Section 2. Ship’s dynamics

Words and Terms to be Remembered

Read the text and find the answers to the following questions.

1. What two main groups are all cargo ships divided into?
2. What is the difference between universal and specialized cargo ships?
3. How can dry cargo vessels be classified in dependence of the cargo handling methods they use?
4. What idea do LASH and container ships have in common?

TYPES OF CARGO SHIPS

Cargo ships make up the largest group of transport ships. On the one hand, all cargo ships are divided into two types - dry cargo ships and tankers, or oil-carrying ships. On the other hand, cargo ships may be divided into universal ships designed to carry general cargoes and specialized ships designed to carry one definite type of cargo. Such specialized ships as bulkers, timber carriers, reefer ships, tankers have long been known.

Bulkers (or bulk carriers) are intended for the carriage of grain, ore, sugar, coal, cement and other bulk cargoes. They are single-decked ships of large size, with no tweendecks in their holds but fitted with special cargo handling equipment such as grabs, suction plants, etc.

Reefer ships are designed to carry vegetables and fruits, cooled and refrigerated cargoes, that's why they are fitted with the refrigeration plant which can keep as low temperature as -18 °C, -30 °C for a long period. Reefers have higher speed to deliver perishables in time.

Timber carriers carry timber in logs, as well as technological chip. Their main cargo handling equipment is heavy cranes, derricks and loaders. Some of the timber is carried on deck.

Tanker is designed to carry oil and oil products of several grades simultaneously. It is one-deck vessel mostly with aft location of the engine room and bridge superstructure. The bridge is connected to the forecastle by the catwalk. The cargo spaces are tanks, all tankers being provided with pipelines and pumps. Nowadays there are mammoth tankers of 300,000 dwt (VLCC - very large crude carrier) and up to 800,000 dwt (ULCC - ultra-large crude carrier). There are gas carriers for the carriage of liquefied natural gases (LNG) and liquefied petroleum gases (LPG).

Three main trends in specialized ships have emerged.

One is cargo ships with cargo handling equipment on board. These ships are also called special purpose ships.

The second trend is Roll-on/Roll-off ships (Ro-Ro). They are specially designed for transportation of various wheeled vehicles (cars, rolling stock, tracked vehicles, trailers), as well as unitized, lengthy/bulky cargo units. The cargo handling operations on the Ro-Ro ships are performed in horizontal direction - by driving on/driving off through different kinds of ramps.

The third trend is a container ship. She is intended for the carriage of goods in containers - special boxes of international standards - and provided with the cellular guides in the holds. TEU (Twenty-foot Equivalent Unit) is 6.1 m container for determining ship's container capacity. One of the features of the container ships is large hatches or large deck opening for intensification of cargo operations.

The use of containers for cargoes has encouraged the design of LASH (Lighter-Aboard Ship) or barge carrying ships in which the container is a 60 foot steel lighter. The benefit of a barge carrying ship is that she can load and unload barges in estuaries away from quays. There are two designs of a barge carrying ship - LASH and Sea Bee, which differ in the method of handling barges and in their internal arrangements.

There are also specialized ships to carry different types of cargo such as OBO ship (oil/bulk/ore carrier), PROBO ship (product/oil/bulk/ore carrier), etc. These are called combined ships or combination carriers.

Exercises and assignments

Ex. 1. For the words given in (a) find the synonyms given in (b):

a) design, taken, timber, refrigerate, plant, benefit, encourage, grade, catwalk, trend, emerge, vehicle, estuary, lighter, definite;

b) delta, barge, certain, intend, oil-carrier, wood, carriage, tendency, passage, sort, advantage, installation, support, cool, appear.

Ex. 2. Fill in the missing words in the table.

Ex. 3. Match the words in the box with the explanations given below. Find in the text sentences in which these words are used and translate into Russian.

1) not refined or manufactured, in a natural state;

2) a connecting passage between the forward and after bridges or between a bridge house and forecastle or poop decks;

3) landing place built of stone or iron alongside which ships can be tied for loading and unloading;

4) goods that go bad if delayed in transit;

5) a cargo composed of miscellaneous goods carried in units;

6) a sloping way from one level to another instead of stairs or steps;

7) device for forcing liquid into or out of or through something;

8) transport vehicle pulled by a tractor or a truck;

9) a standard cargo box;

10)cellular structure of angle bars into which the containers are stowed;

11)a small piece cut or broken off from wood.

