Sec. 72.7 



DESIGN FOR CONFINED WATERS 



6f)5 



TABLE 72.C — Dimensions, Ratios, and Proportions for American River Steamers oi'' the Period 1850-1870 

 The dimensions marked by asterisks (*) are tliose listed by J. Scott Russell [MSNA, 1865, Vol. I, p. 666]. Tlie remaining 

 ratios and coefRcients are derived from the published dimensions. 



To make up partly for this dearth of pubUshed 

 data on large shallow-water vessels in the category 

 under discussion there are given in Table 72. c 

 some dimensions of shallow-draft river steamers 

 plying on the eastern and western rivers of North 

 America prior to 1870. These and other data, 

 published by Normal Scott Russell and John 

 Scott Russell, are verging on the ancient, or at 

 least the historical, for a book on modern ship 

 design. Nevertheless, they form a considerable 

 part of the pubHshed systematic data and they 

 indicate the range of ratios and proportions within 

 which successful shallow-water designs may be 

 evolved. 



Normal Scott Russell, in his paper "On Ameri- 

 can River Steamers" [INA, 1861, Vol. II, pp. 

 105-127 and Pis. IX through XIV], gives on 

 pages 126 and 127 some dimensions of the 

 Commonwealth (old), designed and built for opera- 

 tion on Long Island Sound, and the Mem-phis, for 

 operation on the Mississippi River. On page 127 

 there are two tables of data, one for the "Best 

 Boats on Eastern Waters," and the other for the 

 "Best Boats on Western Waters." The first lists 

 nine vessels, with 14 entries per vessel; the 

 second lists seven vessels, with 14 entries per 

 vessel. J. Scott Russell gives the following data 

 for the City of New York (not to be confused with 

 the New York of Table 72.b) [MSNA, 1865, Vol. 

 I, pp. 664-665; Vol. II, PL 164]: 



Ln^i = 300 ft 

 B = 40 ft 

 H = 8.25 ft 

 L/B = 7.5 

 B/H = 4.85 



Pi = 1,800 horses 

 Ax = 288 ft' 

 Cx = 0.873 

 V = 20mph = 17.4 kt 

 T,= V/VL = 1.005. 



Lines and body plans for ships driven by 

 sternwheels, as distinguished from side paddle- 

 wheels, are to be found in: 



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



SNAME, 1909; lines for a dredge tender are drawn 

 on PI. 30 



(2) 156-ft stern- wheel towboat. Chief of Engineers, War 



Department, SNAME, 1925, Pis. 45-46 



(3) Giroux, C. H., "Performance Tests on Diesel-Electric 



Stern-Wheel Towboats," SNAME, 1926, pp. 185- 

 202, esp. Pis. 87, 88, and 101 



(4) Brodie, J. S., "Modern River Towboats," body plan 



of "Refined Type of Stern wheeler with Scow Bow 

 and Stern and Rudder Recesses," SNAME, 1936, 

 p. 359. 



72.7 Length, Longitudinal Curvature, and 

 Wetted Surface. No ship which is designed to 

 make real speed in shallow water should be 

 crowded into too short a length or have blunt 

 ends. The limited depth of water accentuates the 

 crests and hollows in the wave pattern. The 

 Velox-wave heights should not, if it is avoidable, 

 be accentuated further by full ends and sharp 

 curvature. When the crests of these waves are 

 superposed on a solitary wave of translation the 

 steepness becomes large and the trim excessive. 



For minimum overall resistance, a long, fine 

 hull is advisable, with the greatest length and 

 the least beam permitted by the design specifica- 

 tions. This reduces the longitudinal curvature of 

 waterUnes and diagonals and decreases the wave- 

 making. The chart of Fig. 66.B, showing the 

 regions at which humps in the resistance curve 

 can be avoided, does not apply here because the 

 speeds for a given wave length are less in shallow 

 water than in the deep water for which the chart 

 is drawn. 



Added length involves extra wetted surface, 



