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Author Topic: Polyurethane vs Dope  (Read 1109 times)

Offline kevin king

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Polyurethane vs Dope
« on: November 07, 2018, 09:03:58 AM »
Here's why I'm reluctant to use Polyurethane paint on an open bay balsa wing covered with silkspan: To brittle.

The blue paint is dope. The white is polyurethane
« Last Edit: November 07, 2018, 05:24:47 PM by kevin king »

Offline Ara Dedekian

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Re: Polyurethane vs Dope
« Reply #1 on: November 07, 2018, 10:11:39 AM »


        Here's what happened to the Urethane on my Flying Clown wing just sitting in the attic in extremes of heat and cold. The covering, scuffed up with OOO steel wool,was Doculam, a heavier grade of Phil C's SLC covering. It did adhere to the silkspan over balsa but I may have clear coated the fuselage with the old K&B clear epoxy.


        The urethane was water based System Three Inc. marine paint over their two part primer. Nelson Products, who used to advertise in Model Aviation, distributed the products to modelers.
 
        Ara

Offline Brett Buck

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Re: Polyurethane vs Dope
« Reply #2 on: November 07, 2018, 10:14:56 AM »

        Here's what happened to the Urethane on my Flying Clown wing just sitting in the attic in extremes of heat and cold. The covering, scuffed up with OOO steel wool,was Doculam, a heavier grade of Phil C's SLC covering. It did adhere to the silkspan over balsa but I may have clear coated the fuselage with the old K&B clear epoxy.

    It is not at all surprising that nothing sticks to a slick laminating plastic!  That's why it is not used for stunt planes, generally.


     Brett

Offline Ara Dedekian

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Re: Polyurethane vs Dope
« Reply #3 on: November 07, 2018, 10:44:18 AM »
    It is not at all surprising that nothing sticks to a slick laminating plastic!  That's why it is not used for stunt planes, generally.


     Brett

     Lesson learned, the hard way!

     Ara

Offline Brett Buck

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Re: Polyurethane vs Dope
« Reply #4 on: November 07, 2018, 11:18:05 AM »
     Lesson learned, the hard way!

  Sometimes, you just have to find out for yourself! We have had something experimental go wrong.

    BTW, to the topic, dope would have flaked off almost as soon as it dried, polyurethane had a better chance.

    Brett

Offline john e. holliday

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Re: Polyurethane vs Dope
« Reply #5 on: November 07, 2018, 11:45:22 AM »
I have found using the SLC type covering, it needs a really good buffing and clean surface.  Then spray a good primer before dope or or the Rustoleum paints.    D>K
John E. "DOC" Holliday
10421 West 56th Terrace
Shawnee, KANSAS  66203
AMA 23530  Have fun as I have and I am still breaking a record.

Online kenneth cook

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Re: Polyurethane vs Dope
« Reply #6 on: November 07, 2018, 02:16:12 PM »
             Having talked with Jerry Nelson on numerous occasions and I still use the Systems 3 WBPU it was not intended to go on synthetic films. I'm surprised it lasted that long. It does the same thing in no time at all if used over butyrate dope which is what caused me to have numerous discussions with Jerry. From that point on, I used nitrate as a base and it never failed and has held up better than any dope I ever used. I have numerous planes painted with it. It can be applied over synthetic coverings such as Koverall or nylon when cross linker is applied to keep it from migrating through the weave but film doesn't work.


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