Ex. 4. Choose the terms under the line below for each of the following definitions.

1) A ship intended for the carriage of liquefied gas in bulk is _________.

2) A ship intended for the carriage of different cargoes except for liquid bulk cargo is _________.

3) A ship intended for the carriage of goods in containers of the international standard is _________.

4) A cargo ship intended for transportation of various vehicles on all decks is _________.

5) A ship intended for the carriage of liquid cargoes is _________.

6) A ship designed to carry cargo in large steel barges used as containers is _________.

7) A ship designed to carry dry bulk cargo in its holds is _________.

a) tanker; b) LASH; c) container ship; d) bulker; e) dry cargo ship; f) gas carrier; g) Ro-Ro vessel.

Ex. 5. Using the information in the text expand this diagram of cargo ship classification.

Section 2. Ship’s dynamics

Words and Terms to be Remembered

Read the text and find the answers to the following questions.

1. What forces is the moving ship affected by?
2. What does steerage imply?
3. What are three main motions of a ship?
4. Are there any measures against motions?

Fundamentally the external shape of ships is governed by the known laws of resistance. All objects are affected by them when moving through water, whether self-propeller or towed. These laws concern the underwater portion of the hull, out-of-water portion is subjected to resistance from the air. Both the underwater and abovewater portions are additionally and respectively affected by currents and tides on the one hand, and by storms and winds on the other. Man has always been improving the hull shapes to counteract the laws of resistance so that the ship will attain high speeds at a low expenditure of energy.

Propulsion is ship's ability to move through water at a specified speed and effective work of ship's power plant. The moving ship is affected by two forces - resistance to motion and propulsive (propeller) force. The propulsive device transforms the energy generated by the power plant into the work of propeller force. The propulsive devices are: screw, water-jet and vane propellers, the former being widely used. It consists of a boss or hub carrying radial blades. The screw propeller is generally placed at the after end of the vessel. The speed of ships is measured in knots, one knot being equal to one nautical mile (1852 metres) per hour.

Steerage of a ship is closely connected with her propulsion. It is the effect of the helm on a ship in motion. Helm means the rudder and the gear for turning it. Steering gear (steerer) is the steering wheel, steering engine and fittings by which the rudder is turned. Rudder consists of a rudder plate (blade) and a rudder stock (spindle). The ship's steerage is determined by two diametrically opposite seaworthy qualities - steady course ability and manoeuvrability. Steady course ability is the ship's quality to keep the preset direction of motion, and manoeuvrability is the ship's ability to alter the direction of motion in a proper way for rather short period of time.

Motions imply oscillating movements of a ship relating to her state of equilibrium. Anyone who observes the motion of a ship when floating among long smooth waves can notice that the ship is not carried away as if by a current, but that its motion is confined to rising and falling with a slight swaying to and fro within quite definite limits. A large body like a ship is affected by the depth of immersion, the configuration of the wave and the rotary action of the particles of water composing the waves, all of which produce an inclining effect on the ship. There are three main motions of a ship on waving - rolling, pitching and heaving. They can exist on still water too.

Rolling is the transverse oscillating rotation of a vessel about a longitudinal axis, which results when it meets waves, with crests approximately parallel to the length of the ship. It is rhythmic inclination of a vessel from side to side. This increases ship's resistance to propulsion, and requires a corresponding increase in the propulsive power necessary for a given speed.

Pitching - the angular motion which a ship makes about a transverse axis through her center of gravity in a seaway. It is downward falling of a vessel's bow and stern alternatively caused by head, oncoming waves. Heavy pitching is accompanied by flooding of the deck (coming green water), emersion of the ship's bottom and subsequent slamming, i.e. impact of the ship's hull upon the surface of the water. Pitching can result in shifting cargoes, slowing the speed, sea-sickness of the crew and passengers.

Heaving is the vertical motion given to the ship as a whole, especially noticeable when broadside - on to the waves. The whole ship rises on the crest and then sinks into a trough of a wave; it is periodical rise and fall of a vessel as a whole. In a sea way due to the periodical disturbances the oscillations in other directions will emerge, i.e. additional kinds of motions. They are surging, swaying and yawing.

