Section 3 Shell envelope plating

3.1.1 Where the shell is longitudinally framed in the midship region, this system of framing is to be carried as far aft as practicable.

3.2.1 The scantlings of bar keels at the aft end are to be the same as in the midship region as required by Pt 4, Ch 1, 5 Shell envelope plating.

3.2.2 The thickness and width of plate keels in the aft region are to be the same as required in the midship region for the particular type of ship concerned, see Pt 4 Ship Structures (Ship Types).

3.3.1 The thickness of bottom shell and bilge plating in the aft region is to comply with the requirements of Table 6.3.1 Shell plating aft.

3.3.2 Where the bottom is transversely framed and there are large flat areas of shell plating, the buckling stability of the plating will be specially considered, and increased plate thickness or additional stiffening may be required, see also Pt 3, Ch 6, 5.2 Single bottoms − Transverse framing 5.2.3.

3.3.3 Where longitudinals are omitted in way of radiused bilge plating amidships, the plating thickness aft will be considered in relation to the support derived from the hull form and internal stiffening arrangements.

3.4.1 The thickness of side shell and sheerstrake plating in the aft region is to be not less than the values given in Table 6.3.1 Shell plating aft, but may be required to be increased locally on account of high shear forces, in accordance with Pt 3, Ch 4, 6.5 Permissible still water shear force.

3.4.2 Increased shell plate thickness may be required where the panting stringers required by Pt 3, Ch 6, 4.4 Panting stringers in way of transverse framing 4.4.1 are omitted. The extent and amount of the increase will be specially considered.

3.4.3 The thickness of shell plating is to be increased locally in way of the sternframe, propeller brackets or rudder horn. The increased plate thickness is to be not less than 50 per cent greater than the basic shell end thickness.

3.4.4 The sheerstrake thickness is to be increased by 20 per cent at the ends of a bridge superstructure extending out to the ship's side, irrespective of position. Similar strengthening is to be fitted in way of the end of a poop if this occurs at a position forward of 0,25L from the A.P. No increase is required if the poop end bulkhead lies aft of 0,2L from the A.P. The increase at intermediate positions of end bulkhead is to be obtained by interpolation.

3.5.1 In general, compensation will not be required for holes in the sheerstrake which are clear of the gunwale, or for any deck openings situated outside the line of main hatchways and whose depth does not exceed 20 per cent of the depth of the sheerstrake or 380 mm, whichever is the lesser. Openings are not to be cut in a rounded gunwale. Cargo door openings are to have well rounded corners, and the proposed compensation for the door openings will be individually considered.

Table 6.3.1 Shell plating aft

Location	Thickness, in mm			NOTES
(1) Bottom shell and bilge, see Notes 4 and 5:				Note 1. For ships where L ≤ 70 m this thickness may be reduced by 1 mm, but it is to be not less than 6 mm. Note 2. The taper thickness is to be determined from Table 3.2.1 Taper requirements for hull envelope, see Note 7. Note 3. For thickness of shell plating in way of the cargo tanks of oil tankers or ore carriers, see also Pt 4, Ch 9 Double Hull Oil Tankers, Pt 4, Ch 10 Single Hull Oil Tankers or Pt 4, Ch 11 Ore Carriers, as applicable. Note 4. In offshore supply ships the thickness of side shell is to be not less than 9 mm. Note 5. For trawlers and fishing vessels see Pt 4, Ch 6, 5 Shell envelope plating. Note 6. For oil tankers the thickness is also to be in accordance with Pt 4, Ch 9, 4.3 Deck plating 4.3.3 Note 7. The taper requirements from Table 3.2.1 Taper requirements for hull envelope in Pt 3, Ch 3 Structural Design do not apply to container ships or open ship types, see Pt 3, Ch 4, 2.3 Open type ships, where the requirements of Pt 4, Ch 8, 3.2 Longitudinal strength are applicable, nor to fast cargo ships where the requirements of Pt 4, Ch 1, 3 Longitudinal strength are applicable. See also Pt 3, Ch 4, 5 Hull bending strength for hull section modulus requirement away from the midship area.
(a) Aft of 0,075L from the A.P.	(see Note 1)
(b) Between 0,075L and 0,15L from the A.P., see Note 6	As (1)(a) or the taper thickness, whichever is the greater, see Note 2
(c) Forward of 0,15L from the A.P., see Note 6	The taper thickness, see Note 2
(2) Side shell, see Notes 4 and 5:
(a) Aft of 0,075L from the A.P.	(see Note 1)
(b) Between 0,075L and 0,15L from the A.P., see also Pt 3, Ch 6, 3.4 Side shell and sheerstrake 3.4.2	As (2)(a) or the taper thickness, whichever is the greater, see Note 2
(c) Forward of 0,15L from the A.P.	The taper thickness, see Note 2
(3) Sheerstrake, see Notes 4 and 5 (a) Aft of 0,075L from the A.P.:
where	As (2)(a) for side shell
where	As (4) for a poop
(b) Between 0,075L and 0,15L from the A.P., see Note 6	As (3)(a) or as determined from Table 3.2.1 Taper requirements for hull envelope
(c) Forward of 0,15L from the A.P., see Note 6	The taper thickness, see Note 2
(4) Poop, see Notes 4 and 5
Symbols
L, B, D, T, s, k as defined in Pt 3, Ch 6, 1.4 Symbols and definitions 1.4.1 f2 = factor to be taken as: = but need not be taken greater than 1. L/T is not to be taken greater than 25. s1 = s but to be taken as not less than sb sb = standard frame spacing, in mm, as follows:
Region	Bottom shell sb			Side shell sb
Aft of 0,05L from the A.P.	or 600*		or 600*	below the deck next above the load waterline
		or	or 700*	above the deck next above the load waterline
Between 0,05L and 0,15L from the A.P.	or 850*		or 850*
*whichever is the lesser

3.5.2 Sea inlet and other openings are to have well rounded corners and so far as possible, should be kept clear of the bilge radius. The thickness of sea inlet box plating is generally to be the same as the adjacent shell. It is not, however, to be less than 12,5 mm, and need not exceed 25 mm.