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Wooden sailing boatSailing is the skillful art of controlling the motion of a sailing ship or smaller boat, across a body of water using wind as the source of power.
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The physics of sailing
The force of the wind is used to create motion by using one or more sails. When sailing downwind (away from the wind source) the vessel's motion is derived from the simple force of the wind pushing the sail. When sailing upwind (towards the wind source) the movement of air over the sails acts in the same way as air moving over an aircraft's wing. Air flowing over the sail generates lift. This pulls the sail (and the boat) ahead, but also pushes it slightly downwind. The downwind component is offset by an underwater hydrofoil whose shape resists lateral movement while offering little resistance to forward motion. Without this hydrofoil sailing upwind or across the wind would be virtually impossible. Sailing hydrofoils include keels, centerboards, daggerboards, (less commonly) leeboards, and (particularly in small sailboats or dinghies), the rudder acts as a hydrofoil also, reducing leeway.
The lifting force of the sails also acts to lean the boat over to one side, which is called heeling. In monohull vessels, heeling is counteracted by ballast, either in the form of dense material located deep in the bilge or externally in the keel (usually lead or iron) or in the form of human or water ballast located near the windward rail. In multihull vessels (catamaran, trimaran or proa) righting force may also be created by the counteracting buoyancy of the leeward hull. Too much heeling may lead to a capsize.
Today, for most people, sailing is a hobby. Pleasure sailing can be further divided into Racing, Cruising and Daysailing.
In ancient times (see Odysseus), ships used following or rear-quarter winds. Therefore, they had to either row or wait in port or at sea for the right wind directions.
Basic sailing techniques
First see the notes on points of sail which introduce some important principles.
Turning a sailing boat
When turning a sailing boat, the direction relative to the wind is as important as the direction overall. Thus all turns can be described by one of the following terms:
- Heading up (or luffing up) is turning the boat to sail closer to the direction the wind is coming from. In order to keep the sails correctly trimmed, they must be pulled in towards the centre of the boat. Continuing to head up will bring the bow so close to the wind that the sails will no longer fill - this is called "being in irons", or (especially when teaching) "the no-go zone".
- If the turn is continued through the no-go zone and out the other side, the boat is said to have tacked. Thus, a tack is a turn that takes the bow of the boat through the eye of the wind.
- Bearing away (or falling off) is turning away from the direction the wind is coming from. As with luffing up, the sails must be adjusted during the turn, in this case let out away from the centre of the boat. If the turn is continued, the boat will end up running directly away from the wind, with the sails at around 90º to the hull and acting as simple wind-catchers rather than aerofoils.
- If the turn is continued such that the boat's stern passes through the wind, a gybe results. Gybing causes the boom to swing from one side to the other, sometimes rapidly, as the wind catches the leech of the mainsail on its new upwind side.
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;
- Course to Steer - Turn the boat using the wheel or tiller to the desired course to steer. See points of sail. This may be a definite bearing (e.g steer 270 degrees), or towards a landmark, or at a desired angle to the apparent wind direction.
- Trim - This is the fore and aft balance of the boat. The aim is to adjust the moveable ballast (the crew!) forwards or backwards to achieve an 'even keel'. On an upwind course in a small boat, the crew typically sit forward, when 'running' it is more efficient for the crew to sit to the rear of the boat. The position of the crew matters less as the size (and weight)of the boat increases.
- Balance - This is the port and starboard balance. The aim, once again is to adjust weight 'inboard' or 'outboard' to prevent excessive heeling.
- Sail - Trimming sails is a large topic. However simply put, a sail should be pulled in until it fills with wind, but no further than the point where the front edge of the sail (the luff) is exactly in line with the wind.
- Centreboard - If a moveable centreboard is fitted, then it should be lowered when sailing "close to the wind" but can be raised up on downwind courses to reduce drag. The centreboard prevents lateral motion and allows the boat to sail upwind. A boat with no centreboard will instead have a heavy permanent keel built into the bottom of the hull, which serves the same purposes.
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, but it can also be the most dangerous. 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 jibe accidentally, causing injury to the boat or crew. It's always a good idea to use a preventer to prevent an accidental jibe.
Reaching
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 right angles to the boat). For most modern sailboats, reaching is the fastest way to travel.
Sailing upwind
Using a series of close hauled legs to beat a course upwindA basic rule of sailing is that it is not possible to sail directly into the wind. Generally speaking, a 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).
Since 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 throught 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. The heavier the wind, the rougher the seas, thus boat movement can be more uncomfortable. This can feel like the boat is beating its hull into the waves, hence the term beating.
