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During the manoeuvre the values of
the points of the change of heading speed curve with respect to the rudder
angle can be taken in any order.
The equipment required is a rate-gyro (alternatively, the heading z
given by the gyrocompass can be differentiated to provide r = z),
and an exact indicator of the rudder angle x. The accuracy of
the trial can be improved if the information on the change of heading
speed and the rudder angle are available continuously. If manual control
is used, the helmsman can visualise the instantaneous change of heading
speed in a register or
indicator. The procedure originally proposed by Bech for obtaining a point
in the curve is recommended. The ship is made to approach the desired
change of heading speed or rate of turn, r0 = z0,
applying a moderate rudder angle. Once the desired change of heading rate
is obtained, the rudder is activated to maintain this desired rate of
change of heading as accurately as possible. The helmsman must attempt
to maintain the desired change of heading rate using shorter and shorter
rudder movements until constant values of the ship’s speed and rate of
change of heading are obtained. Normally, a stable change of heading rate
is obtained quite fast, so that it is easier to perform the test using
a rate-gyro than with a normal gyrocompass. |
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