Cold molding and strip plank

Discussion in 'Wooden Boat Building and Restoration' started by arthor, Nov 10, 2009.

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  1. arthor
    Joined: Apr 2008
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    arthor Junior Member

    I have been looking on the web for clear definitions of both of these and feel a bit thick as I am still not sure what the difference is and still have loads of questions.
    I understand that strip planking using something like ceder strips is where you set up frames (and stringers?) and the attach the strips to them. Where I get a bit confused is when there is mention of ply planks that go on with 45 deg angles to each other to the required thickness. This is also mentioned when I have looked at some cold moulding methods.
    Is cold moulding where layers of veneer are used over the same frame set up? What is the difference?
    Another question is that mention is often made of temporary frames. I am thinking that carefully positioned frames would end up staying in as bulkheads etc. Obviously it would be okay to permanently attach stringers, planks etc right onto the frames but what about the temporary frames? How are the stringers attached to them so the frames can come out??
    I see the build as follows:-
    1)Set up the frames etc
    2)Put stringers on
    3)Use ply sheets/strips in layers to the required thickness
    4)Fair it, glass it and fair it again.
    5)Paint it
    6)Get up underneath and remove the redundant frames (this is the bit that generated the question of how to attach the stringers)
    7)Turn it, glass the inside and away you go.

    What build method would that be classed as??

    many thanks
  2. gonzo
    Joined: Aug 2002
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    gonzo Senior Member

    Both cold molded and strip-planking can have no or a variety of framing and reinforcements.
    Strip planking are strips of more less square section that get edge nailed to each other as you lay the planks.
    Cold moded is usually referred to a construction of three or more layers of thin planking set in glue.
  3. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    Gonzo has it about right. A molded hull can take on a few different forms, but all require laminating veneers of wood over a mold (or inside one).

    Strip planking is just as the name suggests as is longitudinal strips laid over a mold, often square, but not always.

    Both strip planking and cold molding have several variants, which can often get confusing. The variety of different methods these two offer can permit a hull shell without any frames or stringers. On the other hand, it's important to use the method the design was engineered for, as scantlings and laminate schedules can change dramatically between the different versions of these methods.

    Attaching planking to temporary molds can be a challenge, but not necessarily hard. A simple tack or finish nail can suffice, pulled out after it's neighbors have dried. Some use fishing line, others are stapled to it's neighbor. In short, what ever works for the situation.

    Veneer angles to the centerline of the hull aren't set and fast, but need to be adjusted to suit the curves of the boat. Plywood can be "molded" to a hull too. Think of this as regular molded construction, but some of the veneers are pre-molded for you. This is one of my favorite methods, and it's called Ashcroft method, which is one form of cold molding. The layers of plywood go in the same direction, rather then oppose each other. This is a little weaker, but you can plank the whole hull in one shot, instead of having to wait until the one layer is down, before you can apply the next. Ashcroft is also a lot easier to repair too.
  4. gonzo
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    gonzo Senior Member

    Yes, they are a lot of variations and combinations.
  5. bertho
    Joined: Aug 2006
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    bertho bertho


    to arthor,
    here some pict on my blog where you can see one way to strip/and cold ! is many other, you can do undervacuum, it's better, but not mandatory..:)
  6. WestVanHan
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    WestVanHan Not a Senior Member

  7. boat fan
    Joined: Sep 2008
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    boat fan Senior Member

    So ...who says....

    So ...who says size does not matter ? :D

    Attached Files:

  8. capt vimes
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    capt vimes Senior Member


    you could of course leave the 'framing' inside as bulkheads...
    here an example from a dix design 38' although this is no cold mould but plywood/epoxy it shows that its possible and relatively easy...

    here an another one in cold mould with several layers of veneer... star1.htm

    how do you glass the inside of the hull with all the bulkheads and stringers already in place? ;)

    here some images of strip planking a hull over temp frames... the glassing of the inside is easy...

    when strip planking a hull no stringers are involved when planking it... a few are added afterwards once the hull is glassed also on the inside...
    a hull like this is pretty strong and since the planks are laid longitudinal there is no need for stringers but a few along the waterline/keelson...

    the planks btw are not fastened to the frames!
    they are nailed/screwed/glued to each other and the transom and bowstem - the frames just keep them 'in shape'

  9. rangebowdrie
    Joined: Nov 2009
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    rangebowdrie Senior Member

    In my own boat,(35' sail), the frames of the building jig were all removed, however, the longitudinal stringers stayed in, as part of the structure.
    The hull was/is two layers of 1/2 ply, installed similar to what is commonly called the "Ashcroft" method. Epoxy glued, and glassed over on the outside, but not on the inside.
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