Surging is oscillations of a ship as a whole along the longitudinal axis due to head or oblique waves.

Swaying is movement of the whole ship to port and then to starboard.

Yawing is angular oscillation of a ship as a whole about a vertical axis approximately through her center of gravity. It is deviations of the bow to port and to starboard alternatively.

In operating the ship it is necessary to avoid heavy sudden rolling. This is achieved by applying special stabilizers - bilge keels, stabilizing tanks, fin stabilizers, etc.

Fig. 9.

1) longitudinal axis; 2) longitudinal motion; 3) rolling; 4) transverse axis;

5) transverse motion; 6) pitching; 7) vertical axis; 8) heaving; 9) yawing

Exercises and assignments

Ex. 1. Give all the derivatives of the verbs "to propel", "to steer", "to move". Find in the text the sentences in which they are used and translate them into Russian.

Ex. 2. Match the words below into the pairs of synonyms:

affect, out-of-water, counteract, steady, alter, stock, motions, configuration, produce, crest, trough, cause, slamming, observe;

spindle, firm, above-water, influence, oppose, hollow, watch, induce, generate, whipping, top, oscillations, change, shape.

Ex. 3. Match the words below into the pairs of antonyms:

move, improve, rise, increase, downward, more, portside, inclined, crest, transverse, stern;

longitudinal, decrease, upright, fall, upward, fall, hollow, bow, starboard, worsen, stop.

Ex. 4. Fill in the blanks. Make use of the active vocabulary items and structures.

1. Propeller is a _________ consisting of a boss or blades carrying radial blades.

2. The propulsive device transforms the energy produced by _________ into the work of propeller force.

3. Man has always been improving the hull shapes to counteract the laws of ______.

4. Steerage is closely connected with _________.

5. Two qualities which feature ship's steering are _________.

6. There are three main motions of a ship on waving: ________________________.

7. _________ is rhythmical inclination of a vessel from side to side.

8. Heavy pitching results in coming _________ on the deck, emersion of the ship's bottom and _________.

9. Avoiding heavy sudden _________ is achieved by applying special _________.

Ex. 5. Match the words in the box with the definitions given below. Find in the text sentences in which they are used and translate them into Russian.

a) inclination of a ship from side to side;

b) oscillating movements of a ship under the action of external disturbances;

c) rate of motion or moving;

d) ship's quality of performing turnings;

e) deviations of the bow to port or starboard;

f) downward falling of a vessel's bow and stern alternately;

g) measure of speed for ships;

h) devise with blades which turns to move a ship;

i) the act of directing a ship on her course;

j) opposing force.

Ex. 6. Expand the table matching the terms (the figures) with their definitions (the capital letters) and indicate for improving of which quality the following measures should be taken (the small letters).

1) buoyancy;

2) stability;

3) unsinkability;

4) propulsion;

5) motions;

6) steerage.

A - oscillating movements performed by a ship freely floating at the water surface;

B - ship's ability to develop the pre-set speed at the certain output of the main engine;

C - ship's ability to keep the steady course or to alter the direction of motion at the navigator's command;

D - ship's ability to preserve her buoyancy and stability with one or more compartments flooded;

E - ship's ability to float in the certain position in relation to water;

F - ship's ability to return to her original upright position when inclined.

a - increase of the watertight hull above the load waterline;

b - arrangement of longitudinal bulkheads;

c - arrangement of transverse bulkheads;

d - bulbous bow, foils under the hull;

e - thrusters, active rudders, vane and water jet propellers;

f - bilge keels, active side rudders.

Ex. 7. Fill in the table matching the terms (the figures) with their definitions (the capital letters).

1) cargo carrying capacity, useful deadweight;

2) deadweight (tonnage);

3) displacement;

4) cargo capacity;

5) speed;

6) sailing range;

7) endurance.

A - a way covered by a ship per a time unit;

B - ship's possible voyage duration (days at sea) without replenishment of stores intended for a crew and passengers;

C - the number of tons of cargo which a vessel can carry;

D - total volume of all cargo spaces (m³);

E - the sum of light ship weight and deadweight;

F - the number of tons that the vessel can lift when loaded;

G - the distance (miles) which can be covered by a ship without replenishment of stores of fuel, oil, feed water needed for power plant operation.

Date: 2014-12-28; view: 2151