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Chapter 9: Using RNS advanced features
To read a polar plot:
Refer to the example shown below and the accompanying definitions:
Top
axis
Target
upwind
Bottom
axis
• The bottom axis shows boat speed range in knots. The maximum/minimum speed
and speed interval are determined on the scale plotted.
• The top axis describes an arc of 180
to the wind. At 0
directly with the wind.
• In this example the lines that lie precisely on the 70
the settings of the Twa1 and Twa2 variables entered in the polar parameters
screen. These lines are displayed in blue.
• The lines that diverge between 30
Target Twa upwind and downwind. These lines are displayed in blue.
• The line that scribes a semi-circle, plots the optimum heading and resultant speed
relative to the Tws range you enter at the bottom of the screen. As the Tws range is
increased, additional lines are plotted onto the graph, showing the heading you
should take to make optimum progress as wind speed increases. These lines are
displayed in black.
• The co-ordinate pop-up shows the current boat speed and heading, as entered into
the data test screen.
Pop-up
box
Twa1
o
you are sailing directly into the wind, at 180
Twa 2
o
representing the boat's direction with respect
o
and 110
o
o
o
and 50
, and 130
and 160
89
Optimum
heading
Target
downwind
o
you are sailing
o
axes correspond to
o
, represent the
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