The purpose of these notes is to ensure uniformity in the
methods employed in the construction and verification of the model as well as the
undertaking and analyses of the model tests, while appreciating that available
facilities and costs will affect in some way this uniformity.
The contents of paragraphs 1 and 2 of the Revised Model Test Method
are considered self-explanatory. Paragraph 3
- Ship model3.1
The material of which the model is
made is not important in itself, provided that the model, both in the intact and
damaged condition, is sufficiently rigid to ensure that its hydrostatic properties
are the same as those of the actual ship and also that the flexural response of the
hull in waves is negligible.
It is also
important to ensure that the damaged compartments are modelled as accurately as
practicably possible to ensure that the correct volume of floodwater is represented.
Since ingress of water (even small amounts)
into the intact parts of the model will affect its behaviour, measures must be taken
so that this ingress does not occur.
tests involving worst SOLAS damages near the ship ends, it was observed that
progressive flooding was not possible because of the tendency of the water on deck
to accumulate near the damage opening and hence flow out. As such models were able
to survive very high sea states, while they capsized in lesser sea states with less
onerous SOLAS damages, away from the ends, the limit ±35% was introduced to prevent
Extensive research carried out for the
purpose of developing appropriate criteria for new vessels has clearly shown that in
addition to the GM and freeboard being important parameters in the survivability of
passenger ships, the area under the residual stability curve is also another major
factor. Consequently in choosing the worst SOLAS damage for compliance with the
requirement of paragraph 3.5.1 the worst damage is to be taken as that which gives
the least area under the residual stability curve. 3.2 Model particulars.1
In recognising that scale effects play
an important role in the behaviour of the model during tests it is important to
ensure that these effects are minimised as much as practically possible. The model
should be as large as possible since details of damaged compartments are easier
constructed in larger models and the scale effects are reduced. It is therefore
required that the model length is not less than that corresponding to 1:40 scale or
3 m, whichever is greater.
It has been found
during tests that the vertical extent of the model can affect the results when
tested dynamically. It is therefore required that the ship be modelled to at least
three superstructure standard heights above the bulkhead (freeboard) deck so that
the large waves of the wave train do not break over the model. .2
The model in way of the assumed damages should be as thin
as practically possible to ensure that the amount of floodwater and its centre of
gravity are adequately represented. The hull thickness should not exceed 4 mm. It is
recognised that it may not be possible for the model hull and the elements of
primary and secondary subdivision in way of the damage to be constructed with
sufficient detail and due to these constructional limitations it may not be possible
to calculate accurately the assumed permeability of the space. .3
It is important that not only the draughts in the intact
condition are verified but also that the draughts of the damaged model are
accurately measured for correlation with those derived from the damaged stability
calculation. For practical reasons a tolerance of +2 mm in any draught is accepted.
After measuring the damaged draughts
it may be found necessary to make adjustments to the permeability of the damaged
compartment by either introducing intact volumes or by adding weights. However, it
is also important to ensure that the centre of gravity of the floodwater is
accurately represented. In this case any adjustments made must err on the side of
If the model is required to be fitted
with barriers on deck and their height is less than the bulkhead height indicated
below, the model should be fitted with CCTV so that any "splashing over" and any
accumulation of water on the undamaged area of the deck can be monitored. In this
case a video recording of the event should form part of the tests records.
The height of transverse or longitudinal bulkheads
which are taken into account as effective to confine the assumed accumulated sea
water in the compartment concerned in the damaged ro-ro deck should be at least 4 m
in height unless the height of water is less than 0.5 m. In such cases the height of
the bulkhead may be calculated in accordance with the following:
- Bh = 8hw
Bh is the bulkhead height;
hw is the height of water.
In any event, the minimum height of the bulkhead should be
not less than 2.2 m. However, in the case of a ship with hanging car decks, the
minimum height of the bulkhead should be not less than the height to the
underside of the hanging car deck when in its lowered position.
