Point of Sail

Point-of-Sail
Point-of-Sail	Wind Direction
In Irons	Into the Wind
Close-Hauled (Beating)	30-40 Deg
Close Reach	70 Deg
Beam Reach	90 Deg
Broad Reach	135 Deg
Running	180 Deg

Wind: The wind is what powers a sailboat. Both the direction and strength of wind is important in setting the sails and maintaining control of the boat. True-wind direction is different from apparent-wind direction. The true-wind is the direction of the wind which makes the waves. The true-wind is perpendicular to the waves. The apparent-wind sails the boat. When the speed of the boat and the velocity of the wind are close, the difference between the apparent and true-wind is the greatest. The apparent wind is forward of the true-wind, except when sailing directly into or away from the true-wind. As one sails faster, the apparent-wind is drawn further forward. When sailing with the wind the apparent-wind has less of a force that the true-wind. When sailing against the wind, in a close reach, the apparent-wind has a greater force than the true wind.

The closer you sail to the wind, the closer the sails are pulled or trimmed to the midline of the boat. As you sail away from the wind, the sails are let out. The exact position of the sails are based upon the direction and speed of the apparent-wind. (The direction of the apparent-wind is determined by the sailboat's tack or relationship to the true-wind and the relationship of the speed of the true-wind to the speed of the boat. If you are a beginner sailor, it is easy to remember the five basic directions of sail ( point-of-sail ) each of which has its distinct characteristics of speed, heel and sail position.

Sailboat Hulls

A sailboat hull is different from any other hull because of its need for lateral resistance surface. For the boat to move ahead the wind forces pushing the boat sideways must be thwarted, and converted to forces that move the boat forward. On a small boat this can be done by extending a board down into the water, and securing it there.
There are several methods, LEEBOARD, CENTERBOARD ­and DAGGERBOARD to name a few.

BALLAST
A low center of gravity will help with the stability of all vessels, but as boats get larger they require an additional righting force in the form of BALLAST. This is usually a lead or iron keel, attached to the boat's hull. If it is lead or iron stowed in the bilge it is called INSIDE BALLAST.
The weight of a boat's ballast may be as much as half of the boats overall displacement, and the keel may extended further below the water than the hull rises above it.
A deep keel, prohibits a sailboat from entering shallow waters, and so a combination KEEL-CENTERBOARD hull was developed where a centerboard operates through a shallow keel. A keel-centerboard boat might draw down below the surface of the water. A FIN-KEEL is one that looks like a fish's fin extending below the boat, and the boat usually has a rudder mounted some distance aft, such as on an additional keel-like exten­sion called a SKEG. A long or FULL-LENGTH KEEL is usually found on cruising boats, because its directional stability is useful on long passages.

Wetted Surface
With a full-length keel, a sacrifice is made in maneu­verability and often in speed through the water, compared to shorter keels with reduced WETTED SUR­FACE-less hull surface beneath the water.
A PLANING HULL is one that lifts out of the water and planes at high speeds. Usually on high­powered motorboats, planing is also possible for boats under sail, such as light-weight, wide, and somewhat flat-bottomed boats, with a lot of sail area to provide the needed power. Higher speeds are possible on these plan­ing hulls, because wetted surface is reduced, eliminating drag, and wave-making resistance of the hull is no longer a limiting factor.

Parts of the Hull That Support Rigging
The hull shape does not necessarily dictate what kind of rig will be above it, but it does determine most of the important handling characteristics of a sailboat. Parts of the hull must be made with extra strength to deal with the strains put on it by the rigging. This means that a certain hull will usually carry a certain rig best suited to it. Here are some parts of the hull that support the rig.
The CHAINPLATES are strong metal straps extending from the rail down toward the keel, on either side of the mast, to accept the rigging holding up the mast. The bottom of the mast usually rests on a part of the keel called the MAST­STEP. On smaller boats, the mast may be stepped directly on the deck or cabin top, where there is often a large hinge-like fitting called a TABERNACLE. This makes it pos­sible to raise and lower the mast on boats that use canals with low bridges, or for trailerable boats, that must have a mast easily unstepped.
A BOWSPRIT may extend forward at the bow of the boat to increase the potential for sail area, and a BOOMKIN (pro­nounced bum-kin) may extend off the stern to accept the backstay further aft enlarging poten­tial sail area.

