nicely.
I was curious as to how well it would hold. When I tightened up at the wing tip, I had to clamp a piece of wood over the top of the wing to get the cloth to contact the last rib. There was a lot of tension on that point. When the Hypec was dry, the wood clamp came off, and the cloth stayed stuck. It's been stuck there for four years now, and holding well. So the stuff works.
The only place thats mechanically fastened is the upper curve of the wing tip. The original aluminum cap strip was riveted over the cloth to hold the shape there.
My plan for recovering is to cut the cloth away between the panels, leaving strips over each rib. I saw this in a book somewhere, maybe the Hypec manual? Anyway, the plan is to lift one end of the strip, and then roll it over a pencil. By rolling the strip of cloth off of the rib on a pencil it should lift off without damaging anything underneath. Alternately, the strip of cloth could be left, sanded smooth, and the new cloth glued over it.
I'm expecting that I will get 15 to 20 years out of the cloth, so I'm not too concerned about the recover project for a while yet.
I have done a few repairs, and it's super easy. Simply clean the top paint from the area where the patch is going with MEK and then glue the patch on with sunbarrier. Once dry, shrink the patch a bit, and put on a coat of sunbarrier to fill the weave, and then paint. Works great.