(1) A trunk or similar structure which does not
extend to the sides of the ship shall be regarded as efficient on
the following conditions:
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(a) the trunk is at least as strong as a superstructure;
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(b) the hatchways are in the trunk deck, and the
hatchway coamings and covers comply with the requirements of Regulations 13 to 16 inclusive and the
width of the trunk deck stringer provides a satisfactory gangway and
sufficient lateral stiffness. However, small access openings with
watertight covers may be permitted in the freeboard deck;
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(c) a permanent working platform fore and aft
fitted with guard rails is provided by the trunk deck, or by detached
trunks connected to superstructures by efficient permanent gangways;
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(d) ventilators are protected by the trunk, by
watertight covers or by other equivalent means;
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(e) open rails are fitted on the weather parts
of the freeboard deck in way of the trunk for at least half their
length;
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(f) the machinery casings are protected by the
trunk, by a superstructure of at least standard height, or by a deckhouse
of the same height and of equivalent strength;
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(g) the breadth of the trunk is at least 60 per
cent of the breadth of the ship; and
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(h) where there is no superstructure, the length
of the trunk is at least 0.6 L.
(2) The full length of an efficient trunk reduced
in the ratio of its mean breadth to B shall be its effective length.
(3) The standard height of a trunk is the standard
height of a superstructure other than a raised quarter deck.
(4) Where the height of a trunk is less than the
standard height, its effective length shall be reduced in the ratio
of the actual to the standard height. Where the height of hatchway
coamings on the trunk deck is less than that required under Regulation 15 (1), a reduction from the
actual height of trunk shall be made which corresponds to the difference
between the actual and the required height of coaming.