Oratex covering question

[Tim213]

I am finally getting ready to start covering my BH with Oratex fabric. I have absolutely zero experience in fabric covering so bare with me on this question.
I saw where at least one builder rib stitched his tail feathers using Oratex, but most I have seen online did not mention doing so. For those Oratex users did you feel the need to rib stich? I am not planning on doing so but thought I better see what others have done first. Thanks for any input.

[AZBearhawk272]

Oratex or not the fabric needs to be secured to the structure, the most time proven method for the Bearhawk structure is to rib stitch.
Adhesives have not proven reliable enough,
some method of mechanical attachment is necessary.
AC43.13 covers the methods as well as
other covering manufactures instructions.

[Bdflies]

No Oratex experience here. I'm anxiously awaiting a proper explanation why one would not stitch (or screw, or rivet, or clip) Oratex to the ribs. In the absence of that convincing explanation, I would suggest Tim begin practicing his stitch of choice! It's actually fun to do.

Bill

[EricP]

At this point we are only gluing it. This glue is extremely strong. It will pull the fabric apart so I think with the glue attaching to so much of the structure it is way more than stitching. Having said that we are still building....

[Mark Goldberg]

Tim, the instructions that the Oratex people give should be followed. I also recommend rib stitching the fabric in the traditional way. There are some planes where it is designed so the fabric can be pop riveted or screwed to the ribs. However, Bob's designs do not have wide enough rib flanges for those methods - according to Bob. You should rib stitch the tail surfaces including the vert stab. Also the ailerons & flaps. The spacing between stitches is largely determined by how fast the plane goes and whether the particular area is in the prop blast.

To ease the rib stitching of the vert stab - do not shrink hard the fabric down below it or it will be harder and the shrinking will suck the fabric away from the vert stab ribs. Do shrink it - but just not as tight as in other places. Mark

[muleyman78]

I just finished covering with Oratex. I rib stiched mine. I know it said its not needed with Oratex but I feel much better knowing I have two forms of adhesion. I also like the look of it.

[Bdflies]

I think this subject deserves discussion, on more than one level. As an old dinosaur, I'm fascinated and interested in this new covering material that eliminates the need for all the various chemical coatings. I'm curious about all the ways it's different than the processes we've used for a long time. I'm also certain that lots of folks, long ago, were curious about how Ceconite could replace cotton. So, there is the aspect of this conversation that addresses differences in the Oratex process. I just might build another plane and choose Oratex as a cover. I'm interested to learn as much as I can. Secondly and perhaps more importantly, there is the real safety of flight issue that the subject raises. Attachment of the fabric to the ribs is not a cosmetic issue, nor is it optional. These are fairly high powered aircraft, operating at significant speeds.
With traditional dacron fabrics, the surface of the ribs that the fabric contacts, is covered with anti-chafe tape. This creates a cushion for the fabric to rest on. The chafe tape prevents the sharp edge of the rib cutting the fabric, as the fabric moves in airflow. Without the anti-chafe tapes, I'd be really concerned about the long term integrity of fabric covered surfaces. Because of this tape, fabric can't be glued to the ribs. You'd be glueing to the tape and the tape adhesive isn't very strong. Thus, the various attachment methods, mentioned in this thread. It's not a question of how strong the glue is, or how well it adheres to the fabric. I've seen a couple of Oratex videos that address glue and shrinking. I don't recall anything addressing treatment of control surfaces or sharp edges. The question in my mind, is how the Oratex process addresses the issue of ribs and sharp edges. If Oratex suggests protecting the fabric with anti-chafe tapes, then it can't be glued to the ribs. If no protection and they suggest glueing directly to each rib, then what protects the fabric as it flutters against the rib edge?
If there's a new and innovative method of attaching and protecting the Oratex, I'm really interested to learn about it. If this isn't the case, I really don't want to read about the loss of fabric from a control surface. I think it's great that Tim posted the question! I'd like to see some definite resolution, that we can all accept. This is a serious subject folks. Who knows, years from now, this thread might help someone that didn't bother to post the question.

Now, someone help me down from this soap box...

Bill

[Collin Campbell]

Bill, Being an "old dinosaur" myself, this thread is interesting to me as well. I have always used the Poly-Fiber system, so can't comment on recommendations for other systems. In reference to the chafe tape issue, I have never used it on ribs. The old "spiral bond " reference manual put out by the Poly Fiber folks recommends not getting carried away with the anti-chafe tape. Obviously, it should go over rivet heads, metal seams, or sharp edges that could cut the fabric. They say you don't need it over smooth ribs or well-prepared wood or aluminum. I take it if you do a good job of smoothing the rib edges, the chafe tape is not necessary. Anyway that's how I have always done it ... Of course there is the reinforcing tape that goes on OVER or on TOP of the fabric. It gives reinforcement for the rib stiching or mechanical fasterners.

My thoughts on rib stiching...Just do it! Besides it's fun, although every time I do it I need to refresh my memory...lol

Collin

[marcusofcotton]

Thanks for bringing up the safety of flight tissue Bill, I know that can be an unpopular thing to do. I like the idea of the oratex system, but there is a history of some folks having adhesion troubles. I know they have improved the glue recently, but the very nice Super Cub they had on display in their booth at Oshkosh last year had multiple locations of the glue letting go. Apparently most folks don't have insurmountable problems with it though.

[muleyman78]

I know that they sent the glue in a 2 part system originally and that had issues with adhesion if not properly mixed. Since they went to the premixed glue it seems to have resolved that issue.

[svyolo]

I just started laying down glue to start the covering process. Started small, trim tabs.

The only issue I see at the moment is the instructions are a bit confusing (the official manual is English translated from German). Some of the written instructions are contradictory on a few details. In general, the written instructions on attaching the fabric are exactly the same that I used 40 years ago to attach heat shrink mylar and fabric (Coverite) to model airplanes. The videos they show, are a completely different matter. A couple of them had me wondering what the heck they were thinking. They completely contradict the written instructions, and I could easily see massively screwing up large, easy to cover panels. That, I don't get.

But overall it looks easy. I did see a few pictures of applying the tape to the rudder/fuselage spine. That part did look a bit tricky.