Point of sail

Apoint of sailis asailingcraft'sdirection of travelunder sail in relation to the truewind directionover 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 ano-gozone, 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 termedbeating,a point of sail when the sails areclose-hauled.At 90° off the wind, a craft is on abeam reach.The point of sail between beating and a beam reach is called aclose reach.At 135° off the wind, a craft is on abroad reach.At 180° off the wind (sailing in the same direction as the wind), a craft isrunning downwind.^[1]

A given point of sail (beating, close reach, beam reach, broad reach, and running downwind) is defined in reference to thetrue wind—the wind felt by a stationary observer. Themotive power,and thus appropriate position of the sails, is determined by theapparent wind:the wind relative to an observer on the sailing craft.^[1]^[2]The apparent wind is the combined effect of thevelocitiesof the true wind and of the sailing craft.^[1]

A sail with the airflow parallel to its surface, while angled into the apparent wind,acts substantially like a wingwith lift as a force acting perpendicular to its surface. A sail with the apparent wind perpendicular to its surface,acts substantially like a parachutewith 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.^[1]

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 theairfoilefficiency of the craft's sails and the craft's lateral resistance on the surface (fromhydrofoils,outriggers,or akeelin the water,runners on ice,orwheels on land). A craft remaining in its no-go zone will slow to a stop—it will be "in irons".^[2]

The points of sail

The recognized points of sail are judged relative to the true wind direction. They include:

Into the windwhere a sailing craft is pointed directly upwind in the middle of theno-go zone,where sails cannot generate power.
Close-hauledwhere a craft is sailing, pointed near the no-go zone.
Reaching,including:
- Close reach:between close-hauled and a beam reach.
- Beam reach:the craft has the true wind at a right angle to its direction (on its beam).
- Broad reach:the true wind is coming from behind, but not directly behind.
Running downwindwhere a craft has the wind coming from directly behind.

A sailboat on three points of sail

The waves give an indication of thetrue winddirection. The flag gives an indication ofapparent winddirection. True wind can also be indicated by a fixed wind indicator (flag, windsock, etc., not attached to the boat or any moving object).

Close-hauled
Reaching
Running downwind

Into the wind

Iceboats parked in irons with sails loose and not generating power, but flapping like a flag.

The range of directions into the wind, where a sailing craft cannot sail is called theno-go zone.^[3]A sailing craft cannotsaildirectly into the wind, nor on acoursethat is too close to thedirectionfrom 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 bein irons.^[4]This is calledmissing stays.To recover, that craft typically must return to its original tack and pick up sufficient speed to complete the maneuver.^[5]^[6]The span of the no-go zone depends on the efficiency of a sailing craft'ssailsand 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.^[4]

A craft stopped in the no-go zone is said to be in irons. Asquare-riggedvessel in irons by accident istaken abackwith the sails blown against the mast^[7]orlaid abackif deliberate.^[8]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.^[9]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.^[10]

Close-hauled

A sailing craft is said to be sailing close-hauled when its sails are trimmed in tightly and are actingsubstantially like a wing,relying on lift to propel the craft forward on a course as close to the wind as the sail can provide lift. This point of sail lets the sailing craft travel upwind, diagonally to the wind direction.^[4]

The smaller the angle between the direction of the true wind and the course of the sailing craft, the higher the craft is said topoint.A craft that can point higher or sail faster upwind is said to be moreweatherly.^[11]Pinchingoccurs as a craft's point of sail approaches the no-go zone and its speed falls off sharply.^[4]

Sailing to windward

Beating upwind in a more- (blue) and less- (red)weatherlywatercraft

In order to sail upwind, sailing craft must zig-zag across the direction of the oncoming wind, calledbeating to windward.The higher a vessel that can point into the wind, the shorter its "course made good" to an upwind destination.^[12]Beating upwind, a vessel alternates between having the wind come on the port and starboard sides (the port and starboard tack). Changing from one tack to the other, by steering through the wind direction, is calledtacking,orgoing about.^[13]

