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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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