Cars turn on the principle that when the steering wheel is put over the wheels rotate and the car follows the wheels. Therefore the pivot point of automobiles doesn’t really change so long as traction is maintained. A vessel operates more on the principle that it tends to track in a forwards direction and the steering apparatus pushes the stern around.
This results in completely different maneuverability. Once a turn is begun, the vessel will continue moving in her original direction even after beginning the turn.
Remember the following:
Pivot Point – this is the pivot point around which the vessel turns. It moves depending on the type of hull form and speed. This is usually 1/3 aft of the bow when going ahead and 1/4 forward of the stern when backing. As a vessel increases speed going ahead the pivot point also moves forward.
Advance – the distance gained in the original direction after turning 90 degrees.
Transfer – the distance gained at right angles to a vessel’s original course after turning 90 degrees.
Turning circle – path followed by the pivot point of a vessel completing a 360 degree turn.
Head reach – if a vessel going ahead in a straight line and the engine placed full astern, then the distance covered while coming to a stop is known as the head reach. Think of it as a vessel’s breaking distance.