Ship’s Characteristics

Ship’s Characteristics Fundamentals of Before we can discuss the techniques used to steer a ship, you’ll have to Shiphandling learn the basics of shiphandling. Use the following table and figure 11-5 to learn the terms associated with a ship’s characteristics. Term Pivot Point Definition A ship’s pivot point is a point on the centerline about which the ship turns when the rudder is put over. The pivot point scribes the ship’s turning circle. Turning Circle A ship’s pivot point is nearly always located about one-third the ship’s length from her bow when moving ahead, and at or near her stern when moving astern. The location of the pivot point will vary with ship’s speed. An increase in speed will shift the pivot point in the direction of the ship’s movement. A ship’s turning circle is the path followed by the ship’s pivot point when making a 360 degree turn. The diameter of the turning circle varies with rudder angle and speed. With constant rudder angle, an increase in speed results in an increased turning circle. Very low speed (those approaching bare steerageway) also increases the turning circle because of reduced rudder effect. Advance Transfer Tactical Diameter Final Diameter Knowledge of the turning characteristics of one’s ship is essential to safe shiphandling, particularly when in restricted waters. Advance is the amount of distance run on the original course until the ship steadies on the new course. Advance is measured from the point where the rudder is first put over. Transfer is the amount of distance gained towards the new course. Tactical diameter is the distance gained to the left or right of the original course after a turn of 180° is completed. Final diameter is the distance perpendicular to the original course measured from the 180° point through 360°. If the ship continued to turn at the same speed and rudder indefinitely, it would turn on this circle. The final diameter is almost always less than the tactical diameter. 11-7