Sailing Explained

Sailing is the art of controlling a boat with large pieces of canvas cloth called sails. By changing the rigging, rudder, and dagger or centre board, a sailor manages the force of the wind on the sails in order to change the direction and speed of a boat. Mastery of the skill requires experience in varying wind and sea conditions, as well as knowledge concerning sailboats.

Current use

Today many people enjoy sailing as a recreational activity. Recreational sailing or yachting can be further divided into racing, cruising, and "daysailing" or dinghy sailing. There are many production sailboats available, and several of these manufactured models have ownership associations, such as the Islander 36 association.

Sailing (racing) is a sport that requires brains, strength, grit, and determination and is accessible to all ages. With many clubs widespread across the world, many world, national, and European championships are held at venues every year, during which sailors of each class of boat compete against one another.

History

Throughout history sailing has been instrumental in the development of civilization. The earliest representation of a ship under sail appears on an Egyptian vase from about 3500 B.C.[1] Advances in sailing technology from the Middle Ages onward enabled Arab, Chinese, Indian and European explorers to make longer voyages into regions with extreme weather and climatic conditions. Improvements were made in the design of sails, masts and rigging, and navigational equipment became more sophisticated. From the 15th century onwards, European ships went further north, stayed longer on the Grand Banks and in the Gulf of St. Lawrence, and eventually began to explore the Pacific Northwest and the Western Arctic.[2]

The Physics of Sailing

Introduction

A sailing vessel moves forward because of the reaction of moving air on its sails. Since the dawn of history this vital technology has afforded mankind greater mobility and capacity for fishing, trade and warfare. From moving the stones of the great pyramids from Aswan to Giza to allowing man to migrate throughout Polynesia to Nelson's defeat of the French and Spanish navies at the Battle of Trafalgar, mankind's history has been intertwined with this seemingly simple technology.

Energy capture

The energy that drives a sailboat is harnessed by manipulating the relative movement of wind and water speed: if there is no difference in movement, such as on a calm day or when the wind and water current are moving in the same direction at the same speed, there is no energy to be extracted and the sailboat will not be able to do anything but drift. Where there is a difference in motion, then there is energy to be extracted at the interface, and the sailboat does this by placing the sail(s) in the air and the hull(s) in the water.

Sails are airfoils that work by using an airflow set up by the wind and the motion of the boat. The combination of the two is the apparent wind, which is the relative velocity of the wind relative to the boat's motion. The sails generate lift using the air that flows around them. The air flowing at the sail surface is not the true wind.[3]

The sail alone is not sufficient to drive the boat in any desired direction, as a sail by itself would only push a boat in the same direction as the wind. Sailboats overcome this by having another physical object below the water line. These include, a keel, centerboard, or some other form of underwater foil or even the hull itself (as in catamarans without centreboard or in a traditional proa). Thus, the physical portion of the boat which is below water can be regarded as functioning as a "second sail". Having two surfaces against the wind and water enables the sailor to travel in almost any direction and to generate an additional source of lift from the water. The flow of water over the underwater hull portions creates a hydrodynamic force. The combination of the aerodynamic force from the sails and the hydrodynamic force from the underwater hull section allows motion in almost any direction, except straight into the wind. This can be likened, in simple terms, to squeezing a wet bar of soap with two hands which causes it to shoot out in a direction perpendicular to both opposing forces. Depending on the efficiency of the rig, the angle of travel relative to the true wind can be as little as 35 degrees to over 80 degrees. This angle is called the tacking angle http://www.storerboatplans.com/Pdr/PDRmeasurepointingleeway.html.With a 35 degree tacking angle on either side of the wind, it is possible for a sailboat to sail directly over 290 degrees of the compass (360 - 2x35 = 290 degrees).

Tacking is essential when sailing upwind. The sails, when correctly adjusted, will generate aerodynamic lift. When sailing downwind, the sails no longer generate aerodynamic lift and airflow is stalled, with the wind push on the sails giving drag only. As the boat is going downwind, the apparent wind is less than the true wind and this, allied to the fact that the sails are not producing aerodynamic lift, serves to limit the downwind speed.[4] When moving, the motion of the boat creates its own apparent wind. Apparent wind is what is experienced onboard and is the wind that the boat is actually sailing by. Sailing into the wind causes the apparent wind to be greater than the true wind and the direction of the apparent wind will be forward[5] of the true wind. Some extreme design boats are capable of traveling faster than the true windspeed.

Some non-traditional rigs purportedly capture energy from the wind in a much different fashion are capable of feats that traditional rigs are not, such as sailing directly into the wind. One such example is the wind turbine boat, also called the windmill boathttp://www.treehugger.com/files/2007/02/windmill_sailbo.php, which uses a large windmill to extract energy from the wind, and a propeller to convert this energy to forward motion of the hull. A similar design, called the autogyro boat, uses a wind turbine without the propellor, and functions in a manner similar to a normal sailhttp://uk.geocities.com/fnsnclr@btinternet.com/yachts/auto/index.htm.

Effects of wind shear

Wind shear affects sailboats in motion by presenting a different wind speed and direction at different heights along the mast. Wind shear occurs because of the greater friction presented by water surface slowing the flow of air, a difference in true wind creates a different apparent wind at different heights. Sailmakers may introduce sail twist in the design of the sail, where the head of the sail is set at a different angle of attack from the foot of the sail in order to change the lift distribution with height. The effect of wind shear can be factored into the selection of twist in the sail design, but this can be difficult to predict since wind shear may vary widely in different weather conditions. Sailors may also adjust the trim of the sail to account for wind gradient, for example using a boom vang.[6]

Points of sail

See also: Points of sail. The points of sail are the most important parts of sail theory to remember. The wind, irons, or no go zone, is about 45° either side of the true wind, for a racing hull and sail plan optimized for upwind work. More commonly and on cruising sailplans, the best angle achievable upwind is 50° to 55° to the true wind. A boat cannot sail directly into the wind; attempting to do so is called luffing. There are 5 main points of sail. In order from the edge of the no go zone to directly downwind they are:

The sail trim (and, on smaller boats, centre board/dagger board position) on a boat is relative to the point of sail one is on: on a beam reach sails are half way out, on a run sails are all the way out, and close hauled sails are pulled in very tightly. A large proportion of the skill of sailing is in trimming the sails correctly for direction and strength of the wind.

Beating

A basic rule of sailing is that it is not possible to sail directly into the wind—at least not for long. Generally speaking, a modern boat can sail 45 degrees off the wind. When a boat is sailing this close to the wind, it is close-hauled or beating (beating to weather).

Because a boat cannot sail directly into the wind, but the destination is often upwind, one can only get there by sailing close-hauled with the wind coming from the port side (the boat is on port tack), then tacking (turning the boat through the eye of the wind) and sailing with the wind coming from the starboard side (the boat is on starboard tack). By this method, it is possible to reach that destination directly upwind. For a yacht beating upwind to a mark at a distance upwind of one mile, it will cover a distance through the water of over 1.42 miles, if it can tack through an angle of 90 degrees. An old adage describes beating as sailing for twice[7] the distance at half the speed and three times the discomfort.

How closely a boat can sail into the wind depends on the boat's design, sail trim, the sea state, and the wind speed, since what the boat "sees" is the apparent wind, the vector sum of the actual wind and the negation of the boat's own velocity. The apparent wind speed is what the anemometer on top of the mast shows. The apparent wind angle while sailing close hauled will be less than the true wind angle. A good, modern sloop can sail within 25 degrees of the apparent wind. An America's Cup racing sloop can sail within 16 degrees—under ideal conditions. Those figures might translate into 45 degrees and 36 degrees relative to the actual wind, depending on boat speed.

Reaching

When the boat is traveling approximately perpendicular to the wind, this is called reaching. A 'beam' reach is with the wind precisely at right angles to the boat, while a 'close' reach is halfway between beating and a beam reach, and a 'broad' reach is a little bit away from the wind.

