Section 7 Bulkheads and deep tanks

7.1.1 Except as otherwise specified within 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 8, Ch 3, 7 Bulkheads and deep tanks for mono-hull craft, using the pressures from Pt 5 Design and Load Criteria appropriate to multi-hull craft.

7.1.2 The scantlings of non-watertight or partial bulkheads are in general to be as required for watertight bulkheads. Non-watertight or partial bulkheads supporting hull framing are to have scantlings equivalent to frames or web frames as appropriate, in the same position.

7.1.3 Sandwich wood bulkheads, plywood bulkheads or other forms of bulkhead construction will be considered on the basis of equivalent strength.

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 two for catamarans and four for trimarans. Quadrimarans and other craft of novel configuration will be specially considered.

7.2.2 The scantlings and arrangements of cross-deck longitudinal bulkheads are to be determined in accordance with the procedures described in Pt 8, Ch 3, 7.3 Watertight bulkheads and Pt 8, Ch 3, 7.4 Deep tanks for bulkheads in mono-hull craft.

7.2.3 In addition the requirements of Pt 8, Ch 4, 7.4 Additional strength required for global loadings in respect of global strength are to be complied with.

7.3.1 The scantlings and arrangements of cross-deck transverse bulkheads are to be determined in accordance with the procedures described in Pt 8, Ch 3, 7.3 Watertight bulkheads and Pt 8, Ch 3, 7.4 Deep tanks for bulkheads in mono-hull craft.

7.3.2 In addition the requirements of Pt 8, Ch 4, 7.4 Additional strength required for global loadings 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 laminate or skin thicknesses may require to be increased. For hull girder strength requirements, see Pt 8, Ch 6, 3 Hull girder strength 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 vessel 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 8, Ch 6, 3 Hull girder strength 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. Due consideration is to be given to the wrinkling and buckling of the skins of sandwich plate laminates. 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. The edges of cut-out in sandwich panels are to be suitably reinforced while those of single skin construction are to be sealed.

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 that form the cross-deck structure are to be suitably strengthened, if necessary, at the ends 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 8, Ch 3, 7.4 Deep tanks. For global considerations of strength, see Pt 8, Ch 6, 3 Hull girder strength for multi-hull craft.