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  • Oratex thread

    I have been P-mailed enough about Oratex I thought I would share my experience so far, including the gotcha's as they arise. Like yesterday. Following the recommendation of a few, including the Oratex folks, I almost wasted a big piece of Oratex, due to a BH geometry issue that I didn't notice either.

    Overall I like the product. I covered the tail pieces and gear last fall and it went OK. Simple shapes are extremely easy, going around curved sections requires a bit of work, and sometimes you need 4-6 hands, and I only had two installed as standard equipment.

    The material is extremely tuff, and super easy to repair. No smell, overspray, sanding, respirators etc. But.............

    The negatives so far are a combination of annoying, and maybe a show stopper for some.

    I would say the annoying is the quality of the documentation. And that is coming from someone for whom documentation isn't that important. I usually only read it after I screw something up. The factory manual is very disorganized, comprised 50% of disclaimers on what not to do, and then translated somewhat poorly from German to English. I haven't looked for videos on youtube for about 6 months, but they were few and very poor in quality and technical accuracy. I wouldn't bother.

    The show stopper might be the space requirements. For smaller bits like control surfaces a spare bedroom would be great. You need space for the control surface, AND space for you to lay out the fabric piece, apply glue twice, and let it dry. This space needs to be clean, and stay clean. No sanding, grinding, spray painting etc. If you are using your shop then the utility of your shop will be compromised while you cover. When you cover the fuselage (or wing on a fabric covered aircraft), you need space for the fuselage, and an equally big table to apply the glue to the fabric and let it dry. That is a lot of space that is tied up for quite a while, which is the other rub with the factory manual.

    There are a lot of disclaimers about doing things exactly one way (very German) including disclaimers on how long you let the glue dry, which I have complied with. But doing that really drags out the covering process. It might take 5-7 days to cover one side of an aileron. Not that amount of man-hours obviously, but a lot of calendar days for one small part. To do a whole airplane in a reasonable amount of time would take a 2000 square foot shop with 4-500 square feet of floor space just for tables to apply and let Oratex dry. If you are doing 1 part at a time in a normal sized 400-1000 square foot, your shop will be tied up for a LONG time. Maybe a lot longer than traditional fabric and paint, even if the actual man-hours of labor are quite a bit less.

    The factory has an installer, and they have folks all over the country that install their product professionally. My guess is they allow the glue to dry a lot less than what the factory specifies, otherwise they would go broke installing Oratex professionally.

  • #2
    Applying Oratex fabric is similar to covering a model airplane with Monokote or Coverite, except you to apply glue to both sides. A bunch of little super magnets helps to hold the fabric in place while you try to get the fabric to lay correctly with minimal wrinkling, etc. You heat it once at a low temp (125F) to get the glue to set initially, then go over it again at 195F for 10 seconds to make the bond permanent. Going around compound curves the fabric can be both shrunk and stretched with heat while applying it (this is when you need 6 hands). The fabric starts shrinking about 200 F. The hotter more shrinkage. The factory claims the total shrinkage is somewhat less than traditional aircraft fabrics, but you can stretch it with heat while applying it also.

    Some of the colors used make the fabric fairly transparent. The yellow I am using has this issue. You have to mark the back of the fabric where you are going to apply glue. I use a light yellow sharpie on the white back. If you use a dark color it will show through the finished fabric.
    Last edited by svyolo; 08-09-2020, 08:39 AM.

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    • #3
      Fuslage covering.

      I spent a bunch of time in the lead up to fuselage covering trying to figure out how to cover the tail in one piece with the side of the fuselage. I was a bit skeptical, and finally decided to put a termination point at the base of the tail and do it separately. That turned out to be a fantastic idea, but not because of the tail itself. The Oratex dealer and a couple of others recommended covering the sides from the bottom longeron, and terminating on the upper stringers. That sounded like a good idea so I tried it assuming it would be no problem now that I had separated the vertical fin from the side piece. I should have just followed the technique that a couple of builders on this forum successfully used, and that is just covering from longeron to longeron.

      I spent over half a day yesterday trying to get the fabric to lay correctly. Most of the fuselage side and top is convex. My upper fuselage is less convex than stock as I reduced my BH "hump" by 75% so it faired into the skylight a bit smoother. But it is still convex.

      But.....and here was what I didn't catch. The upper longeron is convex until you get to the cargo area, then it's becomes concave to match up with the wing root. Maybe Polyfiber can handle this, but Oratex will not. Actually if you had 5 or 6 well trained, knowledgeable guys with 3-4 heat guns you could heat and stretch the Oratex into shape, but that is not realistic.

      I spent way over a half a day trying to figure out some combination of techniques to get the fabric to lay correctly, and finally gave up. I trimmed the fabric above the upper longeron, and will just run the side pieces of the fabric from lower to the upper longeron.

      Heading to the shop now to apply glue to the side and fabric. I will post a couple of pics.
      Last edited by svyolo; 08-09-2020, 08:41 AM.

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      • nichzimmerman
        nichzimmerman commented
        Editing a comment
        Can you expound on your decision to not cover the sides in one piece from the bottom longeron to the top stringer and from the tail post forward? Thats what I was planning...

    • #4
      I don't use the full factory recommended drying times for the couple patches I've done(for adding things).

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      • #5
        Great info, thank you for posting. Depending on your bandwidth, a video showing these challenge areas would be great to see.
        Mark
        Scratch building Patrol #275
        Hood River, OR

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        • svyolo
          svyolo commented
          Editing a comment
          I don't have a tripod, but I will try to take a quick one while I am fixing yesterdays buffoonery.