How close a boat can sail to 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, i.e., the vector sum of the actual wind and the boat's own velocity. The apparent wind speed is what the anemometer on top of the mast shows. A good analogy to this would be walking through an indoor room and feeling the "wind" on your face. The faster you walk, the more wind your feel. The apparent wind angle while sailing close hauled will be less that 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 the right conditions. Those figures might translate into 45 degrees and 36 degrees relative to the actual wind, depending on boat speed.
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: - Slab reefing, which involves lowering the sail by about one-quarter to one-third of its luff length and tightening the lower part of the sail using an outhaul or a pre-loaded reef line through a cringle at the new clew, and hook through a cringle at the new tack. - In-mast (or on-mast) roller-reefing. This method rolls the sail up around a vertical foil either inside a slot in the mast, or affixed to the outside of the mast. It requires a mainsail with either no battens, or newly-developed vertical battens. - In-boom roller-reefing, with a horizontal foil inside the boom. This method allows for standard- or full-length horizontal battens.
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.
Sail trimming
A Contender dinghy on a reach. The helmsman is using a "trapeze" to exert his weight right outside the boat.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 maximise 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.:
- reefing, or reducing the sail area in stronger wind
- altering sail shape to make it flatter in high winds
- raking the mast when going upwind (to tilt the sail towards the rear, this being more stable)
- providing sail twist to cope with gusty conditions
Heeling
When a boat rolls over to one side under wind pressure, it's called 'heeling'. As a sailing boat heels over beyond a certain angle, it begins to sail less efficiently. Several forces can counteract this movement.
- The buoyancy of that part of the hull which is being submerged tends to bring the boat upright.
- Raising the centreboard can paradoxically increase leeway, and therefore reduce heeling.
- A weighted keel, which can in larger boats be canted from side to side, provides additional force to right the boat.
- The crew may move onto the high (upwind) side of the boat, called hiking, changing the centre of gravity significantly in a small boat. They can trapeze where the boat is designed for this (see Dinghy sailing).
- The underwater shape of the hull relative to the sails can be designed to make the boat tend to turn upwind when it heels excessively: this reduces the force on the sails, and allows the boat to right itself. This is known as rounding up.
- The boat can be turned upwind to produce the same effect.
- Wind can be spilled from the sails by 'sheeting out', i.e. loosening the sail.
- Lastly, as the boat rolls farther over, wind spills from the top of the sail.
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 said to have capsized when the tip of the mast is in the water.
Sailing close to the wind
How close a boat can sail to the wind depends on the wind speed, since what the boat "sees" is the apparent wind, i.e., the vector sum of the actual wind and the boat's own velocity. The apparent wind is what the wind indicator on top of the mast shows. Because of this, people often talk about how close a boat can sail to the apparent wind. 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 the right conditions. Those figures might translate into 45 degrees and 36 degrees relative to the actual wind. The angles at which the wind meets the boat are described by the points of sail.
Sailing safety
First and foremost:
- Learn to swim!
- Wear a life vest!
Sailing is intrinsically dangerous, since water is not our natural element. All sailors therefore should take precautions, and when engaged in publicly organized activities they must take certain precautions, as detailed by the authority which regulates the training or racing.
Safety measures include:
- Provision of a safety boat for rescue purposes
- Appropriate first aid and firefighting equipment
- Carrying of a knife suitable for cutting rigging or netting which may entrap a sailor underwater
- Wearing of buoyancy aids
- Understanding and practice of man overboard procedures such as the Anderson turn, the Williamson turn, and the Scharnow turn.
Also, know the 'rules of the road':
- Port tack gives way to Starboard tack (when the paths of two boats on opposite tacks cross, the boat with its port side to windward must give way)
- Windward gives way to the leeward, or downwind boat (if on the same tack)
- Overtaking boat gives way if above do not apply
- Non-Commercial Powerboats usually give way to sailboats (but be careful in shipping lanes, and use common sense)
- It is everybody's responsibility to avoid a collision, and avoiding action must be taken if these rules are ignored.
Sailing hulls and hull shapes
Sailing boats can have one, two, or three hulls. Boats with one hull are known as monohulls, while those with two or more are known as multihulls. Multihulls can be further subdivided into catamarans (two hulls), and trimarans (three hulls). A sailing boat is turned by a rudder which itself is controlled by a tiller or a wheel. 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 yachts. (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 1/3 of the weight of a monohulled sailboat. In the case of a standard catamaran there are two similarly sized and shaped narrow hulls connected 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 smaller hulls reduce the amount of drag caused by friction and inertia when moving through the water.
Types of sails and layouts
On a modern yacht, the mainsail or main is usually the primary driving sail, triangular in shape, and fixed to the largest (or often the only) mast. A headsail, either a jib or genoa, is set in front of the mainsail, attached in such a way that the trailing edge extends back alongside the main. This is also known as an overlapping headsail (pronounced hedsal). Two or more headsails can be used. In addition, some sailboats, ketches and yawls, have another smaller mast called the mizzen mast, on which is set a smaller sail similar to the mainsail and called the mizzen sail.