For most modern sailboats, that is boats with triangular sails, reaching is the fastest way to travel. The direction of the wind is ideal for reaching because it will maximize the lift generated on the sails in the forward direction of the boat, giving the best boat speed. Also when reaching, the boat can be steered exactly in the direction that is most desirable, and the sails can be trimmed for that direction.

Reaching however may put the boat on a parallel course with the waves. When the waves are steep, it may be necessary to sail closer to the wind to avoid waves directly on the beam.

Running

Sailing the boat within roughly 30 degrees either side of dead downwind is called a run. This is the easiest point of sail in terms of comfort, unless in a small dinghy (as cramp can set in), but it can also be the most dangerous. (deathrolls leading to turtles are very common in high winds). When sailing upwind, it's easy to stop the boat by heading into the wind; a sailor has no such easy out when running. Severe rolling is more likely as there is less rolling resistance provided by the sails, which are eased out. And loss of attention by the helmsman could lead the boat to gybe accidentally, causing injury to the boat or crew. (A preventer can be rigged to prevent damage from an accidental gybe.) Alternately, if there is a sudden increase in wind strength, the boat can round up very suddenly and heel excessively, often leading to a capsize in smaller boats. This is called broaching.

Basic sailing techniques

Trim

An important aspect of sailing is keeping the boat in "trim". To achieve this a useful mnemonic (memory aid) is the phrase:

Can This Boat Sail Correctly?

This helps the crew to remember these essential points;

Together, these points are known as 'The Five Essentials' and constitute the central aspects of sailing.

Reducing sail

An important safety aspect of sailing is to adjust the amount of sail to suit the wind conditions. As the wind speed increases the crew should progressively reduce the amount of sail. On a small boat with only jib and mainsail this is done by furling the jib and by partially lowering the mainsail, a process called 'reefing the main'.

Reefing means reducing the area of a sail without actually changing it for a smaller sail. Ideally reefing does not only result in a reduced sail area but also in a lower center of effort from the sails, reducing the heeling moment and keeping the boat more upright.

There are three common methods of reefing the mainsail:

Mainsail furling systems have become increasingly popular on cruising yachts as they can be operated shorthanded and from the cockpit in most cases, however, the sail can become jammed in the mast or boom slot if not operated correctly. Mainsail furling is almost never used while racing because it results in a less efficient sail profile. The classical slab-reefing method is the most widely used. Mainsail furling has an additional disadvantage in that its complicated gear may somewhat increase weight aloft. However, as the size of the boat increases, the benefits of mainsail roller furling increase dramatically.

An old saying goes, "The first time you think of reducing sail you should," and correspondingly, "When you think you are ready to take out a reef, have a cup of tea instead."

Sail trimming

As noted above, sail trimming is a large subject. Basic control of the mainsail consists of setting the sail so that it is at an optimum angle to the wind, (i.e. no flapping at the front, and tell tales flowing evenly off the rear of the sail).

Two or more sails are frequently combined to maximize the smooth flow of air. The sails are adjusted to create a smooth laminar flow over the sail surfaces. This is called the "slot effect". The combined sails fit into an imaginary aerofoil outline, so that the most forward sails are more in line with the wind, whereas the more aft sails are more in line with the course followed. The combined efficiency of this sail plan is greater than the sum of each sail used in isolation.

More detailed aspects include specific control of the sail's shape, e.g.:

Hull trim

Hull trim is the adjustment of a boat's loading so as to change its fore-and-aft attitude in the water. In small boats, it is done by positioning the crew. In larger boats the weight of a person has less effect on the hull trim, but it can be adjusted by shifting gear, fuel, water, or supplies. Different hull trim efforts are required for different kinds of boats and different conditions. Here are just a few examples: In a lightweight racing dinghy like a Thistle, the hull should be kept level, on its designed water line for best performance in all conditions. In many small boats, weight too far aft can cause drag by submerging the transom, especially in light to moderate winds. Weight too far forward can cause the bow to dig into the waves. In heavy winds, a boat with its bow too low may capsize by pitching forward over its bow (pitch-pole) or dive under the waves (submarine). On a run in heavy winds, the forces on the sails tend to drive a boat's bow down, so the crew weight is moved far aft.

