Attained index
Round 2 Discussion: Please see new discussions which are now appended to Appendix 3
New Paragraph 7.3 (ref. SLF 52/17/4 Annex A para. 2.3 - Norway) Add a new paragraph 7.3 for emphasis:
3 Each additional value of A calculated in accordance with paragraph 2 shall comply with regulation 6 and 7.1
Q26. Do you agree that this new paragraph should be added?
Yes China, Finland, Germany, Japan, Norway, CLIA, Italy, Spain, Denmark, UK, US, Sweden
No MI
Comments?:-
US: Note: this provision could be added directly to regulation 7.2.
Round 1 Discussion: There is almost unanimous support for this proposal (12/1) but US suggests that it could be added to Reg. 7.2. This would avoid having to re-number the remaining paragraphs and any possible cross-referencing problems but it might lose some impact; also it would need re-wording slightly:-
3 Each additional value of A calculated in accordance with [paragraph 2]
[these provisions] shall comply with regulation 6 and 7.1
Q26A Given the wide support for Norway’s proposal but acknowledging the US suggestion that the sentence could instead be added to Reg. 7.2 could you please state your preference?
New 7.3 France (with comment), CLIA
Add to 7.2 MI, Germany, Finland, Italy, Japan, Norway (with comment), UK, US (with comment), Sweden, Denmark
Comments?:-
MI: Accept as addition to 7.2.
France: This additional sentence seems to be obvious considering regulation 6.
Norway: We can both support the US suggestion or a new 7.3 as originally proposed.
US: Note: the original Norway proposal was “... comply with regulation 6.1 and 7.1.”
Round 2 Discussion: Apologies. Norway’s proposal was indeed referring to reg. 6.1 Thank you US. So if we add this sentence to reg. 7.2, as the majority agree, then it should read:
[
2 In the calculation of A, the level trim shall be used for the deepest subdivision draught and the partial subdivision draught. The actual service trim shall be used for the light service draught. If in any service condition, the trim variation in comparison with the calculated trim is greater than 0.5% of [Ls] [L], one or more additional calculations of A are to be submitted for the same draughts but different trims so that, for all service conditions, the difference in trim in comparison with the reference trim used for one calculation will be less than 0.5% of [Ls] [L]. Each additional value of A calculated in accordance with [paragraph 2] [these provisions] shall comply with regulation 6.1 and 7.1]
.Proposed Action: As we do not have a unanimous view on whether to append the sentence to reg. 7.2 or add a new reg. 7.3 and in view of the concerns elsewhere regarding interpolation between dl and dp, it is proposed that this discussion be continued in the wider context of an alternative proposal (see Appendix 3) which would change this paragraph considerably.
Further Comments?:-
[Co-ordinators Note: If new paragraph 7.3 is preferred then the subsequent paragraphs and EN shown in blue below will have to be re-numbered.]
3 When determining the positive righting lever (GZ) of the residual stability curve in the final stage of flooding, [Q27B] the displacement used should be that of the intact condition. That is, the constant displacement method of calculation should be used.
[Post SLF 53 note:- It was decided in the WG to add “in the final stage of flooding”, as highlighted in red, above (see also Reg. 7.6, Q27) but not to include a further clarifying sentence at the end saying “During intermediate stages of flooding the added weight method should be used”. However, it was agreed to include a new EN at this point. For origin of this text see discussions under Reg. 7.6, Q27, below]:-
Regulation 7.3
“The purpose of calculation of sequential flooding is to ensure that any intermediate flooding stage or phase will not lead to a lower si value. During intermediate phases of flooding, the added weight method is used and only one free surface needs to be assumed for water in spaces flooded during the current stage. In the final phase (full
phase) of each stage the lost buoyancy [constant displacement] method is used, so one free surface is assumed for all flooded spaces.”
