2.1 The vessel to be Coded shall be subjected
to the stability verification test when as close as practicable to
the loading condition used for the righting moment curve to be checked,
as defined in ISO 12217. The purpose of the test is to verify that
the stability of the vessel is adequately described by the righting
moment curve of the "First of Type" used for ISO 12217 assessment.
Where this is not adequately demonstrated, this curve shall be corrected
as described below before reassessment of the stability compliance.
2.2 The test shall be conducted in calm conditions.
The vessel shall be heeled to both port and starboard as much as practicable
by the application of a heeling moment sufficient to produce a heel
angle of firstly at least three degrees in either direction, and secondly
at least five degrees, i.e.: two heeling moments and four heel angles
in all. The heeling moments and angles of heel shall be recorded as
precisely as practicable.
2.3 The heeling moments shall be applied using
weights that are part of the loaded condition of the vessel, and moved
through a known amount. The righting lever deduced for that angle
of heel is given by:
where:
|
GZ |
= |
righting lever
(m) |
|
w
|
= |
mass
moved to produce the heel angle (kg) |
|
h
|
= |
distance
parallel to design waterline mass was moved through to produce heeling
moment (m) |
|
Φ
|
= |
angle
of heel produced (degrees) |
|
Δ |
= |
displacement
of vessel as used to derive the GZ curve in question (kg) |
2.4 Where the weights used to create the heeling
moment have to be moved vertically from their normal location in order
to generate the necessary heeling moment, the resulting measured righting
moment should be corrected for the change in the vertical centre-of-gravity
of the craft. The correction = GG1sinΦ,
added to the measured GZ when the weights were raised during the heeling
test, where GG1 is the shift in vessel VCG due to the weights
moved.
2.5 The First of Type righting moment curve shall
be considered acceptable for stability assessment if the average deviation
of the four values obtained at 2.3 and corrected according to 2.4
below the righting moment curve is equal to or less than 5%. Where
the deviation is above the curve, no limit shall apply.
2.6 Where the average deviation of the four values
obtained at 2.3 above from the righting moment curve is more than
5%, the First of Type righting moment curve shall be corrected throughout
the range of heel angles by an amount equal to GG1sin Φ, where Φ is any heel angle. The value of
GG1 used for this correction shall be obtained as follows:
where:
|
δn
|
= |
difference
in measured GZ from First of Type GZ curve at angle δn,
for the four values obtained according to 2.2 and calculated according
to 2.3 and 2.4 above.
|
2.7 Where the righting moment curve is modified
in this way, the stability shall then be reassessed using the requirements
of chapter 11 of the Code.