At the Swedish Maritime Administration, Sjöfartsverket, work with updating the nationalregulations on safety at sea and environmental effects has begun. The goal is to update theregulations and present them in a similar way as the international. The new regulation onfreeboard and stability for ships in national traffic are the first where this new structure is tobe applied.
This thesis focus on an analysis of the changes in the regulation on load line and stability andthe effects that this may have on existing ships in some of the sheltered and near coast areas inthe home waters of Sweden.
To achieve this, a number of general ship geometries have been designed to correspond to alarge number of existing ships, so that general conclusions from the study can be drawn.The ships that have been investigated are: traditional passenger ships, taxi boats, charterboats and Sea Trucks.
The ships in the study have been examined with respect to stability, motions in waves andstability after damages to find out if and how the suggested changes of the regulations willaffect the fleet.
But first, which are the major changes?
Freeboard: Today the demand on height of hatch comings, air inlets etc are stipulated as aminimum distance above the freeboard. In the new directives the aim is sharper connectionsbetween freeboard and stability. Therefore the new demands are based on a minimum heelangel to the openings instead of a fixed distance. The minimum heel angel will be 30° ingeneral and 40° to engine room for the E and D areas.
Stability: The Swedish demand on maximum righting lever arm, GZmax, for at least 30° ofheel, and a stability range of at least 60° is suggested to be abolished and replaced by weathercriterion with reduced wind pressure in the C and D areas for ships 24 m or longer.
Stability after damage: The only difference from the current regulations is that restrictedflotation after damage is initiated also in the E area for new passenger ships.
The results from the analysis show on small effects according to stability. On some shipsparticularly air inlets to engine room has to be moved to achieve the demands on freeboard.For ships maintaining service in the D area the ship motion calculation shows that windowsand doors can be exposed to quite large amounts of water for some headings and speeds,which means that windows and doors and there framings need to be of accurate strength.
Finally the analysis shows that there is a possibility to fulfil the restricted demands onstability after damage if the bulkheads are made watertight. The traditional passenger shipwill however only survive damages in the fore and aft peaks. Damages elsewhere willeventually result in loss of the ship.
2003. , 101 p.