Self-Bailing Cockpits
A sailboat hull is designed to heel, and will sometimes take waves over the rail and into the cockpit. Any sailboat that will be taken offshore, large or small, should have a SELF-BAILING COCKPIT to get rid of that water. In a small boat this may be holes at the stern that drain the water as the boat moves ahead. There may be suction valves in the boat's bottom, or there may be large drains in a cockpit whose bottom level is normally above the water level, providing natural drainage. The self-bail­ing feature is best for a boat going offshore and valuable on others as well-because the cockpit may fill with water in rough weather, and must be able to drain with­out assistance from the helmsman.

Tacking and Jibing

The two most important maneuvers in sailing are TACKING­ and JIBING. Either one is a course change in which the sails move from one side of the boat to the other, from starboard to port tack or port to starboard tack. When tacking, the bow of the boat turns into and "across" the wind. In a jibe, the stern of the boat crosses the wind.

Tacking
To tack, the helmsman says "Ready About" to alert crew to the activity about to begin. After the crew has responded "Ready," the helmsman says "Hard-a-lee," to indicate he is pushing the tiller hard to the lee side of the boat, the side the sails are on. He may actually use a wheel instead of a tiller to turn the boat, but the command Hard-a-lee" remains the same.

The boat now turns sharply upwind and the wind is spilled from the sails completely. All the sails luff momentarily. The crew releases the jib. For an instant the boat is heading directly into the wind. Without stopping, the boat continues to turn in the same direction so that the wind now comes across the deck from the boat's other side. The sails begin to fill on the new leeward side. The jib is taken in and all sails must be checked to see if they need adjustment.
The boat is now sailing on a new tack. She has COME ABOUT changed direction, usually no less than 80°.

Jibing

To jib the sailboat also changes course to bring the sails over to the other side, but does so while sailing downwind, it is the stern, not the bow as in tacking, that swings across the wind in a jibe.
The Helmsman says "Prepare to jibe", and at that sig­nal the crew begins to haul in the mainsail until it is amidships. The helmsman waits for the for the sail to be brought in under control, says "Jibe Ho", and pushes the tiller away from the sails so that the wind catches the sails on the other side from aft. (A wheel go the opposite way.)

When sailing downwind the sails are eased way out, and travel some distance across the boat to catch the wind on their other side. A jibe can be dangerous if this maneuver is not carefully controlled. As the wind catches the sails on the new side the crew eases the MAINSHEET (the sheet that that trims the mainsail) and trims the JIBSHEET on the new leeward side.

ACCIDENTAL JIBE - Whenever jibing, or close to a jib, watch for a accidental jib. One for which the crew is no prepared. With inattentive steering the wind may catch the back side of the sail and throw the boom violently across the boat to the other side, risking serious damage rigging and to the heads of crewmembers.

The Milky Way and the Galaxies

Star chart above showing the Milky Way in the region of Scorpius and Sagittarius. Visible nebulae are indicated by the position of the yellow NGC numbers. Star spectral colors of stars, such as red for Antares, are also indicated.

On the Frontiers of the Cosmos: The Milky Way and the Galaxies
One of the most imposing celestial sights is the Milky Way, a band of light produced by billions of stars. The single stars, if they each stood isolated in the sky, would be too faint to be seen, but all of them together combine into a band of light. Interspersed among these billions of stars are clouds of dark dust that in places block the light from reaching Earth and give the Milky Way an uneven, ragged look. The universe includes more than the Milky Way, there are other, similar formations in space that are made up of stars and dust and gasses, each formation is a "galaxy" like our Milky Way. ("Galaxy" and "Milky Way" have the same meaning since gala is Greek for "milk. ")

One of these galaxies is the Large Magellanic Cloud in the southern sky, visible to the naked eye even at full moon as a large, misty area. When viewed through a telescope it turns out to be a huge aggregation of stars. The Magellanic Clouds (there is a small as well as a large one) are named after the navigator Magellan. The Large Magellanic Cloud is at a distance of about 179,000 or about 180,000 light ­years. Astronomers estimate that it contains approximately 15 to 30 billion stars. It also includes many nebulae, star clusters, and other obiects that show up in varied colors in photographs of the clouds.

