What does paint weigh?

Discussion in 'Finishing Techniques' started by DarylP, Apr 25, 2010.

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  1. Apr 25, 2010 #1

    DarylP

    DarylP

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    Hi everyone,
    I was curious about the weight that a good paint job adds to the overall weight of the plane. There is considerable talk on the forum about saving weight, but I have found nothing about the weight of the paint. Also, does painting a fabric take more paint than painting metal? That being said, can you paint sewn Dacron fabric, like many of the kit planes use?
    When I can get back to building the plane I want, I was going to go with a metal covered plane. I would not apply paint to the ailerons, rudder, and elevators, polishing them instead, (then a clear coat to minimize oxidation) in an effort to save weight. I know there will be a savings in weight, albeit maybe very little. Just curious...there seems to be a a lot of good painters here.
     
    Last edited: Apr 26, 2010
  2. Apr 25, 2010 #2

    orion

    orion

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    I fixed your typo.

    Regarding paint, it can actually add a fairly substantial amount of weight, especially if you're using it as a filler of fabric or even a pin hole filler in composites. True, you sand between the coats of primer but of course that does not eliminate all of it so the buildup can add up to a surprisingly big number. Obviously this is a function of how much surface area you have but some time back I talked to a Stinson 108 owner up in Alaska who estimated that the primer and paint alone added as much as 40 to 50 pounds to his plane.

    Interestingly though, it was still a significantly lighter figure than the 108-3 where the company substituted a metal skin for the conventional fabric of the -1 and -2 models. I don't recall how much though.
     
  3. Apr 25, 2010 #3

    Dan Thomas

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    Fabric and its finish weigh less than metal skin, but the fabric-covered airplane needs a heavier internal structure than the metal-skinned airplane. Pretty much a saw-off. When applying finish to fabric, follow the manufacturer's instructions. Using less than recommended leaves the fabric unprotected and it ages much more quickly.

    There are paints and there are paints. The laquers that Cessna used years ago were both cheap and light. The urethanes used now are really good-looking and weather pretty well on metal but are terribly heavy and not so cheap. They start cracking when used on fabric as they lose their flexibility with age.

    A Cessna 172 takes, if I remember right, around six or eight quarts of urethane. Much of the weight is solvent that evaporates, but I'd suppose that there are still 15 or 20 pounds of solids left on the metal once it's cured. Estimates I can find for the paint on a completely-painted 747 run from 500 to 1200 pounds. Many airlines leave a lot of aluminum bare to avoid both the cost of the paint and labor to apply it, and to avoid burning more fuel and giving up payload to carry it around.

    Dan
     
  4. Apr 26, 2010 #4

    MadRocketScientist

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    FWIW on the CriCri (tiny aircraft) the manual states each coat of paint adds between 1/2 to 1kg.

    Shannon.
     
  5. Apr 26, 2010 #5

    lr27

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    I saw a bare aluminum RV-6A at the airport yesterday. It looked great, but then, the workmanship was very good. I think bare metal shows ripples more. There were a few, but it seemed a lot smoother than most of the Cessnas surrounding it.
     
  6. Apr 26, 2010 #6

    BBerson

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    In my paint shop, we used about 4 gallons of white for two coats on a C-172. Then another gallon or so for the trim color. The primer was another gallon or more. Some of the paint ended up on the floor from overspray.
     
  7. Apr 26, 2010 #7

    Dan Thomas

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    That would be about right. We used Endura, which covers really well with one coat, but it's really heavy stuff. I hear that Imron goes on somewhat thinner but have never used it. The zinc chromate primer also adds considerable weight due to the metallic pigment.

    Dan
     
  8. Apr 26, 2010 #8

    lr27

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    Suggest doing one square foot samples and check with a gram scale before and after. (Allow lots of drying/curing time). Then you'll really know what happens with the particular materials and techniques you are using. I'm sure a good triple beam balance, if used religiously, can help save a lot of cumulative weight. It works that way on models. I made scale that could measure down to several milligrams for some models I was building. If weight matters, weigh everything. Of course you're going to need an accurate larger scale too, but the triple beam balance is good from a couple of tenths of a gram up to, with the extra weights, a kilo or two. A little weight saved here, and a little weight saved there adds up after a while.
     
