Dual Maxi Display
10
www.tacktick.com
3.3
During the Race
Sailing upwind.
VMG to Windward
To get to the windward mark as quickly as possible it is
necessary to balance pointing angle against boat speed to
maximise the speed directly towards the wind (this speed is
called the Velocity Made Good to Windward).
The Dual Maxi Display automatically calculates your VMG to windward.
Wind Shift
Like most things in sailing, the wind does not remain
constant in either strength or direction.
Every shift in the wind requires the boat to alter its heading
in order to maintain a close hauled course. A shift that allows the boat to
change its heading closer to the Mean Wind Direction is called a "lift"; a
shift that forces the boat to change course away from the Mean Wind
Direction is known as a "header".
In an
oscillating wind
, a boat that regularly tacks when headed will
spend more of its time sailing a lifted
course and will sail a shorter distance to
the windward mark than a boat that
regularly sails a headed course. This
gives the boat sailing in the lifts a
considerable advantage.
In the diagram, the boat on the right sails
a shorter course by tacking when headed
and thereby sailing mostly in lifts.
The system automatically calculates the
mean wind direction by averaging the
true wind direction over a period of time
Sail your boat for dual Maximum speed and use the Dual Maxi Display
to identify the headers and lifts to help you decide when to tack or gybe.
Permanent wind shifts
can be recognised as a constant header on
one tack, and a constant lift on the other tack. In this situation, you can
reset the mean wind direction as follows: