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Code of Practice
4. Construction and Structural Strength
1.4 General Requirements
A vessel should be fitted with a watertight weather deck and be of structural strength to withstand the sea and weather conditions likely to be encountered in the intended area of operation.
2.4 Structural Strength
2414.1.1 New vessels
4.2..1. The full of a new vessel which has been surveyed and certified by an United Kingdom Load Line Assigning Authority should be acceptable, subject to presentation of a certificate of construction.
4.2..2. United Kingdom Load Line Assigning Authorities are Lloyd's Register of Shipping, the British Technical Committee of American Bureau of Shipping and the British Committees of Bureau Veritas, Det Norske and Germanischer Lloyd.
4.2..3. A new vessel which has not been built under the survey of an United Kingdom Load Line Assigning Authority will be considered to be of adequate strength after a satisfactory examination by an authorised person and if it has been built:-
.1 in accordance with the full certification standards for small craft, set by one of the Authorities; or
.2 in general accord with the standard of a sailing vessel which has a record of at least five years' history of safe operation in an area where the sea and weather conditions are no less severe than those likely to be encountered in the intended area of operation.
4.2..4. A new vessel not built in accordance with either 4.2.1.1 or 4.2.1.3 may be specially considered, provided that full information (including calculations, drawings, details of materials and construction) is presented to and approved by the Certifying Authority.
2414.1.1 Existing vesselts
An existing vessel will be considered to be of acceptable strength if it is in a good state of repair and is:-
4.2..1. built to one of the standards identified in para 4.2.1 for new vessels, or
4.2..2. of a design with a record of at least 5 years history of safe operation in an area where the sea and weather conditions are no less severe than those likely to be encountered in the intended area of the operation.
3.4
DECKS
3414.1.1 Weather deck
A vessel should have a watertight deck which extends from stem to stern. The weather deck may be stepped, recessed or raised provided the stepped, recessed or raised portion is of watertight construction.
3414.1.1 Recesses
(For water freeing arrangements generally, see section 6.)
4.3..1. A recess in the weather deck should be of watertight construction and have:-
.1 A volume (Vc) which does not exceed the value obtained from the following formula:-
Vc = 0.10 x length of vessel x breadth of vessel x freeboard abreast the recess (or cockpit); and
.2 means of drainage capable of efficient operation when the vessel is heeled to 30 degrees, such drainage to have and effective area, excluding grills and baffles, of at least 10 cm² for a vessel operating in area category 2, 3 or 4 and of at least 20 cm² for a vessel operating in area category 0 or 1.
4.3..2. Alternative arrangements for drainage of a recess may be accepted provided it can be demonstrated that, with the vessel upright and at its deepest draught, the recess drains from a swamped condition within 3 minutes.
4.3..3. If a recess is provided with a locker which gives direct access to the interior of the hull, the locker should be fitted with weathertight cover(s). In addition the cover(s) to a locker should be permanently attached to the vessel's structure and fitted with efficient locking devices to secure the cover(s) in the closed position.
4.4 Watertight Bulkheads and Damage Survival (vessels of 15 metres in length and over or carrying 15 or more persons)
4.4.1 New monohull vessels
When a new vessel is of 15 metres in length and over or intended to carry 15 or more persons, watertight bulkheads should be fitted in accordance with the following requirements, except that consideration will be given to the continued acceptance of an existing design which does not meet the requirements in full but is part of a building programme in progress at the time when the Code comes into force for new vessels:-
4.4.1.1 Watertight bulkheads should be so arranged that minor hull damage which results in the free-flooding of any one compartment, will not cause the vessel to float at a waterline which is less than 75 mm below the weather deck at any point. Minor damage should be assumed to occur anywhere in the length of the vessel but not on a watertight bulkhead. Standard permeabilities should be used in this assessment as follows:-
Space Permeability %
Appropriated for stores 60
Appropriated for stores but not by a substantial quantity thereof 95
Appropriated for accommodation 95
Appropriated for machinery 85
Appropriated for liquids 0 or 95 whichever results in the more onerous requirement
4.4.1.2 In the damaged condition, the residual stability should be such that the angle of equilibrium does not exceed 7 degrees from the upright, the resulting righting lever curve has a range to the downflooding angle of at least 15 degrees beyond the angle of equilibrium, the maximum righting lever within that range is not less than 100mm and the area under the curve is not less than 0.015 metre radians.
4.4.1.3 The strength of watertight bulkhead should be adequate for the intended purpose and to the satisfaction of the Certifying Authority.
4.4.1.4 When pipes, cables etc, penetrate watertight bulkheads, they should be provided with valves and/or watertight glands as appropriate.
4.4.1.5 A doorway fitted in a watertight bulkhead should be of watertight construction and be kept closed at sea, unless opened at the discretion of the skipper.
4.4.2 New multihull vessels
4.4.2.1 A new multihull vessel should be so designed that it will float for more than 12 hours after capsizing, either when any two hatches are open, or when any one hull is holed between watertight bulkheads. This requirement may be met by subdivision or built-in flotation, but may not include the effect of air trapped in any compartment that is open to the sea.
4.4.2.2 Compliance with this requirement should be demonstrated by calculation for the maximum displacement condition (as defined in 11.3.1), which should show a minimum reserve buoyancy in the capsized condition of 25% of the displacement.
4.4.2.3 When flotation material is used, it should be adequately protected from accidental damage. When an air tank is used for flotation, it should be clearly marked:-
"AIR TANK - DO NOT PUNCTURE"
and should be provided with means of draining and checking for freedom from water.
4.4.2.4 When an intact compartment which is used to demonstrate positive flotation after capsize is penetrated by a door or hatch, the door or hatch should be of watertight construction, and should be clearly marked on both sides:-
"WATERTIGHT ACCESS - KEEP CLOSED WHEN AT SEA"
4.4.3 Existing vessels
4.4.3.1 In the case of an existing monohull vessel which is of 15 metres in length and over or carrying 15 or more persons, it is most strongly recommended that modifications which cause the vessel to meet the standard given by para 4.4.1 be implemented when the vessel undergoes major structural alterations.
4.4.3.2 In the case of an existing mutlihull vessel, it is most strongly recommended that modifications which cause the vessel to meet the standard given by para 4.4.2 be implemented when the vessel undergoes major structural alterations.
