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Point of sail
A point of sail is a sailing craft's direction of travel under sail in relation to the true wind direction over the surface.
The principal points of sail roughly correspond to 45° segments of a circle, starting with 0° directly into the wind. For many sailing craft 45° on either side of the wind is a no-go zone, where a sail is unable to mobilize power from the wind. Sailing on a course as close to the wind as possible—approximately 45°—is termed beating, a point of sail when the sails are close-hauled. At 90° off the wind, a craft is on a beam reach. The point of sail between beating and a beam reach is called a close reach. At 135° off the wind, a craft is on a broad reach. At 180° off the wind (sailing in the same direction as the wind), a craft is running downwind.
A given point of sail (beating, close reach, beam reach, broad reach, and running downwind) is defined in reference to the true wind—the wind felt by a stationary observer. The motive power, and thus appropriate position of the sails, is determined by the apparent wind: the wind relative to an observer on the sailing craft. The apparent wind is the combined effect of the velocities of the true wind and of the sailing craft.
A sail with the airflow parallel to its surface, while angled into the apparent wind, acts substantially like a wing with lift as a force acting perpendicular to its surface. A sail with the apparent wind perpendicular to its surface, acts substantially like a parachute with the drag on the sail as the dominant force. As a sailing craft transitions from close-hauled to running downwind, the lifting force decreases and the drag force increases. At the same time, the resistance to sidewards motion needed to keep the craft on course also decreases, along with the sideways tipping force.
There is a zone of approximately 45° on either side of the true wind, where a sail cannot generate lift, called the "no-go zone". The angle encompassed by the no-go zone depends on the airfoil efficiency of the craft's sails and the craft's lateral resistance on the surface (from hydrofoils, outriggers, or a keel in the water, runners on ice, or wheels on land). A craft remaining in its no-go zone will slow to a stop—it will be "in irons".
The recognized points of sail are judged relative to the true wind direction. The subcategories of these two situations include:
The range of directions into the wind, where a sailing craft cannot sail is called the no-go zone. A sailing craft cannot sail directly into the wind, nor on a course that is too close to the direction from which the wind is blowing, because the sails cannot generate lift in this no-go zone. A craft passing through the no-go zone to change tacks from one side to the other, must maintain momentum until its sails can draw power on the other side. If it remains in the no-go zone, it will slow to a stop and be in irons. This is called missing stays. To recover, that craft typically must return to its original tack and pick up sufficient speed to complete the maneuver. The span of the no-go zone depends on the efficiency of a sailing craft's sails and its resistance to sideways motion in the water (using a keel or foils) on ice or on land, typically at an angle between 30 and 50 degrees from the wind.
A craft stopped in the no-go zone is said to be in irons. A square-rigged vessel in irons by accident is taken aback with the sails blown against the mast or laid aback if deliberate. In either case, the stopped vessel will be blown backwards, which with proper positioning of the rudder allows the vessel to point outside the no-go zone and resume forward motion, once the sails can draw power. Iceboats are often parked in irons with a brake applied to the ice to prevent motion. To commence sailing, the craft is guided to one side and boarded, once the sail can draw power.
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Point of sail AI simulator
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Point of sail
A point of sail is a sailing craft's direction of travel under sail in relation to the true wind direction over the surface.
The principal points of sail roughly correspond to 45° segments of a circle, starting with 0° directly into the wind. For many sailing craft 45° on either side of the wind is a no-go zone, where a sail is unable to mobilize power from the wind. Sailing on a course as close to the wind as possible—approximately 45°—is termed beating, a point of sail when the sails are close-hauled. At 90° off the wind, a craft is on a beam reach. The point of sail between beating and a beam reach is called a close reach. At 135° off the wind, a craft is on a broad reach. At 180° off the wind (sailing in the same direction as the wind), a craft is running downwind.
A given point of sail (beating, close reach, beam reach, broad reach, and running downwind) is defined in reference to the true wind—the wind felt by a stationary observer. The motive power, and thus appropriate position of the sails, is determined by the apparent wind: the wind relative to an observer on the sailing craft. The apparent wind is the combined effect of the velocities of the true wind and of the sailing craft.
A sail with the airflow parallel to its surface, while angled into the apparent wind, acts substantially like a wing with lift as a force acting perpendicular to its surface. A sail with the apparent wind perpendicular to its surface, acts substantially like a parachute with the drag on the sail as the dominant force. As a sailing craft transitions from close-hauled to running downwind, the lifting force decreases and the drag force increases. At the same time, the resistance to sidewards motion needed to keep the craft on course also decreases, along with the sideways tipping force.
There is a zone of approximately 45° on either side of the true wind, where a sail cannot generate lift, called the "no-go zone". The angle encompassed by the no-go zone depends on the airfoil efficiency of the craft's sails and the craft's lateral resistance on the surface (from hydrofoils, outriggers, or a keel in the water, runners on ice, or wheels on land). A craft remaining in its no-go zone will slow to a stop—it will be "in irons".
The recognized points of sail are judged relative to the true wind direction. The subcategories of these two situations include:
The range of directions into the wind, where a sailing craft cannot sail is called the no-go zone. A sailing craft cannot sail directly into the wind, nor on a course that is too close to the direction from which the wind is blowing, because the sails cannot generate lift in this no-go zone. A craft passing through the no-go zone to change tacks from one side to the other, must maintain momentum until its sails can draw power on the other side. If it remains in the no-go zone, it will slow to a stop and be in irons. This is called missing stays. To recover, that craft typically must return to its original tack and pick up sufficient speed to complete the maneuver. The span of the no-go zone depends on the efficiency of a sailing craft's sails and its resistance to sideways motion in the water (using a keel or foils) on ice or on land, typically at an angle between 30 and 50 degrees from the wind.
A craft stopped in the no-go zone is said to be in irons. A square-rigged vessel in irons by accident is taken aback with the sails blown against the mast or laid aback if deliberate. In either case, the stopped vessel will be blown backwards, which with proper positioning of the rudder allows the vessel to point outside the no-go zone and resume forward motion, once the sails can draw power. Iceboats are often parked in irons with a brake applied to the ice to prevent motion. To commence sailing, the craft is guided to one side and boarded, once the sail can draw power.