ir)0 



HYDRODYNAMICS IN SHIP DESIGN 



Src. 61.3 



TABLE 64.e— Maneuvering 



The restricted waters forming part of the route and 

 the required ship operation in them are described as 

 follows: 



(27) Directly upon leaving its berth at Port Amalo the 

 vessel must make a 180-deg turn in close quarters 

 but tugs are available and will be used 



(28) The ship canal leading from Port Amalo to the sea 

 has a length of 25 mi and a minimum depth of 28 ft. 

 For 16 mi of its length the bottom prism width 

 varies between 400 and 475 ft. Banks and bed of the 

 restricted channel are of hard sand and gravel. At 

 Mile 20 in this restricted portion there is a circular- 

 are bend, with short transition sections at the ends, 

 having a total change in direction of 50 deg and an 

 inside radius of 3,800 ft; see Fig. 64.A. The bottom 

 width at midlength of this bend is 500 ft and the 

 depth is 32 ft. 



(29) Port Correo is at the head of ocean navigation on a 

 long, wide, fresh-water river, 204 mi from the sea, 

 with a minimum and fairly constant depth of 30 ft 

 in the dry season and a soft mud bottom. Large trees 

 and other flood debris are often encountered floating 

 in the river. 



(30) Adequate steering and maneuvering characteristics 

 shall be provided for traveling in the ship canal 

 leading from the sea to Port Amalo, on the basis of 

 meeting other large ships in this canal. It is not 

 necessary to meet these ships in the bend at Mile 20. 

 Similar requirements are established for the passage 

 of the river leading from the sea to Port Correo. 



(31) It shall be possible to berth the vessel at Port Bacine, 

 under its own power, in a slip terminated by U-shaped 

 walls of sohd masonry, 100 ft apart in the clear at 



■ the head of the slip and extending for a distance of 

 100 ft therefrom. An open-work wooden pier prolongs 

 one of these walls for a distance of 450 ft, indicated 

 in Fig. 64.B. The vessel must, under its own power, 

 make a 50- or 60-deg turn after backing out of the 

 sKp and prior to proceeding out of the channel to sea. 

 The clearance to the opposite side of the navigable 



area, measured from the extreme end of the wooden 

 pier and in line with it, is 1,500 ft. 



Specifically, when running at any practicable displace- 

 ment and trim, the ship shall be capable of: 



(32) Executing the transient portions of a turn, swinging 

 first away from and then back into a straight course, 

 involving changes of heading of from 25 to 30 deg 

 for each maneuver, and gaining or losing an offset 

 of 400 ft, perpendicular to the approach path, in a 

 curved run of 2,100 ft. This shall be accomplished in 

 a canal prism having a depth of 32 ft and a bottom 

 width of 400 to 500 ft, at speeds of from 6 to 8 kt, 

 and with not more than one-third the maximum 

 rudder angle. 



(33) Swinging bow to port and stern to starboard, and 

 vice versa, when operating the propulsion device (s) 

 in an astern direction, with negligible wind and in 

 water having a depth-draft ratio not exceeding 1.5, 

 or a maximum depth of 40 ft. It shall be possible to 

 execute this maneuver from a standing start or 

 from a straight approach path when moving astern 

 at a speed not exceeding 13 kt. 



(34) Executing a 180-deg turn within a tactical diameter 

 of 3,000 ft in deep water, with full rudder angle and 

 at an approach speed of 19 kt 



(35) When turning in accordance with (34), the angle of 

 heel shall be limited to 10 deg. A maximum angle 

 riot exceeding 8 deg is preferred. 



(36) At an ahead speed of 20.5 kt, on a straight course, it 

 shall be possible to execute a crash-back maneuver 

 and to stop dead in the water with a head reach not 

 exceeding 6 ship lengths 



(37) The machinery shall be capable of developing an 

 astern torque of 80 per cent of the rated ahead 

 torque, and an astern rate of rotation of 50 per cent 

 of the ahead rate, with the ship stationary in the 

 water, as at the end of a crash-back maneuver 



(38) If left to itself when running ahead in smooth water, 

 with no perceptible swinging motion and the rudder 

 stationary at zero angle, the ship shall not deviate 

 progressively from its original course. In other 



Fio. 64. A Scale Diagram of 50-Deo Bend in Canal Leading prom Port Amalo to the Sea 



