Section 3 Hull envelope plating

3.1.1 The requirements of Pt 4, Ch 1, 5 Hull envelope plating are to be applied together with the requirements of this Section. The thickness of hull envelope plating amidships is to be not less than required in Table 3.3.1 Hull envelope plating, but for ships over 65 m in length, the thickness of the bottom plating and deck plating may require to be increased to obtain the midship section modulus required in Pt 3, Ch 4 Longitudinal Strength.

Table 3.3.1 Hull envelope plating

Item and parameter		Required minimum scantlings
(1)	Plate keel
	Breadth	0,1B m but not less than 0,75 m
	Thickness	As bottom plating tb
		When there is a rise of floor, the thickness is to be increased by 1 mm
(2)	Bottom plating Thickness	Longitudinal framing	Transverse framing
		The greater of :	The greater of :
		mm	mm
		mm	mm
(3)	Bilge plating Thickness	Longitudinal and transverse framing. mm
(4)	Bilge chine bars
	(a) Round bars Diameter	3tb mm but not less than 30 mm
	(b) Square bars Width	3tb mm but not less than 30 mm
	(c) Angle bars Flange thickness	t = 2tb mm
(5)	Side shell plating Thickness	The greater of : mm mm
(6)	Sheerstrake
	Width	0,1 D m but not less than 0,2 m
	Thickness	plus 5 mm
		See note 1
(7)	Deck Plating thickness	Longitudinal framing	Transverse framing
		The greater of:	The greater of:
		mm	mm
		mm	mm
		t = 6 mm	t = 6 mm
		See note 2	See note 2
Symbols
L, B, D, T, S, s, k and t are as defined in Pt 4, Ch 3, 1.5 Symbols and definitions 1.5.1
a 1 = total area of bottom or deck longitudinals, as applicable, in cm2
t b = thickness of bottom plating, in mm
t d = thickness of deck plating connected to the sheerstrake, in mm
C 1 = 1 + 3 where is the ratio of the unstiffened plate panel under consideration
M = the greater of M S and M H
M H = maximum design hogging bending moment, in tm, see Pt 3, Ch 4 Longitudinal Strength
MS = maximum design sagging bending moment, in tm, see Pt 3, Ch 4 Longitudinal Strength
Note 1. Where a substantial welded steel rubbing bar is fitted, the sheerstrake may be of the same thickness as the side shell in way. Note 2. Where the head on deck in metres, h 1, as defined in Pt 3, Ch 3, 4 Design loading exceeds 3,5 m, this thickness is to be increased by the factor

3.2.1 Where openings are made in the deck plating for access, the deck plating in way is, generally, to be increased in thickness to compensate for the material cut out. However, no compensation need be fitted if the loss of sectional area has already been taken into consideration when calculating the actual midship hull section modulus.

3.2.2 Circular openings in deck of a diameter of 150 mm or less need not be compensated, provided they are situated well clear of other openings and the area cut out transversely over the deck does not exceed three per cent of the total area.

3.2.3 Plate panels, in which openings are cut are, where necessary, to be adequately stiffened against compression.

3.2.4 Areas of the deck used by wheeled vehicles are also to comply with the requirements of Pt 3, Ch 9, 2 Decks loaded by wheeled vehicles.