Section 3 Shell envelope plating

3.1.1 Unless otherwise specified within this Section, the scantlings and arrangements for shell envelope plating are to be determined in accordance with the procedures described in, or as required by, Pt 6, Ch 3, 3 Shell envelope plating for mono-hull craft using the pressures from Pt 5 Design and Load Criteria appropriate to multi-hulls.

3.1.2 The thickness of the shell envelope plating is in no case to be less than the appropriate minimum requirement given in Pt 6, Ch 4, 2 Minimum thickness requirements.

3.2.1 The breadth, b _k, and thickness, t _k, of plate keels are not to be taken as less than:

where L _R and k _s are as defined in Pt 6, Ch 4, 1.5 Symbols and definitions 1.5.1.

3.2.2 In no case is the thickness of the keel to be less than that of the adjacent bottom shell plating.

3.2.3 The width and thickness of plate keels are to be maintained throughout the length of the craft from the transom to a point not less than 25 per cent of the freeboard (measured at the forward perpendicular) above the deepest load waterline on the stem. Thereafter the keel thickness may be reduced to that required by Pt 6, Ch 3, 3.3 Plate stem 3.3.1 for the stem.

3.2.4 For large or novel craft and for yachts with externally attached ballast keels, the scantlings of the keel will be specially considered.

3.3.1 The thickness of the bottom outboard plating is to be determined from the general plating equation given in Pt 6, Ch 3, 1.16 Plating general using the design pressure from Pt 5, Ch 3, 3.1 Hull structures or Pt 5, Ch 4, 3.1 Hull structures for non-displacement or displacement craft as appropriate.

3.3.2 For all craft types, the minimum bottom outboard shell thickness requirement given in Pt 6, Ch 4, 2 Minimum thickness requirements is to extend to the chine line or 150 mm above the static load waterline, whichever is the greater.

3.4.1 The thickness of the bottom inboard plating is to be determined from the general plating equation given in Pt 6, Ch 3, 1.16 Plating general using the design pressure from Pt 5, Ch 3, 3.1 Hull structures or Pt 5, Ch 4, 3.1 Hull structures for non-displacement or displacement craft as appropriate.

3.4.2 For all craft types, the minimum bottom inboard shell thickness requirement given in Pt 6, Ch 4, 2 Minimum thickness requirements is to extend to the chine line or 150 mm above the static load waterline, whichever is the greater.

3.5.1 The thickness of the side outboard plating is to be determined from the general plating equation given in Pt 6, Ch 3, 1.16 Plating general using the design pressure from Pt 5, Ch 3, 3.1 Hull structures or Pt 5, Ch 4, 3.1 Hull structures for non-displacement or displacement craft as appropriate.

3.6.1 The thickness of the side inboard plating is to be determined from the general plating equation given in Pt 6, Ch 3, 1.16 Plating general using the design pressure from Pt 5, Ch 3, 3.1 Hull structures or Pt 5, Ch 4, 3.1 Hull structures for non-displacement or displacement craft as appropriate.

3.7.1 The thickness of the wet-deck plating is to be determined from the general plating equation given in Pt 6, Ch 3, 1.16 Plating general using the design pressure from Pt 5, Ch 3, 3.1 Hull structures or Pt 5, Ch 4, 3.1 Hull structures for non-displacement or displacement craft as appropriate.

3.7.2 Additionally, the thickness of the wet-deck plating is in no case to be less than the thickness of the side inboard shell plating determined from Pt 6, Ch 4, 3.6 Side inboard.

3.7.3 The wet-deck plating on the underside of the cross-deck structure may require to be additionally protected, particularly where the air gap is small and there is a high risk of localised impact due to collision with floating debris, ice, etc. in the service area. In such cases the sheathing requirements given in Pt 6, Ch 3, 2.4 Sheathing are to be complied with.

3.8.1 The scantlings and arrangements of the stern or transom are to be not less than that required for the adjacent bottom inboard or side outboard structure as appropriate. Where water jet or sterndrive units are fitted, the scantlings of the plating in way of the nozzles and connections will be specially considered.

3.9.1 For craft above 40 metres in Rule length, L _R, the stresses in the haunch area are to be derived using a two dimensional fine mesh finite element analysis. The model is to extend horizontally into the box structure and vertically into the strut structure. All discontinuities and cut-outs are to be modelled in order to determine shear stresses at critical locations and stresses for the determination of fatigue strength.

3.9.2 Due consideration is to be given to shear lag when determining the effective breadth of the attached plating.

3.10.1 Where the lower hull structure incorporates ring frames and attached shell plating fitted between bulkheads or diaphragms, the thickness of the lower hull shell plating may be derived from an established method for shell analysis or recognised standard for pressure vessels using the design pressure loading from Pt 5, Ch 3, 3.1 Hull structures or Pt 5, Ch 4, 3.1 Hull structures as appropriate. Other loads considered significant for the scantling determination are to be taken into account. Modes of failure to be considered are buckling, frame collapse, inter-frame shell collapse and overall frame shell collapse between bulkheads. A copy of the direct calculations are to be submitted for consideration.

3.11.1 Where the Rules do not specifically define the requirements for plating elements with novel features then the scantlings and arrangements are to be determined by direct calculations. Such calculations are to be carried out on the basis of the Rules, Recognised Standards and good practice, and are to be submitted for consideration.