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HOW IT WORKS

Children's Book Trust, New Delhi

By Navkala RoyUpdated by Aatish Chandra

Designed and illustrated by Monisha Kaul

A hollowed log

Conqueringthe waves

The dock is flooded. The gates, opened.And 'down the ways' she goes to be liftedaway by the sea. Suddenly, this mightystructure, weighing 2,73,000 tons,appears as fragile and light as the tinypaper boat you launched in your bucketthat morning!

Conquering the most terrifying of theelements-water-was one of man's greatestdesires. He had to find a way to overcomethose turbulent waves. And that he did.

Thousands of years ago, mandiscovered that he could ride the waterson a simple log. A tree trunk was sufficientfor his needs, but only if it was notovercrowded with branches.

Later he tried to improve upon the logand make it more comfortable. So hehollowed it out and made a kind of seat forhimself. This turned out to be much safer.Gradually, he learnt that if you tied severallogs together, you could get more stability.And that was how the raft came to be.

Soon a variety of floating platforms orcrafts came to be used in different parts ofthe world. In fact, certain specimens ofancient Indian vessels can be seen eventoday on the Tungabhadra river in theSouth, and on the Ganga. These vary fromthe 'kattumaram' (catamaran) which means'logs tied together' to the 'harigolu'(coracles) which are floating baskets madeof buffalo hide, and 'oolaks' which are bigboats with chains and balconies.

A peep into Indian art and literaturereveals many more representations of theships that were used those days. Theearliest example is the vessel portrayed ona seal excavated at Mohenjo-daro, now in

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Pakistan. It depicts a ship with a sharplyupturned prow and stern.

Marco Polo, the great Venetian travellerwho visited India in the 13th century,speaks of ships so large as to need a crewof 300 men!

Marco Polo onhis voyage

How a hip tay on th wa r

Seeing a ship cruising on the sea, withnot a care in the world, one would think thatit is the most natural thing for it to be there.Yet, many of you must have wondered howthis ship, weighing thousands of tons,stays on the water?

When we play around with water andsplash it on our faces, we feel it is so lightand inconsequential that we hardly give ita thought. But water, especially as a mass,is a force to be reckoned with.

If you were to fill a bucket with water andpress your palm into it, you will realizeimmediately that there is a certain densityand upward force pushing against yourhand. That is the natural force of water.So you can imagine (or perhap you can't!)

helps to hold it up or support it and thusmakes it seem less heavy.

If you repeat this experiment slowly, youwill notice that as more and more of thestone is lifted out of the water, it getsheavier. This is because the upward pushof the water depends on how much of thestone is below the surface. The upwardpush is greatest when the stone iscompletely underwater.

When part of the stone is underwater, ittakes the place of some water. We say thatit displaces this water. The upward push ofthe water on the stone depends on how

the kind of force and density an entireocean would contain.

Yet some things float on water and somesink. What is the reason for this?

The secret lies in 'displacement'.According to Archimedes Principle, 'a bodywhich is wholly or partly immersed in a fluidundergoes a loss in weight equal to theweight of the fluid which it displaces'.

To understand this better, get hold ofa large stone, which is not too easy to lift.Put it into a bucket of water. Now lift thestone out of the water. You will noticeat once, how much easier it is to pickup the stone while it is in the water.

This shows that whenever some­thing is in the water, the water

Water level rises as stone displaces water

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much water it hasdisplaced. If it islarge enough, theupward push willsupport thatobject completelyand it will float.Even if somethingis very heavy, it willstill float if enoughwater is displaced.

However, the size and theweight of the object do not always tally.That is, the weight of the water displacedby an object is not always equal to its ownweight. If the object is large, for instance, itcan displace a volume of water the weightof which may be greater than itself. In thatcase, the object will float on the water. But ifthe opposite happens, that is, the objectdisplaces a volume of water that weighsless than itself, then down, down, downit will go. For example, if you take a sheet of

foil and place it ina bucket filled withwater, it will float.On the contrary,if you crush itinto a ball andthen place it onthe water, it will

go downimmediately.So, it appears

that, the only wayanobject can float is if the weight of the waterdisplaced is equal to or greater than itsown weight. Now you know why big, fatpeople can float easily. It is all a matter ofdisplacement! They displace more waterthan thin people.

