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Question about Poly Spray

B

bob turner

Registered User
Getting ready to do a pair of Twin Beech ailerons. They were covered with Stitts, and either very little Poly Spray was used or the sun baked it off exposing the pink. Of course the Dacron is turning into white powder.

I am guessing Poly Spray needs a top coat - but thought I would seek opinions.

Also, I have not yet stripped them, but it looks like a pretty raw seam behind the aileron hinge - have not encountered a seam like that before. Any hints from experts are welcome - I rarely mess with anything faster than a Decathlon.
 
Poly Spray can be left as a top coat. It is like Poly Tone, soft and more susceptible to staining and chemicals. Not sure what you are referring to with "raw seam". There are minimum glue joint overlaps.
 
Poly Spray is technically a "sub coating" I believe. Just because it CAN be used as a final coating does not mean it's appropriate for the intended service. If in doubt, ask the manufacturer. Call Glen at Consolidated Aircraft Coatings, he knows best ref their products. I have hours on the phone with him matching the correct product to my intended application. Great products, great service.

TR
 
First coat is Poly brush (Pink) applied with a brush and work it in to fill the weave in the poly fiber,
Then a spray coat of pink poly brush.
Then next is two cross coats of Poly Spray (silver) for UV protection of the poly fiber.
Final coat is Poly tone, the color.
 
TR Dunn said:
Poly Spray is technically a "sub coating" I believe. Just because it CAN be used as a final coating does not mean it's appropriate for the intended service. If in doubt, ask the manufacturer. Call Glen at Consolidated Aircraft Coatings, he knows best ref their products. I have hours on the phone with him matching the correct product to my intended application. Great products, great service.

TR
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I think you are thinking of Greg. He runs the show now. After dealing with John Goldenbaum and then Greg I finally got to meet him this past summer when my Dad and I were in Irwindale, CA for the Antique Nationals Drag Races. We visited Consolidated Aircraft Coatings in Riverside and after hours on the phone over the years, finally got to meet Greg and get a tour and an in depth history of Stits/Poly-Fiber etc. It was quite interesting and insightful.
PXL_20240529_222100067.jpg
 
You are correct. It’s Greg. I too had the pleasure of a visit to their location many moons ago. Just to be clear, my intention was only to highlight the expertise of the manufacturers technical support, not to slight your experience in any way.

TR
 
No slight at all, just seeing if we were talking about the same person. Was very interesting visit. I love seeing how things are made and then getting the insight Greg shared was ever better.
 
A finish silver top coat over the poly spray I'm told is the lightest way to go, FWIW, not as light as leaving just the p spray itself I guess though. The idea of course being less finish paint required as both are the same color.
 
I was thinking that maybe the Poly Spray had to be sealed to avoid erosion. It is clear that it was eaten away somehow.

Yes Steve - that is why I am a bit concerned and seeking advice. The hinge is a span-wise piano hinge, and the fabric appears to be glued on the aluminum either side of the hinge. There are no apparent fasteners, and no way to make an overlap.

Maybe it is time to find a maintenance manual?
 
Bob, I know it would be a tedious job. But, if you were to make small cuts at each hinge protrusion leaving enough material to lay over the leading edge, then do all your overlapping below the hinge line along the hidden area, you could avoid the issue you are addressing.
 
That works for Cub hinges, but this piano hinge is too tight to allow a single layer of Dacron.

This one is slightly outside my experience level. I enjoy a challenge now and then - did I tell you I replaced a Stearman spar last year? But I never do these things without advice. Forums are pure gold.
 
bob turner said:
That works for Cub hinges, but this piano hinge is too tight to allow a single layer of Dacron.

This one is slightly outside my experience level. I enjoy a challenge now and then - did I tell you I replaced a Stearman spar last year? But I never do these things without advice. Forums are pure gold.
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Send them up, we have some DC3 stuff to cover. Might be quicker to do a cub wing. Someone forgot the gust locks and the controls departed
 
Yeah, DC-3s are big! And a stitch every inch! A Cub wing goes really quickly in comparison. But a Stearman wing has a million stitches, some of them blind.
 
The fabric can be attached to structure with no overlap and no fasteners. For example fuselage fabric attached to a window/skilight frame or door frame or forward fuselage tube, or fuel tank bay on a cub wing.

For attachment to aluminium, polyfiber recommend etching with alumiprep type cleaner and their conversion chemical (can't remember the number but it's basically alodine) and their epoxy primer in white or green. Fabric is cemented to the scuffed primer with polytack. The joint is supposed to be minimum 1 inch.

Manual says to use one of their topcoats over the polyspray. 6 coats of polyspray are required (3 cross coats) and more coats to replace any material removed by sanding.

You can download the manual for free from the polyfiber website.
 
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I have Manual #1. I will look again. I do not have a Beech Manual - working on that. Does the manual actually say that Poly Spray will erode without a topcoat? That is apparently what happened here.
 
The manual is the specific data required under the STC.

It does not, as far as I can see, allow for no topcoat. It does state the following:

"To comply with the STC, youmust use only Poly-Tone, AeroThane, or Randolph Ranthane overfabric components."

And:
"You must use only Poly-Tone, AeroThane, or Ranthane topcoat paintover fabric components. Poly-Tone,Aero-Thane, and Ranthane have aPMA and have established trackrecords over Poly-Brush" and PolySpray"

I seem to recall a paragraph that talks about silver topcoat, but can't remember (I have enough trouble remembering the stuff that applies to my project)

S
 
Here in the US we can legally use the earlier approved manuals, which are not restrictive as to top coat. I am not concerned with legalities on that front, although I am planning on a silver Poly Tone top coat. I was just wondering if Poly Spray has been known to erode, or bake off in sunlight.
 
