At different points of sail, a sailboat can sail at different speeds. This means that the most effective course towards a destination will most often take the form of a zig-zag pattern, planned in such a way that the boat can take advantage of heigher speeds on different points of sail.

The sailboat will typically alternate its course, going in one direction with the wind coming from either the port or starboard side, and then changing direction to get the wind blowing from the opposite side of the boat. This sailing manoeuvre is called "tacking".

Port and starboard tack

A sailboat is said to be on a "starboard tack" when it is sailing with the wind coming from the starboard side (the right side of the boat), while the boom and sail is set to the port side (the left side) of the boat. The boat is on a "port tack" if the wind blows from the port side, while the boom and sail is set to the starboard side.

When sailing downwind, it can be difficult to figure out from which side of the boat the wind is coming. So, the side the boom is carried will give a clear indication. If the boom is carried on the port side, the sailboat is on a starboard tack. And if the boom is set on the starboard side, the boat is on a port tack.

Coming about

"Coming about" is the procedure of shifting a vessel from one tack to another. A sailboat can be brought about in either of two ways:

Tacking

The boat can be steered to point its bow into the wind and then away from windward on the opposite tack. As the bow points windward, the boat loses speed. The sails "luff" or flap in the wind, unable to generate forward motion, so the boat slows down and can even get pushed backwards by the wind.

As the bow moves away from windward on the opposite tack, the sails will shift to the other side of the vessel. The sails will again fill with wind, and generate forward motion.

While coming about, the sailboat cannot generate forward motion; it must rely on its momentum to steer to the opposite tack. If the boat does not have enough momentum to carry it across to the new tack, stopping with the bow pointing into the wind and the sails useless, it is said to be "in irons" or "head to wind".

Before tacking into the wind, it is important to make sure that the boatspeed will be enough to carry it through to the opposite tack, without getting stuck in irons.

Gybing (Jibing)

The sailboat could also change tack by steering the boat away from windward, until the wind fills the sails from the other side of the boat, and the sailboat finds itself on the opposite tack.

In fore-and-aft-rigged sailing vessels, this manoeuvre is called "gybing". Gybing can be a very dangerous maneuvre.

In a gybe, the wind fills the sails from behind. Turning the vessel from one tack to the other causes the boom to swing quickly from one side to the other. A responsible crew will haul in the mainsheet while turning and apply pressure on the mainsheet, so that the boom will swing slower and can only travel a short distance when the wind pushes the sail to the opposite tack.

When the sailboat is "on a run" (sailing downwind), a slight shift in the wind direction can cause the boat to gybe unintentionally. An unintentional gybe is dangerous because the boom will come sweeping across the deck at high speed. If a crewman is caught unaware, or is just slow to duck, the swinging boom can cause very serious head injuries, or knock someone overboard! But an uncontrolled gybe can also damage the boat; breaking spars and rigging.

Running downwind and experiencing a wild gybe, the crew can momentarily lose control of the boat. On a small boat, or if the seas are high, a wild gybe can cause the boat to "broach" (veer on its side), with danger of swamping or capsizing.

An unintentional gybe in a heavy wind could even have enough force to break the mast right off a sailboat!

Changing tack

To sail a proper course, a sailboat will most often need to come about at least a few times. Knowing how to safely and effectively change from one tack to the opposite one is a required skill for sailing.

Changing tack is what makes sailing interesting, and what allows a sailboat to sail towards a destination. Without tacking, the crew would simply be passangers of the wind.