EPS foam

Discussion in 'Materials' started by cpodest, Mar 31, 2014.

  1. cpodest
    Joined: Mar 2014
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    Location: Ilhabela - Brasil

    cpodest The Beginner

    Dear Fellows,

    I´m trying to build a boat using the Sandwich foam. Sadly, where i´m live I only can get EPS Foam in small plates (1 x 0,5mts and 0,5 ,1 and 2 cm tickness). (take a look at the pict as example only)

    Boat features: 3.5 mts LOA, 1,4 mts beam, 0.125 mts draft. Slow Sailboat to be used in sails training.

    The main concern with this kind of foam are the "hard chines".
    The hull has mainly soft angles (soft "V" bottom aft), but there are some hard angles too (Stern). I can´t bend this material more than a few degrees, so my idea is to make some foam plates and cut the parts of the boat by separately (as stitch and glue, but without the stitch), like, 2 bottoms (for the "V"), sides, transom, etc. and then, with the help of a wood frame put it all together just gluing the parts and then fiberglassing all. On the other hand maybe is not a good idea to have a glued union under my feets!? (even fiberglassed!)

    I was thinking to use foam 2 cm tickness for the bottom and 1,5 cm tickness for the sides.

    Please, any comments, sugestions and ideas are welcome!
    Thanks a lot,
    Carlos
     

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  2. Mr Efficiency
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    Mr Efficiency Senior Member

    When you say "fiberglassing" I hope you don't mean cheaper resins like polyester or vinylester, they will de-compose your foam by chemical reaction.
     
  3. nimblemotors
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    nimblemotors Senior Member

    Epoxy should be used with this kind of foam, polyester will melt it. I've read you can paint it with latex paint first to seal it before using polyester resin, but that doesn't help the lack of sheer strength of this kind of foam, i.e. the fiberglass will peel off easily.

    Can you find any balsa wood in Brasil?
     
  4. hoytedow
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    hoytedow Fly on the Wall - Miss ddt yet?

    Balsa is native to Brasil.
     
  5. cpodest
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    cpodest The Beginner

    No, I mean, Epoxy fiberglassing.

    DO u have any experience with this kind of EPS foam and epoxy fiberglass?

    Any comment or experiencien in this kind of building technique are welcome

    Thanks
    Carlos
     
  6. cpodest
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    cpodest The Beginner

    Of course I can find any kind of boat in Brasil.
    Is just for the pleasure of build something
     
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  7. hoytedow
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    hoytedow Fly on the Wall - Miss ddt yet?

  8. hoytedow
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    hoytedow Fly on the Wall - Miss ddt yet?

  9. Mr Efficiency
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    Mr Efficiency Senior Member

    It has never occurred to me to use the two in conjunction, epoxy is way too expensive to be combined with an inferior core, polystyrene foam, it does not make a lot of economic sense.
     
  10. cpodest
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    cpodest The Beginner

  11. nimblemotors
    Joined: Jun 2009
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    nimblemotors Senior Member

    I recently made some flat panels using EPS foam. I only used epoxy to glue some thin vinyl sheets to the foam, instead of using epoxy to make fiberglass. It took only 2 quarts of epoxy for both sides of a 4x8 panel, total cost about $100, and quick and easy to do. Very lightweight, but I don't think I'd use it for a boat hull, eps foam has poor sheer strength. I used it for a deck that had some supports under it.
    hmm, do I have a picture.. no I don't.

    If you can get some balsa, it would be much easier, better, stronger.
     
  12. cpodest
    Joined: Mar 2014
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    Location: Ilhabela - Brasil

    cpodest The Beginner

    Nimblemotors, thanks a lot for the advice. I can get here any kind of boat, wood, fiber..etc, but I want to build one.

    In fact, the main problem are not the cost or the time that I will take or the mess .... the main problem is that i can´t get the materials in this little island!

    I can´t get the XPS foam, only EPS foam, and also I can´t get the epoxy!

    Today I went to the hardware store to ask for some epoxy... they only have one kind of epoxy.. and they only knows that is for wood gluing. They don´t know why, and they dont have the technical sheet. I called to the factory .. and they said that i need other kind of epoxi for fiberglassing. I didn´t know there was differents kinds of epoxy resin for differents applications.

    Here are some boat repair office, i will go there tomorrow and ask about.

    Thanks a lot
    Carlos
     
  13. nimblemotors
    Joined: Jun 2009
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    nimblemotors Senior Member

    I understand that you can use polyurethane glue on EPS (e.g. gorilla glue), which is available at most hardware stores. It is pretty expensive compared to epoxy. Yes epoxy has all kinds of formulations, boat builders generally mean thin epoxy used for laminating (making fiberglass).

    Can't you buy things online and have it shipped there? And no balsa wood? You don't need epoxy for balsa wood.
     
  14. cpodest
    Joined: Mar 2014
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    Location: Ilhabela - Brasil

    cpodest The Beginner

    Finally, I foud epoxy very close to here (like 200km)... they will send to me be mail.

    Thanks a lot
     

  15. AndrewK
    Joined: Mar 2007
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    AndrewK Senior Member

    Carlos, I have used 24kg EPS foam for a canoe bottom successfully but it was 5cm thick with 400 & 600gsm glass skins. To allow for the low sheer strength of the core you would find that thickness required would make this build uneconomic. Plywood makes most sense.
     
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