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The Merchant Shipping (Passenger Ship Construction: Ships of Classes I, II and II(A)) Regulations 1998

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Double bottoms

11.—(1) Every ship shall be fitted with a watertight double bottom which shall extend from the forepeak bulkhead to the afterpeak bulkhead, as far as this is practicable, provided that a double bottom may be dispensed with in compartments where its fitting would not be compatible with the design and proper working of the ship, subject to the following minimum requirements for fitting such a double bottom—

(a)in ships of 50 metres but less than 61 metres in length, a double bottom shall extend from the machinery space to the collision bulkhead or as near to that bulkhead as is practicable;

(b)in ships of 61 metres but less than 76 metres in length, a double bottom shall extend from the collision bulkhead to the afterpeak bulkhead or as near to those bulkheads as is practicable, but not necessarily in the machinery space; and

(c)in ships of 76 metres in length or over, a double bottom shall be fitted amidships and shall extend from the collision bulkhead to the afterpeak bulkhead or as near to those bulkheads as is practicable.

(2) Any ship of Class II or II(A) may be exempted by the Secretary of State from the requirements for a double bottom in any portion of the ship which is subdivided by application of a factor of subdivision not exceeding 0.5 if it can be shown that the fitting of a double bottom in that portion of the ship would not be compatible with the design and proper working of the ship.

(3) When a double bottom is required by this regulation to be fitted, its moulded depth shall be of a satisfactory height and the inner bottom shall be continued out to the ship’s sides in such a manner as to protect the bottom to the turn of the bilge. The inner bottom shall be deemed to be adequate for this purpose if the line of intersection of the outer edge of the margin plate with the bilge plating is not lower at any point than a horizontal plane passing through the point of intersection with the frame line amidships of a transverse diagonal line inclined at 25 degrees to the base line and cutting it at a point one-half of the ship’s moulded breadth from the centreline.

(4) Wells constructed in the double bottom for the purpose of drainage shall not be larger nor extend downwards more than is necessary for such purpose. The depth of the well shall in no case be more than the depth of the double bottom at the centre line, less 460 millimetres, nor shall the well extend below the horizontal plane referred to in paragraph (3), provided that a well extending to the outer bottom may be constructed at the after end of a watertight shaft tunnel fitted in accordance with regulation 10(3).

(5) Wells for purposes other than drainage shall not be constructed in the double bottom. A ship may be exempted from the requirements of this paragraph in respect of any well if it can be shown that it will not diminish the protection given by the double bottom.

(6) Nothing in this regulation shall require a double bottom to be fitted in way of watertight compartments of moderate size used exclusively for the carriage of liquids if the safety of the ship will not be impaired in the event of bottom or side damage by reason of the absence of a double bottom in that position.

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