Further discussions on Ross et al: "Damage stability characteristics of model RO/RO ferries

I have read, with interest, the proposals put forward in this paper for red ucing the probability of a RO/RO ship capsizing in the event of flooding of the vehicle deck. The results of the model tests in which the underdeck ta nk was subdivided by longitudinal bulkheads showed that, compared with the "conventional skip," flooding of any combination of compartments produced a considerable reduction in list angle for a greater ingress of water. Such results are much as expected since the reduction in free-surface effect ass ociated with the subdivision of a tank by longitudinal bulkheads is well kn own. However, these experiments did highlight the problems associated with the flooding of wing compartments. For both the six- and nine-compartment m odels, flooding of wing compartment No. 1 alone produced very large list an gles. Thus, the idea of the authors to fit quick-acting high-capacity pumps in each compartment is seen to be essential. I am, however, puzzled by the results produced for the model subdivided by two equally spaced bulkheads. The results in Fig. 7 show that when all thre e sections of the ship are flooded, it is assumed to the same depth, the li st angle was smaller than for the flooded "conventional" ship, but the amou nt of water added was greater. I have assumed that flooding of the "convent ional" ship means flooding of the entire car deck space within the end door s. If this same space is subdivided by two equally spaced bulkheads, then s urely when all three spaces are flooded to the same depth as per the "conve ntional" ship, then the weight of added water is the same for both ships an d the total second moment of area of the flooded surface, or "free-surface efffect," would be the same for both skips. Hence, the resulting list angle would be expected to be the same. Could the authors please explain what I have overlooked when comparing these results? Finally, why was the vehicle deck in the experiments divided into three? Was the length of the subdivisi ons based on the practical requirements arising from loading trucks, traile rs and other vehicles, or were three sections chosen purely as the basis fo r an academic exercise?.