Similarly, a ship is designed so that theweight of the water it displaces can supportit and keep it afloat. In fact, the size ofa ship is often expressed in terms of itsdisplacement (or weight) in tons.

a suction force that helped theship to move forward.

Some remarkable sailing shipswere built by the ancient

Greeks and Romans. TheNorsemen, in later yearsknown and dreaded as the

Vikings, in fact, built somemagnificent ships capable of

carrying people to Englandand other countries ofwestern Europe. Villagers

living along the coast ofnorthern Europe at that time

dreaded the sight ofa large square sail onthe horizon. For, itmeant the arrival of

Vikings, who plunderedsettlements and

slaughtered people.By the 15th century, when Columbus

crossed the Atlantic on the SANTA MARIA

Viking ship

With growing powers ofreasoning, by accident andexperiment, man evolved Greek Imeme

better methods forvoyaging across the riversand the seas.

The discovery of thesail was almost asrevolutionary as theidea of floating on thewaters at all.

Sailing ships used thepower of the wind to propelthem in any direction, nomatter which quarter thewind blew from. Theseships had a sail that couldbe shifted around the boat'smast to engage the wind at various angles.The wind inflated the sail, curving it so thatthe sail became an aerofoil producing

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from Spain, and Vasco da Gama fought hisway round the Cape of Good Hope to Indiaon the SAO GABRIEL, ships were thoroughlyseaworthy and could sail reasonably closeto the wind. In fact, Vasco da Gama'sflagship landed at Calicut on May 27, 1498,after a voyage of more than ten monthsfrom Portugal!

It was during the reign of Elizabeth I(1558-1603) in England, that scientificminds were brought to bear upon themaking of ships. It was decided thata really seaworthy ship that was sturdy,safe and yet not difficult to control, needed

The SAO GABRIEL

to be The CLERMONT

designed.Thus,these 'Iow­charged'ships wereconstructed.And it wasthese ships that defeated the SpanishArmada and which, by their hardiness,were able to trade in every corner of theworld. By that time, the single sail on eachmast had developed into a set of three.

Later evolved the 18th and the early19th century 'East Indiamen'. These werefine sailing ships which could carry a bigcargo and a number of passengers, withsufficient guns to defend themselvesagainst enemies. Yet these were stillrestricted in length and size because theywere built entirely of wood. Also they wereat the mercy of the wind which would leavethem quite motionless for days on end.

StE~am h

Some ingenious people got together andtried to evolve the steam engine, whichwould enable the ship to move ahead evenif there was no wind.

A steam engine utilized the energycontained in steam under high pressure.The energy that was released when thesteam expanded was produced to makerotary motion that drove the machines.

By the later 18th century, as soon asNewcomen and Watt had made the steamengine successful on land, experimenters

The SIRIUS

In about A.D. 1100, the Chinese found that ifa piece of magnetic iron-ore was suspendedfreely by a string, it would always pointnorth-south. Some enterprising Indian sailorspicked up this knowledge and made the'matsyayantra'-that is, a thin leaf of magneticiron cut in the shape of a fish and kept afloaton oil. This fish, unlike live ones, pointed north­south constantly and was used on the highseas to determine the direction the ship wastaking. This, in fact, was the beginning ofthe mariner's compass-probably the firstnavigational aid that came into being.

began trying to make it drive ships.The first efficient steamboat, the CLERMONT

was built by an American inventor, RobertFulton. Launched on the Hudson river, itwas the first commercially successful

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experimental period was over.For a long time after, ships continued to

have sails along with engines just in casethe engines were to break down. Most ofthem were also built of wood. But in 1843,Isambard Kingdom Brunei designed theGREAT BRITAIN which was not only built ofiron but was driven by a screw propeller.

As ships became bigger, it was necessaryto fit them with two propellers (or twinscrews) in order to reduce the chance ofbreaking the propeller shaft. Later, triple andquadruple screw ships were built.

