The Navigation Computer: Balancing the Drift
Take the situation:
TAS = 76 knots
Desired Track = 230°
Forecast W/V = 110/40
Start in the usual way. Plot the W/V of 110/40
Put the blue centre circle onto the TAS point of 76 knots.
Now bring the desired track of 230° up to the top.
Now observe that the drift under the wind point is 20° starboard and rotate the disc 20° clockwise to bring the desired track of 230° against 20° on the DRIFT STBD scale.
Look at the wind point. The drift has increased to 25° starboard so rotate the disc 5° clockwise to bring 230° against 25° on the DRIFT STBD scale. Check the drift again. It is now 27°S.
Rotate the disc a further 2° clockwise so that track 230° is against 27° on the DRIFT STBD scale.
Check the wind point again. The drift is still 27° S. Check that 76 is still exactly under the centre dot (the blue circle).
Read off true heading 203° against the TRUE HEADING index and ground speed 87 knots from under the wind point.
Next: Wind Finding