Page 361 - Practical Ship Design

318 Chapter I1

With this change
(A - BB) (C, - 23)
Ff =A-
100
If Ff < 0.50, then F = 0.50 or the value by the formula given in 0 1 1.4.1, whichever
is smaller (Ff = F from formula).
If Ff > 0.50, then F = 0.50.

The factor of subdivision for ships 55 < L (m) < 13 1 lies between 1 .OO and the value
BB with interpolation using the factor S,. Where

3712 - 25L
S, =
19
(S, = 123 for L = 55; S, = 23 for L = 131)

For ships of L < 55, F = 1 .OO, but relaxations may be allowed in a limited number of
compartments.

11.6 PROBABILISTIC RULES FOR CARGO SHIPS

As the present regulations for probabilistic calculations for Passenger Ships given
in IMO Res. A 265 (VIII) are expected to be modified fairly soon to bring them
more into line with the regulations for Cargo Ships set out in IMO MSC 19 (58)
and become a new Part B 1 to SOLAS 74, it seems sensible to deal first, and in more
detail with the cargo ship rules and limit treatment of the passenger ship rules to
highlighting their principal differences from the cargo ship rules.
This section goes into the rules for the subdivision and damaged stability of
cargo ships in much greater detail than this book has given to any of the other rules.
This is done partly because these rules are very new and have yet to take their place
in naval architecture textbooks and, partly because they are very complicated and
require many lengthy calculations. These are so involved that they will almost
invariably be carried out by computer and it will be very difficult for designers to
understand the principles involved, which must be a precondition to them being
able to optimise their designs effectively. It is hoped that the manual treatment
presented here, albeit of a simplified case, will go some way towards helping an
understanding of the rules.
The rules, which apply to ships constructed on or after 1 February 1992, apply at
present to cargo ships with a subdivision length L, of over 100 m, although it is
hoped to extend them, probably with some modifications, to ships under this size.