By 1940, a steamship could make atleast six trips between America and Europe.

Screw propellers,

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steamboat which made its maiden trip in1807 from New York to Albany, a distanceof about 480 km in 62 hours.

The first ship to employ the steampropulsion across the Transatlanticcrossing was the American vessel theSAVANNAH in 1819, followed by the SIRIUSand the GREAT WESTERN which sailedacross to Boston with passengers anda little cargo.

As experience accumulated, engineswere fitted to larger ships. By 1838,steamships had improved greatly and the

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the Admiralty was forced to try theturbine in the fastest destroyers. Italso proved most successful in veryfast cross-channel steamers. Butwhen it came to ships of moderatespeed, it was most uneconomical.That difficulty was not overcome until

cogwheels (wheels with projections) ofdifferent sizes were made to reduce thespeed to the necessary low level. Allturbine ships now have the engine speedthus geared down.

Then came the internal combustionengine usually called the diesel. At first, the

The TUFlBINlA

Meanwhile, Charles Parsons(1854-1931), an inventor,demonstrated that the effect ofsteam on a series of bladesattached to a shaft wouldcause it to turn round.

Parsons tried this in a small vessel whichhe called TURBINIA, and drew attention to herby racing up and down the lines ofwarships at Queen Victoria's DiamondJubilee naval review in 1897. The vesselnaturally attracted plenty of attention and

Turb n

Modern warship

Nuclear-poweredsubmanne

SUbmlarin

The first practicalsubmarine wasa rowboat covered withgreased leather.It was the idea of Cornelius Van Drebbel,a Dutch doctor living in England in 1620.This was powered by 12 rowers pulling byoars that protruded through sealed ports inthe hull. Snorkels or air tubes were heldabove the surface by floats, thus permitting

diesel was used only for the slower ships,but now it is sometimes installed in ships ofover 20 knots speed (about 32 km per hour).

Nuclear power for ship propulsion isdeveloping fast. Its greatest advantage isthe infrequent need to refuel, which is whyit is being used more by warships than bymerchant vessels.

At the beginning of the 20th century, themost important type of warship was thearmoured battleship. After that the aircraft /carrier took its place. Now the submarinehas become the equivalent of thebattleship. This is a ship that can runboth on and below the surface of thesea and can remain stationaryunderwater for a long period of time.A submarine is the best vessel tolaunch torpedo attacks.

A nuclear-powered submarine canoperate not only underwater butunder ice as well for days on end, atspeeds never possible on the surface.

submarine is then less than that of thesurrounding water. As the submarine dives,the ballast tanks are filled with water andair is let out, thereby increasing its overalldensity. Thus the submarine begins to sink.

When the submarine intends to surface,the compressed air flows from the air flasksinto the ballast tank and throws out thewater till the density of the submarine isless than the surrounding water. Thus thesubmarine rises. In an emergency, ballasttanks can be quickly filled with high

pressure air so as to makethe submarine rise to thesurface quickly.

Nowadays, we havesubmarines which arepowered by nuclear reactorswhich produce heat togenerate steam for theturbine. The turbine directlydrives the propellers as wellas the electric generators.

the boat tosubmerge.

Unlike a ship,the buoyancy ofa submarinecan be

controlled, thus allowing it to sink andsurface at will. To control the submarine,a ballast tank is used that can bealternately filled with water or air. When thesubmarine is on the surface, the ballasttanks are filled with air. The density of the

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~:-':.:. :;,:' ~ ;':;.",:, ,::;':',:~,f.fu·;:;',:.~:?,,;,'f.;:"£;.:;; .... 1. Reactor control 8. Rudders 17. Officers' quarters -:.:,;.>,:.' '-.,. . { . '-~~:":;;~~';;:::;,!f!!-.:":!:~:'"::..:;:.~ compartment 9. After hydroplane 18. Electrical space "--,.".

