Understanding the fundamentals of the pivot point is highly required for understanding the alteration of the courses. Pivot point is an imaginary point on the vessel which turns on a circular path on the perimeter of vessel’s turning circle when the vessel makes a turn. The knowledge about the position of the pivot point in a manoeuvring situation provides the ship handler with the information on the geometry of motion of the ship.
This video shows an introduction on the Spiral-Test-Manoeuvre and describes the procedure how to steer through this manoeuvre and measure the data needed. The results will be displayed in a characteristic diagram allowing to identify stable and unstable conditions and related, detailed information, e.g. spiral loop width and height, rudder angle of neutral effect. Samples of stable and unstable ship behaviour demonstrations will be shown by Fast Time Simulation using the SAMMON Planning tool.
Editors note: A film of a pilot boat has just been published on YouTube with the title "How Dangerous being in a Pilot Boat..." on YouTube. I'm not sure if this really shows a dangerous maneuver, maybe the experts can comment on it here.
But in principle it is problematic to approach the ship in such a small Pilot Boat in the wake from astern and cross the waves there. I remember an accident from Finland in December 2017 where the boat capsized and people died. Is this situation shown here...
