Composite cores

Discussion in 'Fiberglass and Composite Boat Building' started by Vanbokklen, Sep 16, 2004.

  1. Vanbokklen
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    Vanbokklen Junior Member

    Are any boat builders using polystyrene as a core for a composite boat?
     
  2. AVMan
    Joined: Sep 2004
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    AVMan Junior Member

    Polystryene cores

    If any builders are, they should not be using styrenated resins (polyester or vinyl ester) as the liquid styrene in the resin will quickly dissolve the foam (I witnessed this first hand when I tried to do a gel test in a polystyrene cup...).

    If one was to use epoxy (or other non-styrene resins) ut could be used as a core, but usually only for non-structural or lightly loaded panels. check the physicals (mainly compression strength, shear strength & modulus) and compare to traditional PVC, SAN, or structural polyurethane foams. From what I remember, polystryene foams are a little bit lacking in some of the structural properties and are usually very low density (1 to 3 lb/c. ft??) and are not recommended for structural core materials.
     
  3. Ilan Voyager
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    Ilan Voyager Senior Member

    Nobody serious uses polystirene foam as structural core for boat building. Its chemical and physical carateristics do not fill any of the requisites asked to structural cores. Polyurethane foams, while used by some in some applications, are not better in boat building.

    The lone exceptions I know, when using polystirene foam in its higher density (the blue or pink qualities) are lost molds, "filler" of empty spaces, or bulkeads in small beach catamarans.
     
  4. JR-Shine
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    JR-Shine SHINE

    We built a canoe out of it for an experiment. It has almost zero peel strength, so delamination started after very little use. I guess you could use it for non-structural applications, but make sure the piece is painted white and/or is out of the sun (the heated epoxy will make it even more likely to peel)

    You can see the canoe here:

    http://www.boatplans-online.com/proddetail.php?prod=Hiawatha

    We used all directional glass and epoxy - it looks quite nice.

    Joel
    Boatbuildercentral.com
     
  5. Wang Sheng-guo
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    Wang Sheng-guo New Member

    :rolleyes: It's a strange question.
     
  6. Herman
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    Herman Senior Member

    Polystyrene for wet environments, or highly loaded environments, are no real option. However, it is used a lot for plug making, as it is easy to route and very cheap. But the result is never intended to actually be a real boat, just a model.

    Please also see www.marinmilling.nl. They produce plugs from polystyrene.
     
  7. nero
    Joined: Aug 2003
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    nero Senior Member

    extruded polystyrene/glass strip idea

    There is a company wrapping several different foam cores in glass and then bonding these in to pannels. They do not use polystyrene. There is another company that drills thousands of holes in pannels and inserts glass rods into them for physically holding the two skins together.

    SO WHAT IF, we enhance the poor qualities of extruded polystyrene by stripping up a pannel and bonding on fibers. The fibers could help enhance the core bonding and the foam would be supporting the fiber in the strips keeping it from buckling. I attached a drawing of the idea.

    There are higher density extruded polystyrene foams (still not very heavy)
    Formular 500 and 600. They may approach the compression strength of Corecell strips. ???
     

    Attached Files:

  8. JR-Shine
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    JR-Shine SHINE

    I am not an engineer, but my first reactions are:

    - Wouldnt this be heavier than say an 8 pound density PVC foam?
    - I would also think that this panel would have less strength in sheer compared to a similar thickness panel made with regular corecell or like brand of core with same lamination.

    Also, the empty spaces could get water logged or provide a chaneel for leaks.

    I do mean this to be constructive. Like Ive heard here before, if people didnt think like you are - "we would still be digging out canoes".

    Joel
     
  9. nero
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    nero Senior Member

    The void inbetween the two strips would be fitted with a strip of foam and put in place with epoxy. The sheer or slip between the two skins should be very little since the glass epoxy micro stringer would be in the same plane. These are all guesses.

    The idea is to have a cheap material cost. Core cell is at $350 a sheet of 2"inch where as the extruded Polystyrene may be as cheap as $25.

    This should be a lot lighter than WRC stripps.
     
  10. JR-Shine
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    JR-Shine SHINE

    How would you manufacture the epoxy/glass micro-stringers. Im thinking of how such a panel could be built economically?

    I seems like most (or all) the strength is coming from the epoxy/glass part of the structure, what does the foam do structurally? I understand it will add insulation and displace water in case of a puncture.

    Joel
     
  11. nero
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    nero Senior Member

    Motivation

    Was trying to find a low-cost, structurally acceptable, easily found core material. (not asking for a lot)smile

    the strips of polystyrene could be ripped with a table saw from pannel stock. (It the idea works they could be extruded commercially)

    The polystyrene serves as an encapsulated form/mold to lay the glass or carbon up on. If it is the higher density foam it could be load transferring like any core. It should also stiffen the glass layed in between it. (keep it from buckling) It would absorb energy from impact. If it is a version with the vertical center web, this could be like a wood core. (structural not just load transfer).

    The idea is that the 4 strip planks could be layed on forms with no fitting. Then the space inbetween could be filled in by fitting a filler piece of foam.

    Nida Core and honeycombs are walls that transfer loads. So I am trying to work in the direction of full-length linear fibers and cross-core fibers as walls. Overcoming the shear flex and pour bonding of extruded polystyrene.
     

  12. Herman
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    Herman Senior Member

    The idea of cross-core fibers are already used by the company "Structiso" from France. Their website is www.structiso.com. Very nice product.

    I also recall a company that made a polystyrene core, with epoxy-glass laminate wrapped aroud it, in bead & cove strips. They used 1 layer of biax 450 around it, overlapping at the bead, so a construction would have 3 layers of EBX450 in cross-core direction.
    However, the stiffness of the product was somewhat disappointing, but the product was good enough to build plugs. (would strips of PS alone also be enough?

    If I recall well, they built a boat as well with the material. Don't know the results however.
     
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