painting dacron

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

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  1. Mar 24, 2015 #41

    mcurcio1989

    mcurcio1989

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    ^ I have definitely thought about it big issue is that I have already cut holes for some hinges and brackets on the wings.


    That said - Gentleman my head is officially hurting, aggressively, from the mountains of circular information I have read on this subject. There is no doubt in my mind that in the 15th year of our lord in this 21st century that there exists an effective means of coloring dacron fabric in situ and then applying clear coat. I know hang glider guys have done it and I know sailors have done it. The problem comes that everyone just references something they saw or bought after the fact but provide no useful information as to the process.

    I have heard from many sources that applying latex paint direct to dacron sailcloth holds up quite well. My only issue is that I don't want this to look too dull and I would like to clear coat over the latex - unless it is possible to get a good finish out of the latex. Again I want to keep weight down as well.

    I do realize that I am asking these questions in the wrong place now. I need to be asking ultralight and sailors specifically. One problem is that when sailors are asked they tend to say "just do what the aiplane guys do" not knowing the differences we have discussed

    I do not doubt rec mobs experience with applying color to sails but my intuition says that if clear can adhere, so could color. My suspicion is that the color coats lacked the flexibilty of the clear and fatigue cause them to fail. Flex additives may be able to solve that. However, what I would really like to do is something more along the lines of silk screening the fabric with a very light coat of color and then clear over that.

    There is no reward to be had without hard work!
     
  2. Mar 24, 2015 #42

    mcurcio1989

    mcurcio1989

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    As an example - I can't find a reason why this guys process would not work. Mek should remove any of these wax coatings that have been mentioned and latex forms a mechanical bond anyways so as long as the fabric weave isn't sealed it should be fine (don't think it is).

    Latex

    I am not intending this to be an argument on latex paint as I know that is highly debated. Just that there is no reason why the method should not work.
     
  3. Mar 24, 2015 #43

    Pops

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    I painted the airplane in the picture on the left with Sherman Williams Krylon urethane enamel. Brushed 2 cross coats of the aluminum, ( heavy with aluminum, so keep it stirred.) and worked it into the weave. Then rolled (4" roller) 2 cross coats of colored. Mixed my own gray color by taking out 14 teaspoons of white and adding 14 teaspoons of black to a quart of paint. Yes, I said rolled on, the paint will flow out and look like it was sprayed. Mixed paint with 30% MEK.
    Painted 7.5 years ago, still looks as good as the day it was painted. I painted a couple test panels first and tested.
    The only problem, Sherman Williams quit selling this paint in quarts or gallons, just in rattle cans. When I bought the paint for my airplane it was $9 a quart. I would like to find more to paint the JMR Special with the same paint.

    Dan
     
  4. Mar 24, 2015 #44

    bmcj

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    Just curious, where did you get your Aluminum powder and in what ratio did you mix it ?
     
  5. Mar 24, 2015 #45

    Hot Wings

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    You can still get aluminum powder from West - which is kind of surprising given the current paranoia of the BATF, Homeland Insecurity, DOT and a few others.
     
  6. Mar 24, 2015 #46

    mcurcio1989

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    Pops - I have come across your project in searches before and It is good to hear that it is still holding strong.

    My biggest question is is does anyone think that I will have issues going this route being that I am using sailcloth? I plan to wipe it down with water and then a rag lightly coated in mek.

    Now the primer is only there to ensure adhesion to and filll the weave correct?

    My other issues I need to figure out is that I am going to have a base coat that is basically primer grey. This will be about 60% covered by accent colors. Obviously I don't want all of that extra useless weight so I need to experiment and figure out how I to feather out the base in areas where it will be covered.
     
  7. Mar 24, 2015 #47

    mcurcio1989

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    I believe this information gives some detail as to the difference with sailcloth key is -calendering

    link to fill text Tutorials: airframe fabrics



    "This heat-set treatment significantly tightens the weave. Full or partial heat setting may be done at the mill by passing the fabric through heated rollers after weaving — or the fabric may leave the mill without heat setting. Sailcloths may be passed through the heated rollers under high pressure (calendered), which also imparts a high sheen to the surface, and minimises porosity and stretch.

