58 ENGINEERING PROGRESS IN THE U. S. NAVY. 



Thus, in the Delaware, North Dakota, and Utah, the engine-room 

 weights and space required are as follows : 



Delaware. North Dakota. Utah. 



Engine-room weights, dry tons 728 .26 731-23 864 . 69 



Engine-room weights, wet tons 773.26 785.93 919.80 



Engine-rooms, length 44 feet 44 feet 60 feet 



Engine-room total width 50.5 feet 50.5 feet 51 feet 



Engine-room, square feet, floor space . . 2,222 2,222 3,060 



While the turbines of the North Dakota appear to be about on an equal- 

 ity with the reciprocating engines of the Delaware in the matters of weight 

 and space, these turbines were extremely uneconomical. Modern turbines 

 of this type would require an engine-room more nearly equal in length to that 

 of the Utah, and the engine-room weights would be considerably increased. 



While the reciprocating engine has a decided advantage in the features 

 of weight and space required, under present conditions, these advantages 

 would disappear should the necessary power to be developed be increased 

 considerably above what is now asked for, and the advantage would rest with 

 the turbine. Should such an increase of power be called for in future designs, 

 or should the ordinary cruising speed be made considerably higher than now 

 used, the Navy Department would undoubtedly abandon the reciprocating 

 engine and adopt one of its rotary rivals for the propulsion of its capital ships. 



Co7iditio7i (g)— Efficient Propellers for Maneuvering. — In considering this 

 condition, the relation of the backing powers of the vessel as compared with 

 the maximum full power ahead, and the time required from full speed ahead 

 until the vessel is dead in the water, will be taken as a comparative measure 

 of this condition. 



On Plate 41 are shown curves of indicated horse-power for backing for 

 the Delaware and of shaft horse-power for backing for the Salem, the 

 abscissae values being indicated horse-power and shaft horse-power in the ahead 

 motion. At the low abscissae values, where more boiler power is always avail- 

 able than is necessary for the actual ahead speed being used, the backing 

 power exceeds very considerably the ahead power in use, as when backing for 

 short periods the throttles can be opened wide and the boiler power available 

 be made use of. 



When all boilers are in use, which in the case of the Delaware occurs at 

 25,000 indicated horse-power for the main engine in the ahead motion, and 

 for the Salem at 14,000 shaft horse-power for the main engine in the ahead 

 motion, the maximum backing powers can be obtained. In the case of the 



