Typically, when graphed, a TRUE W/A table for upwind might have a curve like the
following:
If it has only been possible to achieve reliable values for the TRUE W/S 5, 10 and 20
range and the rest of the table left blank then the table would look as follows:
It is clear to see that the 15, 25, and 30 kt values can be accurately guessed at as
opposed to being left with zero values.
You should repeat the process for reaching and running as well as beating.
2.
TRUE WIND SPEED CALIBRATION (WIND
→
TRUE W/S, CALBRATE
→
CORRECTION)
TRUE W/S errors are seen from sailing upwind to downwind. This is most noticeable
on Mast Head boats, however all yachts are affected to some degree. This is due to
the acceleration of the airflow over the top of the mast and around the sails when
sailing downwind. The introduction of the Vertical Mast Head unit has gone some way
to solving this, however calibration may still be necessary.
As a rule of thumb, it is safe to put a correction of –10% into the table before first
sailing and this is the value entered by B&G as a factory default. Monitoring the
change in TRUE W/S from close hauled to flat running will enable further refinement
of this calibration value. On a B&G Hercules system it is also possible to define the
TRUE W/A at which this correction is applied – typically your downwind target angle.
