As a minimum, the calculation of A shall be carried out at level trim for the deepest subdivision draught d s and the partial subdivision draught d p . The

[actual] [anticipated] service trim shall be used for the light service draught d_l. If in any anticipated service condition within the draught range from d_s to d_p the trim variation in comparison with the calculated trims is greater than 0.5% of L_s, one or more additional calculations of A are to be performed for the same draughts, but including sufficient trims to ensure that for all intended service conditions the difference in trim in comparison with the reference trim used for one calculation will be less than 0.5% of L_s. The partial index A_l is considered constant for the purpose of these calculations.

--- Regulation 7.2

1. The calculations for differing trim should be carried out with the same initial trim for the partial and deepest subdivision draughts. For the light service draught, the actual service trim should be used (refer to the Explanatory Notes for Regulation 2.11).

Regulation 7.2 (ref. SLF 52/17/4 Annex C para. 3- Norway)

3.1 Note 1 does not correspond with the principles in 5-1.4 regarding trims. Note 1 and 2 will in any case become redundant and could be deleted if the regulations are amended as proposed in Annex A of SLF 52/17/4.

2. Each combination of the index within the formula given in regulation 7.1 should not be less than the requirement given in regulation 6.2. Each partial index A should comply with the requirements of regulation 6.1.

3. Example:

Based on the GM limiting curves obtained from damage stability calculations of each trim, an envelope curve covering all calculated trim values should be developed.

Calculations covering different trim values should be carried out in steps not exceeding 1% of Ls. The whole range including intermediate trims should be covered by the damage stability calculations. Refer to the example showing an envelope curve obtained from calculations of 0 trim and 1% of Ls.

Regulation 5-1.3 and 5-1.4 (see also regulation 7.2) (ref. SLF 52/17/4 Annex C para.

1 - Norway)

1.2 The following is transferred from 7.2, note 3 [to 5-1] and amended where underlined:-

3 If multiple GM limiting curves are obtained from damage stability calculations of differing trims in accordance with regulation 7, an envelope curve covering all calculated trim values should be developed. Calculations covering different trim values should be carried out in steps not exceeding 1% of Ls. The whole range including intermediate trims should be covered by the damage stability calculations. Refer to the example showing an envelope curve obtained from calculations of 0 trim and 1% of Ls.

1.3 Move the sketch from 7.2, note 3 accordingly.

Regulation 7.2 (ref. SLF 52/17/4 Annex C para. 3- Norway)

3.2 It is proposed to move the contents of note 3 regarding design of limit curves to 5-1.4 or delete it as redundant.

Q25. Norway proposes to replace the existing text of Reg 7.2 and re-organize and re-number the remaining regulations and EN in association with Reg 5-1.4 (see Appendix 1 for complete version). It is assumed that these amendments are intended to replace Norway’s earlier proposals in SLF 51/3/2. An alternative proposal from the UK in 51/3/2 suggests that maximum allowable KG’s rather than minimum GM’s should be used and that the limiting curves should be presented as a variation against trim for the 3 specified draughts (assuming linear interpolation between draughts). Combined critical KG curves would then cover all the relevant stability criteria, both intact and damage. No specific changes to the text of the Regulations or EN were proposed.

As this is a fairly complex issue we would simply like to ask if there is support at this stage for Norway’s package of proposals for Reg 7 as shown in Appendix 1;

are there any objections, questions or alternative proposals?

Yes (Accept Norwegian proposals in App 1)

China, Finland, Germany, MI (but see comments), Norway, Italy, US

No Japan, Spain (see comments), Denmark, UK, Sweden Comments, reasons, alternative proposals?:-

Finland: Support Norway. No support for UK proposal. Prefer GM-limiting rather than KG-limiting curves.

Germany:Support Norway’s proposal (strong objections against UK proposal!)

Japan: It is not clear how to deal the case that the trim in the loading case between Dp and Dl exceeds the range of calculated trim.

MI: Could support Norway’s proposals because they are in a package but the UK suggestion of using max allowable KGs and resulting combined critical KG curves has considerable merit and should be further discussed before a final decision is made.

CLIA: CSSF EN work.

Italy: See also comments on item 21.

Spain: We accept the proposals except the trim versus draught graph. As we have explained, it is not very clear in our opinion. We have made one proposal:

- To change the axis (e.g. draught X axis and trim Y axis):

Spain (continued): Regarding UK proposal, we think it is more clear than the other proposed trim limit curve (we can accept it), but we think that for the master is more intuitive to have GM or KG curves versus draught (and different curves depending on trim), e.g.:

Max Allowable KG vs Draught

4 4.5 5 5.5 6 6.5 7 7.5 8 8.5

4 4.5 5 5.5 6 6.5 7

Draught (m.)

Critical KG (m.)

Trim Aft Trim 0 Trim Fwd

End of Spain’s Proposals

Denmark: We wonder if it is worth considering whether the trim limits should be restricted to no greater than the calculated conditions, as it is for deterministic damage stability. Consider that if the partial indices are at 0.5R or 0.9R for a particular trim, allowing 0.5%L more trim will most certainly reduce the attained partial indices.

US: We support in principle; details subject to further consideration.

Round 1 Discussion: In view of the complexity of the proposals and the number of comments received, this table has been duplicated in Appendix 1 which contains all the changes proposed by Norway. So please turn to Appendix 1 for continuation of the discussion and the Round 2 questions. This also applies to Q21 and Q23.