752 



HYDRODYNAMICS IN SHIP DESIGN 



Sec. 76.2 



as well as certain important features of self- 

 propelled craft intended to operate in confined 

 waters, are discussed in Chap. 72. 



Special features in the design of tugs, towboats, 

 pushboats, and self-propelled lighters, as well as 

 non-self-propelled barges, scows, and floats, are 

 covered in Part 5 of Volume III, under the general 

 subject of Towing. 



76.2 The Design of Fine, Slender Hulls; 

 Canoes, Racing Shells, and Fast Launches. As 

 long as watercraft are required to be propelled 

 by manpower and as long as men have to handle 

 or carry them there will remain a demand for a 

 craft of small resistance and small weight com- 

 pared to its speed and carrying capacity. Such a 

 demand is met by the birchbark canoe of the 

 American Indian and the kayak of the Eskimo. 

 Canoes of greater fineness but also of greater 

 weight, dug out of single logs or built up of large 

 parts, are still in existence and still used by many 

 peoples of the world. These are driven by as 

 many as a hundred paddlers each [111. London 

 News, 9 Jul 1955, p. 81]. It is entirely probable 

 that many of these fine-ended designs evolved 

 from a desire to minimize water disturbance and 



noise when hunting. For the craft paddled by 

 one or two persons, a reduction of resistance — and 

 thrust — is far more personal and important than 

 if there is an engine available to drive it. 



Dixon Kemp, in his book "A Manual of Yacht 

 and Boat Saihng" [Cox, London, 3rd ed., 1882], 

 devotes Chap. XXVI, on pages 374-381, to 

 "Canoeing." It contains drawings and rather 

 detailed descriptions of a considerable number of 

 British and American canoes. A storj-- and excellent 

 photographs of canoes and kayaks built by the 

 natives of northwestern North America are found 

 on pages 77-79 of the February 1917 issue of the 

 Pacific Marine Review. 



Some historical and technical data on the canoes 

 of America are given by H. I. Chapelle ["American 

 Small Sailing Craft," Norton, New York, 1951, 

 pp. 36-38]. Design features of the modern light- 

 weight canoe, the small-boat version of the long, 

 slender ship, and still popular as a pleasure craft, 

 are discussed and presented by R. P. Beebe 

 [Rudder, Jan 1954, pp. 49-53, 82]. This article 

 illustrates five typical canoe midsections. 



The ultimate in fineness and reduction of both 

 friction and pressure resistance is achieved by 



TABLE 76.b — Comparative Form and Performance Data for Two Types of Manually Propelled Ckaft and 



One Mechanically Propelled Vessel 



These data are taken from published information by F. H. Alexander (see the reference quoted in the text) and by 

 K. C. Barnaby [INA, 1950, p. J13]. 



The circular-constant parameters are those of R. E. Froude; see Appendix 1. 



For comparison with the 8-oared shell, a single-oared shell is about 1 ft wide, and weighs about 28.5 lb, without crew. 



Item 



8-oared 

 Racing Shell 



Whaleboat, 

 10 oars 



Cross-channel 

 Steamer 



Length on LWL, ft 



Beam, extreme, ft 



Draft, ft (estimated) 



Displacement, tons, with crew 



V (estimated), ft' 



Wetted surface, ft^ 



Speed, kt 



Speed, ft per sec 



Value of® 



Value of (S) 



Value of (g) 



Value of© 



Value of V/Vl 



Value of A/f j», tons for 100-ft length 



Resistance, lb 



Resistance, plus still-air Z).5a , lb . . . . 

 Resistance per ton of displacement, lb . . 

 Resistance ratio. Friction /Total . . . . 

 Value of (C) 



62.0 



2.0 



0.5 



0.81 



28.4 



109.5 



10.0 



17.0 



20.2 



11.78 



6.025 



1.34 



1.27 



3.5 



77 



90.0 



95.0 



0.95 



1.162 



28.0 

 6.85 



1.70 



59.5 



133 



6.7 



11.33 



7.17 



8.73 



3.58 



1.34 



1.27 



77.5 



81 



47.6 

 0.51 

 1.662 



320.0 

 40,0 



1,850 



64,750 



12,510 



22.75 



38.4 



7.97 



7.76 



3.78 



1.34 



1.27 



56.5 



87,300 



47.2 

 0.40 

 1.469 



