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Thread: First, Build a Shed

  1. #311
    Senior Member Cherrybark's Avatar
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    Default Re: First, Build a Shed

    As you can imagine, I'm not crazy about posting this picture. But sharing the mistakes is all part of the forum.

    I've described how two glue coated Oratex surfaces have a very strong bond when heat / pressure activated, but you can take advantage of the weaker bond when only one of the surfaces is coated. The technique is to have a sharp glue line on one fabric and a more generous, overlapping glue surface on the second piece. Apply heat and pressure to bond, let cool, then peel back the overlapping fabric to the sharp glue line and trim off the excess. The first time I tried this, overlapping the wing covers, the final creased line was pretty jagged. The second and third time, 2nd wing and 1st fuselage side, gave beautiful lines. This 2nd fuselage side covering gave the mess you see in the photo.

    I had a very generous overlap of fabric but it was more securely bonded than expected in some spots and was a bear to peel back. There really was too much overlap to leave in place and most areas didn't have the double glue bond so it had to be peeled back. The photo shows a couple of spots where the glue bond actually peeled the color layer from the fabric.

    To be clear, trusting a weak single coat bond between two pieces of Oratex is definitely not a factory suggested technique. In the video linked in an earlier post, the overlapping layer was applied to a type of "masking tape" not to a piece of Oratex. The video doesn't say, but Oratex sells a tape that looks like the material in the video. If you are considering Oratex, it would be smart to call Lars (BetterAircraftFabric.com) the US Rep based in Alaska. Lars is a very down to earth guy and will give straight answers to any questions about techniques.

    Oratex glue is activated at 100C and the fabric just begins to shrink at 110C. This conveniently lets you bond the perimeter of the fabric before starting the shrinking process. After some thought, the two situations where I had problems were times that I had completed shrinking, floated a 160C iron over the entire surface, then concentrated heat along the glue lines. In the photo, I was thinking this final step would insure the tubing had heated sufficiently along the entire length. I believe this extra heat "melted" the dried glue and let it bond to both fabric surfaces. When you are applying Oratex to a surface, it's not uncommon to apply a little extra heat release the fabric - to remove a wrinkle for instance. In the two "clean line" situations, I had only used the 110C temp before folding and trimming.

    This isn't an earth shattering situation. It's on the bottom of the fuselage after all. Before applying the finishing tapes, I'll use some spare fabric to make a long "patch" strip to cover the area. This is how minor damage to an Oratex covering is repaired so it is certainly suitable for this cosmetic problem.

    Finally, yes that is a black fuselage tube showing through the Oratex. To be fair, the top of the fuselage isn't covered, the garage door is open on a bright sunny day, and there is a 4-tube florescent light just above. I haven't rolled the plane out in the sunshine yet so I really don't know how much of the skeleton will show. I won't find it unattractive.
    Attached Images Attached Images
    Carl Strange
    Flying
    SS7, 912iS, Oratex, G3X

  2. #312
    Senior Member efwd's Avatar
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    Default Re: First, Build a Shed

    Well Carl, That stinks. Nice thing is, its on the bottom. I had my silver stuff out in the sun and I didn't notice transparency. Not sure if the silver fabric is less transparent or not. The most undesirable thing I have noted is that the yellow 6000 fabric is slightly lighter in color than the thinner 600 fabric that make up the pinked tapes that are applied over it. Eh, not so bad. There is nothing that says I can't use my left over Poly Tone to just paint over the rudder and elevator.

  3. #313
    Senior Member Cherrybark's Avatar
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    Default Re: First, Build a Shed

    It was completely my mistake. But think how good I would be a Oratex after covering three or four planes.
    Carl Strange
    Flying
    SS7, 912iS, Oratex, G3X

  4. #314
    Senior Member colospace's Avatar
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    Default Re: First, Build a Shed

