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February, 1912 Raising the Dry Dock HE dry dock Dewey, which sank at Olon- Gabo; Subic bay, Philippine . Islands, in "May, 1910, "is 2 steel floating dock, 501 ft. over all and 100 ft. wide, with a lifting capacity of 20,000 tons. On the afternoon of May 23, 1910, the dock was lowered to a depth of 26 ft. over the keel blocks, leaving a freeboard of 15 ft. on the side walls. The lowering of the dock a night in advance was in accord- ance with the usual custom of having the dock in readiness and thus avoiding delay. In «the: early morning it° was noted "that. the' "dock had taken 4 slight' list' to port, Pie watchman corrected this by admitting water, but the list again appeared and the dock finally sank from causes then unknown. The raising of the dock formed an interesting paper by Naval Constructor L. S. Adams before the recent meeting of the Society of Naval Architects and Marine Engin- eers, in New York, to which William T. Donnelly, the well-known dock designer, contributed some valuable discussion. Mr. Donnelly said: Credit to the Men. "In contributing to the discussion of this paper, I feel that I must some- what reverse the order of the subjects 2s considered by the paper. To me the most important part is the per- sonal achievement of the men who ac- complished the work of raising the dock. We, the engineers, can plan and cause construction to be created, but after completed and tested they pass out of our charge.and care, and in this instance we have an example of a structure requiring about two years for its completion at a cost of approximately © $1,500,000, 'being to all intents and purposes completely lost or rendered practically valueless within a few hours, save for the knowledge and energy of those en- gineers who happened to be on hand at that particular time, and to them I wish to pay the tribute which I consider due; that is, that the knowl- edge and ability shown in raising and floating the dry dock Dewey un- der the conditions, was as great or greater than that required to design and construct the dock. "To lay out the work for the month's campaign which resulted so ' satisfactorily, was a stupendous un- dertaking. The paper deals with only the barest details of the accomplish- THE MARINE REVIEW WititiAM JT. DoNNELLY ment. The getting together and con- necting up of the pumps with their steam and water piping, the gather- ing of vessels and floats to provide the necessary power, the building of the cofferdams, and the correlating of all this equipment to get the most out of it in the very short time that the continued operation, day and _ night under high pressure, is a test which tries out men and material, and the successful accomplishment of the work should not pass without its 'proper recognition by engineers, and I, for one, am glad to have the oppor- -- tunity to acknowledge the high qual- ity of the work. High Moral Courage. "The second important feature of this paper, to which I should like to call attention, is the very 'high appreciation I have for the bureau of yards and docks, and the naval construction bureau for the very frank and complete manner in which this information has been presented. My entire engineering experience leads me to believe that it takes the very highest kind of moral courage to allow all the facts to speak for themselves under all circumstances, and I am equally certain that, given . this courage, the result will always more than justify the action. "Floating dry docks are of very great importance, both from a military and commercial point of view, and may be said to be an absolute neces- sity. The number, however, is very limited relative to ships, and our ex- perimental and recorded knowledge relative to their operation is corres- pondingly. limited. Therefore, the knowledge contained in this paper is of the very greatest importance to various 43 Dewey those who, like myself, are earnestly studying the problem of their con- struction. ye "T should now like to take up some of the matters of information which the paper contains and comment upon them relative to the effect they should . have upon the future design and con- struction of floating dry docks. "Generally speaking, it would seem 'that the cause of the sinking of this dock was, first, the corrosion of the air discharge pipes, which, being sub- merged when the dock was lowered allowed water to enter on. the port side, causing the dock to list, and that, as soon as this list was estab- lished, the water commenced to flow from the high side to the low side through the center bulkhead, through deteriorated pipe connections to the compartments and through leaky valves, and that, as the list in- creased, the corresponding flow of water also increased very rapidly, re- sulting in that side of the dock be- coming entirely submerged until it rested upon the bottom. Leakage Through Center Bulkhead. "As an indication of the amount of leakage through the center bulkhead, the experience in raising the dock is quite conclusive. It appears that, with a considerable inclination, it was more than could be handled by a 24-in. centrifugal pump. Part of this was through leaky valves and defect- ive piping, but a great portion must have been through defects in the bulkhead itself. The inadequacy of the interior bulkheads was _ also shown by the fact that it was im- possible to raise the dock with com- pressed air, the air escaping in one case through five bulkheads, one of which was the center bulkhead. Bear: ing these facts in mind, what are the lessons that we are to learn and the additional precautions that we should take hereafter in designing similar structures? ; "First, I should like to point out that the dock was provided with pumping machinery only on one side and that, consequently, the center bulkhead was pierced with many pipes, upon the integrity of which and their valves the stability of the structure as a whole was entirely de- pendent. I should lay down as a positive rule that no openings what- ever should be made through the cen- ter bulkhead of a floating dry dock and that évery possible precaution should be taken to have this bulkhead absolutely watertight. I would call