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Thread: Polyfiber or dope?

  1. #1
    59pacer's Avatar
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    Default Polyfiber or dope?

    Is there any easy way to tell the difference between a Polyfiber and dope finish on fabric?
    Looking inside the wings, the fabric is pink, which makes me think that at least the first coats are polyfiber, but a previous owner says that he 'thinks' that he finished the colours in dope! The logbooks are vague at best.
    The finish feels and looks like polyfiber to me, but all my experience has been with dope, so that's a WAG.
    I have to install some inspection rings under the wings and fuselage, so if it's Polyfiber I'm going to have to learn some new techniques!

  2. #2
    DrHook3960's Avatar
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    Default Re: Polyfiber or dope?

    I haven't tried dope yet but I covered 5479Z with polyfiber and its a piece of cake. Each layer of vinyl welds itself to the previous layer and no sanding is needed. The only layer that gets hard enough to sand is the silver polyspray. Dries superfast and you can wipe the paint off with MEK to get down to bare fabric with ease.

  3. #3
    Old3pacer's Avatar
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    Default Re: Polyfiber or dope?

    If you can look at the inside of the fabric, you may see the polyfiber stamp. Poly fiber seems lighter to me than ceconite which has a bit of a canvas feel. MEK will wipe poytone paint off but poyfiber STC also allows an aerothane paint which will not be cut by MEK. The pink you see is usually polybrush. When was the cover job done? Older versions of the STC allowed many paint finishes.

    I would test an area with MEK. There are several processes you can use over any cover but my preference is to stick with the process you have if you can.
    Last edited by Old3pacer; 06-22-2017 at 05:43 AM.

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    Administrator Steve Pierce's Avatar
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    Default Re: Polyfiber or dope?

    Pink would be Polyfiber. I have heard old timers call Polyfiber Stits Dope. I would use some butyrate reducer and see what it does on the belly somewhere or maybe some Polyfiber reducer.

  5. #5
    59pacer's Avatar
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    Default Re: Polyfiber or dope?

    Talking to a previous owner, and experimenting with various solvents, it is becoming more certain that the covering and finishes through to the silver (polyspray) are Polyfiber process, and the dreaded 'someone' has sprayed Randolph coloured dope over that. The dope finish is 8-10 years old at least, and is not showing any signs of loss of adhesion or cracking.
    Has anyone had any experience of dope over polyspray?
    If I was to take off the dope and polyspray/brush back to the fabric (e.g. with MEK), would nitrate dope stick to the residual polybrush?
    This is on an 'experimental', but I'd prefer it to be correct.

  6. #6
    Administrator Steve Pierce's Avatar
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    Default Re: Polyfiber or dope?

    I use to spray dope over polyspray. Never had an issue. The dope had a better shine than the Polytone. Trying to remove all the coating with MEK would be a huge mess I think taking off tapes and probably the glue joints as well.

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    Administrator Steve Pierce's Avatar
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    Default Re: Polyfiber or dope?

    Went back and read your original post. Inspection rings are glued on with the same glue with either dope or Polyfiber. I would use the Stewarts glue if it were me.

  8. #8
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    Default Re: Polyfiber or dope?

    I don't really understand your problem...
    dope finishes were acceptable under older revisions of the poly STC
    and
    your plane is experimental
    so
    what do you think is not "correct" ?

    If the finish and fabric look good, I would NOT remove and replace coats.
    If you need to make repairs,
    several of the fabric processes are approved over the other ones. I believe Stewarts is. Pick the one
    you want to use and go forward with it

  9. #9
    59pacer's Avatar
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    Default Re: Polyfiber or dope?

    Quote Originally Posted by Steve Pierce View Post
    I use to spray dope over polyspray. Never had an issue. The dope had a better shine than the Polytone. Trying to remove all the coating with MEK would be a huge mess I think taking off tapes and probably the glue joints as well.
    Thanks, Steve. I sometimes find it helps to ask a bit of a 'stupid question' to get good answers--that way people don't make assumptions about my knowledge level!.
    The presence of a good dope over polyfiber finish on part of the aircraft already had me thinking that it shouldn't really be a problem, and the fact that you've done it and it works is good info.
    It would be 'last ditch' to go the MEK route. I hate using the stuff more than absolutely necessary. I'll be experimenting with some other options first to try to get it all clean enough to respray.

  10. #10
    Old3pacer's Avatar
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    Default Re: Polyfiber or dope?

    It was in 2006 that polyfiber STC changed such that only 3 top coatings were approved - polytone, aerothane and ranthane. Prior to 2006, the STC specified coats up to and including silver, but choice of topcoats was left to the individual. This would make your application legal if it occurred prior to 2006 - for a certificated aircraft. My understanding [IMBWrong] is that experimental can do what you like.

    I take it, you don't like the color?

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