Any Oratex usage tips?

[raystl1]

After reading Oratex application references, I am wondering how certain factors were dealt with specifically when used on earthstar craft:
Where was anti-chaffe tape used?
Where was finish tape used?
The stabilator has two slots cut in the fabric for the anti-servo push tube. What reinforcement was used around the slots to prevent distortion from the tight fabric?


Any other tips or recommendations gained from experience?


Thanks,
--Ray

[mkoxxy]

Oratex is tough and adheres well - I did not use anti-chafe tape anywhere.
The corners of my horizontal stabilizer got a little chafed by now, but not
to a point where it needs attention.

The only place I used tape was on the leading edges of the wing fabric (top
and bottom). All other airfoils get wrapped with overlap and don't need
tape. Oratex recommended wrapping the fabric all around the wing, too, but
I have not had any problem (but see my previous notes on that).

I did not like simply cutting slits for the trim tab control rod, although
I'm sure it would have been fine, especially with a simple fabric patch for
reinforcement. I made a couple aluminum brackets with slits and riveted
them to the rib. See photo.

[sadowin]

Good Idea making those brackets. I used 3 layers of fabric over the trim control hole. The only other thing is be careful not to get glue beyond your overlap because it discolors with age. Instead of buying anti-chafe tape I just cut strips from the leftover fabric.

Mike

[raystl1]

Thanks guys for the pic and tips.


--Ray

[raystl1]

Since Oratex wants pressure as well as heat for bonding, I have questions for each of you about technique:
Martin:
Did you do anything special, e.g. support underside through the slot with L shaped tool, while applying heat?
Was a gun or iron used?
What thickness did you use?

Mike:
I assume you used 2 layers for your 'patch'. Were they, one above and below main surface, all below or all above? Did you iron the patches to the fabric before wrapping the stabilator? If so how did you handle tightening/shrinkage? If you installed the patches externally after the stabilator was wrapped, then as with aluminum: Did you do anything special, e.g. support underside through the slot with L shaped tool, while applying heat? Was a gun or iron used?

Thanks,
--Ray

[mkoxxy]

If I remember right, all I did was to make sure the reinforcement tabs were
proud of the finished surface a bit. After wrapping, you hit the glue
joints with controlled heat from an iron, but no pressure. It is important
that the heat is high enough to trigger the cure process but low enough to
prevent shrinking the fabric. For ribs and the tabs, a small specialty iron
is nice to have, but for the larger aluminum-backed surfaces, you'll need
something stronger, with more mass, like a clothes iron. Calibrate your
iron with an IR thermometer.

When it is time to make the slit, start small and extend as needed. In my
case, I made a simple slit for slightly improved aerodynamics (friction is
not an issue), but with two or three layers of Oratex, I think you would
have to make a real slot to give the rod room.

[sadowin]

Ray; I put my patches on top after the final shrink. The first patch is about 4" wide and the second only about 2".
You don' need anything underneath to support the fabric while applying the patches if you do it after the final shrink. I used a big clothes iron that I calibrated with a IR gun. I also have a small hobby iron but it only gets hot enough to activated the glue so I never used it much.


Mike

[raystl1]

Now I understand both ways.

Thx

[mkoxxy]

I found a few more photos of the Oratex process.
As I said before, the maker of Oratex does not endorse making fabric
leading edges, even with tape over the edge, but I have had no problems so
far. See photos "wing covering", "rip stop rivets" and illustration "wing
fabric leading edge". But make sure to use glue under the tape.

Fabric overlaps:
Stabilator: under the nose (facing backwards, of course)
Rudder: on the large radius on the front
Ailerons: on the forward spar
Wing: on the rear spar

For the gap seals, I used strips of fabric, not tape.That gave me better
control over where the glue goes (which also helps with flexing).

"Wing fabric, right aileron" shows the wing tip installed. While covering
the wing, you need rivets on the outermost rib, so that the skins don't
cave when shrinking. But they get in the way of a clean wing tip
installation. After the fabric had been shrunk, I drilled out the rivets
that would end up under the wing tip, then drilled, clecoed and riveted a
new set of rivets. On one side, the drilled-out rivets ended up inside the
wing (all ribs face the same direction), but I was able to get most of them
out thru various openings. (Don't forget to make condensation drain holes
(soldering iron) at the lowest corners of each cavity.)

[raystl1]

Lots of good info, Martin. Looks like you used 2 inch tape on D edges. Any tape on the inboard chird edges of the wings?


Thx