Oratex is like Yoga Pants

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Re: Oratex is like Yoga Pants

Postby SheepdogRD » Sun Oct 07, 2018 1:53 pm

BucF16 wrote:I have a few areas that have small pits or gouges in the filler that didn't sand well. 1/16 to 1/32 deep.

You can fill those pinholes in the filler with glazing compound, also called spot putty. It's probably on the store shelf right next to the body filler, or in a package hanging nearby. I used Bondo 907, which is a single-component material... just squeeze some on a blade, and apply.

But the 907 isn't a body filler -- it's a pit filler. It has no structural strength, so you can't fill low areas. It's just a surface smoother. Sand with your finish-grade sandpaper, and you'll have a good, smooth surface. I shot a coat of primer over the finished surface because I wasn't sure how well the Oratex glue would get along with body filler.

I put a lot of effort into getting the strut brackets all smooth and beautiful. But a good bit of that effort was a waste of time and weight... the ones on the front spar end up under the fiberglass leading edge devices. Doh!
Richard Holtz
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Re: Oratex is like Yoga Pants

Postby BDA » Sun Oct 07, 2018 4:37 pm

Ok, I see what you mean. Lars told me no voids because they could promote separation of the glued fabric. So I mashed everything down into the glue. I would definitly take the time to fill and prime.

I used a 2 part epoxy primer in spray can from auto parts store (per Lars). Works great!

Is good for priming the aluminum too
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Re: Oratex is like Yoga Pants

Postby BucF16 » Sun Oct 07, 2018 5:05 pm

Thank you both!!!!
I'm off to work (at AAL going to VCN) tomorrow. 4 days off starting Thursday. I should be finished with fill the cellulite by Sunday :mrgreen:

Cheers!
Bruce
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Re: Oratex is like Yoga Pants

Postby BucF16 » Tue Oct 23, 2018 3:55 pm

Hi Guys, I decided to cover my upgraded horizontal stab first. I'm using a single piece of Oratex joined at the rear. BDA, I see that early in your posts that you used the heat gun to attach the fabric to the perimeter tubing as in the video by Lanitz video, but than in a later post I think you said to use the iron to attach the fabric around the back side of the tubing. The Lantz vid makes it look so easy :shock:. I'm sure I'll have 8 pages of my mistakes :oops:. Jim Pfarr and Bill Tabbert"S Youtube Vids use Iron. I know that the iron is set to 150 to activate the glue and not shrink the fabric. For those that used the heat gun, what temp did you use? The heat gun temp will decrease with distance and time.

Thanks in advance,
Bruce
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Re: Oratex is like Yoga Pants

Postby BDA » Wed Oct 24, 2018 4:52 am

I use the iron set at 110 C to tack the edge down straight and smooth. Then pull straight across the center and tack with iron, then down that edge In both directions with firm tension but no stretch.
Then I go back with heat gun set at 400* F and get it hot and rub it down with felt.
I am not using the heat gun Lars says to use, so my temps wont mean anything to you.

You will know if its not hot Enough because glue wont stick. You will know its too hot because the coating changes and fabric gets weak and rubbery.

You need to find out what temp That is on your gun on scrap BEFORE you start on the real thing.

And dont work too close to upper limit because a little distraction could mean damaged fabric.

Dont worry about stretching it too tight while ironing down, will only cause you grief.
Pactice, and dont be afraid to peel up and do again.
Good luck, call if you get stuck.
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Re: Oratex is like Yoga Pants

Postby BDA » Wed Oct 24, 2018 2:58 pm

Just to be clear
3 different steps - 3 different temps

1 Tack down
2 heat to rub in the glue and activate it
3 shrink

The shrink is the day AFTER you activate the glue, you have to give it time to set.

I will shrink enough to get rid of big wrinkles while tacking and setting but thats all.
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Re: Oratex is like Yoga Pants

Postby BDA » Tue Oct 30, 2018 7:06 pm

I have covered a wing now and can say for sure that you can do a superstol wing with one 13.5’ piece of fabric.

Fabric is 73” wide and does not wrap around to overlap with itself, but both ends make it to the flap cove, and can be joined with scrap piece.

I also covered the fuselage with 2 pieces instead of 3 or 4. So all together saved about 44’ of fabric.

I also used “seconds” for a 20% cost savings.

So I have used 31meters of fabric, 4 bottles of glue, 3 rolls of tape.

I think it adds up to around $4,800
Will have to double check prices

Thats alot better than the $9,500 I was told it would cost at first.

