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 air over the sails acts in the same way as air moving over an
aircraft's wing. Just like on an airplane, air flowing over the sail is
deflected and accelerated. This generates lift, which acts to pull the sail,
and thus the boat ahead, but also slightly downwind. The downwind component is
offset by an underwater hydrofoil (centerboard or keel), whose shape resists
lateral movement while offering little resistance to forward motion. Without a
keel or centerboard, sailing upwind or across the wind would be virtually
impossible. (Other sailing hydrofoils include daggerboards and leeboards).
The lifting force of the sails also acts to lean the boat over to one side,
which is called heeling. This is counteracted by ballast, either in the form of
dense material located in the keel (usually lead or iron) or in the form of
human or water ballast located near the windward rail.
Today, for most people, sailing is a hobby. Pleasure sailing can be further
divided into two areas: Racing and Cruising.
In ancient times (see Odysseus), ships used following or rear-quarter winds.
Therefore, they had to wait in port or at sea for the right wind directions.
Turning a sailing boat
There are four basic maneuvers a sailing boat can perform while underway. They
are:
Tacking is turning the boat so that the bow passes through the eye of the wind
(or "no go zone").
Gybing (or wearing) is turning the boat so that the stern of the boat turns
through the wind. Gybing causes the boom to swing from one side to the other,
sometimes rapidly, as the wind catches the leach of the mainsail on its new
upwind side.
Heading up is turning the boat to sail closer to the direction the wind is
coming from.
Bearing away (or falling off) is turning away from the direction the wind is
coming from.
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.
Running
Downwind
Sailing the boat within 30 degrees of straight downwind is called a run. This
is the easiest point of sail, but it can also be the most dangerous. Sailing
upwind gives you the everpresent possibility of stopping the boat easily by
steering into the wind. Running gives a sailor no such easy out. Be careful and
either use your boom vang or adjust the mainsheet to prevent an accidental
gybe.
Beating an upwind
course
A basic rule of sailing is that it is not possible to sail directly into the direction the wind is coming from. Generally a cruising boat can sail 45 degrees off the wind, a racing boat may aproach 35 degrees. However since it is often necessary to move towards the wind direction, it is necessary to 'beat' upwind.
Beating is simply a series of 'tacks' where the boat sails as close to the wind on each tack as possible, and then switches sides and repeats the process. By this method, it is possible to travel directly into the wind. The heavier the wind the harder the beat, and since you are sailing into oncoming waves at an angle, boat movement can be heavy. This movement can feel like the boat is beating its hull into the waves, hence the name. Since the boat is sailing over oncoming waves, a beat will feel faster than its actually moving.
During a beat, it is important to watch your heading, since the wind will tend to push an unbalanced boat into or away from the wind, depending on the balance problem. If you find yourself having to overcorrect at the helm for sail pressure into the wind, then you are in a condition called weatherhelm, and you are actually slowing the boat with your rudder. To correct this, reduce sail.
A basic rule of sailing is that it is not possible to sail directly into the direction the wind is coming from. Generally a cruising boat can sail 45 degrees off the wind, a racing boat may aproach 35 degrees. However since it is often necessary to move towards the wind direction, it is necessary to 'beat' upwind.
Beating is simply a series of 'tacks' where the boat sails as close to the wind on each tack as possible, and then switches sides and repeats the process. By this method, it is possible to travel directly into the wind. The heavier the wind the harder the beat, and since you are sailing into oncoming waves at an angle, boat movement can be heavy. This movement can feel like the boat is beating its hull into the waves, hence the name. Since the boat is sailing over oncoming waves, a beat will feel faster than its actually moving.
During a beat, it is important to watch your heading, since the wind will tend to push an unbalanced boat into or away from the wind, depending on the balance problem. If you find yourself having to overcorrect at the helm for sail pressure into the wind, then you are in a condition called weatherhelm, and you are actually slowing the boat with your rudder. To correct this, reduce sail.
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 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 center of effort from the sails, keeping the boat more upright.
There are three core 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 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
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 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.
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 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 center of effort from the sails, keeping the boat more upright.
There are three core 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 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
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 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, called hiking, changing the centre of gravity significantly in a small boat. They can trapeze where the boat is designed for this. 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
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