[Further Note from the coordinators post SLF 53:- Maybe we need to consider changing the first sentence of the new EN slightly to introduce the idea that residual GZ is to be calculated for both IS and final stage flooding where appropriate eg:-
“In some damage scenarios it is possible that the residual GZ curve will reach its minimum value during intermediate stages or phases of flooding rather than at the final stage. In these cases, during intermediate etc etc………….
Your comments on this proposed change are invited under Q27B, below. After further discussions in the 2011 CG the following text changes were voted upon:-
Regulation 7.3
During For intermediate phases of flooding (see Reg. 7-2.2 with Explanatory Notes and Reg. 7-2.5.4), [Q27D(1)- 11-0 unanimous vote in favour of change]the added weight method is used and only one free surface needs to be assumed for water in spaces flooded during the current stage. In the final phase (full phase) of each stage the [lost buoyancy] [constant displacement] method is used, so one free surface is assumed for all flooded spaces. [In both cases, GZ is referred to the intact displacement]. [Q27D(2)]
[Should we allow for multiple free surfaces - opinion divided 5 “Yes” 6 “No.”]
[Q27D(3)]
4 The summation indicated by the above formula shall be taken over the ship’s subdivision length (Ls) for all cases of flooding in which a single compartment or two or more adjacent compartments are involved. In the case of unsymmetrical arrangements, the calculated A value should be the mean value obtained from calculations involving both sides. Alternatively, it should be taken as that corresponding to the side which evidently gives the least favourable result.
5 Wherever wing compartments are fitted, contribution to the summation indicated by the formula shall be taken for all cases of flooding in which wing compartments are involved. Additionally, cases of simultaneous flooding of a wing compartment or group of compartments and the adjacent inboard compartment or group of compartments, but excluding damage of transverse extent greater than one half of the ship breadth B, may be added. For the purpose of this regulation, transverse extent is measured inboard from ship’s side, at right angle to the centreline at the level of the deepest subdivision draught.
Regulation 7.5
1. With the same intent as wing tanks, the summation of the attained index A should reflect effects caused by all watertight bulkheads and flooding boundaries within the damaged zone. It is not correct to assume damage only [to the centreline] to one half of the ship breadth B and ignore changes in subdivision that would reflect lesser contributions.
R7.5 EN (Difference between B/2 and centreline)
Comments received from CLIA/CCSF between round 1 and 2:
The EN refer to the centreline of the ship rather than to B/2 for the transverse extent of the damage:
With the same intent as wing tanks, the summation of the attained index A should reflect effects caused by all watertight bulkheads and flooding boundaries within the damaged zone. It is not correct to assume damage only to the centreline to one half of the ship breadth B and ignore changes in subdivision that would reflect lesser contributions.
Coordinator’s Comments: It would seem that the proposal by CLIA/CSSF better reflects the wording in the Regulation – but what is the difference between the centreline and B/2?
CG Member’s Comments?:-
MI: Can agree CLIA proposal which provides more consistent wording.
Germany: At the ends of the vessel B/2 line crosses the CL, so that a different penetration depth is achieved.
France: Agreement on the proposal. B/2 is different from centreline where deepest waterline is not at B/2 from centreline.
Norway: Agree with CLIA, but the following might be clearer:
“It is not correct to assume only a damage penetration equal to one half of the ship breadth B and ignore lesser penetrations that would reflect lesser contributions.”
CLIA: B/2 may create damages beyond the CL, where the waterline has not the full breadth anymore (e.g. Forward end).
UK: No need to change “centreline” reference.
US: We can accept this proposed change.
Round 2 Discussion: There is some support for CLIA’s proposal (apart from UK); Norway has an alternative. We propose that this should go to the WG at SLF 53 to obtain further opinion and views on Norway’s proposal.
CLIA Q2 (for SLF53 WG). Do we prefer CLIA’s proposal or Norway’s amendment or no changes?
CLIA?
Norway ? No change?
Comments?:-
The WG at SLF 53 accepted CLIA’s proposal.
CLIA Q2