Section 3 Shell envelope plating

3.1.1 The requirements of this Section are applicable to longitudinally and transversely framed shell envelope plating.

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 3, 2 Minimum thickness requirements.

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

where L _R and k _s are as defined in Pt 6, Ch 3, 1.5 Symbols and definitions 1.5.1.

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

3.2.3 The width and thickness of the plate keel 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.

3.2.5 For bar keels, see Pt 6, Ch 3, 5.2 Keel 5.2.2.

3.3.1 The thickness of plate stems, t _s, is not to be taken as less than:

where

L _R and k _s are as defined in Pt 6, Ch 3, 1.5 Symbols and definitions 1.5.1.

3.3.2 In no case is the thickness of the plate stem to be taken as less than the thickness of the adjacent shell plating.

3.3.3 Plate stems are to be supported by horizontal diaphragms, and where the stem radius is large, a centreline stiffener or web may be required. Where this is impracticable due to fabrication access considerations, alternative supporting arrangements will be specially considered.

3.3.4 For large or novel craft the scantlings of the stem will be specially considered.

3.3.5 The breadth of plate stems is to be not less than the width of keel as required by Pt 6, Ch 3, 3.2 Plate keel 3.2.1.

3.4.1 The thickness of the bottom shell 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 thickness requirement for bottom shell plating, see Figure 3.3.1 Extent of bottom shell, as detailed in Pt 6, Ch 3, 2 Minimum thickness requirements, is to extend to the chine line or 150 mm above the static load waterline, whichever is the greater.

Figure 3.3.1 Extent of bottom shell

3.5.1 The thickness of the side shell 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 sheerstrake is generally to be taken as the side shell, locally reinforced in way of deck/hull connection and fender attachment. The amount of local reinforcement will be dependent upon the arrangement of structure and the proposed service.

3.6.2 The fendering arrangements for all craft types are the responsibility of the designers/Builders and are outside the scope of classification.

3.6.3 Where the pressure or impact loadings that a particular type of craft will experience in service are considered by the Builder, or subsequent Owner, to be not covered by or be greater than those indicated in Pt 5 Design and Load Criteria of the Rules, details of the loadings together with the calculations of how these will be satisfactorily distributed into the craft's structure, are to be submitted for consideration with the relevant construction plans.

3.6.4 The arrangements indicated in Pt 6, Ch 3, 3.6 Sheerstrake 3.6.5, Pt 6, Ch 3, 3.6 Sheerstrake 3.6.6, Pt 6, Ch 3, 4.18 Structure in way of fenders 4.18.2 and Pt 6, Ch 3, 4.18 Structure in way of fenders 4.18.3 for pilot and fishing craft are for the guidance of the Builder and subsequent Owners/operators of the craft. Where the intended service for either of these types of craft, or other types of craft which may be subject to loadings resulting from contact with other craft, jetties or similar loading or boarding facilities, is such that the loadings are greater than those that can be satisfactorily distributed into the craft's structure by the arrangements indicated, the strengthening arrangements are to be increased accordingly.

3.6.5 For pilot craft which may be subject to repeated impact loadings from contact with other craft etc. the sheerstrake plating is to be increased locally by not less than 50 per cent of the side shell thickness. The increased thickness is to extend from the bow aft over a distance of 0,33L _R or 500 mm aft of the point at which the deckline reaches its greatest breadth, whichever is the greater and forward of the quarter and over the transom for a distance of 0,075L _R or 1,0 m, whichever is the greater. It is in general to extend from the deck edge to below the first longitudinal stiffener, or a vertical distance equivalent to 1/3 the freeboard height whichever is the greater. The additional thickness is then to be tapered out to the side shell thickness in accordance with the Rules.

3.6.6 Fishing craft are in general to have their shell plating scantlings as required to satisfy the Rule loadings, increased by 20 per cent. Additionally the side shell is not to be taken less than as bottom shell thickness, and where there are gallows, gantries, nets, or lines etc. the plating in way is to be further increased locally and/or suitably protected by sheathing or other means.