Reaching

A craft sailing with the true wind on its side (within limits) isreaching.^[4]Wind is flowing over the surface of the sail, creating lift (like a wing) to propel the craft. Because lift is more powerful than drag on this point of sail, sailing craft achieve their highest speeds on a reach.^[12]A variety ofhigh-performance sailing craftsail fastest on a broad reach with the sails close-hauled at speeds several times the true windspeed. Depending on the angle of the true wind with respect to the course sailed, a reach may beclose,beam,orbroad,as follows:

Aclose reachis a course closer to the true wind (more upwindwards) than a beam reach, but below close-hauled; i.e., any angle between a beam reach and close-hauled. The sails are trimmed in (hauled towards the centreline of the hull), but not as tightly as for a close-hauled course.

Abeam reachis when the true wind is at a right angle to the direction of motion (so called because the wind is parallel to the cross-hull beams, if any; seebeam).

Abroad reachis when the wind is coming from behind the sailing craft at an angle. This represents a range of wind angles, between a beam reach (see next paragraph) and running downwind. On a sailboat (but not an iceboat) the sails are eased out away from the sailing craft, but not as much as on a downwind run. If the sailcraft points any further downwind, the sails cease acting substantially like a wing.

Running downwind

Sailing with the wind orrunning before the wind,the sails generate power primarily through drag (like a parachute) with the true wind directly from behind the sailing craft.^[4]A sailing craft running more downwind than a broad reach cannot attain a speed faster than the true wind.

However, higher-performance sailing craft achieve a highervelocity made gooddownwind, by sailing on whatever broad reach is most efficient on that particular craft, and jibing as needed. The longer course is offset by the faster speed. For instance, if a vessel sails alternately in the directions 45° from the downwind direction, it will sail√2(≈1.4) times farther than it would if it sailed dead downwind. However, as long as it can sail faster than 1.4 times its dead downwind speed, the indirect route will allow it to arrive at a chosen point sooner.^[14]^[15]

Craft running downwind increase power from the sails by increasing total area presented to the following wind, sometimes by putting out sails that adapt well to the purpose, such as aspinnakeron a fore-and-aft rigged vessel. Another technique is to place the jib to windward (opposite to the main sail)—called "wing on wing" or one of several other terms—for a fore-and-aft vessel going dead downwind.^[4]In light winds, certain square-rigged vessels may setstudding sails,sails that extend outwards from theyardarms,to create a larger sail area for points of sail, ranging from downwind to a close reach.^[16]^[17]

Downwind

Sails for a fore-and-aft rig and a square rig in use downwind

True wind versus apparent wind

True wind (V_T)combineswith the sailing craft's velocity (V_B) to be theapparent wind velocity(V_A); the air velocity experienced by instrumentation or crew on a moving sailing craft. Apparent wind velocity provides the motive power for the sails on any given point of sail. The apparent wind is equal to the true wind velocity for a stopped craft; it may be faster than the true wind speed on some points of sail, or it may be slower e.g. when a sailing craft sails dead downwind.^[18]

Effect of apparent wind on sailing craft at three points of sail

Sailing craftAis close-hauled. Sailing craftBis on a beam reach. Sailing craftCis on a broad reach.
Boat velocity (in black) generates an equal and opposite apparent wind component (not shown), which adds to the true wind to become apparent wind.

Apparent wind and forces on asailboat.
As the boat sails further from the wind, the apparent wind becomes smaller and the lateral component becomes less; boat speed is highest on the beam reach.
Apparent wind on aniceboat.
As the iceboat sails further from the wind, the apparent wind increases slightly and the boat speed is highest on the broad reach. The sail is sheeted in for all three points of sail.^[2]

The speed of sailboats through the water is limited by the resistance that results from hull drag in the water. Ice boats typically have the least resistance to forward motion of any sailing craft;^[2]consequently, a sailboat experiences a wider range of apparent wind angles than does an ice boat, whose speed is typically great enough to have the apparent wind coming from a few degrees to one side of its course, necessitating sailing with the sail sheeted in for most points of sail. On conventional sail boats, the sails are set to create lift for those points of sail where it's possible to align the leading edge of the sail with the apparent wind.^[4]

