3.1.2.1 The area under the righting lever curve
(GZ curve) should not be less than 0.055 metre-radians up to θ
= 30° angle of heel and not less than 0.09 metre-radians up to θ
= 40° or the angle of downflooding θf
footnote if this angle is less than 40°. Additionally,
the area under the righting lever curve (GZ curve) between the angles
of heel of 30° and 40° or between 30° and θf,
if this angle is less than 40°, should not be less than 0.03 metre-radians.
3.1.2.2 The righting lever GZ should be at least
0.20 m at an angle of heel equal to or greater than 30°.
3.1.2.3 The maximum righting arm should occur
at an angle of heel preferably exceeding 30° but not less than
25°.
3.1.2.4 The initial metacentric height GMo should
not be less than 0.15 m.
3.1.2.5 In addition for passenger ships, the angle
of heel on account of crowding of passengers to one side as defined
in paragraphs 3.5.2.6 to 3.5.2.9 should
not exceed 10°.
3.1.2.6 In addition for passenger ships, the angle
of heel on account of turning should not exceed 10° when calculated
using the following formula:
|
MR
|
= |
heeling
moment in kNm |
|
VO
|
= |
service
speed in m/s |
|
L |
= |
length of ship
at waterline in m |
|
Δ |
= |
displacement
in tonnes |
|
KG |
= |
height of centre
of gravity above baseline in m |
3.1.2.7 Where anti-rolling devices are installed
in a ship, the Administration should be satisfied that the above criteria
can be maintained when the devices are in operation.
3.1.2.8 A number of influences such as beam wind
on ships with large windage area, icing of topsides, water trapped
on deck, rolling characteristics, following seas, etc., adversely
affect stability and the Administration is advised to take these into
account, so far as is deemed necessary.
3.1.2.9 Provisions should be made for a safe margin
of stability at all stages of the voyage, regard being given to additions
of weight, such as those due to absorption of water and icing (details
regarding ice accretion are given in chapter 5)
and to losses of weight such as those due to consumption of fuel and
stores.
3.1.2.10 For ships carrying oil-based pollutants
in bulk, the Administration should be satisfied that the criteria
given in 3.1.2 can be maintained during
all loading and ballasting operations.
3.1.2.11 See also general recommendations of an
operational nature given in section 2.5 above.