Heeling

A boat leaning over to one side under wind pressure, is said to be 'heeling'. When any large ship is listing heavily, perhaps due to damage, it can also said to be heeling. As a sailing boat heels over beyond a certain angle, it begins to sail less efficiently. Several forces can counteract this movement.

Most of the above effects can be used to right a heeling boat and to keep the boat sailing efficiently: if however the boat heels beyond a certain point of stability, it can capsize. A boat is capsized when the tip of the mast is in the water. Yachts are traditionally divided into non-capsizable (which means that they have a heavy keel which in normal weather should stabilize the vessel) and non-drowning (which usually means that the vessel has a centerboard and even in normal circumstances can be capsized, but will not sink).

Sailing hulls and hull shapes

See also: Hull (watercraft). Sailing boats with one hull are "monohulls", those with two are "catamarans", those with three are "trimarans". A boat is turned by a rudder, which itself is controlled by a tiller or a wheel, while at the same time adjusting the sheeting angle of the sails. Smaller sailing boats often have a stabilising, raisable, underwater fin called a centreboard (or daggerboard); larger sailing boats have a fixed (or sometimes canting) keel. As a general rule, the former are called dinghies, the latter keelboats. However, up until the adoption of the Racing Rules of Sailing, any vessel racing under sail was considered a yacht, be it a multi-masted ship-rigged vessel (such as a sailing frigate), a sailboard (more commonly referred to as a windsurfer) or remote-controlled boat, or anything in between. (see Dinghy sailing)

Multihulls use flotation and/or weight positioned away from the centre line of the sailboat to counter the force of the wind. This is in contrast to heavy ballast that can make up to ⅓ of the weight of a monohull sailboat. In the case of a standard catamaran there are two similarly sized and shaped slender hulls connected by beams, which are sometimes overlaid by a deck superstructure. Another catamaran variation is the proa. In the case of trimarans, which have an unballasted centre hull similar to a monohull, two relatively smaller amas are situated parallel to the centre hull to resist the sideways force of the wind. The advantage of multihulled sailboats is that they do not suffer the performance penalty of having to carry heavy ballast, and their relatively lesser draft reduces the amount of drag, caused by friction and inertia, when moving through the water.

Types of sails and layouts

See also: Sailboat. A traditional modern yacht is technically called a "Bermuda sloop" (sometimes a "Bermudan sloop"). A sloop is any boat that has a single mast and a headsail (generally a jib) in addition to the mainsail. The Bermuda designation refers to the fact that the sail, which has its forward edge (the "luff") against the mast (the main sail), is a sail roughly triangular in shape. Additionally, Bermuda sloops only have a single sail behind the mast. Other types of sloops are gaff-rigged sloops and lateen sloops. Gaff-rigged sloops have quadrilateral mainsails with a gaff (a small boom) at their upper edge (the "head" of the sail). Gaff-rigged vessels may also have another sail, called a topsail, above the gaff. Lateen sloops have triangular sails with the upper edge attached to a gaff, and the lower edge attached to the boom, and the boom and gaff are attached to each other via some type of hinge. It is also possible for a sloop to be square rigged (having large square sails like a Napoleonic Wars-era ship of the line). Note that a "sloop of war," in the naval sense, may well have more than one mast, and is not properly a sloop by the modern meaning.

If a boat has two masts, it may be a schooner, a ketch, or a yawl, if it is rigged fore-and-aft on all masts. A schooner may have any number of masts provided the second from the front is the tallest (called the "main mast"). In both a ketch and a yawl, the foremost mast is tallest, and thus the main mast, while the rear mast is shorter, and called the mizzen mast. The difference between a ketch and a yawl is that in a ketch, the mizzen mast is forward of the rudderpost (the axis of rotation for the rudder), while a yawl has its mizzen mast behind the rudderpost. In modern parlance, a brigantine is a vessel whose forward mast is rigged with square sails, while her after mast is rigged fore-and-aft. A brig is a vessel with two masts both rigged square.

