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8.8 Calibrating true wind speed
Even placed a meter away from the mast head on top of a carbon arm, the measure made
by the aerial sensor may suffer from disruption. When sailing downwind, the mainsail
creates an acceleration of the wind. Heel angle also has an influence on wind speed
measurement. For all these reasons we recommend calibrating for wind speed.
The correction table « Adjvt.d » is available in the Processor Regatta at the following
address: ftp://root:pass@192.168.0.232/mnt/flash/processor/tables
It can also be accessed from the home page by pressing the « Calibration » button, and
further the « True Wind Speed » button.
If the table is already filled with values, the corrections will have to be added to the existing
values.
Measurement procedure:
First, place the boat upwind and average the value read for wind speed.
Then, measurements have to be made in various wind strengths ranging from 5 to 30
knots. It is a continuous process. Note the wind speed values as you sail upwind, reaching
and downwind. You may find it useful to populate the correction table with the results from
averaging these values.
An example of the wind speed correction table is shown below. The column on the left
shows the wind speed. For each wind speed there are correction factors at various wind
angles, where V is the correction (in knots) and A is the wind angle (in degrees).
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