Unexplained List After Ro-Ro Cargo Loading
M/V Hordaland, a 12,000 GT ro-ro passenger ferry, is at Bergen preparing to sail for Stavanger with 40 trailers and 120 passengers. Departure draft is 6.2 m, corrected GM is 0.35 m, and the vessel has a 3° starboard list. During loading, a ballast transfer from No.2 port to No.2 starboard was interrupted for a lunch break; No.2 starboard is now 85% full and No.2 port is 20% full. The stability booklet requires a maximum departure list of 2° and a minimum GM of 0.15 m. The forecast for the fjord is west 30 kn on the beam. Cargo lashings have been checked. The chief officer says the list is 'only cosmetic' and the schedule is tight.
1. Diagnose the cause of the list and assess the risk of sailing as loaded.
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The list is not cosmetic. It is caused by a transverse ballast moment: No.2 starboard at 85% against No.2 port at 20% creates a moment to starboard, and both tanks have free surface. The 3° list exceeds the booklet maximum of 2° for departure. With a 30 kn beam wind, wind heel will add to the list, reducing starboard freeboard and increasing the risk of cargo shift, ramp contact, and passenger discomfort. GM 0.35 m is above the minimum 0.15 m, but free surface in two tanks reduces effective GM; the loading computer must be checked with all free-surface corrections included. The chief officer's view is unsafe, and schedule pressure is not a reason to accept a known stability exceedance.
2. How would you correct the list and verify that the vessel meets the departure criteria?
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Correct by transferring ballast from No.2 starboard to No.2 port, or by pressing up one tank completely to eliminate free surface. Calculate the transverse moment from each tank: weight in the tank multiplied by its transverse arm from the centreline. Use the loading computer to iterate until list is 2° or less, preferably 0°, and GM is at least 0.15 m with free-surface corrections applied. Check freeboard at the lowest point, deck-edge immersion, and lashing loads. If the ballast system cannot correct the list before the weather arrives, reduce or redistribute cargo, or delay sailing.
3. What decision and communication should the master make?
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Do not sail on the chief officer's assurance or on schedule pressure. Decide to correct the ballast condition first, then recheck list, GM, freeboard, and lashings. Inform the terminal and passengers of the delay. Document the stability check and the reason for the delay. If the vessel sails after correction, monitor list and GM during the passage, avoid beam seas where possible, and keep passengers clear of the vehicle deck during heavy weather. The final decision rests with the master.