774 



HYDRODYNAMICS IN SHIP DESIGN 



Sec. 76.13 



curves of form arc given in Fig. 11, the following 

 data have been worked out for a 17-ft draft: 



L = 130 ft S/// ratio = 1.76 A/(0.010L)3 = 494 



S = 30 ft A = 1,085 long tons F/(0.10L)3 = 17.32 



£) = 17 ft Cb = 0.648 V = 11.7 mi per 



hr =0= 10.16 kt 

 L/B ratio Cp = 0.732 Cw = 0.88 



= 4.33 Cx = 0.88. 



Trawlers and Sealers 



(47) Symonds, R. F., and Trowbridge, H. O., "The 



Development of Beam Trawling in the North 

 Atlantic," SNAME, 1947, pp. 359-384, esp. pp. 

 371-384 on Trawler Design 



(48) Shearing, Douglas, "152-foot Ti-awlers for French 



Fishing Industry," Diesel Prog., Feb 1948, p. 56, 

 with photograph of trawler Clair de Lune. Single 

 propeller is variable pitch, with D of 8.83 ft, P 

 of 6.175 ft, and 4 blades. Speed is 11 kt with n 

 of 200/60 = 3.33 rps. 



(49) Diesel-engined Sealer (Terra Nove) on Maiden 



Voyage, Diesel Prog., Feb 1948. Lqa is 140 ft, B 

 is 28 ft, and D is 14 ft. Speed is 9 kt. 



(50) French fishing trawler Saint Joan, Proc. Am. Merch. 



Mar. Conf., 1949, p. 292. A photograph shows 

 rather well the form of the hull amidships and the 

 form of the run, with the single propeller and 

 rudder. 



(51) Diesel trawler Giidrun, Diesel Times, Oct 1949, pp. 



1-2. Length is 115 ft and beam 23 ft. 



(52) "A Powerful Motor Trawler," SBSR, 31 Jan 1952, p. 



139. This vessel has a length of 185 ft, a beam of 

 30.5 ft, a depth of 16 ft, and a speed of 13.63 kt. 



(53) Jaeger, H. E., "Large Trawlers," INA, Apr 1954; 



abstracted in the May 1954 issue of The Motor 

 Ship, London, pp. 62-63. 



Whale Catchers 



(54) Matthews, L. H., "South Georgia: The British 



Empire's Subantarctic Outpost," 1931, pp. 123, 

 125-126 



(55) Granberg, W. J., "Diesels go Whahng," Diesel Prog., 



Dec 1949, pp. 34-35. Describes wooden vessels, 

 115 to 140 ft long, for North Pacific whaling. 



(56) Norway's New Whale-Catcher Ships, Nautical 



Gazette, Jan 1951. Mentions a 16-kt speed with a 

 brake power Pb of 2,400 horses. 



(57) Whale catcher Setter II, SBSR, Feb 1952, p. 55. 



This vessel has an Lqa of 177.5 ft, an Lpp of 160 

 ft, a depth D of 17.5 ft, and a mean draft, fully 

 loaded, of about 15.6 ft, including a bar keel 

 about 0.62 ft deep. The displacement correspond- 

 ing is 1,080 long tons. The trial speed is 15.3 kt, 

 and the vessel has a single screw. 



(58) Shearing, Douglas, "The Whaler Enern," Diesel 



Prog., Sep 1953, pp. 36-37. This vessel has an 

 LoA of 210 ft, an Lpp of 186.5 ft, a B of 33 ft, and 

 a D of 18.33 ft. The brake power of the single 

 engine is 2,700 horses; n is 225 rpm or 3.75 rps, 

 and the speed V is 16-17 kt. 



Fisheries Research and Exploration Vessels 



(59) Hanson, H. C, "The Conversion of Pacific Fisheries 



Exploration Vessel," SNAME, Pan. Northwest 

 Sect., Oct 1947 

 (60) Mann, C. F. A., "Diesel Ship John N. Cobb," Diesel 

 Prog., Apr 1950, pp. 40-41. 



76.13 Fireboats or Firefloats. Fireboats as 

 a class are among the earliest of mobile special- 

 service vessels, dating in the Americas from the 

 1870's. In Europe these vessels are normally 

 called firefloats. It is probable that neither the 

 vessels themselves nor the class will ever be large, 

 yet the type is interesting for the complex 

 problems it poses in naval architecture and marine 

 engineering. 



The service requirements involving hydro- 

 dynamics, listed hereunder, are adapted from a 

 paper by A. D. Stevens [SNAME, 1922, pp. 

 137-141 and Pis. 44-52], from a group of excellent 

 articles in Motorship [New York, May 1950, 

 pages 17-57], and from a more recent paper by 

 D. S. Simpson [SNAME, 1951, pp. 564-568]. 

 They are set down more or less in the order of 

 their importance: 



(a) Instant availability and prompt arrival at 

 the fire. This involves free-running speeds of 11 

 to 14 kt, in the present stage of development, 

 depending upon how far the craft has to travel 

 from its station. 



(b) Extreme maneuverability, involving a high 

 degree of handiness, rapid response, and ability 

 to move in almost any direction. In particular, 

 the boat must be able to steer and maneuver 

 when backing. 



(c) Ability to stay put in the position and at the 

 heading desired, under the reaction forces exerted 

 at the discharge nozzles 



(d) Stiffness sufficient to give only a moderate 

 list, say not in excess of 6 deg, when all fire- 

 fighting nozzles are directed horizontally and 

 abeam, and discharging at full capacity 



(e) Flexibility of drive for propulsion and for 

 pumping. The greater part of the power should 

 be available for taking the vessel to the fire; an 

 equally large portion should then be available 

 for pumping water. 



(f) Freedom from clogging of the fire-pump 

 suctions if the boat has to operate in water depths 

 only slightly exceeding its draft. These suctions 

 must also remain clear of ice and debris floating 

 at or near the surface. 



(g) Ability to push or pull on vessels in an 

 emergency, like a tug. This involves propulsion 

 devices with large disc areas or equivalent-disc 

 areas Aa ■ In terms of screw propellers this means 



