Section
5 Shell envelope plating
5.1 General
5.1.1 The
requirements of this Section, unless specified otherwise, are applicable
to all ship types, NS1, NS2 and NS3.
5.2 Plate keel
5.2.1 The
width and thickness of the plate keel are to be maintained throughout
the ship 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 Table 3.2.1 Minimum structural
requirements for
the stem. For ships with an after cut up, the keel thickness aft of
the cut up can be reduced to that of the shell plating.
5.3 Sheerstrake
5.3.1 The
sheerstrake thickness is to be increased by 20 per cent at the ends
of a superstructure extending out to the ship’s side. In the
case of a superstructure longer than 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 sheerstrake.
5.3.2 Where
an angled gunwale is fitted, the top edge of the sheerstrake is to
be kept free of all notches and isolated welded fittings, such as
spurnwaters, fairlead stools, stancheons. Bulwarks are not to be welded
to the top of the sheerstrake within 0,3 to 0,7L
R.
5.3.3 Where
a rounded gunwale is adopted, the welding of fairlead stools, spurnwaters,
stancheons and other fittings to this plate is to be kept to the minimum,
and the design of the fittings is to be such as to minimise stress
concentration. The radius in general is not to be less than 15t
p.
5.4 Skegs
5.4.1 The
thickness of the skeg plating is to be not less than the thickness
of the adjacent bottom shell.
5.5 Transom
5.5.1 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.
5.6 Shell openings
5.6.1 The
thickness of the shell envelope plating around sea inlet or other
opening is to be 2 mm thicker than the adjacent shell plating, or
6 mm, whichever is the greater. Arrangements are to be in accordance
with Vol 1, Pt 3, Ch 2, 3.3 Shell plating
5.6.2 The
detail and steel grade corners of large openings in the side shell
will be specially considered. Generally they are to be in accordance
with the requirements for large deck openings, see
Vol 1, Pt 6, Ch 3, 10.4 Deck openings 10.4.1
5.7 Sea inlet boxes
5.7.1 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. If
the thickness of the adjacent shell plating is greater than 12,5 mm,
the sea inlet box may be the same thickness as the shell and it need
not exceed 25 mm.
5.8 Local reinforcement/Insert plates
5.8.1 The
thickness of the shell envelope plating is to be increased locally
in way of sternframe, propeller brackets, rudder horn, stabilisers,
hawse pipes, anchor recess, sea inlets, sonar openings, etc. by generally
not less than 50 per cent. Details of such reinforcement are to be
submitted for approval.
5.8.2 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
Vol 1, Pt 6, Ch 6, 6.8 Insert plates
5.9 Novel features
5.9.1 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.
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