When a vessel is sailing, regardless of the point of sail, it is on a tack. With the wind coming across the port side of the vessel and the boom out to the starboard side the vessel is on a PORT TACK If the wind is coming across the starboard side of the vessel and the boom is out to port the vessel is on a STARBOARD TACK.
If the wind is passing equally over each side of the sail and no lift is being generated the sail is said to be LUFFING. If forward motion is stopped and the sails continue to luff the vessel is in IRONS.
When steering the vessel, the helmsman can closer approach the direction from which the wind is blowing by HEADING UP. To go away from the direction, the wind is coming from the helmsman can HEAD DOWN or FALL-OFF.
Eventually it becomes necessary for the vessel to cross the direction from which the wind is blowing. There are two means by which the vessel can cross the eye of the wind. The vessel can TACK or GYBE.
Tacking occurs when we are attempting to sail to a destination that is directly into the direction the wind is coming from. A vessel cannot sail directly into the wind, so it must sail a zigzag course toward the destination. Changing the course of the vessel by passing the bow through the eye of the wind is called tacking.
The second method of changing the vessel's relationship to the wind is by passing the stem of the vessel through the eye of the wind. This method is called gibing.
When tacking or gibing there are a series of commands that will be given to assure that the maneuver is completed safely and efficiently.
When it becomes necessary to tack the helmsman will alert everyone by the command, "READY ABOUT". At this signal crewmembers will make ready to adjust the sails as the vessel passes through the eye of the wind. When the crewmembers are prepared they will respond with, "READY". When the helmsman is sure that all are prepared the command "HARD A'LEE" will be given. As the vessel passes through the eye of the wind the sails will cross the centerline and the crew will adjust and secure the sheets as the helmsman steers the new course.
Because a gybe occurs when the wind is aft of the vessel and the boom is usually extended quite far out, more care and preparation is required to safely complete this maneuver. When the helmsman chooses to gybe the command, "PREP ARE TO GYBE" will be given. As the vessel is sailing at a wide angle to the wind the sails will need to be sheeted in. This will give more control and prevent the boom from swinging wildly across when the gybe is in progress. It is important that crewmembers keep clear of the blocks and lines when performing this maneuver. When the crew and helmsman are ready the command "Gybe Ho" will be given. As the stem of the vessel passes through the eye of the wind the sails will shift across the vessel. It is most important to haul in the mainsail as the vessel approaches directly down wind and ease the sail as the Stem passes through the eye of the wind. Once on the new course sheets can be adjusted for the proper sail trim. A successful gybe demands alertness and crew coordination.