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Thread: Rigid epoxy or flexible epoxy ?

  1. #1
    Join Date
    Jun 2019
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    Ciudad Autonoma de Buenos Aires - Argentina
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    Default Rigid epoxy or flexible epoxy ?

    Hello, from the extreme south of America, Argentina. I want to know what glue to use to splice a new stretch of the kelson. It is 7 "x 2" and of length 15 '. I intend to join it with a 17 "bevel Both beams will be fixed with 2 of the keel bolts and I will also use the glue This glue should be rigid epoxy or flexible epoxy Can you advise me?

  2. #2
    Join Date
    Oct 2009
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    South Puget Sound/summer Eastern carib./winter
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    16,386

    Default Re: Rigid epoxy or flexible epoxy ?

    We need to know more about the boat. Photos.
    Construction, size, use.
    Even the word "keelson" means different things to different people.
    Then, I'm not sure what "rigid or flexible"even means.

  3. #3
    Join Date
    Jul 2017
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    Toodyay, Western Australia
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    928

    Default Re: Rigid epoxy or flexible epoxy ?

    Maybe a reference to gflex vs bog standard thickened with microfibre... ?

  4. #4
    Join Date
    Jun 2010
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    Between Bourgeoisie and Proletariat - Australia
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    3,842

    Default Re: Rigid epoxy or flexible epoxy ?

    I only heard of GFlex in the last few days.

    Seems like it'd be the right thing - if i have the correct picture in my head.
    Does the keelson get wet? Does it stay wet? What kind of boat is it? What's the wood?

    https://www.westsystem.com/specialty...ughened-epoxy/

    17" scarf on a 2" board - 8.5:1 - across at least 2 floors, seems enough. Though when you say 2 bolts, is that the same as two floors...?
    It's all fun and games until Darth Vader comes.

  5. #5
    Join Date
    Nov 2004
    Location
    Port Townsend WA
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    12,800

    Default Re: Rigid epoxy or flexible epoxy ?

    G/flex works for wood that is difficult to glue such as oak, teak and Purple Heart as well as for masts that will be subject to bending and compression loads. West System states that it is also good for planking scarfs and laminated frames which would indicate that it should be safe for wood that will be subjected to immersion. When in doubt check with the mfg.
    Jay
    Last edited by Jay Greer; 07-15-2019 at 08:42 PM.

  6. #6
    Join Date
    Jul 2013
    Location
    Emerald Coast, FL
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    729

    Default Re: Rigid epoxy or flexible epoxy ?

    Flexible epoxy will work, it has structural qualities and will move some with the wood. Pettit Flexpoxy is available up here or GFlex. They can be sanded, drilled, panted and are rated for underwater use.
    Cheers
    Kent and Skipper
    Small Boat Restoration blog

  7. #7
    Join Date
    Apr 2012
    Posts
    178

    Default Re: Rigid epoxy or flexible epoxy ?

    Quote Originally Posted by Jay Greer View Post
    G/flex works for wood that is difficult to glue such as oak, teak and Purple Heart as well as for masts that will be subject to bending and compression loads. West System states that it is also good for planking scarfs and laminated frames which would indicate that it should be safe for wood that will be subjected to immersion. When in doubt check with the mfg.
    Jay
    Have you checked with the WEST tech support about gluing masts with G-flex? I have found that it's much easier to call when I need to know something and the answers are often surprising and educational. 866 937 8797 is the number.
    I'm a huge fan of G-Flex and I'm pretty sure it's appropriate for Pancho's application, but maybe not appropriate for gluing masts.

  8. #8
    Join Date
    Jul 2011
    Location
    Lindstrom, MN
    Posts
    2,699

    Default Re: Rigid epoxy or flexible epoxy ?

    The flexibility of the epoxy is not important in this application. Before I continue, the OP is talking about bonding wood. I am going to talk about entirely different materials because that is where the flexibility of the epoxy is important. Wood is a forgiving material than metal or rigid fiberglass reinforced plastic

    The stiffness of the epoxy is much more important on relatively thin, stiff materials. If you bond a rigid part to a 1/4" thick fiberglass panel with a rigid, brittle epoxy and tap the part with a hammer, it will pop right off. If you use a more flexible epoxy, it will be much harder to break it off. The shear strength doesn't matter in this case. A brittle epoxy with 3000 psi shear strength will pop off easily where a 300 psi elastomer will take a beating.

    The ability to adhere to oily hardwoods is another issue that has already been discussed here.
    Management is the art of counting beans. Leadership is the art of making every being count. --Joe Finch

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