.5 In order to ensure that the model motion
characteristics represent those of the actual ship it is important that the
model is inclined in the intact condition so that the intact GM is verified. The
mass distribution should be measured in air. The transverse radius of gyration
of the actual ship should be in the range 0.35B to 0.4B and the longitudinal
radius of gyration should be in the range 0.2L to 0.25L.
While inclining and rolling the model in the damage condition
may be accepted as a check for the purpose of verifying the residual stability
curve, such tests should not be accepted in lieu of the intact tests.
.6 It is assumed that the ventilators
of the damaged compartment of the actual ship are adequate for unhindered
flooding and movement of the floodwater. However in trying to scale down the
ventilating arrangements of the actual ship undesirable scale effects may be
introduced. In order to ensure that these do not occur it is recommended to
construct the ventilating arrangements to a larger scale than that of the model,
ensuring that this does not affect the flow of water on the car deck.
.7 It is deemed appropriate to consider
a damage shape representative of a cross section of the striking ship in the bow
region. The 15° angle is based on a study of the cross section at a distance of
B/5 from the bow for a representative selection of vessels of different types
The isosceles triangular profile
of the prismatic damage shape is that corresponding to the load waterline.
Additionally, in cases where side casings of
width less than B/5 are fitted and in order to avoid any possible scale effects,
the damage length in way of the side casings should not be less than 25 mm.
3.3 In the original model test method
of resolution 14 of the 1995 SOLAS Conference the effect of heeling induced by
the maximum moment deriving from any of passenger crowding, launching of
survival craft, wind and turning was not considered even though this effect was
part of SOLAS. Results from an investigation have shown however that it would be
prudent to take these effects into account and to retain the minimum of 1° heel
towards the damage for practical purposes. It is to be noted that heeling due to
turning was considered not to be relevant.
3.4 In cases where there is a margin in GM in the actual loading
conditions compared to the GM limiting curve (derived from SOLAS 90), the
Administration may accept that this margin is taken advantage of in the model
test. In such cases the GM limiting curve should be adjusted. This adjustment
can be done as follows:
d = dS . 0.6 ( dS -
dS is the subdivision draught; and
dLS is the lightship draught.
The adjusted curve is a straight line between the GM used in the model test at
the subdivision draught and the intersection of the original SOLAS 90 curve and
Paragraph 4 - Procedure for
4.1 Wave spectra
The JONSWAP spectrum should be used as this describes
fetch and duration in limited seas, which correspond to the majority of the
conditions worldwide. In this respect it is important that not only the peak
period of the wave train is verified but also that the zero crossing period is
It is required that for every test
run the wave spectrum be recorded and documented. Measurements for this
recording should be taken at the probe closest to the wave making machine.
It is also required that the model be
instrumented so that its motions (roll, heave and pitch) as well as its attitude
(heel, sinkage and trim) are monitored and recorded.
It has been found that it is not practical to set absolute
limits for significant wave heights, peak periods and zero crossing periods of
the model wave spectra, therefore an acceptable margin has been introduced.
4.2 To avoid interference of the
mooring system with the ship dynamics, the towing carriage (to which the mooring
system is attached) should follow the model at its actual drifting speed. In a
sea state with irregular waves the drift speed will not be constant; a constant
carriage speed would result in low frequency, large amplitude drift
oscillations, which may affect the model behaviour.
4.3 A sufficient number of tests in different wave trains
are necessary to ensure statistical reliability, i.e. the objective is to
determine with a high degree of confidence that an unsafe ship will capsize in
the selected conditions. A minimum number of 10 runs are considered to provide a
reasonable level of reliability.
Paragraph 5 - Survival criteria
The contents of this paragraph are
- Test approval
The following documents should be part of
the report to the Administration:
damage stability calculations for worst SOLAS and midship damage (if different);
.2 general arrangement drawing of
the model together with details of construction and instrumentation;
.3 inclining experiment and
measurements of radii of gyration;
nominal and measured wave spectra (at the 3 different locations for a
representative realisation and for the tests with the model from the probe
closest to the wave maker);
representative records of model motions, attitude and drift; and
.6 relevant video recordings.
Note: All tests must be witnessed by