Sailing
Sailing is motion across a body of water in a sailing ship, or smaller boat, powered by wind.
How sailing works
The force of the wind is used to create motion by using one or more sails. The movement of the air over the sails acts in the same way that air moves over an aircraft's wing. The pressure difference created on either side of the sail(s) produces a driving force.
Sailboats also have a keel or centerboard, a structure whose broad, thin shape resists lateral movement of the hull while offering little resistance to forward motion through the water. Without such a structure, sailing upwind or across the wind is impossible.
Today, for most people, sailing is a hobby. Sailing can be further divided into two areas: Racing and Cruising.
In ancient times (see Odysseus), ships used following or rear-quarter winds. They therefore had to 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
There are four basic maneuvers a sailing boat can perform while underway. They are:
- Tack - Tacking is turning the boat so that the bow turns through the wind (or "no go zone").
- Gybe - Gybing is turning the boat so that the stern of the boat turns through the wind.
- Heading or Luffing up is turning the boat to sail closer to the direction the wind is coming from.
- Bearing away is turning away from the direction the wind is coming from.
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, and also provides stability to keep the boat from rolling over. A boat with no centreboard will instead have a heavy permanent keel built into the bottom of the hull, which serves the same purposes.
Beating an upwind course
By linking together a series of 'close-hauled' legs it is possible for the boat to make progress towards the wind. In between in each leg the boat 'tacks' through the 'no go zone'.
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 a jib and mainsheet this is done by furling in the jib and by partially lowering the mainsail (this is called 'reefing').
Reefing basically means reducing the size of a sail without changing them. Ideally reefing does not only result in a reduced sail area but also in a lower pressure point of the sails propulsing force and a lower center of gravity.
There are three core methods of reefing the mainsail: - Lower the sail and fix the sail using the outhaul and a device like a hook near the mast. (Classical method). - Furl the sail into the mast. - Furl the sail into the boom.
Mainsail furling systems have become increasingly popular on cruising yachts as they can be operated from the cockpit in most cases. The sail can become seriously stuck in the mast or boom however if not operated correctly. Mainsail furling is almost never used while racing because it results in a less efficient sail profile. The classical method is the most widely used. Mast furling has an additional disadvantage as it does not lower weight of the sail.
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 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
See this detailed information on the quest for the perfect sail shape and then try it out for yourself.
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 increasingly inefficiently. Several forces can counteract this movement.
- The buoyancy of that part of the hull which is being submerged tends to bring the boat upright.
- Pressure on the centreboard or keel moving at a slight 'leeway' angle through the water tends to balance the rolling force.
- Raising the centreboard can paradoxically increase leeway, and therefore reduce heeling.
- A weighted keel provides additional force to right the boat.
- The crew may move onto the high (upwind) side of the boat, 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.
- 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.
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 windex 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 organised 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
Also, know the 'rules of the road':
- Port tack gives way to Starboard tack (when the paths of two boats 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
- 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)
Types of Sails and layouts
The "mainsail" or "main" is usually the primary driving sail, triangular in shape, and fixed to the largest mast on the boat. A headsail, either a "jib" or "genoa", is placed 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, so-called ketches and yawls, have another sail near the back of the boat attached to a smaller mast called the "mizzen mast".
A 'spinnaker' is a very large sail that is only used when sailing 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).
Too many ropes!
Actually, only a few of the "ropes" on a boat are called ropes.
Ropes or wires that hold up masts are collectively known as standing rigging and are called shrouds or stays. (The one from the mast to the bow is usually called the "fore stay", and side ones are usually referred to as just "shrouds".)
Ropes or wires that control the sails are known collectively as running rigging. Those that raise and lower sails are called halyards. Ropes that adjust (trim) the sails are called sheets. These are often referred to using the name of the sail they control (eg. "main sheet", or "jib sheet").
Ropes used to tie the boat up when alongside are called lines or springs.
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'. 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." "Pooped" refers to the aftermost deck of a ship, taken from "puppis" the Latin word for "stern". "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. Often, the barnicles on the hull would cause lacerations, making this a particularly unpleasant punishment.
Sailing regulations
Sailors are expected to know the essentials of boating safety which include;
- The right-of-way rules known as "rules of the road" or more fully as the International Regulations for Preventing Collisions at Sea (or "ColRegs" in the UK, "NavRules" in the USA) are particularly relevant to sailors because of their limited manoeuvrability 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.
Sailing traditions and etiquette
There are many, more esoteric, etiquette rules, traditions, and customs that will demonstrate to others advanced knowledge of boating protocol such as; pulling up the fenders when you're not in port, the use of flags.
See also
Sail, Yachting, ketch, sail-plan, cat boat and sloop, Catamaran, Dinghy sailing, Dinghy racing, Yacht racing, Day sailer, Planing (sailing).