6.1.1 Detailed plans are to be submitted clearly indicating the positions, supporting
structures and design loads for retractable and non-retractable fin stabilisers.
6.1.2 The design, construction, operational performance and control of fin stabilisers are
outside the scope of classification.
6.1.3 Stabiliser fins are to be positioned so that the openings for the fins is
between a pair of transverse watertight bulkheads which form a watertight compartment.
Where stabiliser fins extend across watertight bulkheads, these bulkheads are not
included in the compartment definition, see
Figure 13.6.1 Stabiliser fin positioning. If this compartment is
subjected to flooding due to stabiliser damage, calculations and information are to be
submitted showing that the bulkhead deck does not become submerged and that essential
systems remain operational. A water ingress detector and alarm are to be provided, as
well as indication on the navigation bridge.
Figure 13.6.1 Stabiliser fin positioning
6.1.4 Shell insert plates are to be fitted in way of stabilisers. The thickness of
the insert plate is to be at least 50 per cent greater than the shell thickness in way,
and is to extend over a minimum area formed by 1,25 times the stabiliser root chord
length ‘c’ and covering all operational angles of the fin, see
Figure 13.6.2 Shell insert. In addition, for retractable stabilisers the
insert is to extend beyond the shell opening for a distance of not less than 25 per cent
of the length of the root chord. The insert plate is to extend above and below the
opening for the stabiliser for a minimum distance equal to the opening height.
Figure 13.6.2 Shell insert
6.1.5 The stabiliser foundation and surrounding hull structure is to be adequately supported
and stiffened, and is to be examined for the following load cases:
- Fatigue load. In the absence of a load derived from operational
lifecycle data, the fatigue load may be taken as the maximum working load in heavy
weather at 90 per cent of the allowable speed V, where V is defined
in Pt 3, Ch 1, 6.1 Principal particulars. The fatigue
load is additionally not to be taken as less than the maximum working load at zero
speed. Nominal bending stress in the structure for the fatigue load is not to
exceed 39 N/mm2 in steel (mild or high-tensile).
- Shaft breaking load. The surrounding hull structure is not to yield under this
load case. The load is to be applied in both the longitudinal and transverse
directions
6.1.7 Shaft bearing materials and seals are to be of an approved type.
6.1.8 The watertight enclosure into which the stabilisers retract is to have a perimeter
plating thickness of the surrounding shell plating plus 2 mm and stiffened to an
equivalent standard.
6.1.9 In general, full penetration welds are to be applied in way of the stabiliser pedestal
and surrounding hull structure. Welds are to be smooth and notch-free. Construction
details are to be carefully designed to avoid structural discontinuities and stress
concentrations.
6.1.10 Non-retractable or retracted stabiliser fins are, in general, not to extend beyond the
beam of the hull or below the keel.
6.1.11 On ice class ships, non-retractable stabiliser fins are not to be fitted to ships with
an Ice Class 1Cor higher. Where fitted, the fins are to be positioned at least
500 mm below the ice light waterline in all operating positions.