B&G Deckman - Manual (Page 102)

Understanding Polars
6.3
degrees true wind angle and is only necessary to make sure that the
curve turns up again for the purpose of the optimisation routines.
Note. It is possible to have the polar tables displayed using seconds per
nautical mile instead of boat speed, as used on IMS rating certificates
for instance. When you have a polars window open, select menu>use
seconds/Nm to turn this feature on or off. When turned on, the numbers
that define the upwind and downwind targets are VMG speeds and not
boat speeds.
To choose which wind speed values you want to see on the plot, click
File>select wind speeds. In example on the previous page the points for
12 knots of wind can be seen.
The value in every box in the table is adjustable. This means you can
alter the wind speeds in the first column. This is particularly useful if
you have a velocity prediction program (VPP) which presents the
information at different wind speeds to Deckman’s standard. To alter the
wind speed click on the value you wish to change.
The second column of percentage symbols allows you to alter all five
boat speeds at a single wind speed by a percentage. To increase the
speeds by 10% enter 110 on the numeric keypad; to decrease by 10%
enter 90. The percentage symbols in the second row of the table
similarly adjust all the values in a column: if your target upwind speeds
were 10% too low at every wind speed, you could correct this by
entering the value 110 after pressing the % button in the v1 column.
Any of the individual values in the polar table, either boat speeds or true
wind angles, can be altered individually by clicking on the relevant
number. The need to be able to alter the boat speed is obvious. Being
able to change the angles means that you can also control the true wind
angle used by each of the five points. Again this means that you can
adapt the format of Deckman’s polar table to any polar table that you
might have for the boat.