UNIT 18. CATHEDRALL HULL

I. Master the active vocabulary:

trimaran – тримаран

to approach – приближаться

resemblance – сходство

bow – нос

rectangular – прямоугольный

beam – бимс, ширина судна

knot – узел

fiberglass – стекловолокно

stability – устойчивость

a deep – vee hull – глубокий V – образный корпус

side skirts – боковые обтекатели

to extend – расширяться

handling characteristics – характеристика управляемости

II. Read and translate the following text:

A cathedral hull is a hull shape used in modern boats, usually power-driven. It can be thought of as a kind of vestigial trimaran in which the center hull has two smaller side hulls which are so close to the main hull that there is no longer any open space. In fact a cathedral hull is a vee-bottomed boat with side skirts which extend almost as far forward as the main hull. The airspace between the hulls may be very small or nonexistent.

Depending on the proportions of the side skirts and the depth of the main hull, the cathedral hull can approach the handling characteristics of either the Hickman sea sled, or the deep-vee hull.

The term "cathedral hull" refers to the resemblance of a section through an inverted boat to that of a medieval cathedral.

The cathedral hull configuration tends to result in a very broad bow; many such boats are completely rectangular. This provides the maximum cargo or working space for a given length and beam. The hull shape is also very stable compared to a conventional v-shaped bottom, and in either light chop conditions or above 40 knots or so is faster than a flat bottom, for the same weight, length and beam.

Cathedral hulls became popular in the 1960's and 1970's. It was the use of fiberglass which made economical production of this hull-form possible. The undesirable aspects of the cathedral hull are greater weight and cost, pounding in rough water, and a boxy appearance. Their advantages include high water plane area at rest (good initial stability) a dry ride in light chop, and reasonable fuel economy at planning speeds. In exposed waters this hull form has been almost totally replaced by the modified-vee and dee-vee hull-forms. After a period of reduced popularity, they live on in modified form as "deck boats" which are very popular in the inland lakes and rivers, especially in the south and Midwest.

III. Answer the following questions:

1. What does the term “cathedral hull” refer to?

2. What is a cathedral hull?

3. The cathedral hull configuration tends to result in a very broad bow, doesn’t it?

4. When did cathedral hulls become popular?

5. What are the advantages of cathedral hulls?

IV. Read and translate the text: “ABS Steels”

ABS Steels are types of structural steel which are standardized by the American Bureau of Shipping for use in shipbuilding.

ABS steels come many grades in ordinary-strength and two levels of higher-strength specifications. All of these steels have been engineered to be optimal long-lived shipbuilding steels. ABS does permit the use of other steels in shipbuilding, but discourages it, and requires more detailed engineering analysis. All ABS steels are standard carbon steels. As with other grades of steel, they have a specific gravity of 7.8.

Ordinary-strength ABS shipbuilding steel comes in a number of grades, A, B, D, E, DS, and CS. On certified steels, the plates are marked with the grade and a preceding "AB/", i.e. AB/A etc.

Yield point for all ordinary-strength ABS steels is specified as 34,000 psi (235 MPa), except for ABS A in thicknesses of greater than 1 inch (25 mm) which has yield strength of 32,000 psi (225 MPa), and cold flange rolled sections, which have yield strength of 30,000 psi (205 MPa). Ultimate tensile strength of ordinary strength alloys is 58,000 - 71,000 psi (400-490 MPa), except for ABS A shapes and bars with 58,000 - 80,000 psi (400-550 MPa), and cold flanged sections with 55,000 - 65,000 psi (380-450 MPa).

The various grades have slightly differing alloy chemical ingredients, and differing fracture toughness. Higher-strength ABS shipbuilding steel comes in six grades of two strengths, AH32, DH32, EH32, AH36, DH36, and EH36.^[2]

The 32 grades have yield strength of 45,500 psi (315 MPa), and ultimate tensile strength of 68,000 - 85,000 psi (475-590 MPa). The 36 grades have yield strength of 51,000 psi (355 MPa), and ultimate tensile strength of 71,000 - 90,000 psi (495-630 MPa).

V. Complete the following sentences, using the text:

1. A cathedral hull is a hull shape used …

2. In fact a cathedral hull is …

3. Depending on the proportions of the side skirts …

4. The term “cathedral hull” refers to …

5. The hull shape is also very stable …

6. The undesirable aspects of the cathedral hull are …

7. After a period of reduced popularity …

VI. Use the following words and word combinations in sentences of your own:

To be used in modern boats, a kind of vestigial trimaran, to be a vee – bottomed boat, nonexistent, to depend on the proportions of smth, to approach the handling characteristics, to refer to the resemblance of smth, deep – vee hull, to result in a very broad bow, to provide the maximum cargo, to become popular, waterplane area, to be replaced by smth.

VII. Retell the text “Cathedral hull.”

UNIT 19. BULBOUS BOW

I. Master the active vocabulary:

bulbous – бульбообразный

waterline – ватерлиния

to modify – варьировать, видоизменять, модифицировать

drag – сопротивление

fuel efficiency – кпд топлива, топливная экономичность (двигателя)

to increase – увеличивать

freighter – грузовой корабль

to excite – вызывать

to flow up – подниматься

pressure distribution – распределение давления

trim – отделка

II. Read and translate the following text:

A bulbous bow, a feature of many modern ship hulls, is a protruding bulb at the bow (or front) below the waterline. Usually visible only when a ship is in drydock, the bulb modifies how water flows around the hull, reducing drag and increasing speed, range, and fuel efficiency. Ships with bulbous bows generally have 12 to 15 percent better fuel efficiency than similar vessels without them.

The first bulbous bows appeared in the USA being fitted to the USS Delaware [BB28] which entered service in 1910 and the design is credited to David Watson Taylor, naval architect and Chief Constructor of the Navy.

Bulbous bows achieve maximum effect at a narrow range of speeds over 6 knots (Bray, website). At other speeds, they can increase drag. They have the greatest effect on large ships such as freighters, navy vessels and various passenger ships. They are rarer on recreational boats designed for wide speed ranges and planing over the water.

Поиск по сайту: