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    Re: Setting a course when sailing into the wind.
    From: Bill B
    Date: 2016 Jul 27, 22:15 -0400

    On 7/27/2016 8:58 PM, Bob Goethe wrote:
    > If you are only competing against yourself, then the length of your
    > tacks will be determined by a desire to avoid wind shadows or eddies if
    > near land, and by weather patterns offshore (e.g. you want to avoid
    > steering through the middle of the North Pacific High, even if your most
    > direct path goes that way).
    
    Graham
    
    With wind shifts when beating to weather one of two things will happen.
    The wind moves forward which cause you to sail lower than optimal (away
    from the upwind or the mark, called "headed"), or the winds shifts to
    the aft which allows you to sail higher (more directly upwind or toward
    the mark, called "lifted").
    
    One of the things you look for in longer distance sailing are persistent
    wind shifts as the inter-meshed gears of a low and high pressure system
    boundary crosses your path. Backing is a persistent CC change, veering
    is a persistent CW sift,  You may then sail an initial course that will
    in essence lift you, then change tacks when it shifts and heads you so
    you are again lifted.
    
    Getting a bit (more) off topic:
    
    In local pond sailing or racing one tries to determine the mean
    direction of the wind before the start. When you are headed by a wind
    shift off the mean you tack. When it returns to the mean you hold unless
    there are tactical reasons for not holding on the mean direction. When
    it shifts again in the opposite direction and heads you, you again tack
    to be lifted .
    
    Odd winds you may experience may be caused by surrounding topography as
    mentioned and be *quite* pronounced, especially on lakes formed by
    dammed rivers. Quite often you will hear club racers on a small lake
    proclaim, "If you can sail here, you can sail anywhere!" It is not
    unusual for a winner in another club to come to guest lake and be smoked
    by the entire fleet--even the perennial losers. I imagine local
    knowledge can play a huge roll in the San Fransico bay,
    
    Another which can be most frustrating is being in the middle of a lake
    and when something called a "cats paw" arrives. A burst of wind comes
    straight down and then spreads out in all directions once it hits the
    water. If you are directly under its arrival point you will feel wind
    but can't use it--like being in a wind hole but with wind. As it starts
    to spread racers to either side of you may be going in exactly the same
    direction but on different tacks. On larger bodies of water you may play
    in cloud alleys where the wind is better. All said and done, that's why
    major-event sailing teams have a host of weather people doing weather
    mapping on long races, and trying to determine which side of a course
    has more wind (called "pressure") on closed courses. All said and done
    its part topographical experience in different wind conditions on a
    local pond, and in any case part luck and part science.
    
    BTW. If you are sailing in light winds do not use polarized sun glasses.
    You can't read the wind-induced ripples as well.
    
    Bill
    
    
    

       
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