Sec. 76.16 



DESIGN OF SPECIAL-PURPOSE CRAFT 



779 



bound to the dumping ground and inward bound 

 to the dredging area, traveUng like a normal 

 vessel, for about 31 per cent of the total time 

 [SNAME, 1908, p. 249]. 



Since the dumping ground must of necessity 

 be some deepwater area where the refuse will not 

 interfere with navigation in the future, and since 

 it may be rather well out to sea, self-propelled 

 dredges must possess a reasonable amount of 

 freeboard, sheer, and reserve buoyancy. 



A brief list of references, limited almost exclu- 

 sively to seagoing, self-propelled dredges of the 

 hopper type, follows: 



(1) Robinson, A. W., "Hydraulic Dredging," Cassier's 



Mag., Nov 1896, pp. 37-47 



(2) Cornbrooks, T. M., "Sea-Going Suction Dredges," 



SNAME, 1908, pp. 247-249 and Pis. 140-146 



(3) "The United States Suction Dredge New Orleans," 



Scientific American, 1 Jun 1912, front cover and p. 

 494. This vessel had a single centerline drag pipe, 

 with water jets on the scoop to help break up the 

 mud in the river bed. 



(4) Styer, W. D., "Hydraulic Seagoing Hopper Dredges," 



SNAME, 1924, pp. 28-48 



(5) Vaughn, H. B., Jr., "Seagoing Hydraulic Hopper 



Dredges," SNAME, 1941, pp. 262-299 



(6) Barakovsky, V., "The Dredgers," Schip en Werf, 



10 and 24 Jan 1947 



(7) Freeh, F. F., "Design and Construction of Seagoing 



Hopper Dredges with Special Reference to 

 Essayms," SNAME, Phila. Sect., 27 Apr 1949. 

 Abstracted in the publication Motorship, New 

 York, issue of Sep 1949, beginning on p. 38. See 

 also MESR, Dec. 1952, pp. 74-75, and Mar. 

 Eng'g., Mar 1954, pp. 48-57. 



(8) McCarthy, E. W., "Hopper Dredge (Ciudad de 



Barranquilla) for Government of Colombia," 

 Naut. Gaz., Mar 1950, pp. 14-15, 37. This is a 

 twin-screw dredge having a hopper capacity of 

 1,000 cu yd, an overall length of 240.5 ft and a 

 speed of 11 kt. 



(9) The general features of six shallow-water self- 



propelled twin-screw hopper-type dredges are 

 described and illustrated in Diesel Times, Apr 

 1951. This article also describes the seagoing, self- 

 propelled, twin-screw hopper dredge Pacific, built 

 in 1937, as well as the self-propelled hopper dredge 

 Sandpiper, built in Montreal and used on the 

 Lake Maracaibo Bar in Venezuela. 



(ID) Low, D. W., "Considering Dredgmg Craft," lESS, 

 1951-1952, Vol. 95, Part 6, pp. 438-484, esp. pp. 

 463-474; also Part 7, pp. 485-491. Paper is con- 

 cerned only with self-propelled dredges. There are 

 no diagrams of hopper recesses or doors but there 

 are discussions of them on pp. 472, 483. 



(11) French suction dredger Charles Belleville, MENA, 

 May 1952, p. 221 



LoA 309 ft D 19.75 ft 



Lbp 291 ft H 13.83 ft in fresh water 



Be 49.25 ft Hopper capacity is 35,310 ft^ 



There are two 27.5-inch diameter suction pipes, one 



on each side, with swivel joints below the waterline. 



The pipes are 72 ft long and the vessel can dredge in 



water up to 50 ft deep. There are twin spade rudders 



and 9 hopper doors under the bottom. 



(12) Scheffauer, F. C. (editor-in-chief), "The Hopper 



Dredge; Its History, Development and Operation," 



Off. of Chief of Engineers, U.S. Army, Washington, 



Gov't. Print. Off., 1954. An extensive bibliography 



is given on pages 375-376 of this reference. The 



following is taken from the Preface on page ix, as 



applying to this book: 



"It is not a manual by the use of which a novice 

 may design a dredge, but rather a guide for the use of 

 those who may be engaged in the construction and 

 operation of plant of this character." 



76.15 Self-Propelled Box-Shaped Vessels. 



There is a constant demand for a craft which has 

 the carrying capacity of the customary barge, 

 hghter, or scow but which is able to move itself 

 from place to place without the services of a tug. 

 Very often an equally important requirement is 

 that the craft be simple, cheaply or rapidly built, 

 or both, with hull boundaries having easy curva- 

 ture or else none at all. The ultimate in this respect 

 was probably reached by the so-called "rhino 

 ferries" of World War II, built up in the field 

 by bolting together standard steel boxes having 

 the form of rectangular parallelepipeds. 



The requirements for this group treat the 

 propulsion characteristics as being definitely 

 secondary to the load-carrying characteristics, yet 

 they are of httle practical use unless they can be 

 seK-propelled. The answer to this problem is to 

 accept the square corners and the flat sides and 

 to push or pull them, or both, by outboard drives 

 with propellers whose discs he below the bottom 

 plane of the box. Swinging these propellers about 

 a vertical axis solves the problem of steering, 

 backing, sidUng, and maneuvering, all at once. 

 Lifting them up about a horizontal axis solves the 

 shallow-water, repair, and maintenance problem. 

 The complete power plants, in packaged units 

 that float, are inserted in niches or slots provided 

 for them in the box assemblies, or are attached 

 temporarily in any convenient manner. 



A power unit with a rotating-blade propeller 

 might be used to propel a box-shaped craft, 

 except that the vertical blades projecting below 

 the plane of the bottom of the box would be 

 vulnerable in shallow water. 



76.16 Self-Propelled Floating Drydocks. A 

 floating drydock which can propel itself in the 

 open sea at a reasonable speed when nominally 

 unloaded, which can maneuver after a fashion, 



