Poly-Fiber patches

[PA1195]

Re: Poly-Fiber patches

Stewarts is indeed approved over ANY fabric system for a repair. Just follow the manual... I used it for many many years until I just couldn't use it any more, healthwise...John

I have most of my inspection rings installed over Poly with Stewarts. Still stuck and looking good.

And yes, nothing like walking into a hangar full of smiling Poly-Fiber Zombie People doing fabric and stoned enough to slow their speech and activity. Great fun if you leave early and often.

Gary

[Edwin Otha]

Re: Poly-Fiber patches

Polyurethane finish is extremely flexible. Early types (Imron) were sprayed on to rubber sheets to display their flexibility. Imron had a film thickness about 4 times the thickness of current urethanes, this caused the cracking. The film thickness, not the product.
Stitts, being vinyl based, never gets tight enough to stop the inflight stretch. Not shrinking the fabric the product installed on the fabric. If you look at the top surface of the Stitts wing in flight the fabric is ballooned between the ribs. This shouldn't happen and it changes the airfoil. Big fat airfoils are slower. I have been involved with aircraft that were recovered with Stitts and all of them were slower. Just my experience.
EO

[Scott]

Re: Poly-Fiber patches

So in an attempt to answer the questions posed in the OP, yes you need to remove all the topcoat. The closer you can get to bare fabric the better and here's why:

Nothing actually sticks all that well to polyesters. This is why the first coat is brushed on and why the procedure for attaching fabric, tapes, doilies etc is to apply the fabric into wet polytak, poly brush etc.

This causes the the liquid to be forced into and through the weave creating a mechanical joint that has good shear strength. Whether applying a gusset or making a repair, we need to achieve this shear strength the same way.

Irrespective of what other manufacturers might claim, Polyfiber provides specific instructions on how to make repairs in order for the STC to remain valid.

The manual is available for download on the Polyfiber website.
S

[N96337]

Re: Poly-Fiber patches

Irrespective of what other manufacturers might claim, Polyfiber provides specific instructions on how to make repairs in order for the STC to remain valid.

The manual is available for download on the Polyfiber website.
S

Not quite... the Stewarts is a legal, approved repair over any of the other systems. They did testing and had it approved by the FAA when the STC was approved. So unless you use an approved repair system, you're exactly right.
You also are REQUIRED to have the current copy of the manual of the system/repair system that you are using, on hand as you do that repair and are required to follow it. I've seen mechanics busted for not having the proper documents on hand when performing work.

[Scott]

Re: Poly-Fiber patches

Not quite... the Stewarts is a legal, approved repair over any of the other systems. They did testing and had it approved by the FAA when the STC was approved. So unless you use an approved repair system, you're exactly right.
You also are REQUIRED to have the current copy of the manual of the system/repair system that you are using, on hand as you do that repair and are required to follow it. I've seen mechanics busted for not having the proper documents on hand when performing work.

I believe you. Adequate practical results aside, I'm curious how to reconcile Polyfiber's prohibition on using any other products i.e... "SUBSTITUTIONS WILL VOID THE
STC AND YOUR AIRWORTHINESS CERTIFICATE....." So Stewart says it's ok but is that the full story if Polyfiber doesn't agree? I guess FAA authorization is the bottom line?

[Edwin Otha]

Re: Poly-Fiber patches

The easiest way is don't use it.
Went to hear Ray talk about his covering method after his fabric blew off an Airmaster and killed all on board. Everything was somebody else's fault. If you didn't use ALL of his products he threatened all of the attendees that he would personally go to the FAA and have your A/W certificate revoked. A really class act. His system works and is approved, but that was a long time ago. There are some very good products on the market that didn't exist when he developed his process. It would be in the best interest of all dope and fabric guys to investigate some of these fine products.
EO

[3Dreaming]

Re: Poly-Fiber patches

I believe you. Adequate practical results aside, I'm curious how to reconcile Polyfiber's prohibition on using any other products i.e... "SUBSTITUTIONS WILL VOID THE
STC AND YOUR AIRWORTHINESS CERTIFICATE....." So Stewart says it's ok but is that the full story if Polyfiber doesn't agree? I guess FAA authorization is the bottom line?

Scott, I agree that the STC says no substitutions, but isn't that for original fabric application? Once installed the aircraft has been properly modified. If another company has a STC for repair of any fabric system, and you find it is compatible with any previous modifications then you should be OK from a legal standpoint.

[SpecialT]

Re: Poly-Fiber patches

This Poly-Brush stuff looks like an orange plastic coating reduced with MEK. Short of a fresh air respirator what type of filter would give your lungs the best protection when spraying? My mask has an organic filter that says it's good for chlorine, hydrogen chloride, sulfer dioxide, chlorine dioxide and hydrogen. I guess I got the volcano covered but I don't live in Hawaii anymore, and since I don't smoke the wacky tabacky they grow out her I'll skip the plastic coating for the lungs.

[N96337]

Re: Poly-Fiber patches

This Poly-Brush stuff looks like an orange plastic coating reduced with MEK. Short of a fresh air respirator what type of filter would give your lungs the best protection when spraying? My mask has an organic filter that says it's good for chlorine, hydrogen chloride, sulfer dioxide, chlorine dioxide and hydrogen. I guess I got the volcano covered but I don't live in Hawaii anymore, and since I don't smoke the wacky tabacky they grow out her I'll skip the plastic coating for the lungs.