      • #6
        I guess I would say Oratex save man-hours but wastes a huge amount of shop floor space/calender days if you wait overnight for glue to dry. I think a lot of builders spend an hour a day on their project, they probably don't mind.

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        • #7
          I covered my Rans S7 in silver oratex and must admit that it was certainly stressful at times due to the threat of screwing up a big piece of very expensive fabric. Looking back on it though, the covering was the most rewarding part of my build. I like Oratex and if I build a BH5 (considering), it will be in Oratex. Definitely some head scratching involved when it comes to curves. I agree that the “manual” is poor. Take a look at the poly fiber manual, presented in a very easy to follow manner, Oratex would be smart to adopt a similar format. Which motivates me to reach out to Lars and suggest this. I found the most cumbersome part of the process was the use of Oratex scraps as anti chafe. This is just adhesive tape when using using the legacy processes. Not as big of a hurdle when building a Bearhawk due to the metal wings. I spent an eternity applying antichafe Oratex to my S7 wings prior to attaching the panels of fabric. I also agree on the space management issue. I found the ping pong table in our game room to be a real winner.

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          • svyolo
            svyolo commented
            Editing a comment
            I haven't minded that as much as I did them slowly over time.

          • m.mooney
            m.mooney commented
            Editing a comment
            I applied anti chafe Oratex to all of the wing ribs and anywhere that might be a potential wear point, Leading edge wrap, etc.. it adds up. Very little anti chafe applied to the fuselage, in comparison. Bearhawk would be easy in this regard. Having disparaged the Oratex anti chafe process though, I absolutely guarantee that it is a better process in the long run, no tape adhesive to fail and let go. Wait, I can’t really say that because Oratex is still somewhat unproven as for longevity.

        • #8
          Where have you all applied anti chafe (extra oratex) on the Bearhawk? Lars made is seem to me like there weren't many areas requiring it so long as there were no sharp edges.

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          • svyolo
            svyolo commented
            Editing a comment
            I am just doing the fin and horizontal stabs. The elevator and rudder ribs were pretty well rounded.

          • m.mooney
            m.mooney commented
            Editing a comment
            I would do the ribs unless they’re without sharp edges, as svyolo says. Basically, apply anti chafe at any potential wear point

        • #9
          Here is a pic of my fabric yesterday trying to cover the side from the lower longeron to the upper stringer. fabric.jpg
          I don't know if polyfiber would have hacked this as I have never used it.

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          • nichzimmerman
            nichzimmerman commented
            Editing a comment
            Can you point me to your source for those magnets? I was using clamps and these seem a lot more useful.

          • svyolo
            svyolo commented
            Editing a comment
            I have bought several sets of them off amazon the last year. Just search on Neodymium super magets. I just did but couldn't find the specific ones I bought. They are really handy for a lot of things.

          • svyolo
            svyolo commented
            Editing a comment
            I remember the best ones I bought came from Eastwood. Extremely strong but a bit more expensive. Most of them I got off Amazon. Lots cheaper, not as strong, but more than strong enough for a lot of things.

            The stronger ones are great for holding steel together for welding.

        • #10
          I bought a Steinel digital heat gun and the TOKO iron that they recommend. The TOKO was too big for detail work so I bought a little detail iron from Spruce.

          I am not sure I have a lot of use for the TOKO iron. Final shrinking is done with an iron, but I think I would rather use a full size iron for that. So far I would say I would pass on the TOKO iron. I might change my mind later.

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          • #11
            I am applying the second coat of glue to the left side of the fuselage now. One of the "extra's" with Oratex is it doesn't like unsupported edges. Kind of like the aluminum straps Mark showed to go around the strap hinges on the elevator and rudder. I used those. But wherever the fabric isn't well supported, it is good to put something behind it. I used a combination of scrap .016 AL and in some places used some scrap kevlar. Things like the rudder stop on the tailpost, welded tabs for the stab wire and support rod, grab handles. If there isn't support, you could shrink the fabric away from the tube. Kind of like blowing out an edge when welding.

            Comment


            • #12
              Ruh Roh;
              Before I started covering the fuselage, I went over it with my eyes and hands to make sure I didn't have some really ugly high spots on the welds on the clusters. Seemed pretty good, I didn't grind any down. I did on a couple of spots on the tail. I just finished permanently glueing (>195 F) to all the perimeter of the left side of the fuselage, plus the window frame. I started the initial shrink, and then the Ruh Roh. At the cluster where the upper string terminates, there were two high spots on the tubing weld that i didn't catch. They are more than bad enough that I have to fix it.

              Preferably put something under the fabric, or over the fabric. Last choice - grind through the fabric, flatten the metal, and repair the fabric. Probably with a carbide burr on a dremel.

              $#@%&!!!!! It was going pretty well up to that point.

              Comment


              • zkelley2
                zkelley2 commented
                Editing a comment
                Use the heat gun to unstick the glue, pull the fabric back, fix the weld, apply new glue, activate the glue.

                I've done this at 3 spots on my plane due to poor workmanship of the guy I bought it from. Every time I'm so thankful on how easy oratex is to fix.

              • svyolo
                svyolo commented
                Editing a comment
                Because it was very quick, I cut a 1 inch circle of Kevlar. Heated the fabric/kevlar/epoxy to 270 F and pushed with felt for a few seconds. Looks pretty darn good. It is behind a removable interior panel and easy to get to.
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