Poly-Fiber patches

[SpecialT]

Well I got to the bottom of the tear in the rudder fabric. A patch had been previously applied, but the patch was not pinked, and a tear developed again along the patch edge when it came in hard contact with the elevator. It also appears as if the patch was a different type of material than the underlying Poly-Fiber covering. It's green.

So two questions.

1) How "clean" does the area need to be before applying Poly-Tac and putting on a Poly-fiber patch. Can small remnants of the aerothane live under the new patch, especially where the patch covers a tape edge? It's difficult to sand out some of the aerothane in the pinked edges without fraying or cutting the underlying fabric.

2) Is it just me, or when MEK'ing down to the pink Poly-fiber covering does it seem like you are working on a corpse, what with the pinkish flesh tone and strong embalming fluid smell?

[Edwin Otha]

Re: Poly-Fiber patches

Lots of times strange things are used to make a field repair. I've had problems with ACA's "Superflight" type process. I have used Stewart System glue to make some of these minor repairs with great success. That stuff is tough and might work for you.
EO

[astjp2]

Re: Poly-Fiber patches

Its a major NO NO to mix processes, just dont mix processes! That is what killed Whitman...his wings peeled apart because he mixed processes and didnt follow established rules of fabricing!

[SpecialT]

Re: Poly-Fiber patches

Uh Oh, you had to bring up Whitman, it's hard for me to imagine he owned a plane that didn't have the fabric installed properly. The NTSB just stated missing dope. What was the real story? Maybe I started it talking about cadavers.

So any recommendations on the first pic repair? Do you think I need to remove the green patch, it's on there pretty good. I used a soldering iron to burn back the edges of the tear and was thinking of applying a pinked tape over the existing tear/hole would be sufficient. Poly-tac the patch on, Poly-brush coats over the top, then Poly-spray, then paint. No mixing going on here.

[Robert Lees]

Re: Poly-Fiber patches

Its a major NO NO to mix processes, just dont mix processes! That is what killed Whitman...his wings peeled apart because he mixed processes and didnt follow established rules of fabricing!

Indeed. It looks like the original repair to SpecialT's aircraft is mixing-and-not-matching the processes. Ceconite/Randolph uses dope (cellulose-based) and Poly-Fiber is vinyl-based. The two processes to not adhere together.

Rob

(Incidentally, Tim, I understood that the Wittman cause was an aileron fabric mis-repair that caused fabric failure, leading to flutter, leading to the wing failure to which you refer...but as I say, that's just my understanding. It led to the FAA mandating the non mix-and-match in each of the STCs that had probably, inadvertently, being happening for years).

[Edwin Otha]

Re: Poly-Fiber patches

Not talking about mixing process components. Talking about minor repairs.
There are many wings covered with one process and the fuselage with another.
ACA actually mixes automotive products with dacron fabric via their production certificate.
EO

[astjp2]

Re: Poly-Fiber patches

Ok, to clarify, you dont use polyfiber patches on Ceconite or vise versa. I saw an experienced mechanic cut a large section of a fuselage that was originally ceconite, he used poly tack to glue poly fiber to the original ceconite fabric and then used brush and spray then finished with a good 5 coats of Imeron......how long do you think that fabric job looked good for? about a year, the imeron started cracking because there was no flex agent and the poly tack started to separate from the ceconite......Whitman's wings were not covered IAW standard practices and from what I remember, it was one process on top of the wing and a second on the bottom, and the fabric separated from the structure of the wing.

[Ray36048]

Re: Poly-Fiber patches

As I recall, Whitman applied the fabric over a plywood wing. It was the heat shrunk and dope was the applied to the fabric. The dope did not penetrate the fabric for adhesion to the wing. With time, it became loose. I also understand he used this same process for many years on other airplanes. It was an experimental aircraft, so he was free to do whatever he wanted.

[Robert Lees]

Re: Poly-Fiber patches

Steve Wittman. No "h" in the spelling. Those that have been to Oshkosh or have seen a Wittman Tailwind should recognise the name .

Rob

[Edwin Otha]

Re: Poly-Fiber patches

With experience comes wisdom. Don't use Stitts on anything you don't want to slow down. Don't use Imron on fabric it's too thick. Polyurethane enamel coatings are much more flexible than dope finishes. Make sure the nitrate, coats the fabric. USE all of the covering methods before commenting as fact.
EO

[Robert Lees]

Re: Poly-Fiber patches

With experience comes wisdom. Don't use Stitts on anything you don't want to slow down. Don't use Imron on fabric it's too thick. Polyurethane enamel coatings are much more flexible than dope finishes. Make sure the nitrate, coats the fabric. USE all of the covering methods before commenting as fact.
EO

Ed: What do you mean by "Don't use Stitts on anything you don't want to slow down"...that doesn't make sense?
Also, I disagree with your statement "Polyurethane enamel coatings are much more flexible than dope finishes".

Rob

[Garry Crookham]

Re: Poly-Fiber patches

I'm a Poly Fiber user and agree that processes shouldn't be mixed, however according to Stewart System Procedure Manual 21 (STC SA01734SE):STEWART SYSTEMS is certified to repair any other certified covering
system using the following procedure..............
Anyone tried this?

[Guest]

Re: Poly-Fiber patches

I thought about that too.

However the same manual says the top coat is fuel proof yet I discovered that is not true.

So I have been reluctant to suggest it.

[3Dreaming]

Re: Poly-Fiber patches

I think Oratex also has a patch approved for any covering system. Glue it on, shrink it, and done. No painting.

[N96337]

Re: Poly-Fiber patches

Stewarts is indeed approved over ANY fabric system for a repair. Just follow the manual.
Yes, Dave had a disaster with the topcoat and autofuel... I've had some soaking in autofuel and no problems as well as others have too...it totally depends on the particular fuel.
If you don't mind working with Polyfiber, go for it....that's a great system, and there are very specific repair criteria called out in their current manual. You need to follow those procedures to do a repair on their system with their products. I used it for many many years until I just couldn't use it any more, healthwise.
I haven't gotten to work with Oratex yet.... but am looking forward to it.
John