GOP Home Build

Discussion in 'Boat Design' started by schultzfactor, Oct 25, 2013.

  1. schultzfactor
    Joined: Oct 2013
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    schultzfactor Senior Member

    Hi there I have been tinkering with a set of Plywood cat hulls and building them into a centre console fisher. I was hoping to begin this thread to get some constructive feedback in the construction process.

    First question: Using Sailing hulls with a Rocker, how essential is flattening the rocker out toward the stern?
     

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  2. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    Welcome to the forum.

    If you expect the boat to get up on plane, then you'll have to kiss off what you know about sailboat cat hulls. The shapes employed are quite a bit different. What design are you working with?
     
  3. schultzfactor
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    schultzfactor Senior Member

    The hulls are two old sailboat hulls I picked up and I want to have a single power unit planing cat. I understand that I might have to build out the rocker to float the stern?
     
  4. schultzfactor
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    schultzfactor Senior Member

    No design in particular, I have drafted a few plans, but I am very much an amateur with no real boat building experience to speak of. To be honest, I am pretty much winging it at this stage.
     
  5. PAR
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    PAR Yacht Designer/Builder

    Making sailboat hulls act as full plane powerboat hulls isn't very practical. You'll have to reshape the after half of both hulls. The lack of building experience can be overcome easily enough, but the design portion of the project, isn't nearly as easy. Which sailboat are these hulls?
     
  6. Mr Efficiency
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    Mr Efficiency Senior Member

  7. dskira

    dskira Previous Member

    Goop On Plywood :D
     
  8. Mr Efficiency
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    Mr Efficiency Senior Member

    Can't think what else it could be !
     
  9. Mr Efficiency
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    Mr Efficiency Senior Member

    Years ago I encountered a couple of blokes who decided to motorize a 14' Hobie cat with a 25 hp outboard, the result could best be described as (near) Death By Hobby-horsing. Not sure if they went out more than the once in it.
     
  10. schultzfactor
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    schultzfactor Senior Member

    Glass over ply smart ***.

    I have started building up the aft portion of the Hulls. I am putting in a stringer from the Transom forward in each of the hulls . I only figure I have to build them up about 10 cm, so no biggie. First job is to flip the structure over now! need to get a few mates around for that, and will then start on the Aft build up, Transom and tunnel skin.
     
  11. michael pierzga
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    michael pierzga Senior Member

    What is the power and desired speed ?
     
  12. schultzfactor
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    schultzfactor Senior Member

    Not Sure yet about power, anywhere from 60 to 90 HP. desired speed is around 40knots?
     
  13. PAR
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    PAR Yacht Designer/Builder

    You are absolutely kidding yourself at 40 knots and a home brew modification, without a clue about planing hull hydrodynamics. You'll be inviting longitudinal instability around 20 knots and 40 is well, just way out there in terms of reality. The real test will be taking bets as how much over 20 you can get, before she'll self pitch pole. Of course, the beach cat hulls (my assumption) aren't intended for this level of punishment, so maybe you'll get lucky and just stove one in, long before the sterns try to swap ends with one or both bows.
     
  14. schultzfactor
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    schultzfactor Senior Member

    Ok good to know> Ill keep trucking and see how it comes out.
     

  15. schultzfactor
    Joined: Oct 2013
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    schultzfactor Senior Member

    if after the whole effort it becomes a 5knot trout barge then so be it, but I'll give it a blast and see what happens.
     
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