Polyspray is designed to provide defence against the sun. Without it UV will quickly destroy the polyester.

It is not designed to resist various other elements that an aircraft will be exposed to, for example detergents, acids and alkalines and other chemicals contained in, say, bird droppings, insects and a large number of pollutants that contaminate the air.

Emmisions from vehicles and various mills and plants for example contain sulfur dioxide. When mixed with precipitation the result is corrosive (aka acid rain).
 
That is the answer I was looking for. Any chance you could divulge your source?

Got my hands on the maintenance manual. And started to strip them today. I believe I can tie fabric to fabric along the hinge. The interesting thing is they must be balanced after covering.

The fabric has been on for a very long time. The fiber tape used under the rib stitches has not been available for over thirty years. It deteriorated worse than the fabric.

Except for the hinge area, and maybe the trim tab area, these are going to be easier than Cub ailerons. Cub ailerons are 8 1/2 feet long with complicated cove areas. These are just over 9 feet long, and skinny in comparison.
 
Source is the polyfiber manual and limited experience working with polyspray, which clearly does what it's designed to do, but is not a particularily tough coating.

Polyfiber, as with other STC holders, make a big deal of their covering "system." So for example Polyfiber anti-chafe and reinforcing tapes must be used. So even if you could still get the original tapes, you must use the polyfiber products to be in compliance with the stc.

Now cynics might claim other reasons for these restrictions and restrictions on topcoats, but recovering an aircraft is (or should be) done with a 30 year expectation. The Stc does not contemplate using polyspray as a topcoat (although I'm sure it happens) but is reasonably clear in stating one of their 3 topcoats must be used.

Some may argue that there's nothing preventing the use of polyspray for a topcoat, but in that case something other than the Stc needs to be referenced as acceptable data for certificated aircraft. (Don't know of anything)
S
 
I have been covering with Poly Fiber for almost 30 years and don't recall being required to use their chafe tape. I don't see where a top coat is required but the newer version of the manual does spell out what top coats may be applied. If I quote the older manual in my 337 I can apply any top coat I wish. Jon Goldenbaum himself verified this to me many years ago. He said the only way he can make the old manual null and void would be to issue an AD against it and he would never do that. I am a Ranthane fan, Polytone works well and is easy but does stain and wear easier. Cub Crafters and Aviat have use PPG truck paint for years with excellent results. I used butyrate dope over Poly-Fiber years ago with great results as did a good friends log time mentor. I stick with the current STC because it is proven in my experience but other do things differently sometimes with good results.
 
While I suspect that Poly Spray is not a good finish and probably does erode, I was looking mostly for corroboration. It was a new thing, walking up to this Beech with my patch kit, and seeing the pink Poly Brush showing !

Scott is trying to be helpful, but like Steve, I have not found definitive statements in any manuals.

I have been using Stitts since 1969, and picked up my first batch from Ray himself at Fla-Bob. The original certified reinforcing tapes were fiber tape. I liked them better until I discovered the polyester tapes had to be stabilized wth Poly Brush before stitching.

Steve’s statements above are gospel in the states - we are protected by the Administrative Procedures Act. My personal Cub is Stitts plus Butyrate (1972), re-coated with auto acrylic in 1981. Looks almost as good as Aerothane.
All quite legal.
 
Seve and Scott really know their stuff. I personally prefer aerothane as the top coat. I've learned it's personality and prefer it to ranthane. According to Gregg, aerothane was extensively reformulated in the early 2000's from what he said, the paint was designed specifically around flexibility, whereas previously it and other coatings were augmented with "flex agents" i don't know if ranthane was reformulated at this time. I've repaired a lot of painted fabric, both poly-f and ceconite-dope... several aviat ac as well... the ppg is magnificent stuff.... on steel, the chip sizes that pop off their application process are alarming to me personally, so for my own ac ppg is out.... except as a trim color over aerothane. If your after the poly spray look use polytone silver or aerothane with flatener, that's something Gregg has nailed cold.
Lastly, im not the least bit concerned about aerothane repairs anymore as lars has oratex patches that are usable directly on aerothane.
 
I agree - if I had the facilities, Aerothane would be my choice. I have the equipment (Citation turbine) but not the booth. Top coat will be Poly Tone, just plain old silver. The Beech originally came with silver Butyrate, or maybe even nitrate dope.

I can spray the non-catalyzed stuff, legally, outside. Steve is correct; spray it on wet, and it will give a reasonable gloss. HVLP has been my salvation.

By the way, I re-did a Stearman wing three years ago - we could not figure out how to match the color in Aerothane, so we had Artcraft shoot it with PPG. Memory says “Evolution” but I always get that wrong. Very expensive, but drop-dead beautiful! We did try to have a pro shoot the catalyzed top coat locally, but they messed it up completely. I mean color, finish, everything. We had to sand it all off!
 
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Fair enough re anti-chafe tape but the polyfiber reinforcing tape is mandatory.

As a relevant aside, I recently came across a rattle can lid that I had used to hold some mixed Ranthane for touch ups around 2016. The hardened paint has a consistency only slightly less flexible than Proseal.

So, although I don't like the, call it user unfriendlyness, of polyfiber urethane, the benefit in terms of longevity is clear.
 
We had a cult recently that did not have any reinforcing tapes and all the stitches on the tail had pulled through the fabric. It was a mess. No issue at all with Poly-Fiber reinforcing tapes although the new style do not stick like the previous version.

I am curious about the Ranthane in a spray can if that was something someone mixed or what. Ranthane is a catalyzed polyurethane so would be interested in how that worked, 2 parts in a can that mixed somehow?
 
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