Question about cold moulding

Discussion in 'Boatbuilding' started by stonedpirate, Sep 4, 2011.

  1. stonedpirate
    Joined: Nov 2009
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    stonedpirate Senior Member

    Hello,

    I am doing a double diagonal hull but dont like the horizontal wood on the inside of the hull.

    Is it possible to make the first layer complete with horizontal wood then double diagonal over the top or does that just add unnecessary weight with no strength adding properties.


    Sorry if i didnt explain that well enough.

    Basicaly, i just want to know if i can do the first layer horizotal or or is it better to just use enough to make the frame?

    Thanks
     
  2. gonzo
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    gonzo Senior Member

    The first layer is on the inside. If you don't want it to be horizontal, then the first layer has to be diagonal. I don't understand what do you mean by "enough to make the frame". I think that asking the designer is the best option. There may be a structural reason for the way the laminates are oriented.
     
  3. Steve W
    Joined: Jul 2004
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    Steve W Senior Member

    Sure, you can strip plank to give a smooth inside and then double diagonal over that, i fully understand the desire to not have the typical longitudinal stringers as the do make it dificult to keep the boat clean.
    Steve.
     
  4. stonedpirate
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    stonedpirate Senior Member

    Thanks Steve.

    Is that common practice?

    I havent seen it done before.
     
  5. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    You can arrange the veneer layers as you like, but if you don't like the horizontal layer look, then I'd suggest you investigate the Ashcroft molding method, which produces only diagonal layers. It is also the fast form of cold molding as both layers can go down at the same time.
     
  6. Steve W
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    Steve W Senior Member

    Stonedpirate, yes it is fairly common to do double diagonal over strip planking for the main reason being to get rid of the longitudinal stringers wh ich tend to make it difficult to keep the bilge area clean which can lead to shorter life expectancy. Perhaps you can elaborate on the design you are building and the reason why you are interested in changing the construction method, ie, i was guessing it was to eliminate the stringers where Par is guessing its a cosmetic thing. What are the basic scantlings of your boat as designed?
    Steve.
     
  7. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    Steve is correct. Molding over strip planking acts much like a heavy sheathing, in fact can be used instead of sheathing, but without knowing what the scantlings and build type are (there are about a dozen types of distinctly different strip plank schedules), the rest is just guess work, which generally isn't good for the budget, let alone the structural integrity.
     

  8. BATAAN
    Joined: Apr 2010
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    BATAAN Senior Member

    I was taught the New Zealand method of cold molding which consists of all diagonal layers, 1/8" x 4-6", as close to 45 degrees from the W/L as you can manage. They were using plastic resin "Weldwood" glue and plastic staples and built a 40 footer's shell in 6 days.
    This can be done over permanent stringers, or a removable mold.
     
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