202 



LAUNCHING OF SHIPS IN RESTRICTED WATERS. 



twentieth of the launching weight to bring the vessel to rest in from 200 to 300 

 feet after leaving the ways. 



The large building slip at the More Island Navy Yard is set nearly at right 

 angles to the channel, which is 1,230 feet wide. It is therefore necessary to check 

 any large vessel by other means than anchors, as the space available is not sufficient 

 for direct checking or for slewing the stern. The Prometheus (fleet collier) was 

 launched in 1908, using chain drags to stop her. Although the drags successfully 

 stopped the vessel within 200 feet, the work necessary to pile the chain, to com- 

 pletely clear the slip of obstructions (blocking, shoring, etc.), and finally to un- 

 tangle the masses of chain, was extensive and costly. The next vessel launched 

 (August, 1912) was the fleet collier Jupiter, of 19,000 tons loaded displacement and 

 5,207 tons launching weight. The problem of stopping this vessel was gone into 

 very carefully, and the final conclusion was to use chain drags. Friction brakes 

 were considered, but the development of the idea at that time was not sufficient 

 to warrant the trial. A description of the chain drags as used in launching the 

 Jupiter will be of interest. In all 390 tons of chain were used, coiled in fourteen 

 coils ranging from 10 to 50 tons each, the smaller coils or drags being arranged 

 to take up first in succession to minimize the danger of parting the cables due to a 

 too sudden stress. Seven piles of chain were placed on each side, connected up as 

 shown below to three 2-inch (diameter) wire ropes attached to pads on the ship. The 

 disposition of drags, wire ropes, and pads was as follows: — 



As a further precaution, two 3,000-pound anchors, one port and one starboard, 

 were secured on the side of the ship at frame 136, each with lo-inch hawser stopped 

 up at intervals and carried through stern chocks. One of these anchors was to be 

 dropped on a signal given from the bridge should the drags fail to act. These 

 anchors were intended to turn the stern up or down stream as seemed most 

 expedient. 



