Section 7 Bulkheads and deep tanks

7.1.1 Unless otherwise specified in this Section, the scantlings and arrangements for bulkheads and deep tanks are to be determined in accordance with the procedures described in, or as required by Pt 7, Ch 3, 7 Bulkheads and deep tanks for mono-hull craft using the pressures from Pt 5 Design and Load Criteria appropriate to multi-hulls.

7.2.1 Longitudinal bulkheads are to be fitted within the cross-deck structure to prevent cross flooding and the spread of flame and smoke. The minimum number of such bulkheads is to be:

• one for catamarans of Rule length, L _R, less than or equal to 24 m;
• two for catamarans of Rule length, L _R, greater than 24 m; and
• four for trimarans.

Quadrimarans and other craft of novel configuration will be specially considered.

7.2.2 The scantlings and arrangements for cross-deck longitudinal bulkheads are to be determined in accordance with the procedures described in Pt 6, Ch 3, 7.2 Watertight bulkhead plating and Pt 6, Ch 3, 7.3 Watertight bulkhead stiffening for bulkheads in mono-hull craft.

7.2.3 In addition the requirements of Pt 6, Ch 4, 7.4 Additional strength required for global loading with regard to global strength are to be complied with.

7.3.1 The scantlings of cross-deck transverse bulkheads are to be determined in accordance with the procedures described in Pt 6, Ch 3, 7.2 Watertight bulkhead plating and Pt 6, Ch 3, 7.3 Watertight bulkhead stiffening for bulkheads in mono-hull craft.

7.3.2 In addition the requirements of Pt 6, Ch 4, 7.4 Additional strength required for global loading in respect of global strength are to be complied with.

7.4.1 Where transverse bulkheads or deep tank bulkheads within the cross-deck structure are to assist in resisting torsional or bending loads between the hulls, then the watertight/deep tank bulkheads may be required to be additionally stiffened and the plating or skin thicknesses may require to be increased. For hull girder strength requirements, see Pt 6, Ch 6, 3 Additional hull girder strength requirements for multi-hull craft.

7.4.2 Longitudinal bulkheads within the cross-deck structure that are to assist in maintaining the longitudinal strength of the craft are to satisfy both bulkhead/deep tank and longitudinal strength requirements. This may require additional stiffening and increase in plate thickness requirements. For hull girder strength requirements, see Pt 6, Ch 6, 3 Additional hull girder strength requirements for multi-hull craft.

7.4.3 Where longitudinal or transverse cross-deck bulkheads/deep tanks are to carry global loads, detailed calculations are to be submitted.

7.4.4 For longitudinal or transverse cross-deck members carrying global loads, consideration is to be given to stiffener arrangement, alignment, and continuity in order to maximise the rigidity and stiffness of the structure, in resisting the torsional/bending loads. Discontinuity of structural bulkheads is to be avoided.

7.5.1 Access through the cross-deck structure may be permitted, provided that the global strength requirements are satisfied. Cut outs through the bulkhead are not to exceed 50 per cent of its depth, see also Pt 6, Ch 3, 7.18 Access

7.5.2 Where the cross-deck structure acts as a watertight bulkhead pipe or cable runs through the watertight bulkheads are to be fitted with suitable watertight glands.

7.6.1 Bulkheads forming the cross-deck structure are to be suitably strengthened, if necessary, in way of deck girders and where subjected to concentrated loads.

7.7.1 Where the cross-deck structure forms the boundaries of deep tanks, the scantlings of these boundaries are to satisfy both deep tank and global strength requirements. For general and structural requirements for deep tanks, see Pt 6, Ch 3, 7 Bulkheads and deep tanks. For global considerations of strength, see Pt 6, Ch 6, 3 Additional hull girder strength requirements for multi-hull craft.