    Both heat-treated and untreated fabric categories have airframe use. Sailcloth, generally used for mechanically attaching (rather than chemically bonding) the covering to trikes and slower-speed three-axis aircraft, is normally heat-set (perhaps calendered), stabilised and colour-dyed at the mill. Thus it can be cut and sewn to form an aircraft covering, with little further treatment required. Colour-dyeing processes could alter a sailcloth's elastic properties, which might affect the behaviour of a trike wing incorporating multicolour panels."

    "Various substances are used as lubricants during the yarn-making and cloth-weaving processes. These substances may still be in the fabric delivered to the end-user."
     
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  8. Mar 27, 2015 #48

    mcurcio1989

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    Based on the information that I wrote above I decided that my best shot was to do a trial run. First thing I did was cut a bit of material and throw it on our 15k microscope at work. I was hoping to see if I could tell what the texture on the fabric is. Unfortunately, the opacity of the material that is calendered on is such that I was not able to really see it. I was able to see the fibers of the cloth and it was pretty cool! It is no wonder the latex bites it so well.

    My suspicion is that plastic coating on the Dacron is so thin that there is still quite a bit of texture for the latex to bite. You can feel a lot of texture just touching it. So I taped off a 1 foot square portion of fabric on my flaps that I am redoing. I wanted to tape of the area so that I could paint over the tape and then try and get the paint to peel off from the seem there. I did my first couple coats of the primer extra thin to help it penetrate the weave. I used a brush on the primer and a roller on the paint. I ended up doing 7 coats of primer and 4 of color. My primer was still thinner than it should have been. I did a lot of sanding in between coats including top coats. I have not wet sanded yet but I was amazed by how well the finish came out even from a roller without any wet sanding. It would be a 10 foot paint job with no wet sanding. I pealed the tape off trying to get the paint to lift. Interestingly enough I could get the top coat to lift from the primer but I could not get the primer to lift from the fabric at all. I then tried to peel /scrape off some of the finish right on the edge with my nail. As latex is not nearly as hard as urethane I could get it to sort of scrape off but not peel or chip. I think if it was allowed to fully cure this will not be the case. I will let it cure more and then see if it will scrape or peel off (try something better than my nail) I'm very optimistic at this point.

    Next step is going to be to let it cure more, wet sand to practice that and see how good I can get it and if I have enough thickness. Then I am going to cut this sample out and cut a piece of bare fabric out to figure out how much it weighs. Then I'm going to put this sample through the wash a bunch of times and generally submit it to the worst treatment I can and see if it holds up at all. Part of my optimism comes because I know there are sail companies that recommend that decals be applied to there sails with the use of latex paint. There isn't a whole lot of talk of latex being applied to sailcloth and that makes sense since generally the reason it is used is to save weight. In my case I don't think it will affect much since most builders on my kit clear them anyways so your getting inferior uv protection for probably much less weight than this (but you still have to fill the weave if it is to look decent). If this will hold up I don't think the added weight will be that significant and I think it would be justifiable if it hold up well enough the lengthen the life of the sails -plus ultimately this is an aesthetic thing for me and I can cope with the weight.
     
    Last edited: Mar 27, 2015
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  9. Mar 27, 2015 #49

    StarJar

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    Nice bit of testing there. Thanks for sharing it.
     
  10. Mar 27, 2015 #50

    Hot Wings

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    ^ Agree! This is the difference between an Experimental aircraft builder and a home-built aircraft kit assembler.
     
  11. Mar 27, 2015 #51

    bmcj

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    Nice write up mcucio. Just be sure you don't sand (cut) through the paint and into the fibers.
     
  12. Mar 27, 2015 #52

    Dana

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    Seven coats of primer???
     
  13. Mar 27, 2015 #53

    bmcj

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    Does seem excessive, unless they were very thin coats.
     
  14. Mar 27, 2015 #54

    mcurcio1989

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    They were very thin maybe 1.3 times the viscosity of water. Not going to lie, that was an accident since I added to much water and had no paint left to add but I do think that the thinner the paint on initial primer coats the better it will be able to settle / filter down into the weave and grab. I barely even covered the weave with the primer. In fact the top coat is taking care of some of that. I'm no expert but as I understand it poly fiber says 3 cross coats of poly brush which is essentially there primer and that amounts to 6 "coats". I had 3.5 "cross coats".

    I really thought I would be able to get away with less coats of primer since the weave should already be filled somewhat by the coating they calander on. Its sort of a good thing if that isn't the case but none the less.