  9. Apr 26, 2010 #9

    DarylP

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    Thanks so much...
    So using as little paint as possible would be good, if you are trying to save weight. So I guess the Dacron covered planes like Rans has the right idea, as you get a decent look without adding a lot of weight. I think that Rans has a decent structure, not adding a lot of structural support weight. I could be wrong though.

    I am saving for a Zenith CH750, wanting it for many reasons, but mainly because of its durability and the ability to apply a nice finish. I wanted to do extensive airbrush work, (I did that on another plane I owned) and that is why decided I could save some weight by polishing the ailerons, elevator and rudder. I suppose I am splitting hairs, but hey, I will have it figured out sooner or later. At least with this forums help. :)

    DP
     
  10. Apr 26, 2010 #10

    wally

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    Just keep in mind that dacron is very sensitive to UV light in sunlight and will loose strength quickly. It must have a UV blocking layer in the finish process or it won't last more than a year or so.
    Wally
     
  11. May 3, 2010 #11

    DarylP

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    So somewhat related, what about leaving sections bare aluminum? I wanted to polish those to a shiny finish and then clear them so that it does not oxidize. So, does that aluminum polish up real nice? Oh, and once you polish it, how well would it take the clear coat?

    Thanks:grin:
     
  12. May 3, 2010 #12

    challenger_II

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    Regarding clear coating polished aluminum...

    It will crack, and flake off, in short order. First off, One needs to etch the metal, so that paint will sticl. Next, One needs a primer, so that the paint will stick better.

    On a polished surface, the clear coat will not adhere well. Without a primer,
    the clear coat will not adhere well. Also, when you shoot clear coat over polished aluminum, it has a bit of a hazy, yellowish look. Sort of ruins the effect.

    On another note, I read that the Army insisted Boeing, and her subcontractors, furnish the B-29 without painted airframes. It was stated that leaveng the airframes bare saved 600-800 pounds of weight.
     
  13. May 3, 2010 #13

    addaon

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    Daryl, polished aluminum doesn't need to be clearcoated, necessarily. There are quite a few Zenith designs flying around polished (6061, rather than the more common 2024, helps a bit with corrosion concerns). It's a maintenance pain -- I've heard one builder estimate 20 hours a year keeping things shiny -- but it can be gorgeous. There's an 801 that was at the last Zenith fly-in that was 90% polished, with navy blue trim; worked great.
     
  14. May 4, 2010 #14

    MadRocketScientist

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    From what I hear is the more highly polished it is, the easier it is to keep it that way. The polished surface tends to stop the corrosion starting.

    Shannon.
     
  15. May 4, 2010 #15

    jhausch

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    I think the Stewart Systems guys have a clear finish for bare/polished metal. I don't know much'bout it, but I've heard others comment favorably.
     
  16. May 4, 2010 #16

    MadRocketScientist

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    Nuvite have some good articles on polishing and why the clear coat isn't needed.
    Nuvite Home Pg

    Shannon.
     
  17. May 5, 2010 #17

    DarylP

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    I had a 650 Yamaha that I owned a long time ago, and I wanted to make the cases look really nice. I had read a magazine that had an article on making mag wheels look like new and decided to give it a try. The reason I mention this is because I had to sand off a clear finish, that was there to keep the cases from oxidizing. It was a bugger to get all that stuff off, having to use very coarse sandpaper. I used progressively finer and finer sandpaper, going to wet eventually. It took me most of the winter to do the side cases, but man, when it was done everyone thought I had chromed it. That's why I figured that I would have to clear the parts on the plane. However, I do remember that I never bothered to clear those cases, and polished them from time to time. So I guess that is what I will do when I get to this project. I bet it will look awesome though.
     
  18. May 22, 2010 #18

    challenger_II

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    A polised-metal airplane does attract a lot of attention.
    I have had a 1962 Cessna 150, and a 1946 Cessna 140, with mostly natural metal. It was a bear to keep them polished. Any water that gets on them, from a passing rain shower, to washing the bird, makes water marks, and you have to start all over. I made a decision, then, that I would always have a painted finish.
     
  19. May 22, 2010 #19

    DarylP

    DarylP

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    Challenger,
    I don't think that i would mind the polishing, as it is just personal time. One thing is for sure, that when a guy like you sees the plane, you would appreciate the work that went into it.

    DP
     
  20. May 23, 2010 #20

    dafranklin

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    From "Evans Lightplane Designer's Handbook", First Edition. Paint will weight about 0.04 lbs per square foot.
     

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