Thursday, May 8, 2008

Shiphandling: Stopping While Maintaining Control Over Heading

Your ship is proceeding at 6 knots on a selected base course. The rudder is put left and as the ship begins to swing to port, the engine is backed. The ship loses headway while the swing left decreases in rate and finally reverses. When the bow starts swinging right, come ahead again with left rudder to check and reverse the swing. Repeat these maneuvers as required until the ship is down to the desired speed.

It may be necessary to put the rudder amidships when the engine is going astern, so that the ship loses her swing to the left as desired. This can only be determined by trial so it is important to practice this maneuver when you get the chance. Don't wait until the ship is proceeding up a narrow river on a rainy, windy night to learn how the ship behaves when the engine is put astern.

This particular maneuver is obviously important since it is used to stop or reduce a ship's speed so a tug can be made up, to shape up for docking, or any number of other maneuvers in confined waters. There is little need to collect data during this maneuver since this is primarily a shiphandling exercise that yields little quantitative data.

Keep in mind that bottom configuration and the proximity of a bank affect this maneuver. A ship may back "the wrong way," especially if the starboard quarter is close to the bank or a shoal area at the edge of the channel, so that the swing to the left is not checked. This effect is minimized if the ship is kept at or near midchannel when backed.
These possible variations in ship's behavior make shiphandling interesting and assure that the handling of ships will always be an art rather than a science.