Building a dinghy - cold molded vs. FG

Discussion in 'Materials' started by J.M., Feb 10, 2018.

  1. J.M.
    Joined: Feb 2018
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    Location: Chesapeake Bay

    J.M. New Member

    First time post here. I have plans for an 11' sailing dinghy that was designed for cold molded construction. I have more comfort working with FG and was wondering if it would be too much of a problem to just build the dinghy as a solid FG boat over the male mold. The dinghy is to be used as a tender and just-for-fun sailing dink. I imagine the FG method will result in a heavier boat than the cold molded approach, but the thought of all that fitting and stapling is daunting. Thanks for any input.
     
  2. PAR
    Joined: Nov 2003
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    Location: Eustis, FL

    PAR Yacht Designer/Builder

    Welcome to the forum.

    Yes, you're correct in that the design would end up heavier, probably considerably, so check with the designer to see if this is appropriate, as small craft can't tolerate much being over weight, before performance and capacity are dramatically affected. Which design is this?
     
  3. J.M.
    Joined: Feb 2018
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    Location: Chesapeake Bay

    J.M. New Member

    It's a Wittholz 11' sailing dinghy so checking with the designer would be tough. This is a beamy (5'-0") sailing/rowing dinghy. (Photos attached from a Great Lakes Boat Building School project.) When I was looking for these images I found a couple of posts on the Woodenboat forum mirroring my desire to build this boat in another method other than cold molding so I guess I'm not alone in this project.

    WittholzDingy_01.jpg WittholzDingy_09.jpg
     
  4. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    Most have issue trying to get their head around the process, but it can be relatively easy, if slightly tedious or hard like the bagged arrangement pictured. The design is beamy because it needs to be, given its length and anticipated capacity. Reverse curved hulls like this, do tend to be a pain in the butt to mold, but veneer thickness and technique can over come much of it.

    As to a one off 'glass version, scantlings and laminate schedule would need to be worked out, but not that difficult either. Try Dave Gerr's book "Elements of Boat Strength" for a reasonably easy method to make these conversions.
     
  5. Rumars
    Joined: Mar 2013
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    Rumars Senior Member

    Why not strip plank it with fiberglass in an out?
     
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  6. PAR
    Joined: Nov 2003
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    Location: Eustis, FL

    PAR Yacht Designer/Builder

    I find glued lapstrake a much easier and faster method than strip planking and not nearly as tedious, with a whole lot less 'glass work too. The weight will rival a molded hull as well.
     
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