.:~-r:.-,;,.,"",",.':..,~~;;!'i:..''':;;:;;~''':_~ 2. Auxiliary 10. Surtacebridge 19. Forward~ machinery 11. Periscope hydroplane

3. Diesel generator 12. Radar 20. Torpedo space4. Escape hatch 13. Snort 21. Torpedo tubes5. Main condenser 14. Control room 22. Stowed anchor6. Main turbines 15. Electric batteries 23. Galley7. Electric motor 16. Crew's quarters 24. Store rooms

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Hovercrafts

The Hovercrafts are another modernand successful invention of the twentiethcentury. It was invented by ChristopherCockerell in 1956.

A Hovercraft is usually described as anair cushion vehicle or ground effect vehicle.It can travel on land as well as water.A hovercraft consists of a body or a hull inwhich a rotor is fixed in a way that it createsan air cushion on which the craft issupported. Thus there is no contactbetween the craft and the ground and nofriction to overcome.

F t hip

Even in fair weather, ships battle wavesof their own making. As a ship movesthrough, it displaces water and createswaves. The faster it moves, the largerthese disturbances become and mergeinto a single wave called the captive wave.A captive wave can present seriousproblem as it creates additional drag, thusmaking the stern of the ship sink. Hence,a few marine engineers got together and·created a fast moving ship, 'FastShip', withadvanced hull design and propulsiontechnology, and an innovative loading

Ancient Indians built some of the largest'"ships of the time and sailed to distant landsincluding Thailand and China. We hear of brisksea-borne trade between Rome and Indiaduring the first century A.D. Ancient books andrecords mention a large number of these ports,some of which continue to be in use even today.

Muziris (now Cranganore) in Kerala is onesuch port. It had ships coming in with cargo fromArabia, Greece and Rome. According to someancient Tamil books, Yavanas (a name forGreeks and Romans) paid in gold at this portin exchange for pepper and other products.

Their great skill in navigation took Indians to'" many lands carrying trade and culture.

India's maritimeheritage goes wellbeyond in the pastthan some of us mightcomprehend. With theHimalayas in the north,Indians for centuries have depended on

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system. It is deep V-shaped to cut throughthe waves. Because of its stability,a FastShip readily maintains the speedeven in terrible weather.

The FastShip can transport cargo acrossthe North Atlantic in five to seven days,whereas conventional freighters takeanywhere between 14 to 35 days to do thesame job.

Produced by FastShips Atlantic, theship's top speed will be around 43 knots(about 50 miles per hour). Each vesselwill be powered by five Rolls-Royce marineTrent engines-the most powerful gas·turbine propulsion unit available tothe ship operators as against the earlierdiesel engine.

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sea routes for trade and communicationwith the rest of the world. Vital sea links,therefore, emerged over a period of timefor the exchange of trade, commerce andculture. Historians and scholars havetraced our associations with the sea way

back to theHarappan culture,around 3000 B.C.

The first Indiansteamboat was builtin 1819 by anEnglishman forGhazi-ud-DinHaider, the Nawabof Oudh. In 1919,

The first ocean-going modern ship built in Indiawas launched in 1948 by Pandit JawaharlalNehru. The launching site was the Scindia Ship­bUilding Yard in Vishakhapatnam, now knownas the Hindustan Shipyard. She was a generalcargo steamship of 8000 dw tons and wasemployed in coastal trade.

two very enterprisingIndians, Narottam Morarjeeand Walchand Hirachand,started the Scindia SteamNavigation Company.On April 5, 1919, thecompany's first ship,S.S. LOYALTY, left fromBombay to the UnitedKingdom carrying passengers and cargo.

The Indian Marine was formed in 1613 inEngland for the protection of the East IndiaCompany's ships and trade. The companyestablished its first trading centre at Suratand expanded further. The Indian Marine,therefore, continued to grow with anincreasing number of ships. By 1735, a full­fledged shipbuilding dockyard wasestablished and named Bombay Dockyard.The Indian Marine thereafter acquired thename Bombay Marine. Early in thetwentieth century, Bombay Marine wasrenamed 'The Royal Indian Marine'.

In 1950, when India became a Republic,the term 'Royal' was dropped and thename was changed to just Indian Navy.