All the galaxies together, many of them millions or billions of light years away make up the universe, which today's astronomers can explore with a vast array of instruments: radio telescopes like the 300-foot (100-m) antenna in Effelsberg/Eifel, sophisticated mirror telescopes like the one at the European Observatory in Chile that can cancel out air disturbances automatically, and the Hubble space telescope, which is able to photograph distant celestial bodies with previously unattainable accuracy.

The Hubble space telescope and other instruments have recently made possible the discovery of planets outside our solar system. By the middle of 2006, about 170 such planets were found. More sophisticated instruments are scanning the skies and more, smaller "extra-solar" planets are being dis­covered. This increases the likelihood of discovering intelligent life on another world. Such a discovery would be the most profound in the history of our planet.

The Constellations

According to Greek mythology, Queen Cassiopeia and her husband Cepheus once ruled over Ethiopia. One day Cassiopeia bragged that their daughter Andromeda was more beautiful than the Nereids, the daughters of the sea god, Nereus. When the Nereids complained to their father about Cassiopeia's arrogance, Nereus sent a sea monster to ravage the shore of Ethiopia. In desperation King Cepheus consulted the oracle of Delphi. There he was told that the only way to save his country was to sacrifice Andromeda to the monster. Andromeda was chained to a rock by the sea. However, salvation came at the last minute in the form of Perseus, who managed to subdue and kill the sea monster in a ferocious battle. As his reward Perseus received Andromeda in marriage and Ethiopia as her dowry. The gods later immortalized all the participants as constellations in the heavens, including the sea monster, which appears there as Cetus, the Whale.

This is just one of many stories told by ancient bards, stories whose protagonists the Greeks thought they recognized in the skies. These ancient people looked for bright stars and com­bined them in patterns that they then named after legendary figures. In the southern half of the celestial sphere, we find startlingly different names, such as Antlia, the Air Pump. Many of the southern constellations were not named until the eighteenth century, when astronomers no longer had much use for ancient mythology and preferred to elevate the most recent scientific inventions to the heavens one of which was the air pump.
From a number of different traditions modern astronomers have selected a total of 88 constellations and drawn up internationally recognized boundaries between them. Each constellation has its own characteristic shape. Today the constellations no longer have meaning beyond orienting the observer of the starry sky, they constitute a kind of "coordinate grid" of the sky.

Stars: Points of Light in the Cosmos

Cosmic Bolts of light
Often during a clear night what we call meteors or shooting stars streak briefly across the sky. These bright trails of light that move across the sky at lightning speed are caused by tiny metallic and rock particles that enter Earth's atmosphere from outer space. The particles become extremely hot, excite the air to incandescence with their great speed, and are incinerated completely in the process. A grain of dust weighing less than one gram can give rise to a meteor that momentarily appears brighter than the brightest stars.

The Stars: Points of light in the Cosmos
If one looks up at the sky during a clear night and far from the air pollution of cities, one has the impression of seeing innumer­able stars. In fact, "only" about 2,500 stars are visible to the naked eye. When one looks through binoculars or a telescope, the number of visible stars increases to hundreds of thousands or several million. All the stars rise and set in the sky just like
the sun, moon, and planets, because Earth rotates once a day. Apart from this nightly rising and setting, the stars exhibit practically no motion, their position in relation to each other remains essentially constant. Because of this apparent immobility the astronomers of antiquity called them the "fixed stars."
The reason why the stars seem to be glued to their places in the sky is that they are separated from Earth by incredibly vast distances. The stars are so very far removed from Earth that astronomers had to invent a new unit for measuring distance, the light-year.
One light-year is the distance that light travels (at a speed per second of 186,282 miles or 300,000 km, a distance equal to 7 1/2 times around Earth's equator) in exactly one year. It is equivalent to 5.88 trillion miles (9.46 trillion km). (A trillion is a "1" followed by 12 zeroes.)

