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Crown Princess

Crown Princess. Vessel Dynamics. Overview. Ship dynamics under INS 2 nd officer’s manual inputs Two opposing heeling responses Lag between wheel input and rudder/ship response Motion cues. Primary Motion. Yaw Axis Heading Turn rate Turn acceleration Roll Axis Heel angle Heel rate

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Crown Princess

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  1. Crown Princess Vessel Dynamics

  2. Overview • Ship dynamics under INS • 2nd officer’s manual inputs • Two opposing heeling responses • Lag between wheel input and rudder/ship response • Motion cues

  3. Primary Motion • Yaw Axis • Heading • Turn rate • Turn acceleration • Roll Axis • Heel angle • Heel rate • Heel acceleration

  4. Recorded Motion

  5. Manual Steering Begins

  6. Manual Steering Begins

  7. Manual Steering Begins

  8. Turning a ship • Wheel command to rudder

  9. Rudder force

  10. Rudder force

  11. Rudder force

  12. Rudder force

  13. Ship’s Response to Rudder

  14. Direct Rudder Heeling Moment

  15. Direct Rudder Heeling Moment

  16. Response Lag • Direct rudder effect • Immediate heel response to rudder • Sideslip effect • Ship must first yaw in response to rudder • Takes longer • Much stronger

  17. Saturated Rudder

  18. 42 sec Manual Steering

  19. Motion Cues • Positive correlation with: • Heel angular acceleration • Heel rate

  20. Summary • The 2nd officer’s commanded rudder changes faster than the rudder could respond • During a 30 deg starboard rudder command the rudder actually port

  21. Summary (cont.) • Two effects of rudder on heel • Short term direct response in direction of rudder input • Longer term more powerful sideslip effect in opposite direction

  22. Summary (cont.) • Rudder commands modulated heel rate (while turn rate continued to increase) • Port rudder initially slowed starboard heel rate • But at longer term expense of increased starboard sideslip • Starboard sideslip overwhelmed direct rudder effect producing starboard heel

  23. Summary (cont.) • Opposing long term and short term effects complicate the 2nd officer’s efforts to control the heel

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