First, there is a distinction between the port tack and the starboard tack. If the wind is coming from anywhere on the port side, the boat is on port tack. Likewise if the wind is coming from the starboard side, the boat is on starboard tack. Except when head to wind, a boat will be on either port or starboard tack while on any point of sail. For purposes of the racing rules and "rules of the road," the wind is assumed to be coming from the side opposite that which the boom is carried.
In the sport of yacht racing, the current rules do not recognize a state in which a boat is on neither port nor starboard tack. Boats which are lying head to wind are either considered to be on their old tack, or on their new tack but in the act of tacking, and therefore required to stay clear of other boats.
The size of the no-go zone will differ based on the performance characteristics of the particular sailboat. For example, racing sailboats can usually sail much closer to the wind (i.e., fewer degrees off the wind direction) than cruising yachts. This is known as "pointing higher." Pointing ability is very important for racing sailboats as the real goal in a race is almost always velocity made good (VMG). VMG is the speed at which the boat is approaching the destination (usually a buoy or mark) as opposed to the speed at which the boat is moving through the water (boat speed). These two speeds almost always vary because, during a race, a boat usually cannot sail directly to the next mark. VMG may also refer to the upwind vector of boat speed (this is often the VMG expressed on sailing instruments).
If a sailboat is tacking and turning into the wind with sufficient speed to complete the tack, when the boat is facing into the wind, the tacking boat is "luffing" but, due to forward speed, is still turning under control.
If the boat attempts to tack with a slow initial speed, or otherwise stops forward motion while heading into the wind, the sailboat is said to be "in irons." Since there is no speed (no water flow past the rudder) there is no normal control of the direction of the boat, and it tends to drift directly backwards. To recover from this situation, the jib or forward most sail, can be backed (tightened and pushed out) on the side that is the desired tack until the boat is at a sufficient angle to the wind for sailing, and/or the rudder can be turned to the side that is the desired tack (the tiller pointed in the desired direction that you wish to go) and held until the boat is at the correct angle to the wind and resumes forward motion.
A boat is sailing close hauled when its sails are trimmed in tightly and it is sailing as close to the wind as it can without entering the No-Go Zone. This point of sail lets the boat travel diagonally upwind. This is a precise point of sail. However, the exact angle relative to the wind direction varies from boat to boat. A boat is considered to be "pinching" if the helmsman tries to sail above an efficient close-hauled course and the sails begin to luff slightly.
When the boat is traveling approximately perpendicular to the wind, this is called reaching. A 'close' reach is somewhat toward the wind, and 'broad' reach is a little bit away from the wind (a 'beam' reach is with the wind precisely at a right angle to the boat). For most modern sailboats, reaching is the fastest way to travel. Different boats have different performance characteristics -- on some boats, the beam reach is the fastest point of sail; on others, a broad reach is faster.
On this point of sail, the wind is coming from directly behind the boat. Because running is the most difficult point of sail for modern yachts, and can be dangerous to those on board in the event of an accidental jibe, it is often called the "don't go zone". Modern racing yacht design favors sailing rigs that can point very high to windward, which means a high aspect ratio sail. Downwind performance suffers, but that is overcome by the use of a low aspect ratio spinnaker for running.
When running, the mainsail is eased out as far as it will go. The jib will collapse because the mainsail blocks its wind, and must either be lowered and replaced by a spinnaker or set instead on the windward side of the boat. Running with the jib to windward is known as gull wing, goose wing, butterflying or wing and wing. A genoa gull-wings well, especially if stabilized by a whisker pole, which is similar to, but lighter than a spinnaker pole. In 'non-extras' or 'no flying sails' class races where spinnakers are not permitted, poled-out genoas are often used when running downwind.
Cruising yachtsmen, when running downwind, will often set either a poled-out genoa or a pole-less cruising 'chute (or gennaker). When running downwind for protracted periods, for example when ocean-crossing in steady trade winds, cruisers sometimes set twin poled-out jibs without a mainsail. All of these options are more stable and require less trimming effort than a spinnaker.
Steering is difficult when running because there is often little or no pressure on the tiller to provide feedback to the helmsman, so the boat may easily go off course. This tendency to turn off course when running can be dangerous, as the boat is least stable and can jibe accidentally if the lee side of the sail catches the wind. A preventer can be used on yachts to avoid this. Another problem with running in modern high aspect rigs is the fact that having the sail set at right angles to the wind guarantees a stall, and the stalled out wing sheds 'bubbles' of turbulence. Combined with the sea- and steering-induced rolling of the boat, this can build up a rolling resonance and lead to a broach or a death roll.
Square rigged ships, since the sails develop lift off the top edges of the sails, and so are not necessarily stalled even on a dead run, are far better at running, since the conditions that lead to broaching are not present. They still, however, are difficult to keep on course, and require constant attention at the helm; when sailing on a reaching course, the boat is in a stable state, and it is possible to tie off the wheel and still maintain a steady course.
WIPO PUBLISHES PATENT OF JAB SAILING FOR "WIND INDICATOR DEVICE, METHOD AND COMPUTER PROGRAM PRODUCT FOR SAILING" (BRITISH INVENTORS)
Mar 08, 2012; GENEVA, March 6 -- Publication No. WO/2012/025743 was published on March 1. Title of the invention: "WIND INDICATOR DEVICE,...