Effect of Revision 20 on Stits processed a/c???

[mhorowit]

Prior to 2001 you used the Stits process 'thru the silver', then any finish you wanted. FAA discovered some coatings didn't hold well so Revision 20 came out saying the only coating you could use were polythane/tone.

Now; what if you used the Stits process prior to 2001 and used butyrate dope for the finishing coats? Are you now running under an illegal STC? Certainly everyone using the pre-2001 process isn't going back to silver and refinishing! but how else is one to repair the coating and remain legal? - Mike (looking at a Tcraft with this problem)

[Robert Lees]

Re: Effect of Revision 20 on Stits processed a/c???

Illegal? No you are not.
Repair. Repair what's there.

[mhorowit]

Re: Effect of Revision 20 on Stits processed a/c???

Repair what's there.

Good morning Rob - Let's look at two examples (Stits process used thru silver, butyrate coats after):

1. For some reason, the dope finish in one area of the wing is peeling off, down to silver. Would one recoat with dope or Poly-Tone/Thane?

2. Assume an area needs a fabric patch applied. I assume one would take the coating back to fabric, apply the patch with Poly-Tack, heat shrink, apply Poly-Brush, Poly-Spray, then Poly-Tone/Thane. Now we have a 1 square foot of the wing with a Poly-Tone/Thane finish, and the surrounding area using dope (also the Poly finish is overlapping the dope). Any problem?

[alwaysoar]

Re: Effect of Revision 20 on Stits processed a/c???

The 337 for the 2001 recover job should give the date of the manual used. I believe the original polyfiber manual was dated May 20, 1965. If the 337 refers to this manual, then you can use the procedures in this manual for repairs--you are "grandfathered." If the 337 gives the revised date, and the job was done after the revised date, then it was done improperly and there is a big problem. How big are the areas needing repair, and can they be done by the owner under "preventative maintenance" in Part 43?

[Vasey fan]

Re: Effect of Revision 20 on Stits processed a/c???

This is another one of those "grey areas".

I know that Cub Crafters is still (or was, as of last year) using the Stits process through silver, then finishing with Ditzler polyurethane. It looks good, but it's a royal b*tch to repair. The beauty of Stits is that when you use their process through color, you can repair it at any layer with minimal stripping.

[N96337]

Re: Effect of Revision 20 on Stits processed a/c???

Alwaysoar is correct. You need to repair using the existing process. This was the advice that I was given by PolyFiber, as well as our local FSDO a while ago. If there are lots of areas that need repaired, I'd be more inclined to strip the fabric off, and do it right.
As far as Cub Crafters, there's a gray area there, and they may have had an approval from their local MIDO or FSDO, or maybe even a DER or DAR. When we were selling to American Champion a few years ago, they were using a combination of lots of systems to finish their aircraft at the factory... none of which was any one system from start to finish... I guess it's whatever you can get away with in that case.... Being as they are a principal manufacturer, it's a whole different can of worms.
I for one am very glad that PolyFiber finally came out with that revision.. I got sick of people bragging about their "auto" finishes with flex additive (which dissolves in a few years, if not sooner) and then whining when it started to crack!
John H.

[Robert Lees]

Re: Effect of Revision 20 on Stits processed a/c???

one area of the wing is peeling off, down to silver

That to me sounds like a mis-match of dopes/paints. If the top coats are just lying on the surface of the silver, with no mechanical or chemical bond, the top coats will delaminate in very short order. If it happened in one area, it's going to happen elsewhere too.
No problem with your No.2 repair, Mike, except that the new Stits paint would not bond to the existing paint around the edges. Stits products will not chemically bond with any other product, so you would have to make sure of a mechanical bond (sanding).
Personally, I would not purchase the aircraft without some financial allowance for removing all the paint back to silver & spraying properly.

[mhorowit]

Re: Effect of Revision 20 on Stits processed a/c???

