Page 355 - Practical Ship Design

312 Chapter 11

(vii) Bow height correction

If the bow height is less than the minimum set by the formula below, the freeboard
must be increased by the deficiency.
[ 1.361
Min bow height = 56 L[ 1 - L/500]
cb + 0.68

L need not be taken as more than 250 m
Cb not to be taken as less than 0.68

Finally it should be noted that the use of a standard calculation sheet such as that
given in Fig. 1 1.1 eases and speeds the task and, above all, helps to avoid omissions.

11.3 SUBDIVISION - GENERAL

There have been international rules for the subdivision of passenger ships (carrying
more than 12 passengers) since the 1929 International Conference on Safety of
Life at Sea. The standard of subdivision required and the various factors involved
in the supporting calculations have been modified over the years but remain much
the same in the present rules, which are as set by the International Convention for
the Safety of Life at Sea (SOLAS) 1974 as modified by the 1978 protocol and 1981
and 1983 amendments.
The method of calculation in general use has however changed with the advent
of computers which make direct calculations easy and ended the use of the “B.0.T
floodable length curves” method.
The requirements of these rules were set out in a deterministic format, but have
now been joined by the alternative Passenger Ship Equivalent Regulations adopted
as IMO Resolution A.265 (VIII), which employs a probabilistic approach.
Until very recently, the only subdivision requirements for cargo ships were for
those with reduced freeboards (B-60) and classification societies requirement for a
minimum number of bulkheads, but this changed with the adoption by IMO in
1990 of Resolution MSC 19(58) which added a new part B 1 to the 1974 SOLAS.
This follows the general line of, but improves on, the passenger ship probabil-
istic method and it is expected that the latter will be modified in due course to bring
it more in line with the cargo ship method.
The probabilistic approach addresses the probability of damage occurring at any
particular location throughout the ship. It considers the likelihood of damage