3.6.7 Individual consideration will be given to lesser scantlings than those required by Pt 6, Ch 3, 3.6 Sheerstrake 3.6.3. for fishing craft used for pleasure, light duties, etc.; details of the service are to be submitted.

3.6.8 Where a rounded sheerstrake is adopted the radius is, in general, to be not less than 15 times the thickness.

3.6.9 The sheerstrake thickness is to be increased by 20 per cent at the ends of a bridge superstructure extending out to the craft's side. In the case of a bridge superstructure exceeding 0,15L _R, the side plating at the ends of the superstructure is also to be increased by 25 per cent and tapered gradually into the upper deck sheerstrake.

3.6.10 In general, compensation will not be required for openings in the sheerstrake which are clear of the gunwale or deck openings and whose depth does not exceed 20 per cent of the depth of the sheerstrake. Openings are not to be cut in a rounded gunwale.

3.7.1 The chine plate thickness is to be equivalent to the bottom shell thickness required to satisfy the Rule pressure loading, increased by 20 per cent, or 6 mm, whichever is the greater.

3.7.2 Where tube is used in chine construction, the minimum wall thickness is to be not less than the thickness of the bottom shell plating increased by 20 per cent.

3.7.3 Full penetration welding of shell plating in way of chines is always to be maintained.

3.7.4 Chine details are to be such that the continuity of structural strength across the panel is maintained. Details of chines are to be submitted for consideration. See also LR's Guidance Notes for Structural Details.

3.8.1 The thickness of the skeg plating is to be not less than the thickness of the adjacent bottom shell and additionally is to satisfy the requirements for solepieces given in Pt 3, Ch 3, 3 Sternframes and appendages.

3.9.1 The thickness of the stern or transom is to be not less than that required for the side or bottom shell 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.

3.10.1 The thickness of the plating is to be increased locally in way of the fin and tuck areas of yachts which have either internal fixed ballast or external attached ballast keels.

3.10.2 The plating thickness is to be not less than 1,25 times the thickness of the adjacent shell plating but need not be greater than the plate keel thickness as required by Pt 6, Ch 3, 3.2 Plate keel.

3.11.1 Sea-inlets, or other openings, are to have well rounded corners and, so far as is practicable, are to be kept clear of the bilge radius, chine or radiused sheerstrake. Arrangements are to be made to maintain the strength in way of the openings.

3.11.2 Openings on or near the bilge radius may be accepted provided that they are of elliptical shape, or equivalent, to minimize stress concentrations and are, in general, to be cut clear of weld connections.

3.12.1 The thickness of the sea inlet box plating is to be 2 mm thicker than the adjacent shell plating, or 6 mm, whichever is the greater.

3.13.1 The thickness of the shell envelope plating determined in accordance with Pt 6, Ch 3, 3.4 Bottom shell plating and Pt 6, Ch 3, 3.5 Side shell plating is to be increased locally, by generally not less than 50 per cent in way of sternframe, propeller brackets, rudder horn, stabilisers, hawse pipes, anchor recess, etc. Details of such reinforcement are to be submitted for approval.

3.13.2 Insert plates are to extend outside the line of adjacent supporting structure and then be tapered over a distance of not less than three times the difference in thickness, see also Pt 6, Ch 2, 4.21 Riveting of light structure.

3.14.1 The scantlings of appendages will be subject to special consideration on the basis of the Rules and the design loadings anticipated, but are, in no case, to be taken as less than that of the surrounding structure.

3.15.1 Wood belting and fenders are to be bolted to lugs welded to a ground bar attached to the shell and not through-bolted to the shell plating.

3.16.1 Where the Rules do not specifically define the requirements for novel features then the scantlings and arrangements are to be determined by direct calculation. Such calculations are be carried out on the basis of the Rules or recognised standards. Details are to be submitted for consideration.