So here is what the flap cove looks like.
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Re: Oratex is like Yoga Pants

Postby BDA » Tue Oct 30, 2018 7:45 pm

I did some more experimenting with glue application for less brush strokes and ugly spots under the fabric and think I figured it out.
First air bubbles
If you have ever watched someone who really knows how to do verathane on wood, the brush strokes are very controled to eliminate air bubbles from the bristles lifting at the end of the stroke - its like that.
Keep the brush wet, and slow, smooth strokes, no “flicking” the bristles at the end.
Those little micro air bubbles are impossible to fix without scraping it all off

Brush stroke ridges:
This is a tough one, any visible brush stoke will show through the fabric, the larger it is the more visible.
What seems to work the best for me - put the glue on with wet brush and do a large area, then go back and brush over with continuous stroke end to end to spread it thin and even.
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What it should look like dry
C92BAA5D-2DBB-4F61-BD28-A0FA8F9F73D2.jpeg
Brush it out smooth
501C5D72-2D0D-451E-B4CC-53FE6BA56751.jpeg
Put it on wet
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Re: Oratex is like Yoga Pants

Postby BDA » Tue Oct 30, 2018 9:44 pm

Another problem with goobers under the fabric is caused by dried “chunks” that get brushed on and dry into little bumps.

The glue can start to dry on your brush if you are painting glue for awhile, or reusing a brush. Its not worth the bumps, throw it away, and get a new one.

When you pour glue out of the jug, pour through a strainer - always.

Some brushes work better than others, avoid the ones that have a feathered tip.
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Peel a goober off and you might get too much glue
19F4365C-52FE-4A21-9F8B-D5E9B0ED657E.jpeg
A normal paint strainer works good
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Re: Oratex is like Yoga Pants

Postby BDA » Wed Oct 31, 2018 12:34 am

Back to my mistakes
When u cover the wing with 1 piece of fabric, the smallest misalignment of the fabric will create a wrinkle that has to be shrunk out.
So I thought I would clamp along the trailing edge to keep it straight.
Then i started to iron it down trailing edge and toward the leading edge.

I ended up with a 6” tall fold in the middle that had to be shrunk out.
SO
DONT START AT THE EDGE

As I said before, start in the middle.
Drape the fabric over the wing - leading edge up, vertical.

Pull tight down both sides and clamp.
Then you can start ironing in the center (leading edge)

A wing rotating fixture is imprtant for this reason
I am using 2 engine stands facing each other
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Re: Oratex is like Yoga Pants

Postby BDA » Wed Oct 31, 2018 1:12 am

These are the bubbles that can dry in the glue if you are not careful brushing it on

Zoom in
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Re: Oratex is like Yoga Pants

Postby BDA » Wed Oct 31, 2018 1:17 am

There are 2 dried goobers here if you zoom in

You have to inspect the glue aplication carefully for these before it dries.

If you iron fabric over them the bumps stick out like a sore thumb.
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Re: Oratex is like Yoga Pants

Postby BDA » Wed Oct 31, 2018 2:09 pm

All in all very happy with how it turned out

Although it would go alot faster if I wasnt such a dumbass haha!
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Re: Oratex is like Yoga Pants

Postby BDA » Sun Nov 04, 2018 5:29 pm

One thing that I ran into while covering the wings that is important to plan for while using Oratex.

I have mentioned before that the glue has a “set time”, You have about 24 hours give or take- once you put heat on a piece to get it the way you want. The glue can be heated and pulled back or fabric can be ironed down better untill that point.
BUT NOT AFTER
The glue has set after that, and to remove it you must use much much more heat to remove it, and the glue is then ruined and must be reapplied.

Why does this matter? Cause the wings are large and require ALOT of iron time to get the fabric attached to the aluminum properly, and iron around all those rivets. Once the glue has been heated you only have 24 hrs to get finished.

So if you are like me, and screw around getting everything perfect inside the wing and dont get started ironing until late in the day, you wont finish until tomorrow, and you always see something that you want to fix the next day - so if you get pulled away the next morning on honey doos - the way you left it at midnight the night before is what you are stuck with.

When you iron fabric to the aluminum leading edge the heat makes the aluminum expand, so that when it cools and contracts you can have voids that are not stuck down, You HAVE TO GO OVER EVERYTHING WITH HEAT GUN AND FELT BLADE.

The felt blade pushes the fabric into the glue and makes the bond.

I had a few places on the fuselage where I had fabric that didn’t want to stick. Figured out that I had heated and set the glue there and not pushed the fabric down into it before it set. Fortunately they were on an edge and more glue fixed it.

So - get all the little stuff done and dont start the big covering jobs untill the next morning.
An extra iron and/ or heat gun with helper is good too!!
Last edited by BDA on Sun Nov 04, 2018 6:10 pm, edited 1 time in total.
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Re: Oratex is like Yoga Pants

Postby BDA » Sun Nov 04, 2018 5:55 pm

I used a long stick with masking tape to blunt the tip to push under the fabric with heat to lift and fix wrinkles as I aplied fabric.
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09E54C61-34E0-4045-ABA7-3328A5F21681.png
Top of the wing before heating and tightening the bays
25388470-3A63-465A-A28D-7F4CFFAFAB61.png
Bottom of wing w loose fabric after ironing the top
35C54607-C3FA-4C6F-BA0C-05A1BED2F7C9.png
Before covering I took pictures with tape pulled from root to locate inspection holes
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