As one gets into three or more masts the number of combinations rises and one gets barques, barquentines, and full rigged ships.

A spinnaker is a large, full sail that is only used when sailing off wind either reaching or downwind, to catch the maximum amount of wind.

Sailing terminology

See also: Glossary of nautical terms. Sailors use traditional nautical terms for the parts of or directions on a vessel; starboard (right), port (left), forward or fore (front), aft (rearward), bow (forward part of the hull), stern (aft part of the hull), beam (the widest part). Vertical spars are masts, horizontal spars are booms (if they can hit the sailor), gaffs (if they are too high to reach) or poles (if they cannot hit the sailor).

Rope and lines

Rope is the term used only for raw material; once a section of rope is designated for a particular purpose on a vessel, it generally is called a line, as in outhaul line or dock line. A very thick line is considered a cable. Lines that are attached to sails to control their shapes are called sheets, as in mainsheet If a rope is made of wire, it maintains its rope name as in 'wire rope' halyard.

Lines (generally steel cables) that support masts are stationary and are collectively known as a vessel's standing rigging, and individually as shrouds or stays (the stay running forward from a mast to the bow is called the forestay or headstay).

Moveable lines that control sails or other equipment are known collectively as a vessel's running rigging. Lines that raise sails are called halyards while those that strike them are called downhauls or cunninghams. Lines that adjust (trim) the sails are called sheets. These are often referred to using the name of the sail they control (such as main sheet, or jib sheet). Sail trim may also be controlled with smaller lines attached to the forward section of a boom; such a line is called a vang, or a kicker in the United Kingdom.

Lines used to tie a boat up when alongside are called docklines, docking cables or mooring warps.

Some lines are referred to as ropes: A bell rope (to ring the bell), a bolt rope (attached to the edge of a sail for extra strength), a foot rope (on old square riggers for the sailors to stand on while reefing or furling the sails), and a tiller rope (to temporarily hold the tiller and keep the boat on course). A rode is what keeps an anchor attached to the boat when the anchor is in use. It may be chain, rope, or a combination of the two.

Other terms

Walls are called bulkheads or ceilings, while the surfaces referred to as ceilings on land are called 'overheads'. Floors are called 'soles' or decks. The toilet is traditionally called the 'head', the kitchen is the galley. Lines are rarely tied off, they are almost always 'made fast' or 'belayed.' Sails in different sail plans have unchanging names, however. For the naming of sails, see sail-plan.

Knots

Knots are among the most important things a sailor needs to know. Although only a few are required, the bowline in particular is essential. By also learning the clove hitch and "round turn and two half hitches," one can easily cope with all of the knot requirements of a boat. A more complete grasp of knot-tying includes mastery of the following knots:

Additional knots are available List of knots

Even experienced sailors may forget their knots if they are not performed on a regular basis. Forgetting how to tie an important knot can damage a boat or cause injury.

Sailing regulations

There are three basic rules for avoiding a collision at sea, but this is a simplification of a detailed set of regulations:

  1. A yacht using sails as motive power on port tack[8] gives way to one on starboard tack.[9] .
  2. The more maneuverable vessel gives way to the less maneuverable vessel. It is generally assumed that this means that power 'gives way' to sail, but this is not always the case. It is prudent for a small sailing vessel to stay out of the way of large power driven ships by making an early and obvious alteration in course to signal both recognition of a potential collision situation and that avoiding action has been taken. It is mandatory, by port and harbour regulations, that sailing vessels shall stay clear of shipping in a buoyed channel.
  3. If a collision is imminent both vessels must take avoiding action even if one vessel (this is the 'stand-on' vessel) would normally take no action. Not to do so, if there is an opportunity, may make the sailor the guilty party at an inquiry. The use of the term 'right of way' is borrowed from yacht racing environment, does not appear in internationally recognised rules for vessels not racing and is inappropriate to all other vessels and situations.