Your respirator is fine for that. If you ever get to spray the Aerothane (or any other solvent borne polyurethane) then you need the fresh air system.
John

[N96337]

Re: Poly-Fiber patches

Scott, I agree that the STC says no substitutions, but isn't that for original fabric application? Once installed the aircraft has been properly modified. If another company has a STC for repair of any fabric system, and you find it is compatible with any previous modifications then you should be OK from a legal standpoint.

Right. At the time of original certification, there wasn't anything else certified to use with that. I'm all for using what's on there originally, but I just can't take the exposure to the chemicals anymore...too many years of thinking I was bulletproof.
What they were having problems with , was the people that thought they'd mix and match systems. Not everything is compatible with everything else, even if it smells the same or works great on the other system. There were some real problems that were tracked back to someone thinking they really understood things enough to start engineering themselves. A recipe for disaster, as evidenced by the Whittman accident. That accident, like it or not, spurred quite a few changes in the fabric covering industry, partially because of the high profile nature.

[PA1195]

Re: Poly-Fiber patches

The potential problem with Stits (and possibly other solvent based systems) is even when not spraying and just brushing solvent off gassing is present. I helped with a few projects including mine and would not do it again without a mask. Too many headaches and huffing. Maybe that's why Ray Stits smoked a cigar while demonstrating.

[Robert Lees]

Re: Poly-Fiber patches

This Poly-Brush stuff looks like an orange plastic coating reduced with MEK.....

{snip}

Not MEK, but their own reducer 65-75

Rob

[Scott]

Re: Poly-Fiber patches

Scott, I agree that the STC says no substitutions, but isn't that for original fabric application? Once installed the aircraft has been properly modified. If another company has a STC for repair of any fabric system, and you find it is compatible with any previous modifications then you should be OK from a legal standpoint.

The stipulation is in the general section near the front of the manual. I certainly read it as applying to the whole process including repairs. The website is less emphatic but not inconsistent (assuming this plus the fact that the manual has been recently updated, represents Polyfiber's current position on the issue). From another perspective, I suspect if asked the question directly (can I use Stewart to repair my polyfiber covering) the answer would be no. But then the decision is ultimately for the governing body. Not sure about the FAA but Transport Canada views "manufacturers requirements" as the bottom line.

[Scott]

Re: Poly-Fiber patches

I hear you guys with regard to solvent exposure. I found the Polyfiber representatives at OSH to be far too relaxed in their discussions on safety precautions. Good recommendations to use barrier cream to prevent absorption through the skin, but no real concern about solvent fumes (except while spraying).

I purchased a HobbyAir fresh air supply when I did my 172 and I'd have to say it's one of the best investments I've made. Virtually no operating costs and the best possible safety protection. The hose is a pain in the butt yes, but only a little bit less convenient compared to a mask. I believe it has more than paid for itself.

I used it for everything, including application of tapes, gussets, doilies, all polybrush, polyspray and topcoat applications. I even used it for heavy polytac work when it was too cold to run my extraction fan full-time, and while wet-sanding topcoat.

It actually forced me to be a bit more organized in that I spent the first part of the day preparing (cutting, fitting, marking positions of tapes etc.) before even opening a can, then the Hobbyair goes on for the rest of the day. A low extraction airflow left on overnight so the next morning the air is good to start again.

I think the hazards of working with two-part urethanes and primers are well known these days. It wasn't 30 years ago or so and it took a while for the industry to catch up. A lot of people developed sensitivities and health issues. We really don't know all the hazards associated with any of these products (including water-based) so my motto is, just use the Hobbyair or similar.
S

ps here's what I use. Not a small investment but well worth it imo: https://axispro.com/index.php?l=product_detail&p=4

[otrcman]

Re: Poly-Fiber patches

Scott,

I think you have pretty well covered it, but maybe I could add just two small items:

First, the FAA would be hard pressed to violate you for doing a Stewart System patch on Poly fiber, since they have approved both STC's as written. They have simply written a built-in conflict into the regs. That's their problem, not yours'.

On the other hand, Poly Fiber would probably declare themselves off the liability hook because you violated their instructions. And I bet that would successfully cloud the issue on any future liability claim against them.

Second, about the supplied air breathing system. I'm 100% with you there. I'm an emphysema case who never smoked a day in my life. Exposure to solvents probably isn't the sole cause of my health problem, but it probably was a significant contributor. And I have been (I thought) fairly careful all my life.

My biggest problem with the HobbyAir is, like you, the hose. When spray painting, I wind up holding both hoses (spray gun air and breathing air) in one hand to prevent the hoses from touching my work. That leaves the other hand free to hold the spray gun. But, what about when applying tapes, & doilies ? Then I need both hands to lay down the fabric. My latest solution has been to make a new air supply hose that goes from the belt clip to the mask. The new hose attaches to the belt clip (just like the old hose), but goes around to my back where I have a Y-fitting that splits into two 18" flex hoses which go symmetrically over my shoulders and join back together at the mask inlet. Sort of like an old style Aqua Lung where the regulator was at the top of the tank. The new Y-hose arrangement is made from three 18" lengths of CPAP flex hose and a couple of modified PVC sprinkler fittings. The quick disconnect at the belt clip is taken from the original hose and the new Y-fitting at the mask just pushes onto the stub of the mask. No permanent modifications to HobbyAir system. The CPAP hoses have pre-molded ends, so they are just push-on connections. The entire project cost about $15 in materials and 2 or 3 hours on the lathe to modify the ends of the PVC fittings. Now, my air supply hoses rest comfortably on my back and do not sag to touch my work surface.

Dick