For a sailboat, point of sail significantly affects the lateral force to which the boat is subjected. The higher the boat points into the wind, the stronger the lateral force, which results in both increased leeway and heeling. Leeway, the effect of the boat moving sideways through the water, can be counteracted by a keel or other underwater foils, including daggerboard, centerboard, skeg and rudder. Lateral force also induces heeling in a sailboat, which is resisted by the shape and configuration of the hull (or hulls, in the case of catamarans) and the weight of ballast, and can be further resisted by the weight of the crew. As the boat points off the wind, lateral force and the forces required to resist it become reduced.^[19] Onice boatsandsand yachts,lateral forces are countered by the lateral resistance of the blades on ice or of the wheels on sand, and of their distance apart, which generally prevents heeling.^[14]

References

^^a ^b ^c ^dRousmaniere, John (7 January 2014).The Annapolis book of seamanship.Smith, Mark (Mark E.) (Fourth ed.). New York. pp. 47–9.ISBN 978-1-4516-5019-8.OCLC 862092350.{{cite book}}:CS1 maint: location missing publisher (link)
^^a ^b ^c ^d Kimball, John (2009).Physics of Sailing.CRC Press. p. 296.ISBN 978-1466502666.
^ Cunliffe, Tom (2016).The Complete Day Skipper: Skippering with Confidence Right From the Start(5 ed.). Bloomsbury Publishing. p. 208.ISBN 9781472924186.
^^a ^b ^c ^d ^e ^f ^g ^hJobson, Gary (2008).Sailing Fundamentals.New York: Simon and Schuster. pp. 72–75.ISBN 9781439136782.
^"Sailing Terms You Need To Know".asa.27 November 2012.Retrieved19 April2018.
^Cunliffe, Tom (1994).The Complete Yachtmaster.London: Adlard Coles Nautical. pp. 43, 45.ISBN 0-7136-3617-3.
^"Sailing the seas of nautical language - OxfordWords blog".oxforddictionaries.30 June 2014. Archived fromthe originalon July 6, 2014.Retrieved19 April2018.
^"WORKING TO WINDWARD".Text-Book of Seamanship.Originally published by "SMITH & MCDOUGAL, ELECTROTYPERS"; digital copy posted by the Historic Naval Ships Association. 1891.{{cite book}}:|website=ignored (help)
^Jobson, Gary (2008-09-08).Sailing Fundamentals.Simon and Schuster. pp. 46–48.ISBN 978-1-4391-3678-2.
^Harris, William (2009-10-05)."How Ice Sailing Works".HowStuffWorks.Retrieved2022-02-28.
^Jett, Stephen C. (2017).Ancient Ocean Crossings: Reconsidering the Case for Contacts with the Pre-Columbian Americas.University of Alabama Press. p. 528.ISBN 9780817319397.
^^a ^b"What Is The Fastest Point Of Sail?".16 September 2020.
^Kemp, Dixon (1882).A Manual of Yacht and Boat Sailing.H. Cox. pp.97.fetch.
^^a ^b Bethwaite, Frank (2007).High Performance Sailing.Adlard Coles Nautical.ISBN 978-0-7136-6704-2.
^Batchelor, Andy; Frailey, Lisa B. (2016).Cruising Catamarans Made Easy: The Official Manual For The ASA Cruising Catamaran Course (ASA 114).American Sailing Association. p. 50.ISBN 9780982102541.
^King, Dean (2000).A Sea of Words(3 ed.). Henry Holt. p. 424.ISBN 978-0-8050-6615-9.
^Luce, Stephen Bleecker (1868).Seamanship, Compiled from Various Authorities, and Illustrated with Numerous Original and Select Designs, for the Use of the United States Naval Academy.D. van Nostrand. pp. 190–472.
^Jobson, Gary (1990).Championship Tactics: How Anyone Can Sail Faster, Smarter, and Win Races.New York: St. Martin's Press. pp.323.ISBN 0-312-04278-7.
^ Marchaj, C. A. (2002),Sail Performance: Techniques to Maximize Sail Power(2 ed.), International Marine/Ragged Mountain Press, p. 416,ISBN 978-0071413107

