Rigging a pointy skiff for sail

Discussion in 'Sailboats' started by hospadar, Apr 12, 2011.

  1. hospadar
    Joined: Apr 2011
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    hospadar Junior Member

    I started on this thread: http://www.boatdesign.net/forums/sailboats/hull-shape-simple-sailing-scow-37499.html but my current train of though is unrelated, so I'm starting a new one.

    I really like P. Bolger's pointy skiff but I want someting I can sail. I can't see any reason why I couldn't rig this boat with a mast and centerboard. I don't know how to guess the placement of the centerboard.

    What's a good way to figure out where it should go? If I put it in the wrong place, how bad can it be? Does anyone know of any similar plans that are drawn up with a sailing rig I could compare to?

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    BATAAN Senior Member

    Use a Peruvian leeboard which consists of a 5.5'x12" board with some lead in the bottom end and a 24" long 2x2 screwed on crossways about 1.5 feet from the top. There is a hole in the top of the board and also in the middle of the center thwart of the skiff. A rope with stopper knots connects the holes. The board is always on lee side, water pressure holding it to the hull and the 2x2 resting on gunwale stopping board from cocking aft and holding it vertical. Rope holds the lee pressure. Board can be slid fore and aft for perfect balance. When tacking pick it up and throw it over the other side. Water pressure pushes it into place.
    Too simple for most people.
  3. philSweet
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    philSweet Senior Member

    The link is to a design by Payson, not Bolger.

    You're going to want a rudder as well as a board.

    Personally, I prefer to build the board and guess at where to put the mast:D

    What you need to do is to figure out where the center of effort is for the sail plan you want to use. You then design the appendages to place the hull's center of resistance to sideslip in the proper relation to the CofE of the sail plan.

    CofE is usually just a simple geometry measurement of the sail plan.

    The hull's resistance is a bit more complicated because the board is a bit more effective on a "per area" basis than the hull. The rudder is usually derated also. So you need a weighted average of the three centers of effort of the three different submerged surfaces.

    The relative horizontal position between the above two items is termed the lead. It is basically a fudge factor that varies according to the type of boat and rig. It's easier to use one fudge factor at the end than to use a whole bunch of them as you work along, so don't worry too much if the methods seam really approximate, it all gets fixed in the fudge factor. This is why you don't want to get too "experimental" with your rig selection.

    A bit of googling around will show you plenty of example calculations. There are also several well known sailing dinks of similar size so you have something to compare to when you are through.

    Some comparable craft here: http://www.selway-fisher.com/Other1013.htm
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