Regulation 25-4
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Statutory Documents - IMO Publications and Documents - Resolutions - Assembly - IMO Resolution A.684(17) – Explanatory Notes to the Solas Regulations on Subdivision and Damage Stability of Cargo Ships of 100 Metres In Length and Over – (Adopted on 6 November 1991) - Annex - Explanatory Notes to the SOLAS Regulations on Subdivision and Damage Stability of Cargo Ships of 100 Metres in Length and Over - Part B - Regulation 25-4

Regulation 25-4

Parent topic: Part B

Paragraph 1

 The regulations do not specify at which side of the ship damage should be assumed. Where there is 100% symmetry about the ship centreline of:

  • the main hull,
  • erections which are given credit for buoyancy in the damage stability calculations,
  • the internal subdivision restricting the extent of flooding for the damage stability calculations,

 it is clear that damage may be assumed on either the port or starboard sides, each producing the same value of A.

 It is rare for complete symmetry to exist and therefore, in theory, two calculations for A should be made, one assuming port damage and the other starboard damage.

 However, the calculated A value may be taken as that which evidently gives the less favourable result. Otherwise the mean value obtained from calculations involving both sides is to be used.

Paragraph 2

where:
p i = is independent of the draught but includes the factor r;
s i = is dependent on the draught and includes the factor v; and is a weighted average of s-factors calculated at draughts of dl and dp .

 It is recommended that the product pisi should be calculated using five decimal places, while the final results, i.e. the indices A and R should be to at least three decimal places.

Paragraph 3

 For any ship, including those with a raked keel, the design waterline should be used as a reference for level trim.

Paragraph 6

 See figures in appendix 2.

 When there is more than one longitudinal subdivision to consider, penetration need not extend to the ship's centreline if such penetration does not provide any contribution to the attained subdivision index.

 For example, when a pipe tunnel in the centre of a ship is fitted, damage to this tunnel may cause heavy progressive flooding leading to loss of the vessel. In this instance the penetration may be stopped outside the pipe tunnel, and the p-factor multiplied by the factor r, as calculated for a penetration in a wing compartment only. If a wing compartment is fitted in addition, it is possible to take account of two different penetrations, and applying the factor (r2-r1 ) rather than (1-r), as obtained when the damage is extended to the centreline.

  r 2 is then the r-value for penetration to the pipe tunnel only, and r1 is the r-value for penetration to the longitudinal bulkhead only. See Figure A-11 (VHi) in appendix 3.

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