painting dacron

Discussion in 'Finishing Techniques' started by mcurcio1989, Mar 16, 2015.

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  1. Mar 16, 2015 #1

    mcurcio1989

    mcurcio1989

    mcurcio1989

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    The aircraft I am building uses pre-sewn dacron socks which typically just have clear coat applied over them. The color scheme I had in mind did not lend itself well to a solid color or the patterns they had so I got solid white and I'm going to apply color before the clear. I want to keep weight and cost down (who doesn't). I've seen people talking about using various poly fiber products as base coats and this seems like it is going to add a lot of weight and cost.

    My confusion really stems from the fact that it seems like most ultralight style aircraft I have seen are just bare fabric with clear coat yet when i read up on poly fiber it makes it sounds very necessary to use there multi step method

    I am going to have a three tone paint scheme so my background with automotive says primer, top coats, and then clear coat

    However poly fiber says poly brush, poly spray, and top coat (no clear?)

    Is the main advantage of poly fiber the UV protection that it offers? Can clear be applied over it?
     
  2. Mar 16, 2015 #2

    Hot Wings

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    A couple of suggestions:

    Check out the Stewart system. It's water based and the glue is probably very close to the contact cement you can pick up at just about any hardware store - after all this is Experimental ;)

    For paint some like to use Latex house paint.

    Robin Ultralight

    Robin Ultralight - Page 3

    Google search - to get you started.
     
  3. Mar 16, 2015 #3

    Aesquire

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    The dacron used with the polyfiber system is not pre-shrunk. Heat is used to shrink the fabric to the frame, and the variety of coatings used to make the fabric air tight and protect against UV damage. Different companies use different coatings and they may not be compatible with each other.

    BUT!!!!


    The presewn dacron used in ultralights is shrunk to final size and coated before sewing. Using the wrong paints will damage the fabric and ruin your day. Contact the fabric manufacturer to see what works on their sail cloth.
     
    Last edited: Mar 16, 2015
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  4. Mar 16, 2015 #4

    TFF

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    Ultralites tend to just accept that in time the covering will be rotted and it will have to be replaced. Usually sold before to un-assuming buyer. Airplanes are painted to the standard that UV will not be what degrades the fabric. Stewarts is nice because of no smell; it is the heaviest. The lightest is dope; but not the shiniest. Polyfiber is the easiest; and easiest to fix, but it really is just a special dope. Then you have the Aerothane if you want poly/ dope shinny. Auto paint cracks in time; a lot faster than the real aircraft paint. Laytex is great for something like a Legal Eagle. If you are not building a low end aircraft; you need to spend the money on the right kind of paint.
     
  5. Mar 16, 2015 #5

    bmcj

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    As Aesquire said, there is a difference between regular aircraft grade covering materials and sailcloth (coverings like you see on Quicksilvers and other old school ultralights and hang gliders, typically presewn into "socks").

    The ultralight sailcloth is preshrunk, and pre-coated (usually with a plasticized coating with some UV resistance, and usually with colors too, but clear can be done too.

    Conventional aircraft coverings are a stretched Dacron that is attached to the aircraft (in sheets or sewn socks) with glue at the edges, then heat-shrunk taut like a drum. Then a clear coat is applied (usually brushed on to insure it penetrates the weave). The clear coat seals the weave, aids adhesion of the fabric to the structure, and gives a surface for the other layers of paint to bond with. Next comes reinforcement tapes over areas prone to high wear (such as corners and tops of ribs); the tapes are 'glued' on with a brush and clear paint. Now comes the silver coat which is (for the most part) a clear paint with Aluminum powder mixed in. This silver coat provides exceptional UV protection (Dacron can degrade with UV exposure), and is also a sandable medium so you can sort of hide small flaws or edges (if can also be used to fill in the weave pattern, but that adds a lot of weight to completely hide the weave). After silver (and sanding), comes your color coats. A properly applied silver coat gives a good, uniform base for you colors so that your color coats look uniform throughout.
     
  6. Mar 16, 2015 #6

    Aesquire

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    Painting on Dacron - Hang Gliding Org - Worlds largest Hang Gliding community, discover Hang Gliding

    I'm still looking for an answer. There are literally a handful of sail cloth makers that make almost all cloth used in hang gliding, sailing, and paragliders.

