The RFI loss scenario thus considered that the forward trim of the vessel (brought about by flooding of the stores spaces, chain lockers and forepeak) was the initiating factor in a chain events leading to the final loss.
Whilst the evidence indicating that the Derbyshire’s hatch covers had failed due to seawater loading is conclusive, the court was unable to demonstrate in a satisfactory manner that the vessel’s slight forward trim was indeed the causative factor of that failure.
Having noted the limitations of the MARIN model tests used by the RFI, we argue, on the contrary, that the forward trim that was taken into account would not necessarily have been sufficient in itself to bring about the tragedy.
The loss of forward freeboard due to flooding and trim, about 1.3m only (excluding flooding of the Fuel Oil Deep tank), was not of a magnitude that could significantly alter the ‘ballpark’ hatch cover loads expected to arise from the large waves and ship motions generated by typhoon Orchid. The hatch covers in this trimmed condition would still be about 8.9m above the sea surface and only about 630 mm below their normal position, with the ship in an undamaged but fully laden condition.
Therefore, the small trim by the bow could not realistically and satisfactorily explain the cycle of floodings and the resulting sinking that were suggested by the inquiry. Yet, under the label of unknown and unforeseen causes for the loss of the vessel, the RFI piled together and discarded many other possible alternatives.
Out of this class of unforeseen causes, we have now decided to present one alternative theory in which the spare propeller carried onboard the vessel, due to its position and location on the upper deck as well as due to its securing arrangements, becomes detached from its deck supports and wreaks damage to adjacent weathertight structures.
The damage to these structures, it is argued, would lead to flooding, the failure of the hatch covers, flooding and ultimately to the loss of the vessel.
Quite understandably, this alternative scenario, again, opens up discussions about liability and compensation, and this was something, which the RFI tried very hard to avoid.
(More details, explanations, diagrams and supporting evidence are contained in the attached DOCUMENT)