Now the Indian fleet numbers over 100combat naval vessels, of which 15 aresubmarines, two are aircraft carriers, andanother 23 are destroyers and fast frigates.

A total of ten diesel-powered 'Project 877'submarines, known as the Sindhu class,are equipped with the antiship cruisemissiles with a range of 220 km.

India has a number of foreign-producedcruise missile systems in its arsenal,such as Exocet, Styx, Starbright, SeaEagle and so on. It also has someindigenous cruise missile systems underdevelopment, such as the Sagarika andthe Lakshya variant.

r Around 130 A.D. the first map of the lands and'"seas then known was produced. It includedlatitudes and longitudes and its creator was theastronomer, mathematician and geographer~~e~ ~

India has been working since 1985 todevelop an indigenously constructednuclear-powered submarine, one that isbased on the Soviet Charlie II-classdesign. The Indian nuclear-powered attacksubmarine design is said to havea 4,000 ton displacement and a single­shaft nuclear power plant of Indian origin.Once the vessel is completed, it may beequipped with Danush or Sagarika cruisemissiles and an advanced sonar system.

5t pping into a hip

The ship is divided into two main parts­fore or front part and aft or hind part.Between these is the engine.

In the old-fashioned steamships, theboiler and engines were exactly in themiddle, with one or more funnels jutting outand spewing heavy, dark smoke from theboiler. The engine in a motor ship, however,is not in the middle but more towards aft.

A motor ship gives off only a little smoke.But it too has a big funnel, mainly to give ita balanced appearance. There are severalcompartments inside the funnel.

A ship's engine looks extremelyimpressive. It covers almost a third of

its height and its entire width. In the earlierdays, many hands were required in theengine room for cleaning, repairing andfitting parts Today's diesel engines,however, are highly automated andcontrolled. They are operated by pushbuttons and some are so sophisticated thatno one needs to remain permanently in theengine room.

Above the engine is the superstructure.This consists of a number of roomsincluding the wheelhouse, navigationroom, wireless room and so on. In the largepassenger liners, the superstructure mayalso include sports decks and sun decks.The captain and his officers have their

open-mouthed hollow, hockeystick-likeprojections. These are air vents, whichallow the hot and foul air in the hatches andunder-decks to escape.

Every ship carries a port and a starboardanchor in its bows. An anchor is a heavymetal piece, weighing several tons, withtwo hook-like arms at one end. When thecaptain orders 'drop anchor', the anchor isdropped into the sea at the end of a longanchor cable. The flukes (hooks) dig intothe seabed and prevent the ship fromdrifting away. When he orders 'weighanchor', a powerful steam winch (hoistingmachine) pulls in the heavy cables and theship moves again. Anchors can be ofdifferent weights and sizes. Some warshipscarry as many as eight anchors.

Double fluked anchor

StockJess anchor

Stocked anchor

cabins here. It is also the place where themost sensitive equipment is housed. In thecentre of the superstructure stands theship's navigating bridge, the top of whichmight carry the radar antenna.

On the deck are square or rectangularholes called hatches. These are closedwatertight by hatch-covers. When thehatch-covers are opened, one can seeright into the holds, where the cargo isstowed. The ship's front end has a raisedplatform called the forecastle. At the tip ofthis is the jackstaff to fly the ship's flag.

Also, at several points on the deck, are

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Gyrocompass

Liquidcompass

•

Mariner's compass

t a

When we saysomeone is'at sea', weimply thatsomeone istotally lost orperplexed. But when a ship is at sea, well,that can be dangerous! That is why sailorsneed navigating instruments to help themsteer and position their ship in the required

. direction.The most essential instrument for

navigation is the compass. In thepast, ships used a specialkind of magnetic compasscalled a mariner'scompass. It was designedso that the ship's motionwould affect it as little aspossible. Modern shipshave a very accurate

Oth r hips

Most ships are powered by some kind ofsteam engine, but motor ships arepowered by diesel. This is the kind ofengine that is widely used for heavy lorriesand buses on land, called the internalcombustion engine, because it burns itsfuel inside the cylinders of the engine itself.

