Sharpies, Bruce Kirby etc

Discussion in 'Boat Design' started by Anatol, Jun 3, 2015.

  1. Anatol
    Joined: Feb 2015
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    Anatol Senior Member

    Does anyone have experience with Bruce Kirby sharpies (the NIS boats etc), and other similar hull forms? The simplicity of the three sided ply build is very attractive. Some caution that pounding is an issue.
    thx
     
  2. fredrosse
    Joined: Jan 2005
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    Location: Philadelphia PA

    fredrosse USACE Steam

    Plywood Sharpie

    I built my steam sidewheeler with a classic Sharpie hull form, for the reasons you mention. 5/8 marine ply bottom, 1/2 marine ply sides, frames 16 inches on centers, with 10 Oz fiberglass/epoxy over the entire hull. It took only several weeks to build the hull. It has given very satisfactory service, and pounding has not been a problem, but then the 20 foot boat weighs over a ton before passengers and stores come aboard!

    In a light weight sailboat pounding would be more relevant, but many have found the Sharpie a worthwhile hull.
     

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  3. rwatson
    Joined: Aug 2007
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    rwatson Senior Member

    What does 'experience' mean ?? You mean building, sailing, towing etc etc ?

    The simple 3 panel shape hides the huge amount of work inside with framing, interior setup etc. Review any NIS build blog to find out.

    Its the same with any boat - the external hull panels are just a fraction of the total construction load.

    Phil Bolgers designs look simple too - but they all have the 'hidden' work to cope with.

    If on the other hand, you mean sailing - time and time again the owners say that the heeling under sail considerable reduces the pounding that a flat bottom might otherwise create. Pounding at anchor is a potential issue, except that with a flat bottom you can get much closer to a beach or creek bank, out of the way of waves.
     
    Last edited: Jun 4, 2015
  4. phum
    Joined: Apr 2009
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    Location: Sunny QLD. in the great South Land

    phum Junior Member

    I have had a NIS 23 for 15 years and it is my favourite boat to sail. The good bits, quick and easy to rig, easy and fast to sail. The bad bit, not much room below by modern standards.
    Can't comment on construction other than to say there is a lot of timber in it. I would think that useing more modern methods , stitch and glue and takeing full use of modern epoxies construction could be simplyfied.
    Mine rarely pounds,a light breeze and a big chop is the worst sea state for it but that is seldom encounted.
     
  5. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    The sharpie hull form is an old and well loved one and like everything in yacht design, has it's good and bad points to consider.

    A real sharpie is skinny and shoal. This means you need at least 35' boat for standing real headroom, yet you'll still be shy on elbow room, by modern standards. You can sneak up and beach on a soft shore if you like, but ultimate stability will be an issue. This low AVS point means the hull can't tolerate a tall superstructure. There are lots of good and bad things about them, so can you refine your questions a bit?
     

  6. Anatol
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    Anatol Senior Member

    thanks all

    rwatson " The simple 3 panel shape hides the huge amount of work inside with framing, interior setup etc."

    Not more than another shape though? And as phum says "useing more modern methods , stitch and glue and takeing full use of modern epoxies construction could be simplyfied."

    par : "you need at least 35' boat for standing real headroom, yet you'll still be shy on elbow room, by modern standards. ... This low AVS point means the hull can't tolerate a tall superstructure. ...can you refine your questions a bit? "

    OK. I'm actually thinking of using the design for a proa vaka. Slim and double ended. In this case it won't heel significantly, and the rig will be short as the boat will be light. I'm thinking 30', as for headroom, I was thinking about a big pop-top. Low windage when underway, headroom when moored, when you want it.

    The alternative is a single chine shape. Lateral resistance will be taken care of by foils, so its really a matter of whether the increased build complexity of a chine is worht the trouble. Any opinions?
     
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