Early Stage Planned Build - Beach Cat

Discussion in 'Multihulls' started by jsheehan, Apr 26, 2010.

  1. jsheehan
    Joined: Apr 2010
    Posts: 4
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: Boston

    jsheehan New Member

    Design:
    My orginal inspiration for this project
    comes from Hobie Cat beach catamarans -
    they've always looked like so much fun!
    Looking around for existing designs that
    meet my needs hasn't turned up anything
    I'm prepared to run with, but has given
    me some ideas. I've all but settled on a
    modular catamaran vaugely similar to the
    RebelCat, which uses large diameter PVC
    pipe for its hulls, although I'm still
    open to suggestions on this front.
    As far as I'm concerned, building is easy,
    knowing what to build is the tricky part -
    and that's why I'm here, for some help and
    input, and to avoid getting ahead of myself
    in the whole process.
    ----------------------------------------------------------------------
    Objectives:
    ----------------------------------------------------------------------
    High Level:
    Portable:
    Must be reasonable for 1 person to
    transport/assemble
    Storable:
    Disassembled storage footprint must
    be as small as possible
    Cost Effective:
    I'm a college student, and most of
    my earnings have already been allocated
    to the beer fund.
    Ease of Assembly:
    Not as critical at this point but I'd
    like for assembly time not to be longer
    than 30-60 minutes for 1 able person.
    Will be spending most of its life
    unassembled.
    ----------------------------------------------------------------------
    Operational:
    Flexible Payload:
    Will often be operated by 1 person
    (~150lbs) but needs to be able to
    perform well carrying up to ~400lbs
    (to account for myself and 2-3 lovely
    ladies).
    Weather:
    Most of its time will probably be spent
    in light to medium winds, but I want a
    design robust enough to push the envelope
    and handle heavier weather every once in
    a while.
    -----------------------------------------------------------------------
    Sizing:
    This is the stage I'm in now and where
    I'm in search of a bit of help from the
    more experienced.
    -----------------------------------------------------------------------
    Things I Know:
    LOA:
    I'm using LOA as a starting point to build
    upon as storage space is my biggest design
    constraint.
    LOA will be 10-12 feet (smaller is better
    unless the extra length is absolutely
    critical).
    Displacement:
    As noted above, displacement will vary
    between boat weight + 150 to 400lbs.
    Things to be Determined:
    Sail Area:
    Based on displacement and looking at other
    small cat designs I was surprised to find
    a SA of ~100 sq. ft. All of my sailing
    experience has been monohull, so I don't
    have a good feel for this on a cat - is
    this too much sail? I'm especially concerned
    with this parameter since I'll be switching
    between sailing alone and with company.
    Lateral Plane:
    Lack of experience strikes again; I'm
    familiar with recommendations of SA/LP for
    monohulls, but the game is different with
    cats. As I understand it, since stability is
    less of a concern due to the wide beam, the
    required lateral plane is smaller, but if
    it is undersized the boat will drift leeward;
    can anyone help me with this ratio for a cat?
    Beam:
    From what I've seen most catamarans this size
    have a waterline beam to lenth ratio of about
    0.4-0.6 - so that would put my beam around
    5ft... sound good?
    Rudder:
    I've seen both dual and single rudder designs,
    I'm inclined to believe that at this size a
    single rudder will do just fine - any cautions
    against this approach? Also, is there any
    standard ratio of the rudder area to total
    lateral plane / sail area / etc?
    ------------------------------------------------------------------------

    I'll be tackling the design and build in the next couple months
    (hopefully before summer is in full swing) once I've settled on
    specs to design to. Looking forward to some input!

    Cheers,
    JS
     
  2. Doug Lord
    Joined: May 2009
    Posts: 16,662
    Likes: 332, Points: 93, Legacy Rep: 1362
    Location: Cocoa, Florida

    Doug Lord Flight Ready

    Seems to me you'd be better off from a time, money and beer perspective to go for an existing beachcat-Hobie 14's and 16's are over the place pretty inexpensively. I seriously doubt you'd save any money starting from scratch.
    Good Luck!
     
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