Owner's manual

HB-0845-06 71
It can then be scaled to your rating using the RATING
Menu choice, which is at the same level, and found by:
PERFORM → TACKING, CALBRATE →
→→
→ CAL VAL2 (RATING)
These values are entered in the normal manner.
Once you have understood and developed the polar table it
will improve all the performance functions: reaching and
tacking performance, optimum wind angle and target boat
speed, as well as the predictions of next leg.
We can see from Figure 4 how the target boat speed is
obtained from the polar tables. It is the point at which a
perpendicular drawn to the 0 degree true wind angle first
touches the curve, hence optimising speed in a windward
direction. The boat speed on the curve at this point becomes
the target boat speed for that wind speed, and the true wind
angle at that point becomes the optimum wind angle. The
two combined give the optimum VMG and so allow us to
calculate tacking performance.
2.9.44 Target True Wind Angle
Menu heading: PERFORM
Function text: TARG TWA
Update rate: 1Hz
Units: Degrees
Notes
1. Derived from Polar Table.
2. Requires Performance Processor.
The True Wind Angle at which the optimum VMG will be
achieved according to the Polar Table.