Bibliography

Rousmaniere, John,The Annapolis Book of Seamanship,Simon & Schuster, 1999
Chapman Book of Piloting(various contributors), Hearst Corporation, 1999
Herreshoff, Halsey (consulting editor),The Sailor’s Handbook,Little Brown and Company, 1983
Seidman, David,The Complete Sailor,International Marine, 1995
Jobson, Gary,Sailing Fundamentals,Simon & Schuster, 1987

[:2-1] Rousmaniere, John (7 January 2014).The Annapolis book of seamanship.Smith, Mark (Mark E.) (Fourth ed.). New York. pp. 47–9.ISBN 978-1-4516-5019-8.OCLC 862092350.{{cite book}}:CS1 maint: location missing publisher (link)

[Kimball-2] Kimball, John (2009).Physics of Sailing.CRC Press. p. 296.ISBN 978-1466502666.

[Complete-3] Cunliffe, Tom (2016).The Complete Day Skipper: Skippering with Confidence Right From the Start(5 ed.). Bloomsbury Publishing. p. 208.ISBN 9781472924186.

[Jobson-4] ^^a ^b ^c ^d ^e ^f ^g ^hJobson, Gary (2008).Sailing Fundamentals.New York: Simon and Schuster. pp. 72–75.ISBN 9781439136782.

[5] "Sailing Terms You Need To Know".asa.27 November 2012.Retrieved19 April2018.

[6] Cunliffe, Tom (1994).The Complete Yachtmaster.London: Adlard Coles Nautical. pp. 43, 45.ISBN 0-7136-3617-3.

[7] "Sailing the seas of nautical language - OxfordWords blog".oxforddictionaries.30 June 2014. Archived fromthe originalon July 6, 2014.Retrieved19 April2018.

[hnsa-8] "WORKING TO WINDWARD".Text-Book of Seamanship.Originally published by "SMITH & MCDOUGAL, ELECTROTYPERS"; digital copy posted by the Historic Naval Ships Association. 1891.{{cite book}}:|website=ignored (help)

[9] Jobson, Gary (2008-09-08).Sailing Fundamentals.Simon and Schuster. pp. 46–48.ISBN 978-1-4391-3678-2.

[10] Harris, William (2009-10-05)."How Ice Sailing Works".HowStuffWorks.Retrieved2022-02-28.

[Jett-11] Jett, Stephen C. (2017).Ancient Ocean Crossings: Reconsidering the Case for Contacts with the Pre-Columbian Americas.University of Alabama Press. p. 528.ISBN 9780817319397.

[fastest-12] "What Is The Fastest Point Of Sail?".16 September 2020.

[13] Kemp, Dixon (1882).A Manual of Yacht and Boat Sailing.H. Cox. pp.97.fetch.

[:0-14] Bethwaite, Frank (2007).High Performance Sailing.Adlard Coles Nautical.ISBN 978-0-7136-6704-2.

[:1-15] Batchelor, Andy; Frailey, Lisa B. (2016).Cruising Catamarans Made Easy: The Official Manual For The ASA Cruising Catamaran Course (ASA 114).American Sailing Association. p. 50.ISBN 9780982102541.

[king424-16] King, Dean (2000).A Sea of Words(3 ed.). Henry Holt. p. 424.ISBN 978-0-8050-6615-9.

[Luce-17] Luce, Stephen Bleecker (1868).Seamanship, Compiled from Various Authorities, and Illustrated with Numerous Original and Select Designs, for the Use of the United States Naval Academy.D. van Nostrand. pp. 190–472.

[Jobson2-18] Jobson, Gary (1990).Championship Tactics: How Anyone Can Sail Faster, Smarter, and Win Races.New York: St. Martin's Press. pp.323.ISBN 0-312-04278-7.

[Marchaj1-19] Marchaj, C. A. (2002),Sail Performance: Techniques to Maximize Sail Power(2 ed.), International Marine/Ragged Mountain Press, p. 416,ISBN 978-0071413107

[1]

[2]

[3]

[4]

[5]

[6]

[7]

[8]

[9]

[10]

[11]

[12]

[13]

[14]

[15]

[16]

[17]

[18]

[19]