    I'm going to do more tests and I will try it out with the primer at the thicker viscosity. I also need to get a can of primer tinted grey. I didn't realize it until after i started applying but white primer on white cloth does not give a good indication if you sand too much, as bmcj warned of.

    FYI this is the procedure I tried to follow. This is the same person who gave that presentation on this at Oshkosh. He may be on this forum as well. http://wienerdogaero.com/Latex.php He has a good procedure here, good videos, and his work turns out great.
     
  15. Mar 28, 2015 #55

    Aesquire

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    Good work... but forget all about how you do Polybrush. It's for not calendered fabric, and is to fill the weave and make otherwise very porous cloth wind tight.

    This is going to sound silly, but maybe try just latex? No primer at all.

    Also, since you don't have to fill the weave for aerodynamic reasons, and you don't have a laminar airfoil anyway, what difference does it make if you can see the fibers up close?

    It's not brain surgery, but it may be rocket science.
     
  16. Mar 28, 2015 #56

    Pops

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    Its in the Kryron Aluminum paint.

    Dan
     
  17. Mar 29, 2015 #57

    mcurcio1989

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    Aesquire, I really like where your head is at. I was thinkig the exact same thing. My only thought is that the primer may be designed to grip better than the high gloss paint. I think I will try doing just a very thin cross coat of primer and then a patch with no primer at all. While the lack of porosity makes filling the weave not necessary I have to believe it reduces the paints ability to grip. Making a "gripping primer" perhaps more important. Of course that may just be marketing by paint companies.

    That said,

    after three days of testing I am still feeling good. I was a bit nervous because after day 1. I set the material in soapy water for about ten minutes and scrunches it up - it seemed to soften the paint and allow me to peel it more easily but it still would have to be aggressively scraped from an edge to do so. I now believe that was due to it not having near enough time to cure. After leaving it inside a couple of days it seems to have cured a lot and even after immersing it in the hot tube for 30 minutes it didn't want to come off. We already know that latex holds up to the elements I just need to prove to myself that it can grip the calandered fabric and I think these results are positive.

    I weighed the sample before messing with it and my paint doubled the weight of my 4oz fabric. I'm fine with that weight as I don't think it is amounts more than a couple pounds than clear overall would add and it is giving me way better uv protection. I'm definitely going to see if I can get that weight down by using less primer and allowing the weave to show through.
     
  18. Mar 29, 2015 #58

    Aesquire

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    Hang gliders also use calendered sails, but the paint problem is that you roll the sail up every flight, ( unless you store it in a hanger where you air tow, but that's unusual, since you can fit dozens of folded gliders on a rack in the same space. The tow planes are seldom folded. )

    Every flight can mean 5 or more times a day. Then they spend most of their times rolled up, bouncing on roof racks, and laying on racks or hanging from ceilings. All that is very hard on any kind of paint applied to cloth.

    The fixed, relatively rigid wings on your plane should be much easier on paint.

    I'd still expect a relatively short lifespan, but relative to Piper Cubs, so that's years.
     
  19. Mar 30, 2015 #59

    mcurcio1989

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    Well I tried just putting the paint straight on the fabric. I wanted this test to kind of be what happens if I do the least. I didn't sand at all in between coats. I brushed the first coat on with a foam brush then followed it up with 3 coats of the high gloss "topcoat". That was yesterday. Once it was dry to the touch I cut it out and took it inside to cure.

    I tried pealing off a little this morning and it seems to be sticking every bit as good as the primer (too early to say tho). I'm going to let it dry a couple days before messing with it. The weave is very visible but I don't really mind that. It is glossier than if the fabric was not painted and the weave sort of hides imperfections and looks uniform. One thing I will do differently is a light sanding in between coats and I'm going to try adding floetrol. Some of the bubbles didn't go away on there own and I think flowtrol / sanding will help that. Other than that I'd be happy with this finish as is. Hopefully this test holds up as this will save a lot of time and weight.
     
    Last edited: Mar 30, 2015
  20. Mar 31, 2015 #60

    mcurcio1989

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    Okay after letting this dry for 2 days it seems to actually hold much better than when I put the primer on first. I'm not sure if that is because it is thinner or what but I can't get it to chip or scrape off of the fabric no matter what I do.
     

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