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6.1: Applications- Winds Over the Seas

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    85105
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    One of the first practical applications of wind power by humans was to use it as a “propellants” for sailing boats. In the Mediterranean area, extensive trade already existed one thousand years before the beginning of the modern era. Many nations and tribes were scattered on numerous islands and peninsulas in that area. Transporting goods by boats was a convenient (and sometimes the only possible) way of delivering them to customers. The traders quickly learned to take advantage of winds – if they were blowing in the right direction; otherwise, the merchants had to use oars (driven by slaves), or, if their boats were not equipped with such “propulsion system”, they had simply to for a wind blowing in a favorable direction.

    The angle of the sail with respect to the wind direction used to tack or sail upwind
    Figure \(\PageIndex{1}\):: Left: possible sailing directions relative to the wind. Only the directions closer than about 45◦ to up-wind direction are excluded. Until the mid-16th century Europeans used sails that allowed only sailing downwind and in the “beam reach” direction. The art of sailing “upwind”, as close as 45◦ relative to the wind was known to Arabs long before the Europeans learned it by observing Arab boats at the Mediterranean. Right: the tacking maneuver, by zigzagging the boat can effectively sail upwind, or “beat to windward” according to the old nautical terminology.

    Over a period of two thousand years, the sails did not change very much – they were just big fabric rectangles. Seamen call such sailing square-rigged . The upper edge of the sail is carried by a spar, i.e., a horizontal bar with its center attached to the mast. A boat with such a sail can only travel downwind. Going far into the Atlantic in such sailboats was too risky – how would one return home, if there was no guarantee that there would be a wind blowing in the right direction? Even the Vikings, the Scandinavian warrior tribes who were perhaps the best sailors of all times, in the X and XI century had enough courage to sail thousands of miles away from their bases only because they always carried oars to be used if the wind was blowing in their faces.

    Drawings of a Viking long boat and a Spanish gallion, both square rigged and not able to sail upwind
    Figure \(\PageIndex{2}\): Left: a Viking boat with the oars hidden. Right: a galeon with several square-rigged sails, but still not able to sail up-wind.

    In Portugal and in Spain, where the shipbuilding technology was pretty well developed, in the XIV century the shipyards were able to build large galleons with the capacity up to 200 tons, but still square rigged, so that they were not yet worthy ocean-going crafts.

    A real technological revolution took place only in the XV century. Technically, what happened, was the beginning of a widespread use of the so-called lateen sail or latin-rig which is a triangular sail with one side carried by a lateen, i.e., a long rod mounted at an angle on the mast.

    It’s not exactly known who and when had invented the lateen sail, but it is clear that such a rig was used long before the XV century in the Middle East and at the Indian Ocean. Then it was used by Arabs and the Moors at the Mediterranean Sea at their characteristic boats they called dhows and feluccas. The Western Europeans did not pay much attention to them – until a Portuguese prince Henry the Navigator realized that they had the ability the square-rigged ships lacked – namely, to “beat to windward”, i.e., to go closer than 90 to the up-wind direction. Under Henrys sponsorship, the Portuguese shipyards developed a highly successful new vessel type, the Caravel.

    Drawings of a lanteen rigged flucca (left) and a British ship (right)
    Figure \(\PageIndex{3}\): Left: a felucca, a boat sailed by Arabs, capable of “beating to windward” due to its lateen-rigged triangular sails. As far as beating to windward is concerned, the caption below the picture on the right (hard to read) states: “His Grace the Duke of Portland Yacht Pantaloon beating to Windward with the Frigates &c. of Sir Edward Codrington’s Fleet off the Dodman on the 21st July 1831”. Portland? An Oregonian accent? No, apparently no relation to our Portland.
    Monumnet of Discoverers in Lisbon, a large stone cross incorporated into a stone ships prow
    Figure \(\PageIndex{4}\): : Back side of the Monument of Discoverers in Lisbon, Portugal. The “discoveries” made by Portuguese navigators who had reached and had taken “into the possession of Portuguese Crown” lands located thousands of miles from their homeland brought an enormous prosperity to that small European nation. And it’s clear who paid for that wealth. Perhaps, it’s the reason why the name of the monument emphasizes that those brave sailors were “discoverers”, but it omits the fact that they were often brutal colonizers.
    Front side of the monment with Prince Henri at the tip and two other figures behind him
    Figure \(\PageIndex{5}\):Front side of the monument, with the statue of Prince Henry the Navigator, holding a model of a caravel – note the two lateen sails it carries (both pictures taken by the Author).

    One of the first task of the caravel captains was to explore the western coast of Africa. As can be seen in Fig. 3, after passing the “Bulge of Africa” – the westernmost part of the continent – the ships encountered a steady south- eastern headwind. For the square-rigged boats it was not possible to proceed any further along the coast. The caravels changed everything, by the end of the XV century the Portuguese reached the southern tip of Africa and proceeded further, eventually reaching India. Christopher Columbus also used caravels in his historic trip in 1492.

    New “discoveries” of more and more remote lands followed. The caravels were modified, favors were returned to square-rigged sails because with the wind blowing from the back the square-rigged boats could run even faster than lateen-rigged ones. Therefore, new designs carried both types of rigging. Those types of vessels could reach any region on the globe. New trade routes were opened, regular communication between all continents was established. Until mid-XIX century sailing boats “ruled the waves”. In the mid-1800s incredibly fast sailing vessels, called “clippers”, or “tall ships”, carrying a pyramid of sails, maintained a regular communication across Atlantic and Pacific and between Great Britain and Australia (see the image of a “clipper” at the front page of this Chapter). However, in the mid-1800-s a new type of propulsion for boats emerged – namely, the steam engine – and was quickly taking over. By the end of XIX century the era of big sailing boats was over, it was steam that ruled the waves since then. And then, steam engines had to give way to giant Diesel motors. It’s them who rule the waves today.

    Anyway, today there are probably more sailing boats than ever before. But not the big ones with pyramids of sails. Several tens of “tall ships” still exist over the world, maintained by merchant fleets, or navies, for training young people to become hardened seamen. Those “tall ships” converge every 8 or 12 years at galas called Operation Sail or OpSail . But the “center of gravity” has moved to small sailing boats, used mostly for tourism, recreational sailing or racing. Such boats carry only triangular sails, the so-called “Bermuda rig” (with time, the lateen rig evolved to gaff rig, and eventually to Bermuda rig).

    But who knows? One day the tall ships may come back to the oceans. The wind is a “fuel” that costs nothing and produces no CO2 emission at all. The progress in material science has made it possible to produce new ultralight but sturdy masts and sails. In the old days, the tall ships had to carry crews up to several tens of sailors because all operations on sails were manual and required climbing the masts. For example, the famous clipper Cutty Sark with displacement of 2100 tons needed a crew of more than 30 men. It is expected that a new-generation merchant ship with ten times or even larger displacement and with fully automated operation of the sails, will need less than ten crew members.


    6.1: Applications- Winds Over the Seas is shared under a CC BY 1.3 license and was authored, remixed, and/or curated by Tom Giebultowicz.

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