In diesel-electric ships, a diesel engineturns an electric generator and the electricityproduced is used to power electric motorswhich turn the propellers. The latestsubmarines and a few surface ships use theheat from a nuclear reactor. The 'fuel' usedin the reactor is a rare metal called uranium.

gyrocompass, which contains a rapidlyspinning gyroscope wheel It is completelyunaffected by the movement of the ship.

The navigator can find the ship'sestimated position at any time by plottingon a chart the distance and the directionthe ship has travelled. He knows thedirection from the ship's compass. Hecalculates the distance by means of theship's log which is a device for measuringthe speed and the distance travelled.

Navigators frequently check their correctposition by observing the position of theheavenly bodies in the sky-the sunduring the day and the stars and planets atnight. This iscalled celestialnavigation. Thenavigatorobserves thedirection ofseveral starsand the angle

Detection and tracking of targets

they make with the horizon. For this, heuses an instrument known as the sextant,which gives the altitude of the heavenlybody above the horizon. By consulting abook of tables called the nautical almanac,and a very accurate clock, or chronometer,he can calculate how far he is from theso-called earthly position of each star atany time. He draws lines of position basedon each star 'fix', and .the point where theyintersect gives the ship's exact position.

Today, electronic methods of navigationare being increasingly used. Ships haveradio direction-finders, which 'fix' on

lighthouses. By obtaining 'fixes' from twosuch beacons, the navigator can find hisexact position.

Radar is another valuable navigationalaid. It shows the ship's position in relationto other ships in the area. It is especiallyused in foggy, stormy weather or at night.This electronic device sends out radiowaves. When they hit an object, they arereflected back as an echo. The echoshows up on a radar screen, which is verymuch like a TV screen, as a visible dash or'blip'. The distance and the direction of theobject can be calculated from the positionof the blip on the screen.

Measuring the depth

The echo-sounder,which indicates whatdepth of water liesbeneath the vessel,is essential for coastaland shallow waternavigation. This isa device in the keel(bottom) of the vesselwhich transmits soundwaves down into thewater and receivesback the echo as thesewaves are reflectedfrom the seabed. Thetime the echo takes toreturn is an indicationof the depth of water atthat point. The depth isrecorded on a chart or ona dial in the wheelhouse on the bridge.

Bearing scale

StemmarKershowingposition of own ship

~ Status data

U Data of marker

::J- Data of own ship Dep of h n

The radar screen

Classilication?ou Isymbols l{

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Surprisingly, it is only when a ship entersthe shallow waters of estuaries, rivers andother port approaches that she is mostvulnerable and not when she is far out inthe deep ocean. Unless of course,a hurricane strikes!

To take these ships through their lastdifficult journey, a pilot comes aboard. He,from long experience and intense training,knows the waters and approaches of the

port where he is based. He is familiar withthe currents and tides, with hazards suchas rocks, reefs and the hidden shape ofthe sea. He also knows best the shapeand design of the ship.

If the ship is sailing light (unladen), thepilot has to allow for the way in which thewind and the tide Will swing her about.Fifty feet this way or that may put the shipaground and might even break her· back.It is an exacting profession, calling for theutmost concentration and nerve.

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The of he

Many of us tend to think mainly in termsof aircraft as the essence of scientificprogress. But there are immensely excitingpossibilities in the realm of navalarchitecture and marine engineering too.

Partly because of this challenge and alsobecause of the beauty and wildness of the

When Jules Verne wrote Twenty ThousandLeagues Under the Sea it was science fiction.Today, it is a reality. Oceanographic ships,bathyscaphes and underwater laboratoriescarry out research on the seabed for variousreasons-from the search for oil-bearingminerals through biological and physicalobservations, to archaeological investigations

sea itself, life on a ship has a uniqueattraction.

There is a shade of adventure in thetimeless and rhythmical movement of thewater; sparkling in the sun, mysterious atnight; its mood forever changing.That is why perhaps it is said of the sea­'only those that brave its dangerscomprehend its mystery!'

ISBN 81-7011-457-8