LAUNCHING OF SHIPS IN RESTRICTED WATERS. 203 



The actual results of the action of the chain drags were as follows : — 



Velocity of ship at time of pivoting (also maximum) 16.2 feet per sec. 



Velocity of ship when fully afloat 15 feet per sec. 



Distance run after first drag took up 213 feet. 



Drags i-A — Port and starboard moved 213 feet. 



i-B — Port and starboard moved 200 feet. 



i-C — Port and starboard moved 190 feet. 



2- A— Port and starboard moved 166 feet. 



2-B — Port and starboard moved 158 feet. 



3-A — Port and starboard moved 126 feet. 



3-B — Were not moved. 



The total weight of chain drags actually coming into play was therefore 290 



launching weight 

 tons or ^-r s — . 



18 



Early in 1913, in preparing for the lavmching of the next ship, the fleet oiler 

 Kanawha, the development of friction brakes was actively taken up and experi- 

 ments conducted which gave assurance of the practicability of friction brakes, using 

 wire ropes passing through steel blocks under pressure. In the future design and 

 development of these brakes advantage was taken of the data on this subject pre- 

 sented by Mr. A. Hiley, Associate Member of the Institute of Naval Architects, in 

 a paper prepared by him and published in September, 191 3, issue of The Shipbuilder. 



The launching weight of the Kanawha was estimated at 4,000 tons (actually 

 was 4,100 tons), and it was therefore estimated, from friction data obtained in 

 experiments, that two launching brakes would be sufficient. A description of the 

 launching brakes used and other precautions taken to check the ship is given as 

 follows : — 



"The brakes were securely anchored on each side of the slip, 22 feet from the 

 center and about 80 feet aft from the bow. In each brake the friction length em- 

 ployed was two 2-inch diameter steel wire ropes (6 strands of 37 wires each), 600 

 feet long wound on reels fitted with brakes placed about 50 feet from the brake. 

 Springs tightened by screws produced the requisite pressure upon the ropes, which are 

 gripped between grooves in the upper and lower steel castings. In order that the pres- 

 sure applied by the tightening screws might bear equally on the two ropes, the 

 upper casting is formed with a ridge at the center to which the pressure is trans- 

 mitted by beams formed of channel sections and plate. To regulate the pressure on 

 the rope at will, three hand winches were provided and bull wheels fastened to the 

 nuts over the spring washers. These were connected by a ^-inch (diameter) end- 

 less wire rope. The two friction cables were connected by a heart shackle to a single 

 2-inch (diameter) wire steel hawser, 560 feet long, which was shackled to a pad on 

 the ship's side at frame 46 and on line with the second stringer, the same arrange- 



