146 CHANGE OF SHAPE OF RECENT COLLIERS. 



tained ; but these observations have been based largely on the idea that a steel ship 

 does not change much, and that if much change of shape occurs, something 

 is wrong. It would probably surprise a good many owners to learn that a 500- 

 foot ship can bend over 6 inches due to loading and be none the worse for it ; also to 

 know that a rise in temperature of only 7 degrees may change the shape by an inch. 



The amount of change in shape in the keel line of battleships is another matter 

 which is not as fully realized as it ought to be, especially in the case of the new 

 ships with several turrets, and I hope that some one of the members of the Society 

 who is in possession of the data, will take the trouble to give us the results found 

 by comparing the alignment of turret roller paths afloat and in dry dock. 



The observations shown on Tables i, 2, and 3, Plates 83 and 84, were taken 

 on the colliers built for the Navy by the Maryland Steel Company at Sparrow's 

 Point, the Neptune, Orion and Jason. The last two were sister ships, built on 

 what is generally known as the Isherwood System, while the first was similar but 

 slightly longer and built with transverse framing. 



The Neptune was the first ship built and shows considerably more change of 

 shape than the two ships with longitudinal framing, having a maximum of 6Y2 

 inches against less than 5 inches for the Jason and only 3^ inches for the Orion. 

 In this statement I omit the Jason's condition of April 3, 1913, as she was at that 

 time damaged by a dynamite explosion on a vessel lying near her. 



From these tables the curves shown on Plates 85, 86 and 87 have been 

 plotted. I shall not attempt any detailed discussion of the data, as they speak for 

 themselves, but a few points of general importance will be referred to. 



The sister ships show surprisingly different results. The Orion showed con- 

 siderable hogging immediately after launching, while the Jason, like the Neptune, 

 remained nearly straight. Moreover, the Orion when loaded showed no sagging, 

 but the point of maximum hogging simply moved aft somewhat as if her cargo 

 had rolled her "hump" toward the stern. The Jason, on the other hand, behaved 

 like the transverse-framed Neptune and changed from slight hogging when light to 

 a considerable sag when loaded. The cause may lie in the difference in the tank 

 tops, as I shall explain. 



After the observations had been made on the Neptune, the question arose : "If 

 a ship bends, that is, if the main deck is forced up or down, what happens to the 

 bottom?" As a result of this, on the two later vessels sights were taken through 

 openings left near the foot of each bulkhead in the cargo holds. Observations of 

 the height of the sight line above tank tops are given on Tables 2 and 3, Plates 

 83 and 84, while corresponding curves are plotted on Plates 86 and 87 ; these show 

 that the Orion's tank top was convex, while the Jason's was concave before launch- 

 ing. As all three of these vessels were built on the same ways, it is unlikely that the 

 blocks settled so differently, and it is therefore probable that the curve in the tank 

 top was due to slight structural unfairness. This initial convexity in the Orion, 

 which remained even when loaded, would seem a desirable thing, as it apparently 

 resulted in reducing considerably the maximum change of shape, and may have 

 acted to a small extent after the manner of an arch. 



