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2.9.2 True wind tables
The data measured by the wind sensor placed on top of the mast, even when on a
long carbon arm, is affected by the sails.
The wind flow is disturbed around the sails and rig. This is called the “upwash”.
This “upwash” affects the measured raw data measured for the calculation of the true
wind direction. Therefore, the true wind direction may be different from one tack to
another and the wind speed varies from upwind to downwind.
The errors due to upwash can be repeated with sail configurations and wind speed
combinations making it possible to apply corrections. A correction table can be filled
for true wind speed and angle.
Warning:
The true wind correction tables only work with the HR or Carbowind sensors
featuring the V2.5 (or newer) firmware.
2.9.3 True wind angle table
The true wind angle table allows correction of the true wind angle value without
researching the causes of angle’s errors. It corrects all repeatable errors (twist, flow
over-speed downwind, sensor).
The true wind data is calibrated by logging the true wind direction differences from
one tack to another repeatedly. It is recommended that these calibration sessions are
run from 5 to 50 knots in winds that are stable in direction.
TWD port tack > TWD starboard tack:
Add half of the difference between the two True Wind Directions.
10°
45°
45°
TWD 260°
TWD 250°
Heading 300°
Heading 210°
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