    Lucky for you you almost certainly don't have triaxial or other exotic dacron.

    Bad news is you can't easily dye it, although a tie dye job can be done....but won't last.
    I loath armor-all. It looks good for a while but causes long term damage.

    What aircraft? If you don't roll the wings up like a hang glider or trike wing, but it's secured to a wing frame like a Rans s-7 then latex house paint is ok for roundels or other marking. I wouldn't paint the whole thing.
     
  7. Mar 16, 2015 #7

    Aesquire

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    Glue! I skipped the Glue!

    This is apples and oranges time. Both conventional cloth airplane covering and presewn ultralight sails work but are very different in How you treat them.

    Presewn cloth is generally not glued on, it won't work.

    Wills Wing has a decent faq on sails but no mention of color.
    It's generally accepted that white cloth is more stable. Almost all high performance hang gliders use white cloth on the top surface of the wing for that reason, colors on the bottom only. ( and "cloth" is like calling Ferrari just a car. Mylar coating with triaxial ripstop and even more exotic stuff is used )

    On a nominal rectangle wing colors aren't that big an issue. The fabric used is sophisticated, but not the racing fabric.
    It really only shares the name dacron with what's on a Cub.
     
  8. Mar 16, 2015 #8

    mcurcio1989

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    These socks are not pre-shrunk. This is an Aventura II similar to the Sea Rey it. I say ultralight style because it has ladder frames with tubes inserted in slots rather than ribs with rib lacing and glued on fabric etc. Inserted into the frame, shrunk, and then it is advised by the kit builder that clear coat be applied over them.

    Its not an RV-7 but it is def not a low end aircraft (in my mind) I would prefer to a good job painting it and allow my paint job and the fabric last longer.
     
  9. Mar 16, 2015 #9

    mcurcio1989

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    This is honestly by far the most confusing facet of this project there are a countless opinions, considerations, options, factors, and methods regarding paint. I'm struggling to make sense of what route I should go.
     
  10. Mar 16, 2015 #10

    TFF

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    Rule 1: do what the manufacture says. They have to have a spec on it.
     
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  11. Mar 16, 2015 #11

    bmcj

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    Pre-shrunk was perhaps a bad choice of words. In reality, the sailcloth is not shrunk, it is provided in its original woven form. The heat shrinkable Dacron for conventional aircraft covering (if my understanding is correct) is made heat shrinkable by "pre-stretching" it. Heating it then allows it to return to(ward) its original unstretched dimensions. The heat required to shrink it can damage paint; that is why the paint is applied after the shrinking. Sailcloths can be made to final size and pre-coated because they will not go through a heatshrink process.

    As far as which direction to go, I recommend following the Aventura manufacturer's recommendation of which paints to use. They have already dome the research and know what works best. I'm sure the clearcoat is used to help protect the fabric from the water spray so that it does not absorb water (weight gain) or salt (corrosive). they probably don't use coler because it adds unnecessary weight.

    Just a last note, aircraft Dacron (not sailcloth) should have at least a clear coat of paint to seal it against air leakage through the fabric.
     
    Last edited: Mar 16, 2015
  12. Mar 16, 2015 #12

    Aesquire

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    Nifty little plane. An RV-7 is a nice plane too, but it's no Aventura II. Although, technically, you could land an RV in water, once.

    I'm watching the tips video now to see what exactly you are talking about... it's Not glued on. That's pre-coated cloth.

    Contact the maker, Which Clear Coat do they use? That's the Chemical family for paint.
     
    Last edited: Mar 16, 2015
  13. Mar 16, 2015 #13

    TFF

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    Someone has an RV7 on floats.
     
  14. Mar 16, 2015 #14

    mcurcio1989

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    Most all of the Aventura's that I know off have just been Dacron with clearcoat. The only one that I know of that has paint used the poly fiber process. I have asked the factory and they are not much help as this is not what they typically do. When I bought the kit we discussed my options for wing color and they advised that I purchase white and paint it as I wanted. The salesman that advised stated that I could use automotive paint but did not express any recommended process. He has since died and I have found that he was not a person of honesty. He may have just been saying that but did not actually know. I was naive in believing it would be simpler to determine a method than it actually is.

    I do believe that most of the other builders out there just go the clear coat route for simplicity and to save weight.
     
