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Author Topic: The real manouvering characteristics of a large Azipod-equipped ship  (Read 6428 times)

vampire

  • Forum member
  • Posts: 10

The following information is from the Pilot Card and Wheelhouse Poster of a Vista-class ship.  They are from the sea trials of the Zuiderdam and the Oosterdam.

Stopping distance from Full ahead to Full Astern
Speed 20.91kts Time 0 min
Speed 17.13kts Time 1 min Distance approx 550m
Speed 12.11kts Time 2 min Distance approx 1050m
Speed 8.87kts Time 3 min Distance approx 1350m
Speed 6.48kts TIme 4 min Distance approx 1700m
Speed 0kts Time 6min 18sec Distance 1848m

Turning rate at 0 knots : 3 bow thrusters : 26 degrees per minute.  There is a 3-second delay from signalling full bow thrust until full thrust comes into effect.
Turning rate at 0 knots, Combined (bow thrusters + 1 azipod) 46 degrees per minute.
The bow thrusters are not effective about 15 knots

Engine RPM vs. speed :
Full sea speed : 142.9 rpm, speed 24.18 knots
Full ahead      : 131.3 rpm  speed 22.56 knots
Half ahead     : 114.5 rpm speed 20.04 knots
Slow ahead    : 70 rpm, speed approx 11 knots
Dead slow ahead : 50 rpm, speed approximately 6 knots.
Astern power is 60% of ahead power.

Steering characteristics, both pods running:
At 21.42 knots, 35 degrees of rudder (max rudder angle in sea mode) applied.
At 1 minute 17 seconds, the course has changed by 90 degrees, the speed has dropped to 10.59 knots, and the centre of the ship is 542m forward of where it was.
At 2 minutes 44 seconds, the ship has changed course by another 90 degrees, i.e. is heading back the way she came.  The speed is 7.52 knots, and the course is 531m away from the original course.
At 4 minutes 21 seconds, the speed is 7.05 knots, and the course has altered by another 90 degrees.
At 5 minutes 55 seconds, the speed is 7.02 knots, the course has altered by another 90 degrees, i.e. the ship is now on the original course.

From 35 degrees port (hard over) to 35 degrees starboard (hard over) takes 24 seconds with one steering power unit operating, or 12.5 seconds with two power units operating.  Normally, only one power unit is operating.

The minimum speed to maintain course with the propellors stopped is 2.5 knots.

I understand that the characteristics of a Spirit-class ship are very similar.

VP
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Denis

  • Global Moderator
  • Posts: 1040

Hi Vampire,

thanks for this very interesting post.

At least, I know what is the max rudder angle used for steering in sea mode ! I suppose for the Ocean Star, the  35° angle should be not far away from the reality.

« Last Edit: July 17, 2008, 16:04:27 by Denis »
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