Pontoon/tunnel/deckboat design

Discussion in 'Boat Design' started by YotaTruck, Aug 2, 2015.

  1. YotaTruck
    Joined: Jun 2013
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    Location: NJ

    YotaTruck Junior Member

    After taking into consideration the advice given on my previous threads regarding building an alternative to a pontoon boat I came up with this:

    24' LOA
    23'-6" LWL
    8'-0" Max beam
    2'-0" Max hull beam
    6" Draft @ 2300lbs displacement

    It's not really a pontoon or a cataraman and its kind of like a tunnel hull I suppose.

    [​IMG]

    [​IMG]

    [​IMG]

    [​IMG]

    [​IMG]

    Construction would be from 1/2" plywood frames every 24" with battens screwed/glued around the edges to create a place for the top decking, side and bottom planking to screw/glue to. A small box beam would fastened to each frame to ensure rigidity between the hulls.

    All I'm looking for out of this thing is to be able to cruise at hull speed (6.5 knots) at 1/2 to 3/4 throttle with a 15 HP motor. I figure at worst, the boat would perform no better than a 24' pontoon sitting on aluminum logs, and at best, it will perform a bit better. At the very least it will look better doing it, plus I can use the compartments between the frames for storage. Comments, criticism, and suggestions welcomed.
     
  2. messabout
    Joined: Jan 2006
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    messabout Senior Member

    If it is to be a low powered displacement type boat, then get the transoms up at least to the waters surface and preferably a little above. In short, put some aft rocker in the boat. If you want it to turn easily, do not let the forefeet go much below the waterline. Forward rocker then.
     
  3. Ad Hoc
    Joined: Oct 2008
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    Ad Hoc Naval Architect

    YotaTruck

    Nice, easy simple.

    Only comments..the displacement seems optimistic. I get less on the 6inch draft..thus i would increase the clearance from the waterline to the wetdeck (underside of raft).

    As for power..i would say circa 10-15hp..would suit you..so around 5-7hp per side should suffice.

    OH..i should also point out. Call this a catmaran and nothing else.. Since the images above are just hulls. It is not a 'design' per se. Since if you place a casino on top the design would be different from that if you place say a hospital on top or a bar and disco. Thus the design...your objective (in this sense)...call it what you will. BUT...the images of the hull above and to avoid any confusion, call them what it is...a catamaran, nothing else.
     
  4. Jamie Kennedy
    Joined: Jun 2015
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    Location: Saint John New Brunswick

    Jamie Kennedy Senior Member

    Does anyone know what the ideal prismatic coefficient is, for a given speed, of two hulls versus one hull? Also how much to make them asymmetric depending on how close together they are, for a given speed?

    I like the concept. More control over shape than a typical pontoon boat. Also I think it might be easier to build some useful cargo space into the hulls for your engine or motor, batteries, fresh water, rum, misbehaving children, etc.
     
  5. Rurudyne
    Joined: Mar 2014
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    Location: North Texas

    Rurudyne Senior Member

    "The only thing gassed up in that Jeep was us." -- Hawkeye, M.A.S.H.
     
  6. YotaTruck
    Joined: Jun 2013
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    Location: NJ

    YotaTruck Junior Member

    I'd love to know this myself. I was just going on guesses formed from comments on other catamaran designs and Richard Woods' approach to asymmetric hulls.

    Thanks-yes, basically I'm looking to build a better pontoon. definitely more cargo space as the hulls are nearly a constant 24" deep and 24" wide at max beam. Definitely a good space for batteries and fuel (properly vented of course).
     

  7. Ad Hoc
    Joined: Oct 2008
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    Ad Hoc Naval Architect

    For your application, not worth considering. It wont influence your hull shape one bit, nor your objective.

    But for those that wish to view numbers:

    Cp Curve.jpg Cp Curve-1.jpg Cp Curve-2.jpg
     
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