  15. Mar 16, 2015 #15

    Aesquire

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    You are not going to have to paint multiple cross coats, just a color coat and clear on top. I'd suggest not painting the whole wing, just patterns, since I'm not sure how well the color coat is going to stick. Do you know which brand & type clear coat they use?
     
  16. Mar 16, 2015 #16

    mcurcio1989

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    ^I do not. what do you mean by not have to paint multiple cross coats are you saying you would not apply the silvering coat? I don't get the second sentence either. Why would color not stick?

    It sounds like the safest bet for me is to use either stewarts or poly fiber for painting the dacron. If I were to go with poly fiber it would be 1 brushed coat of poly brush, 2 sprayed on coats of poly brush, 3 cross coats of poly spray, and then 3 top coats.

    I understand that poly fiber and stewarts are fairly comparable in cost and durability. Obviously they are very different compounds. I'm leaning towards stewarts right now due to the less hazardous chemicals
     
    Last edited: Mar 16, 2015
  17. Mar 16, 2015 #17

    bmcj

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    I'd get a fabric sample and try both coatings. I have never tried painting the precolored sailcloth, but I have my concerns on how well a paint might stick to the alreaudy plastic-like weatherproof coating.
     
  18. Mar 16, 2015 #18

    mcurcio1989

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    The dacron I have is not precolored I got bare white so that I could paint it. I don't believe there is any coating on it. My understanding from the factory is that it is bare dacron fabric.
     
  19. Mar 16, 2015 #19

    Aesquire

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    My experience here is in pre-sewn cloth for Quicksilvers, etc, which are pulled into place, tension applied in a variety of ways, and you are done. No heat guns, no painting.

    The fabric in the "tips & tricks" video Tips and Tricks | Aero Adventure doesn't look like regular aircraft covering dacron.

    He talks in the video about how "heat treat" is next, then a clear UV protectant coat.

    I assume, since I can't find the next video, you take a heat gun to finish tautening the fabric and get the wrinkles out. Is that what your instructions call for?

    In any event you sure don't need to spray paint the sequence of "1 brushed coat of poly brush, 2 sprayed on coats of poly brush, 3 cross coats of poly spray, and then 3 top coats."

    The poly brush is to fill the weave of open weave, unshrunk fabric.

    Most fabric gets pre-shrunk in processing so it doesn't change size & shape when sewn into cloths, sails, sleeping bags, etc. Giant machine, rollers, heat, coatings if used.

    Only cloth meant to be "doped" into size & for airplanes is taken off the machines BEFORE the shrink step. Old school they used cotton and linen, Glued it to the frame, and used water to shrink it tight, the used "dope" ( glue ) to fill the weave and make it air tight.

    UV stuff came much later. Because. They went from flammable Dope & linen to synthetic fabric. It won't shrink with water, so you heat it with hot air guns and irons. The old glues don't work on synthetics, ( dacron ) because they don't "wet" the fabric. So you push glue through the fabric to encapsulate in it glue. Once glued on you heat it to shrink tight, then use the multiple coats to fill the weave to make it air tight, cover the fibers to protect against UV, which slowly decays the Dacron, and color coats to look pretty.

    The fabric in the picture looks like pre-coated and wind proof fabric to start with, and I'm guessing you just spray on a clear UV protective coat. Am I right?

    If so, you sure don't need all those coats of paint and primer needed for a raw dacron sail. You use the same chemistry color coat as the UV clear coat, and you have a colored plane.

    Only the latest Hang Glider cloth has the UV coating applied at the factory. The Sailcloth factory. The top surface on a modern competition glider is a fairly stiff laminate of multiple layers of cloth, kevlar ripstop, mylar, or unobtanium. We just know that you have X number of hours exposed to Y amount of light. Almost all UV damage takes place while you are parked, waiting to fly or fold up . You can test the fabric with a meter that tries to puncture/rip it. When it's shot you get new sails, or in an older hang glider, buy a new one. On an Ultralight or Ultralight inspired design like the Adventura, or Pterodactyl, you just replace the sails.

    So I suppose my next question did they send you a white wing cloth like the video above, or completely not coated material that you need to go multiple coats on? Hold it up to a light, do you see light through a thousand holes?
     
  20. Mar 16, 2015 #20

    Aesquire

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