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
Sailors use many 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). Vertical spars are masts, horizontal spars are booms (if they can hit you), gaffs (if they're too high to reach) or poles (if they can't hit you).
Rope & line
Standing rigging (on the left) and running rigging (on the right), on a sailing boatActually, only a few of the "ropes" on a boat are called ropes, most are called lines.
Ropes or wires that hold up masts are collectively known as standing rigging and are called shrouds or stays (the stay connecting the top of the mast to the bow is called the forestay or headstay).
Ropes or wires that control the sails are known collectively as running rigging or lines. Those that raise sails are called halyards while those that strike them are called downhauls. Ropes that adjust (trim) the sails are called sheets. These are often referred to using the name of the sail they control (e.g. "main sheet", or "jib sheet").
Ropes used to tie the boat up when alongside are called docklines.
There are some ropes: A few examples, the 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.
Other terms
Walls are called 'bulkheads' or 'ceilings', while the surfaces referred to as 'ceilings' on land are called 'overheads'. Floors are called 'soles'. The toilet is traditionally called the 'head', the kitchen is the 'galley'. Sails in different sail plans have unchanging names, however. For the naming of sails, see sail-plan.
Sailing terms have entered popular language in many ways. "Broken up" was the fate of a ship that hit a "rocky point." "Poop" refers to the aftermost deck of a ship, taken from "puppis" the Latin word for "stern". "Pooped" refers to a wave breaking over the stern and filling the cockpit with water. "In the doldrums" referred to being becalmed, windless, especially in the narrow band of hot windless water "the doldrums", near the equator. "Adrift" meant literally that a ship's anchor had come loose, and the ship was out of control near land and therefore in serious danger. "Keel-hauled and hung out to dry." was the rather nasty process of attaching a sailor to a rope, and drawing him under the sailboat while underway, and then hanging him from a yard-arm (under his shoulders usually, not by his neck), where officers and crew could mock him. This was a particularly unpleasant punishment; apart from the risk of drowning, the sailor would be lacerated by the barnacles on the ship's hull.
Sailing regulations
There are two very basic rules for avoiding a collision at sea: 1) Power gives way to sail 2) Port gives way to starboard. This second point means that boats who have their sails set for a breeze coming from the left hand side of the boat (port) must give way to yachts that have their sails set for a breeze coming from the right side of the boat (starboard). If both boats have their sails set on the same side of the boat, then the boat closer to where the wind is coming from (the windward boat) must give way to the leeward boat.
However there are many other rules besides and sailors are expected to know the essentials of boating safety which include;
- The rules of the road or International Regulations for Preventing Collisions at Sea set forth by the International Maritime Organization are particularly relevant to sailors because of their limited maneuverability compared to powered vessels.
- The IALA International Association of Lighthouse Authorities standards for lateral marks, lights, signals, and buoyage and various rules designed to support safe navigation.
- The SOLAS (Safety of Life at Sea) regulations place the obligations for safety on the owners and operators of any boat. These regulations specify the safety equipment needed and emergency procedures to be used.
Sailboat racing
Although most sailboat racing is done in sheltered coastal or inland waters, in terms of endurance and risk to life, ocean racing, from 100 mile races between two ports to around the world races such as the Volvo Ocean 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 flow 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 ISAF, and the rules under which competitors race is the Racing Rules of Sailing, which can be found on the ISAF web site.
Sailing traditions and etiquette
There are many, more esoteric, etiquette rules, traditions, and customs that will demonstrate to others advanced knowledge of boating protocol. Fenders should be pulled up outside ports, the flag of the host country should be shown, flags are to be taken down at night, no whistling aboard etc.
See also
- catboat and sloop
- catamaran
- day sailer
- dinghy sailing
- dinghy racing
- ketch
- land sailing
- list of nautical terms
- planing (sailing)
- sail
- sail-plan
- yachting
- yacht racing
External links
- Sailr, A community run sailing news website
- Interactive Training-Graphic for Sailing
- Quest for the perfect sail shape
- Online glossary of sailing terms
- Another online glossary
- Mark Rosenstein's extensive list of sailing links
- Open Directory Project - Sailing
- Yahoo! - Sailing
- Sailing news
- Sailing Magazines
- Sailing articles and information at sailnet.com
- Sailing Scuttlebutt daily news about sailboat racing
- Sailing Anarchy website with news and forums about sailboat racing and other topics
- Sailing and the Tech Dinghy -- MIT's dinghy sailing instruction booklet