That to me sounds like a mis-match of dopes/paints. If the top coats are just lying on the surface of the silver, with no mechanical or chemical bond, the top coats will delaminate in very short order. If it happened in one area, it's going to happen elsewhere too.

The first time the A&P looked at the A/C we didn't look at logs; we're going back next week to check the engine and review the logs. Before we knew it was Stits, he did say that the dope was peeling off the silver because the silver was too dense i.e. they had mixed the powder with the dope at the wrong ratio. Now that I know it's the Stits process, I'll go back to him and say "now what?" - Mike

[mhorowit]

Re: Effect of Revision 20 on Stits processed a/c???

Personally, I would not purchase the aircraft without some financial allowance for removing all the paint back to silver & spraying properly.

Bingo - Mike

[VictorBravo]

Re: Effect of Revision 20 on Stits processed a/c???

If I am remembering correctly, the Stits manual allows you to make certain small repairs by doping a patch right over the existing finish (assuming it is a Stits finish). So you do not always have to scrape off the paint down to the fabric.

If you have a pre-2001 cover job with some other type of final paint, in order to make you remove that paint, the FAA would have to issue an emergency AD to ground all airplanes using non-Stits paint over Stits silver and order them repainted. That is unlikely to happen.

Chances are that you would be grandfathered in if you had to repair Brand X paint used over Stits.

chances are strong that if you re-covered an entire wing with Stits, then tried to put on Brand X on top of it like the rest of the airplane, your IA might be able to say that he can't sign it off.

All that being said, the Stits silver is a pretty good primer... any reasonable amount of care and proper prep work should allow most other types of paint to stick to it.

Just how many airplanes over all these years had properly applied Brand X paint peel off of stits silver? I have never seen it. I have never heard of it. It would have to be an extremely extremely extreme situation to have the outer layer of Brand X peel off Stits silver in such a way to cause a legitimate air safety concern.

On the other hand, I have heard more than once about the problems with Maule/Ceconite/Butyrate factory finishes peeling off in big chunks! I think that Ceconite needs a revision a lot sooner than Stits does

[flyguy]

Re: Effect of Revision 20 on Stits processed a/c???

The examples I've seen of problems with "flex added automotive paint" is that they don't peel off the stits silver, but rather crack and that cracks the silver under it. Had three Tcarts finished that way. Had three Tcarts with cracks. PITA to repair and has a cracking percentage with me of 100 percent so far. Would NEVER use paint over aircraft silver of ANY kind on any original cover. I do it ALL the time on repairs, but that is only because I don't have any other reasonable options (that I Know of.) Don't mean to hassle anyone, but that is just my experience.
Mike you refer to "dope" over the Stits polyspray. What are you referring to when you say "dope?"
Darryl

[mhorowit]

Re: Effect of Revision 20 on Stits processed a/c???

Mike you refer to "dope" over the Stits polyspray. What are you referring to when you say "dope?"
Darryl

Butyrate dope - Mike

[flyguy]

Re: Effect of Revision 20 on Stits processed a/c???

So people actually put butylrate dope over stits silver. Wow. Didn't know that.
Suppose it's logical; it's shiny and more or less flexible.
D.

[N96337]

Re: Effect of Revision 20 on Stits processed a/c???

I just went through the PolyFiber manuals, both old and new and nowhere did it say you could use Butyrate dope in conjunction with any of PolyFiber's products.
It does say that if you have the aircraft topcoated with Polytone, you don't have to take it to bare fabric for a small patch. If you have it topcoated with Aerothane, you definately do need to get the Aerothane off, then go on with the patch and PolyTak.
John H.

[mhorowit]

Re: Effect of Revision 20 on Stits processed a/c???

I just went through the PolyFiber manuals, both old and new and nowhere did it say you could use Butyrate dope in conjunction with any of PolyFiber's products.
.

John - the change came about in 2001; could your manuals be too new?or maybe the stuff I'm reading is cockeyed; who knows. - Mike