How is it possible for us to see stars at all at such incredible, "astronomical" distances? Because they emit huge amounts of heat and light, just like our sun. All fixed stars are suns, some bigger, some smaller than ours.
Fixed stars and planets are two entirely different things. Stars are spheres of incandescent gas that produce their own light, the planets are solid, cold bodies that orbit around the sun and are illuminated by it. The stars are light ­years away from us, trillions of miles - while the plan­ets move much closer to Earth, being separated from us by "mere" millions or billions of miles. The other big difference between stars and planets is that the latter do not stay in one place in the sky. They revolve around the sun and keep changing their positions as seen from Earth, appearing now in one constellation, now in another.

Astronomy (Sun,Moon,and Earth)

Sun, Moon, and Earth
For us, Earth is the most important celestial body. Earth is a spherical object 7,926 miles (12,756 km) in diameter and enveloped by a layer of air (the atmosphere) that, by protecting us from dangerous cosmic radiation, makes life possible for us. Once a day, every 24 hours, Earth rotates around its own axis, which is an imaginary straight line that runs from the north to the south pole. Because of Earth's rotation we see the stars rise in the east and set in the west. In the course of the night the starry sky changes its appearance completely. New stars appear, and others vanish from sight.

The sun is crucial for Earth and its inhabitants. It is a huge, blazing ball of gas, in whose core atomic nuclei are fused in a process that releases energy. Thanks to the incredibly vast amounts of energy produced, the sun radiates great quanti­ties of light and heat toward Earth and provides the energy that is necessary for life to emerge. The rising and setting of the sun create our days and nights.

When the sun is in the sky during the day, it shines so brightly that all other celestial bodies which are overhead not just at night but during the day as well, fade from sight. It is only in the evening, when the sun sinks below the horizon and darkness falls, that we can see the other, much less luminous celestial bodies.

The sun's disk frequently displays dark spots. The number of these so-called sunspots fluctuates in an eleven-year cycle. The "solar activity" associated with sunspots will increase during most of the period from 2007-2010. Astronomers expect the next sunspot flare-up in about 2011.
Only one other celestial body is sometimes visible during the day, the moon, which measures 2,159 miles (3,476 km) in diameter and is considerably smaller than Earth. The moon revolves around Earth approximately once a month. It is Earth's companion or satellite, a cold celestial body that is inhospitable to life. Humans first set foot on the moon on July 20, 1969.

Like Earth, the moon derives its light from the sun, and it reflects this light back to Earth. The moon appears to us in continually changing form as it circles around Earth, and we speak of its "waxing" and "waning" as, in the course of 29 1/2 days, it passes through the different phases of the lunar cycle. Depending on the moon's position in relation to the sun, we see sometimes the entire lit-up side of the moon (full moon), sometimes only half of the lit-up side (half-moon) and when the moon is closest to the sun, we don't see anything at all because the side of the moon facing us is unlit (new moon).

As it revolves around Earth, the moon occasionally produces the most dramatic celestial events we can observe, lunar and solar eclipses. Earth and the moon throw shadows, like any other body that is lit up. When Earth's shadow falls on the moon, we see a lunar eclipse, when the moon's shadow hits Earth, it causes a solar eclipse. Solar eclipses are always visible from only a small part of Earth's surface lunar eclipses on the other hand can be seen on about half of Earth's night side.

Although the moon goes completely into the Earth's shadow during a totol lunar eclipse, it does not completely disappear. Earth's atmosphere deflects the sun's rays into the shadows and colors them red. This gives the moon an impressive copper tone during an eclipse. Both lunar and solar eclipses can be total or partial depending on whether the solar or lunar disk is entirely covered up or only partially. In a total solar eclipse we can see the sun's corona for a few minutes. This ring of radiating light consists of highly diffused gases heated to a temperature of several million degrees Celsius, but its luminosily is too small to be seen except during total eclipses.
Solar and lunar eclipses are quite rare, and they are not visible from all parts of Earth.