14 foot Skiff "Javelin" hull materials

Discussion in 'Materials' started by BlunderBus, Oct 27, 2013.

  1. BlunderBus
    Joined: Oct 2013
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    Location: New Zealand

    BlunderBus Junior Member

    I'm doing some research in to hull materials as I'm keen to build a new Javelin to take to the 2016 South Pacific's in Perth.

    Now the costly choice is to go for carbon, epoxy and foam to sandwich.
    Or is it, considering time as well in the cost equation?

    Or am I better to go with ply and a glass finish? (I'm assuming Carbon is a waste of time if ply is used)

    Other useful info:
    1. The Javelin has a 70Kg minimum weight (excluding rig and foils) so there is a little play with.
    2. The rules also specify hard chines. (class rules can be found here: http://javelins.org/Technical/TechnicalIndex.html)

    I'd be grateful for some well founded feedback, thoughts and ideas.
    Thanks,
    Hamish
     
  2. PAR
    Joined: Nov 2003
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    Location: Eustis, FL

    PAR Yacht Designer/Builder

    You can build a Javelin at weight with both building techniques, though a high tech build might permit a fixed ballast, built into the hull, in an ideal location, so it can't be removed during her weigh in.

    The high tech approach of course will cost a fair bit more in materials, but if use to these materials not much a problem building the boat. A plywood boat might be easier on the pocket book and possibly the builder, of course depending on familiarity with wood working. A combination approach might be considered too, where 1/8" (3 mm) plywood is used throughout the build, but stiffened with high tech fabrics. You'd save on some material costs and the self fairing properties of plywood can be taken advantage off, saving build effort.

    In the end, you'll be the best judge of which path you'll take. A take no prisoners approach would mean a carbon/kevlar and/or spectra build, which has obvious advantages.
     
  3. SukiSolo
    Joined: Dec 2012
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    Location: Hampshire UK

    SukiSolo Senior Member

    You could also use a hybrid technique, strip plank and glass/carbon either face. This is in my opinion a v good technique as it allows you to get a very good lightweight 'core' then put a stiff sheath on it at reasonable cost. If both sides are glass it will be cheap but still stiff and obviously carbon would stiffen it more.
    Also it may be possible to use a strip plank bottom, where you have max curvature and a ply upper. This has been done quite a bit on 14s National 12s and other stuff in the UK.
    Hope this might open up another avenue. WR Cedar density around 0.38 Gaboon around 0.55 Balsa 0.20 and foams anywhere between 0.2 and 0.4. Also that African timber (name escapes me) at 0.38, smells like monkeys pee when you saw it though and prone to shakes so I prefer WR Cedar.
     
  4. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    If I was considering a wooden core, I'd use as light a material as practical, say eastern white spruce (27 cu. ft. - .33 specific gravity).
     
  5. SukiSolo
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    Location: Hampshire UK

    SukiSolo Senior Member

    Eastern White Cedar is pretty hard to get in the UK. Poster is in NZ so there may be local useable timbers there, Kauri is protected. Maybe an Aussie species?.
    I understand EW cedar was used a lot for draws in furniture as moths hate it. WR Cedar certainly is used against them, and its dust keeps mosquitos down a lot. EA used for pencils mainly, I have heard and in short supply but you guys in the US will be more familiar with availability etc.
    As it happens I have a small quantity of EW in stock and it smells quite nice. Not enough to plank a boat. Not quite sure what to use it for so I might use it as a local core material in the future.
     
  6. NoEyeDeer
    Joined: Jun 2010
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    NoEyeDeer Senior Member

    Best timber to use in NZ would be paulownia. Freely available in Australia, so I assume the Kiwis could get it fairly easily too.

    ETA: First Google hit on "paulownia timber nz" is http://www.paulownia.co.nz/
     
  7. redreuben
    Joined: Jan 2009
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    Location: Beaconsfield Western Australia

    redreuben redreuben

    + 1

    Paulownia 17-21lbs cube, specific gravity .23-30
     
  8. BlunderBus
    Joined: Oct 2013
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    Location: New Zealand

    BlunderBus Junior Member

    Hi Guys,

    Thank you all for your replies.
    I like the idea of Paulownia.
    So I think it'll be a modern approach as in a sandwich of either foam or paulownia between carbon.

    Thanks again
     

  9. Steve W
    Joined: Jul 2004
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    Steve W Senior Member

    Russ Bowler built some very light 18 footers sponsored by Benson and Hedges out of polystyrene with a layer of glass cloth each side, all the loads were taken by an aluminum space frame so all the hull had to do was keep the water out and provide
    shape.

    Steve.
     
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