1 A sister ship is a ship built by the same yard
from the same plans.
2 A lightweight check is considered the acceptable
means of being satisfied that the data from a lead sister ship’s
inclining test can be used for a subsequent ship. The Administration
may request regular repeats of inclining tests and/or require each
individual passenger ship to be inclined, as detailed below.
3 For any newly built sister ship with known differences
from the lead sister ship, a detailed weights and centres calculation
to adjust the lead ship’s lightship properties should be carried
out. The validity of the calculated lightship properties should be
assessed by carrying out a lightweight check unless the implications
regarding the stability of the ship indicate that an inclining test
should be performed. The acceptable deviation of lightship displacement
should be:
|
|
For
L≤50m
|
2% of the lightship displacement of
the lead ship.
|
|
|
For
L≥160m
|
1% of the lightship displacement of
the lead ship.
|
|
|
For
intermediate length
|
by linear interpolation.
|
In addition, the deviation of lightship
longitudinal centre of gravity should not exceed 0.5% of the LBP of
the lead ship. Where the deviation exceeds either of these limits,
an inclining test should be carried out. Where the deviation is within
these limits the actual lightship weight and longitudinal centre of
gravity derived from the lightship check should be used in conjunction
with the higher of either the lead ship’s vertical centre of
gravity or the calculated value.
4 For a ship in service which undergoes alterations
with calculable differences in lightship properties which materially
affect the stability information supplied to the master, a detailed
weights and centres calculation to adjust the lightship properties
should be carried out. To avoid an inclining test, the deviation of
lightship displacement should not exceed 2% of the original approved
lightweight or 2 tonnes, whichever is greater, or that approved following
the most recent major alteration or conversion. In addition, the deviation
of lightship longitudinal centre of gravity from the original or that
approved following the most recent major alteration or conversion
should not exceed 1% of the LBP of the ship. Where the deviation exceeds
either of these limits, an inclining test should be carried out. Where
a ship is within these limits the calculated values of lightweight,
lightship LCG and lightship VCG should be used in all subsequent stability
information supplied to the master.
5 For all passenger ships, a lightship survey
should be carried out at periodical intervals not exceeding five years
to verify any changes in lightship displacement and longitudinal centre
of gravity. The ship should be re-inclined whenever, in comparison
with the originally approved stability information or that approved
following the most recent major alteration or conversion, the deviation
of the lightweight and/or lightship longitudinal centre of gravity
exceeds the limits in paragraph 4 above. Where a ship is within these
limits, the values of lightweight and lightship LCG derived from the
lightship survey should be used in conjunction with the VCG derived
from the most recent inclining experiment in all subsequent stability
information supplied to the master.