BUOYANCY AND STABILITY OF TROOP TRANSPORTS. 159 



Undoubtedly most of you are familiar with the method of making a ship unsinkable by 

 the use of watertight buoyancy boxes, which are inserted between the frames, under the 

 decks between the deck beams and supplemented by tiers of boxes installed along the sides 

 of the cargo holds — such a method, in fact, as was used on the Lucia. I understand that 

 this method was primarily designed for use on ships where a sufficient number of transverse 

 bulkheads did not exist, and where it would have required docking and considerable delay 

 in fitting extra bulkheads. However, in order to make this system efficient, enough boxes 

 would have to be installed to interfere seriously with the deadweight carrying capacity of 

 the vessel except in those cases where the cargo consisted of coal, steel, or materials of 

 great density. 



In peace times, the subdivision of passenger vessels by Professor Hovgaard's method 

 would appear to me to be more important than troop ships. In cargo vessels the question 

 of sufficient length of holds for stowing piles, shapes, rails, etc., can possibly be solved, with- 

 out destroying the permissible fioodable length, by fitting watertight ports or doors near the 

 tops of transverse bulkheads in line with the hatches. Such openings would permit the load- 

 ing and discharging through the hatches of pieces approximately the length of the cargo 

 hold. Even with long cargo holds it is sometimes difficult to stow material through the 

 hatches, and I heard of one case, during the war, where some 60-foot piles that were be- 

 ing sent to France were sawn in two in order to get them into the ship. 



Referring to ships, where such information as the design data, displacement curves, 

 rolling or inclining experiments are not available, it is interesting to note that charts have 

 been developed, which are to be published in the forthcoming issue of the Shipbuilding Cy- 

 clopedia, whereby the position of the transverse metacenter above base can be obtained by 

 inspection. The charts are so plotted that the intersection of the abscissa from the desired 

 draft with the curve of constant beam fitting the vessel will give the height of metacenter 

 above base. The accuracy of the height of the metacenter above base can be determined 

 by these charts to within one-tenth of a foot, providing the ships are not freaks or radically 

 different in shape from the ordinary form. 



Rear Admiral D. W. Taylor, C. C, U. S. N., Honorary Vice-President (Communi- 

 cated) : — This paper summarizes in a general way a very large amount of work done by Pro- 

 fessor Hovgaard when temporarily a valued member of the staff of the Bureau of Construc- 

 tion and Repair during the Great War. To the naval architect of the present day, given the 

 plans of a ship, the position of her center of gravity, and plenty of time, solutions of questions 

 of buoyancy and stability are easy. In the stress of the war, as a usual thing there were no 

 plans, and no time. A former German vessel between 500 and 900 feet was to be fitted at 

 a yard tO' carry the maximum number of troops, and must sail the moment she is so fitted, 

 and the damages done the machinery by her former owners had been made good. Three 

 things were done as a rule: — 



First, structural additions helpful to buoyancy and stability that could be completed 

 within the time and with the facilities available were made. 



Second, holes were cut in longitudinal bulkheads to render it reasonably certain that, 

 if a transport were sunk by a submarine, she would not first capsize. 



Third, fixed ballast was added as necessary, such that, combined with the available 

 water ballast, acceptable metacentric heights were obtainable, as explained in the paper. 



