1. For decked vessels with a length less than
30 m, the following approximate formula for the minimum metacentric
height GMmin (in metres) for all operating conditions should
be used as the criterion:
where
|
L |
= |
Length of the
vessel on the waterline in maximum load condition (in metres) |
|
ls
|
= |
Actual
length of enclosed superstructure extending from side to side of the
vessel (in metres) |
|
B |
= |
Extreme breadth
of the vessel on the waterline in maximum load condition (in metres) |
|
D |
= |
Depth of the vessel
measured vertically amidships from the base line to the top of the
upper deck at side (in metres) |
|
f |
= |
= Smallest freeboard measured vertically
from the top of the upper deck at side to the actual waterline (in
metres) |
The formula is applicable for vessels having:
-
(i)
between 0.02 and 0.20;
-
(ii)
smaller than 0.60;
-
(iii)
between 1.75 and 2.15;
-
(iv) sheer fore and aft at least equal to or exceeding
the standard sheer prescribed in Regulation 38(8) of
the International Convention on Load Lines, 1966;
-
(v) height of superstructure included in the calculation
not less than 1.8 m.
For ships with parameters outside of the above limits the formula
should be applied with special care.
2. The above formula is not intended as a replacement
for the basic IMCO criteria (Resolution A.168(ES.IV)), but is to be
used only if circumstances are such that cross curves of stability,
KM curve and subsequent GZ curves are not and cannot be made available
for judging a particular vessel's stability.
3. The calculated value of GMmin
footnote should be compared with actual GM values
of the vessel in all loading conditions. If a rolling testfootnote, an inclining experiment based on estimated
displacement or another approximate method of determining the actual
GM is used, a safety margin should be added to the calculated GMmin.
Figure 1 Simplified Stability Criteria (fishing vessels under 30 m in
length)