    Carl, I had to ponder a while over my Chipotle burrito tonight before I recalled how I trimmed my overlaps. Back in that long ago time, there were no videos really and little in the way of instruction. (And as I was doing the work from early in the morning, I soon learned that Lars was essentially living on German time, so I tried not to call him except if I truly got stuck.)
    Anyway, I'll try to relate how I worked out to do the trimming that went well for me 99% of the time.
    I would of course apply adhesive in the desired width to the underlying layer of fabric. I would apply adhesive excessively wide to the underside of the outer layer. When dry, I would insure I was happy with the positioning of the fabric and then tack bond around the periphery well away from where I expected the final trim line to be. When happy with that, I would run the iron down that same "line" around the periphery (again, this is 1, 2 or 3 inches away from the final cut depending on how much overlap is required). I would then typically fold the top layer fabric back so I could see were the edge of the adhesive was on the underlying layer and pinch a small fold into the outer layer fabric periodically along the edge. Using these pinched locations, I could lay a straight edge in place to draw a light pencil line on the inside of the outer layer fabric. I would then just run my scissors along the line to shear-cut the fabric. Then it was a simple matter to finish ironing down the complete overlap. I would apply a couple of lines of adhesive along the cut edge as recommended and, once dry, proceed to the finish tape.
    Hope that was clear. Seemed simple and worked well for me.
    - Gary
    S7 SuperSport Tri-gear
    w/Rotax 912, Oratex, Dynon

  5. #315
    Senior Member Cherrybark's Avatar
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    Default Re: First, Build a Shed

    Gary,

    That's pretty much the same process I used, except using a thumbnail to press a crease in the fold as a cut line. It was just in this instance, the glue on the overlapping made a very "good" bond where there wasn't a glued surface on the second fabric. I think this was caused by a hotter iron than the 100C required to bond the glue but I'm just guessing.

    I will continue to use the technique while finishing covering the fuselage - only using a 100C iron on the overlaps.
    Carl Strange
    Flying
    SS7, 912iS, Oratex, G3X

  6. #316
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    Default Re: First, Build a Shed

    What did you do on the wingtips and top of the rudder? Isn’t there a foam peice that you had to shape? Wondering if the heat will melt the foam parts you had to mold? I am guessing you fiberglass’s them?

  7. #317
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    Default Re: First, Build a Shed

    Not sure what Carl did but I used Hysol over the foam on all empennage tips and had no issues with melting Hysol or foam at iron temperatures up to 350F. As long as you don’t hold the iron for too long in the one spot you should be ok.
    David
    SS7 Builder

  8. #318
    Senior Member Cherrybark's Avatar
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    Default Re: First, Build a Shed

    Much the same as David, except I used West Marine epoxy with a fairing additive to make it easy to shape and sand the tips. No particular reason to use this product other than I had it on hand and have used it for years in other applications. No problems with the heat but didn't rest the iron in one spot.

    Also have the thin, fiberglass Laker Leading Edge. No problems with heat but was aware of the potential and kept the iron moving.
    Carl Strange
    Flying
    SS7, 912iS, Oratex, G3X

  9. #319
    Senior Member efwd's Avatar
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    Default Re: First, Build a Shed

    I have recently mentioned my problem in another post. I used foam and Hysol. I had significant difficulty wrapping the Oratex smooth on top of the rudder. I spoke with Lars and it was recommended to use 400 degrees to get the fabric to shrink and smooth. Well, I couldn't do it without melting foam. I could feel it softening the foam as well as the Hysol. Needless to say, I have what appears to be a first graders paper mache project on the top of the rudder. I will always recommend that you use wood or some other more heat resistant substance. Somehow, my horizontal stabilizer tips worked out fine. And others have succeeded as well. So, Im not saying it will definitely be a problem. The foam I used on the rudder was of substantial size. I didn't just fill in the gap between the rib and the perimeter metal. I built it up to provide a more flat top. That may explain why Carl and others got away with it without problems.
    Eddie

  10. #320
    Senior Member colospace's Avatar
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    Default Re: First, Build a Shed

    I only used the kit supplied foam on the horiz. stab and coated with Hysol. After that aggravating experience, I went to using balsa for all the remaining tips. Having said that, I did not have any heat issues with doing the Oratex over the foam.
    - Gary
    S7 SuperSport Tri-gear
    w/Rotax 912, Oratex, Dynon

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