Because sailing relies on the wind, the direction of the boat's movement in relation to the wind (the point of sail) is very important. A "point of sail" is a sailing boat's course, in relation to the direction of the wind.

A sailboat can basically sail upwind, downwind, or across the wind. But the different points of sail are known by names such as "no-sail-zone", "head to wind", "close hauled", "reach", and "running". So, a bit of explanation of the different points of sail would be in order, wouldn't it?

No-sail-zone

The "no-sail-zone" is the windward points of sail where the boat is pointing too close to windward for the sails to generate any power. In the no-sail-zone, the sails will usually "luff", or flap in the breeze, more like a flag than a sail.

The no-sail-zone will differ in size (degrees), depending on the performance characteristics of the sailboat. Racing sailboats usually has a small no-sail-zone and can sail effectively even when pointing very close to windward. Cruising yachts usually have a larger no-sail-zone.

The racing yacht is said to be able to "point higher" than the cruising yacht. In other words the racing yacht can effectively sail a course of fewer degrees from windward than the cruising yacht.

A sailboat's pointing ability is very important for racing.

Pointing head to wind

"Head to wind" is a point of sail inside the no-sail-zone. When a boat is "head to wind" the bow of the boat is pointing directly into the wind.

Calling head to wind a "point of sail" can be confusing, because you are not sailing when your boat points head to wind - you are stalling! The sails luff and the boat loses power - except if you hold up the jib (called backing the jib) to catch some wind to push you backwards.

When a boat performs a tack, it does, however, turn through the head to wind point of sail. It is best to turn through the head to wind point of sail as quickly as possible, to prevent losing too much speed. When pointing head to wind, the boat is neither on port tack, nor starboard tack.

Because the boat cannot sail directly into the wind, it is easy to lose steerage. If a boat is pointing head to wind and cannot steer to a point of sail outside the "no-sail-zone", it is said to be "in irons". When a boat is in irons, it may begin to travel slowly backwards.

To break out of this head to wind point of sail, the jib sail has to be backed to one side of the boat, with the tiller pushed to the same side. This sails the boat backwards and steers the stern towards the wind, resulting in the bow being pushed away from the wind and out of the no-sail-zone.

Sailboats are often purposefully pointed head to wind when raising or lowering sails, because it is safer and easier to raise and lower the sails when they are not under power.

Close-hauled

"Close hauled" is a point of sail just outside of the no-sail-zone. A boat is sailing close hauled when its sails are trimmed in tightly and it is sailing as close to windward as possible.

The close-hauled point of sail allows the boat to sail diagonally upwind. To sail a close-hauled course, the helmsman has to know what his boat is capable of. Sailing close-hauled requires precision, because the no-sail-zone varies from boat to boat.

If the helmsman misjudges his course and tries to sail above an efficient close-hauled course, allowing the sails to luff slightly, he is said to be "pinching".

Reach

A boat is said to be sailing at a "reach" when the boat is travelling approximately perpendicular to the wind.

The point of sale when a boat sails at a right angle to the wind direction is called a 'beam' reach. A beam reach is the fastest point of sail for most modern sailboats, allowing some boats to reach speeds exceeding the wind speed.

A 'close' reach is a reaching course somewhat toward windward, anywhere between close hauled and a beam reach. The wind will be coming at an angle from the fore, with the sails set far abeam (away from the centre line of the boat).

A 'broad' reach is a reaching course more than 90 degrees away from windward, between a beam reach and running downwind. The wind will be coming at an angle from astern (from behind the boat), with the sails set far abeam (away from the centre line of the boat).

Running downwind

When the wind is coming from directly behind the boat, the boat is said to be "on a run", "on a dead run", or "running downwind". Some sailors call running downwind the "don't sail zone", because it is the most unstable and dangerous point of sail for modern yachts.

When running downwind, the sailboat's mainsail is eased out as far as it will go. This sail position, with the wind full astern, means that the jib sail will be blocked from the wind. The jib will collapse, unless it is set to fly on the windward side of the boat.

Running with the jib to windward is known as "goose winging", "gull winging", or "running wing and wing". A genoa sail goose-wings well, especially if it is stabilized by a "whisker pole", and is often used when running downwind.

Cruising yachtsmen might also opt to fly a gennaker (a pole-less cruising 'chute), when running downwind. Yachts running downwind for extended periods of time, as when ocean-crossing in steady trade winds, sometimes set twin poled-out jibs, without a mainsail. But a racing yacht will make use of a high performance low aspect ratio spinnaker, when on a run.

Modern racing yachts are designed to favour pointing very high to windward. The high aspect ratio sail that facilitates pointing high, also causes downwind performance to suffer. The low aspect ratio spinnaker is therefore needed to compensate, when running downwind. A spinnaker requires more trimming than the other running rigs and the crew would be well advised to exercise constant vigilance when flying one.

Running downwind can be dangerous to the people on board, because the boom can come swinging across the deck of the boat at very high speed, in the event of an unexpected jibe.

The helmsman also has a difficult job steering the boat running downwind, because there is little or no pressure on the tiller, to provide some feedback. The boat is unstable and may easily go off course, resulting in an accidental jibe, if the leeward side of the sail catches the wind. (A "preventer" can be rigged for a downwind run, to avoid an accidental jibe.)

Modern sailboats are unstable when running downwind, because the sail position at right angles to the wind causes turbulence. These 'bubbles' of turbulence, combined with the natural rolling of the boat, can build up a "rolling resonance", which can cause the bow to be pushed under the water. When the bow dips under water, the boat suddenly slows down, while the wind keep pushing forward. This can result in a "broach" or a "death roll", where the boat flips over violently.

The sails on square-rigged ships develop "lift" off the top edges of the sails. They therefore don't necessarily stall, even on a dead run. The conditions that lead to broaching are not present. But square-rigged sailboats are still difficult to keep on course, when on a run, and require constant attention at the helm.