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    Leeway angles
    From: Joe Shields
    Date: 1999 Jul 19, 9:34 PM

    I also have that formula: 58.5 * heel / boatspeed**3
    as well as another: 8 * heel / boatspeed**2
    for leeway angle (which I found somewhere and copied into my notebook)
    
    but I also found (somewhere) a table that seems easier to use:
    
    -------------------       -----------------WIND STRENGTH & POINTS OF
    SAIL------------------
    BOAT TYPE        3-10 knots        11-21 knots         22-33 knots
    34-65 knots
                              beat  reach        beat   reach        beat
    reach       beat    reach
    -------------------       ----------------        -----------------
    ------------------       ------------------
    shallow-keel        10       5              8         4            12
    10          20         12
    cruising sailboat
    
    deep-keel racer     6       4              4         2              6
    4          12          6
    
    Large cruising       4       2              6         4            10
    8         20         12
    sailboat
    under power
    
           10      4              8         4            12
    12          20         15
    under sail
    ------------------------------------------------------------------------
    -----------------------------------------------
                                             LEEWAY ANGLES (in degrees)
    
    I have no idea how accurate this is or how it was constructed.  I've
    used it as a guide in trying to keep a straight track to short range
    destinations and have usually been rewarded by not needing an extra tack
    to reach the harbor.  (Other boats that crossed my path obviously
    steering directly towards the lighthouse marking the mouth of the harbor
    needed the extra jog).  It also seems to put me on the mark when
    practicing DR using the Coastal Crusing Simulator (by Posey Yacht
    Design).
    
    Anybody else familiar with this table?  Can't remember where I got it.
    Could be Dutton.
    
    -- Joe Shields
    
    > ----------
    > From-         Bill Murdoch[SMTP:WSMurdoch{at}AOL.COM]
    > Reply To:     Navigation Mailing List
    > Sent:         Monday, July 19, 1999 10:03 PM
    > To:   NAVIGATION-L{at}LISTSERV.WEBKAHUNA.COM
    > Subject:      Re: True vs Magnetic
    >
    > In a message dated 7/18/99 12:19:28 PM EST, lu.abel{at}ATT.NET writes:
    >
    > > PS - Does anyone know how to calculate leeway (for either power or
    > sail)?
    >
    > Some time ago I wrote myself a note, "for modern sailing hulls: Leeway
    > = 58.5
    > * heel angle in degrees / boat speed in knots cubed, Ocean Navigator
    > #45 3/92
    > page 72.  It makes sense that increasing heel would indicate
    > increasing
    > leeway and that lower speeds would indicate higher leeway, but the
    > numbers do
    > not seem to fit.  Does anyone have the back issue to see if I wrote
    > the
    > formula correctly ?  My own experience is that sea state also has a
    > big
    > effect.
    >
    > Bill Murdoch
    >
    

       
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