Expanding marine foam for composite centers?

Discussion in 'Materials' started by John Smithson, Aug 22, 2021.

  1. John Smithson
    Joined: Aug 2021
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    Location: Kansas

    John Smithson Junior Member

    Anyone tried using expanding marine foam as a composite center? Instead of the much more expensive sheets or wood?

    Seems like it could be a much cheaper alternative.

    Either pouring the foam into a mold to get the pieces and then glassing those. Or for something larger, putting down the layer of glass and foaming on top, then sanding it down to the thickness / smoothness you are after and glassing on top.
     
  2. kapnD
    Joined: Jan 2003
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    kapnD Senior Member

    Boston Whaler does that, several others.
    I blew surfboard blanks way back when, we used very heavy two part concrete molds. I have no idea how much they weighed, but a little too much foam would easily lift the top!
    Don’t underestimate foams expansive properties!
     
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  3. Mr Efficiency
    Joined: Oct 2010
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    Mr Efficiency Senior Member

    You can of course buy the pre-expanded polyurethane foam in cut sheets of various thicknesses. The typical 2lbs/cu ft variety is quite friable, and not to considered as structural. 4lbs/cu ft does have much better physical properties, and in less critical applications makes a reasonable core.
     
  4. fallguy
    Joined: Dec 2016
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    fallguy Senior Member

    The problem is controlling the expansion.

    Boston Whaler and Ranger and probably Tuffy and a few others build this way..but it is a highly engineered process and costly to mould.

    From what I am told, even corecell is made with an expansion reaction in a mould, but have not seen it done.
     

  5. Mr Efficiency
    Joined: Oct 2010
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    Mr Efficiency Senior Member

    Expanding the foam into a core isn't practicable or cheaper
     
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