Power driven vessel A that is on a potential collision course crossing the port side of power driven vessel B must give way. Sailing boats with their sails set on the same side of the boat, require that[10] the windward boat shall give way to the leeward boat.[11] Vessel A overtaking vessel B normally must keep clear of them . Head on collisions are avoided by vessels both turning to Starboard.

If these rules are not followed in a yacht race, a protest may be called by one of the skippers. A hearing of protestor and protestee by the protest committee panel will decide who wins the rule breach.

However there are many other rules besides these, that are applicable and sailors are required to know these, which are fundamental boating safety rules including:

After sunset all boats racing are bound by the International Regulations for Preventing Collisions at Sea (COLREGS) rather than the Racing Rules of Sailing.

Sailboat racing

Sailboat racing ranges from single person dinghy racing to large boats with 10 or 20 crew and from small boats costing a few hundred dollars to multi-million dollar America's Cup or Sydney to Hobart Yacht Race campaigns. The costs of participating in the high end large boat competitions make this type of sailing one of the most expensive sports in the world. However, there are relatively inexpensive ways to get involved in sailboat racing, such as at community sailing clubs, and in some relatively inexpensive dinghy and small catamaran classes. Additionally high schools and colleges may offer sailboat racing programs through the Interscholastic Sailing Association (in the USA) and the Intercollegiate Sailing Association (in the USA and some parts of Canada). Under these conditions, sailboat racing can be comparable to or less expensive than sports such as golf and skiing. Sailboat racing is one of the few sports in which people of all ages and genders can regularly compete with and against each other.

Most sailboat and yacht racing is done in sheltered coastal or inland waters. However, in terms of endurance and risk to life, ocean races such as the Volvo Ocean Race, the solo VELUX 5 Oceans Race, and the non-stop solo Vendée Globe, rate as some of the most extreme and dangerous sporting events. Not only do participants compete for days with little rest, but an unexpected storm, a single equipment failure, or collision with an ice floe could result in the sailboat being disabled or sunk hundreds or thousands of miles from search and rescue.

The sport of Sailboat racing is governed by the International Sailing Federation (ISAF), and the rules under which competitors race are the Racing Rules of Sailing, which can be found on the ISAF web site.

As well as these there is the "mini transats" in which very small craft and a solo sailer cross the Atlantic Ocean. The Vendee Globe is another race for larger boats.Other races include the Fastnet race from Cowes, around the Fastnet rock just of the coast of Ireland and back again to the Plymouth. There is also the Sydney to Hobart race. Other race much important is Valtur World Cup for Amateurs disputated in Pollina (Italy) in 2001.

See also

References

External links

Notes and References

  1. Casson, Lionel. 1971. Ships and Seamanship in the Ancient World
  2. "Transportation and Maps" in Virtual Vault,the art of the boat is sofa an online exhibition of Canadian historical art at Library and Archives Canada
  3. As would be seen by a wind in relation to the boat which also has a velocity. The curved surface of a sail serves to deflect the air. Deflecting the air results in a reaction force on the sail and rigging, which pushes the boat in a direction opposite to the deflection. It is often said that lift is generated by the pressure differential on the sails, but this is not entirely true--the pressure differential deflects the air, but it is the deflection that generates the force. Since the air behind the sailboat has been deflected, it now has less energy and is slower and is often called dirty air. Racing sailors try to avoid sailing in dirty air and attempt to give dirty air to opponents where possible. A common technique is trying to get upwind of an opponent, and make them sail in your dirty air, slowing them down
  4. Large sails of big area, spinnakers serve to increase the sail area for more performance downwind
  5. Forward of means making a smaller angle relative to the bow than the angle that the true wind makes relative to the bow
  6. Book: Garrett, Ross. The Symmetry of Sailing. Sheridan House. Dobbs Ferry. 1996. 97–99. 1574090003.
  7. Each leg at 45 degrees to the true wind is 0.71miles, but in reality is longer as tacking angles greater than 45 degrees are the norm and leeway is significant also,
  8. Sails set for a breeze coming from the left hand side of the boat
  9. Sails set for a breeze coming from the right side of the boat
  10. the boat closer to where the wind is coming from,
  11. Boat further away from the wind