See. 72.17 



DESIGN FOR CONFINED WATERS 



ri73 



In this connection it is to be noted from Figs. 

 72.E and 72.F that whereas the Hillman boat 

 depicted there carries a pair of screw propellers 

 having a diameter large in proportion to the 

 draft, there is only a vestige of a tunnel in the 

 afterbody plan. Further, the down slope abaft 

 the propeller position is rather small. This craft 

 is reported to perform excellently in all respects, 

 and the principal reason given is the free flow of 

 water to the wheels [E. W. Easter, unpubl. Itr. 

 of 2 Feb 1951 to HES]. 



72.16 Handling of the Vibration Problem in 

 Shallow Water. Sees. 35.13 and 35.14 describe 

 the manner in which vibration of the ship hull 

 and its many smaller elements is manifested in 

 motion of the water and is magnified in a shallow- 

 water region. The only known method of avoiding 

 these objectionable effects is to eliminate the 

 vibratory forces at their source. The periodic 

 forces generated by the blades of various pro- 

 pulsion devices are reduced, as explained in 

 Sec. 33.15, first by reducing the thrust loading, 

 using larger thrust-producing areas and lower 

 slip ratios; then by cutting down the high loading 

 in certain regions, such as those of high wake. 



When water can not flow freely to a propulsion- 

 device position from one direction, because of 

 confined-water limitations, good design dictates 

 that means be provided whereby it can come in 

 from another direction. This is the reasoning 

 behind the oblique tunnels described in Sec. 

 72.13. However, it can not always be assumed, 

 without the confirmation of flow tests with 

 geometrically similar boundaries, that the water 

 will follow man-made paths, no matter how 

 attractive they may appear to the eye. 



72.17 Partial Bibliography on Tunnel-Stem 

 Vessels. There is a vast technical literature on 

 self-propelled shallow-water craft with tunnel 

 sterns but unfortunately much of it is superficial 

 and descriptive. The partial bibliography of this 

 section lists some of the older technical references 

 and most of the modern ones, omitting many of 

 those containing general descriptions only: 



(1) Thomycroft, Sir John, "Steamers for Shallow 



Rivers," Cassier's Magazine, Marine Number, 

 Jul-Aug 1897, Vol. XII 



(2) The twin-screw river gunboat H.M.S. Sheikh is 



described briefly in ASNE, Feb 1898, Vol. X, p. 230 



(3) Notes concerning the "Ught^draught gunboats" 



Heron and Jackdaw, built for the British Navy, 

 are to be found in ASNE, Feb 1898, Vol. X, pp. 

 227-228 and May 1898, pp. 556-559. These 

 vessels are 100 ft long by 20 ft wide by 2 ft draft. 



Twin screws 3.41 ft in diameter are fitted in twin 

 tunnel recesses. The speed is 10.5 mph or 9.13 kt. 



(4) Brief notes on "light-draught steamers," specifically 



the Melik and the Sullan, are to be found in 

 ASNE, May 1898, Vol. X, pp. 509-510; also 

 ASNE, Aug 1898, Vol. X, pp. 783-785 



(5) Ward, C. E., "Speed and Power Trials of a Light- 



Draught Steam Launch," ASNE, Feb 1898, Vol. X, 

 pp. 183-192. This was a tunnel-stern, single-screw 

 craft, 60.5 ft by 10.5 ft by 4 ft depth, with a draft 

 of 1.83 to 2.0 ft and a weight of 12.03 tons. The 

 propeller had a diameter of 2.5 ft. The art of 

 designing these craft would have advanced much 

 more rapidly than it did if all trial results had 

 been published in as complete a form as given here. 



(6) De Berlhe, B., "Note sur la Construction et I'fichan- 



tillonnage des Navires Destines h. la Navigation 

 Int^rieure (Note on the Construction and Inspec- 

 tion of Ships for Inland Waters)," ATMA, 1903, 

 Vol. 14, pp. 298-300. This paper contains drawings 

 of eight types of tunnel sterns for shallow-draft 

 ships. 



(7) Yarrow, A. F., "The Screw as a Means of Propulsion 



for Shallow Draught Vessels," INA, 1903, pp. 

 106-117 



(8) Ward, C. E., "Shallow-Draught River Steamers," 



SNAME, 1909, pp. 79-106 and Pis. 23-86; 

 especially pp. 96-101 



(9) Teubert, O., "Die Biuuenschiffahrt (Ship Operation 



on Inland Waterways)," Leipzig, 1912, Vol. I, 

 pp. 476-481. A second edition, not much different 

 from the first, appeared in 1932. 



(10) -Wilson R. C, "Construction and Operation of 



Western River Steamers," SNAME, 1913, pp. 

 59-66 



(11) "Mississippi- Warrior River Towboats," Mar. Eng'g., 



Jun 1921, pp. 432-437. This article describes and 

 illustrates the vessels of the Natchez class, 200 ft 

 long by 40 ft beam by 10 ft depth, with a draft of 

 6.5 to 7 ft. There are two propellers operating in 

 tunnels, with a tip emergence at rest of about 

 0.37D. Each propeller has four blades, with 

 D = 9.33 ft and P = 8.5 ft. 



(12) "Experimental Towboats," House (of Representa- 



tives), 63rd Congress, 2nd Session, Document 857, 

 1914, Vol. 27. This is the full report of a most 

 comprehensive investigation, both in America and 

 abroad, to determine the best type of shallow-water 

 towboat and towed barges for inland waters. It 

 gives the results of a multitude of model tests on 

 vessel forms for paddlewheel and screw-propeUer 

 drive and of comparative tests on models of radial 

 and feathering paddlewheels. 



(13) "Experimental Towboats," House (of Representa- 



tives) 67th Congress, 1st Session, Document 108, 

 1922, Vol. 9. This report, of 194 pages, describes 

 the full-scale trials made as a result of the recom- 

 mendations in House Document 857. Since so many 

 different experiments were tried by modifying at 

 least three different existing craft, the results were 

 inconclusive, as could have been expected before 

 they were begun. 



(14) McEntee, W., "Model Experiments with River 



