Section
3 Shell envelope plating
3.1 General
3.1.1 Where
the shell is longitudinally framed in the midship region, this system
of framing is to be carried as far forward as practicable. In the
case of oil tankers (see
Pt 3, Ch 5, 1.1 Application 1.1.4), longitudinal framing is to extend at least to the forward
end of the cargo tanks.
3.2 Keel
3.2.2 The
thickness and width of plate keels in the forward 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 Stem
3.3.2 The
scantlings of plate stems are to be determined from Table 5.3.1 Shell plating forward. Plate stems are to
be supported by horizontal diaphragms positioned in line with the
side stringers or perforated flats with intermediate breasthook diaphragms.
Diaphragms are to be spaced not more than 1,5 m apart, measured along
the stem. Where the stem plate radius is large, a centreline stiffener
or web will be required.
3.4 Bottom shell and bilge
3.4.1 The
thickness of bottom shell and bilge plating in the forward region
for ships not requiring additional strengthening of bottom is to comply
with Table 5.3.1 Shell plating forward.
3.4.3 Where
longitudinals are omitted in way of radiused bilge plating amidships,
the plating thickness forward will be considered in relation to the
support derived from the hull form and internal stiffening arrangements.
3.5 Side shell and sheerstrake
3.5.2 For
transversely framed side shells where panting stringers are omitted, see
Pt 3, Ch 5, 4.4 Panting stringers in way of transverse framing, the side shell
plating in the region concerned is to be increased in thickness by
the percentages given below:
-
15 per cent, where L ≤ 150 m
-
5 per cent, where L ≥ 215 m
For intermediate values of L, the percentage increase
is to be obtained by interpolation.
3.5.3 The
side shell plating of increased thickness required by Pt 3, Ch 5, 3.5 Side shell and sheerstrake 3.5.2 is to be continued forward
past the fore peak or collision bulkhead. In addition, horizontal
brackets in line with the fore peak stringers are to be fitted at
the aft side of the bulkhead where practicable. The brackets are to
be the same thickness as the side shell and are to extend from the
bulkhead to the adjacent shell frame and be connected thereto. Transversely
the toes of the brackets are to extend past the outboard stiffener
of the bulkhead to clear any cut out in the bulkhead stringer.
3.5.4 The
sheerstrake taper 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 forecastle if this occurs at a position aft of 0,25L from
the F.P. No increase is required if the forecastle end bulkhead lies
forward of 0,2L from the F.P. The increase at intermediate
positions of end bulkhead is to be obtained by interpolation.
3.6 Shell openings
3.6.1 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.
3.6.2 Sea
inlet and other openings are to have well rounded corners. The thickness
of sea inlet box plating is generally to be the same as the adjacent
shell. It is however, to be not less than 12,5 mm, and need not exceed
25 mm.
Table 5.3.1 Shell plating forward
| Location
|
Thickness, in mm
|
Notes (Part only
shown)
|
| (1)
|
Bottom shell and bilge, see
also
Pt 3, Ch 5, 1.5 Strengthening of bottom forward and Note 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.
|
| (a)
|
Forward of
0,075L from the F.P.
|
 (see Note 1)
|
|
| (b)
|
Between 0,075L
and 0,25L from the F.P.,see Note 7
|
As
(1)(a) or the taper thickness, whichever is the greater
|
|
| (c)
|
Aft of 0,25L
from the F.P., see Note 7
|
The
taper thickness, (see Note 2)
|
Note
4. In offshore supply ships
the thickness of side shell is to be not less than 9 mm.
|
| (2)
|
Side shell, see
Notes 4 and 5:
|
|
|
| (a)
|
Forward of
0,075L from the F.P.
|
 (see Note 1)
|
|
| (b)
|
Between
0,075L and 0,2L from the F.P., see also
Pt 3, Ch 5, 3.5 Side shell and sheerstrake 3.5.2
|
As (2)(a) or the taper thickness, whichever is the
greater
|
|
| (c)
|
Aft of
0,2L from the F.P.
|
The taper thickness, (see Note 2)
|
Note
8. The taper requirements
from Table 3.2.1 Taper requirements for hull
envelope in Pt 3, Ch 3 Structural Designdo 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.
|
| (3)
|
Sheerstrake,
see Notes 4 and 5:
|
|
| (a)
|
Forward of
0,075L from the F.P.:
|
|
|
|
where 
|
As (2)(a) for side shell
|
|
|
where 
|
As (4) for a forecastle
|
| (b)
|
Between
0,075L and 0,2L from the F.P., see Note 7
|
As (3)(a) or as determined from Table 3.2.1 in
Chapter 3
|
| (c)
|
Aft of 0,2L
from the F.P., see Note 7
|
The taper thickness, (see Note 2)
|
| (4)
|
Forecastle, see
Notes 4 and 5
|
|
|
| (5)
|
Stem, see Notes
4 and 5
|
|
|
| (a)
|
Bar
stem:
below load waterline
|
|
A
1
|
= |
(1,6L - 32) cm2 or L
cm2 whichever is the greater |
|
|
|
|
at stem
head
|
|
|
| (b)
|
Plate
stem:
below load waterline
|
|
t
|
= |
(5,0 + 0,083L
2)  mm |
|
|
|
|
at stem head
|
|
t
|
= |
as (2)(a) for side shell |
|
|
| Symbols
|
|
L, B, D, T, s, k as defined in
Pt 3, Ch 5, 1.4 Symbols and definitions 1.4.1
s
1 = s, but to be taken as not less than s
b
f2 = factor to be taken as:
- f2 =
 but need not be taken greater than
1. L/T is not to be taken greater than 25
s
b = standard frame spacing, in mm, as follows:
|
| Region
|
Bottom shell s
b
|
Side
shell s
b
|
|
Forward of 0,05L from the F.P.
|
 or 600*
|
 or 600*
|
|
Between 0,05L and 0,2L from the F.P.
|
 or 700*
|
 or 700*
|
|
Between 0,2L and 0,25L from the F.P.
|
|
*
whichever is the lesser
|
|
A
1
|
= |
cross-sectional area of bar stem below load waterline,
in cm2
|
|
A
2
|
= |
cross-sectional area of bar stem at stem head, in cm
2
|
|
L
2
|
= |
L, but need not be taken greater than 215 m |
|
|