VII. Speak on types of a keel. Unit 15. Ballast tank

I. Master the active vocabulary:

a compartment – перегородка

to include smth – включать что – либо

forepeak tank – форпиковая цистерна

center of gravity – центр притяжения

the draft of the vessel – проект судна

to adjust – регулировать, устанавливать

stability – стабильность

to be light weight – иметь легкий вес

to submerge – опускать, погружать в воду

buoyancy – плавучесть

compressed air – сжатый воздух

to dive – нырять

discharged water – отработавшая вода

II. Read and translate the following text:

A ballast tank is a compartment within a boat or ship that holds water. A vessel may have a single ballast tank near its center or multiple ballast tanks typically on either side. A large vessel typically will have several ballast tanks including double bottom tanks, wing tanks as well as forepeak and aft peak tanks. Adding ballast to a vessel lowers its center of gravity, and increases the draft of the vessel. Increase draft may be required for proper propeller immersion.

Fig. 17. Example of ballast tank.

A ballast tank can be filled or emptied in order to adjust the amount of ballast force. Ships designed for carrying large amounts of cargo must take on ballast water for proper stability when travelling with light loads and discharge water when heavily laden with cargo. Small sailboats designed to be light weight for being pulled behind automobiles on trailers are often designed with ballast tanks that can be emptied when the boat is removed from the water.

In submarines ballast tanks are used to allow the vessel to submerge, water being taken in to alter the vessels buoyancy and allow the submarine to dive. When the submarine surfaces, water is blown out from the tanks using compressed air, and the vessel becomes positively buoyant again, allowing it to rise to the surface. A submarine may have several types of ballast tank, the main ballast tanks, which are the main tanks used for diving and surfacing, and trimming tanks, which are used to adjust the submarine's attitude (its 'trim') both on the surface and when underwater.

III. Answer the following questions:

1. What is a ballast tank?

2. How many ballast tanks may a vessel have?

3. Does adding ballast to a vessel lower its center of gravity?

4. What must ships take on ballast water for?

5. Small sailboats are often designed with ballast tanks, aren’t they?

6. What tanks may a submarine have?

IV. Read and translate the text “Aka”

The aka of a multihull sailboat is a member of the framework that connects the hull to the ama(s) (outrigger).

The design of the akas depends on the forces it will encounter when sailing. For example, there are two modern variations of the proa, the traditional or Pacific proa, with the ama to the windward side, and the modern Atlantic proa, with the ama to the leeward. The windward ama provides stability by placing the center of gravity far to the windward of the sail, so it is generally heavy. Ropes leading from the mast to the ama provide the force to lift the ama, so the akas must contend mainly with compressive forces, and the weight of the crew, who generally ride on a platform running between the akas.

An Atlantic proa or a trimaran relies on an ama to leeward to provide stability. The ama provides stability by moving the center of buoyancy to the leeward side, and well designed leeward amas will also provide dynamic lift to increase the stability further. The aka for a leeward ama must be designed to handle significant amounts of torque from the lift produced by the ama.

The term vaka, like the related terms aka and ama, come from the Malay and Micronesian language group terms for parts of the outrigger canoe, and vaka can be roughly translated as canoe. A proa consists of a vaka, the main canoe-like hull; an ama, the outrigger; and akas, the poles connecting the ama to the vaka.

V. Translate the following sentences from Russian into English:

1. Большое судно имеет несколько балластных цистерн.

2. Балласт повышает осадку судна.

3. Судно с тяжелым грузом должно сбрасывать воду.

4. Балласт позволяет подводной лодке погружаться.

5. На судне балласт понижает центр тяжести.

VI. Complete the following sentences, using the text:

1. A ballast tank is a compartment …

2. A large vessel typically will have …

3. A ballast tank can be filled …

4. Small sailboats designed to be light …

5. When the submarine surfaces …

6. A submarine may have …

VII. Retell the text “Ballast tank”