Sec. 68.15 



ABOVEWATER-FORM LAYOUT 



565 



(10) Ower, E., and Burge, C. H., "Funnel Design and 



Smoke Abatement," INA, 1950, Vol. 92, pp. 

 J19-J37; also ASNE, Aug 1951, p. 704. Seven 

 references are listed on p. 730 of this latter article. 



(11) Acker, H. G., "Stack Design to Avoid Smoke 



Nuisance," SNAME, New England Sect., Oct 1951 



(12) Valensi, J., "Sur un Moyen Propre h Eviter le 



Rabatteraent des Fumfees sur les Fonts des Navires 

 (On a Good Method of Getting Rid of the Smoke 

 Settling on the Decks of Ships)," Bull. Tech. du 

 Veritas, Mar 1952 



(13) Thieme, H., "A Contribution to Funnel Aerody- 



namics," Schiff und Hafen, Nov 1952, p. 453 



(14) Richter, E., "Neuzeitliche Schornsteinformen (New 



Forms of Stacks)," Schiffstechnik, Aug 1954, pp. 

 36-44 



(15) Craig, R. K., "Passenger Liner with Engines Aft," 



IME, Deo 1955, Vol. LXVII, Figs. 21 and 22, pp. 

 446-447; abstracted in SBMEB, Dec 1955, pp. 

 689-693. 



The obvious advantages of placing the pro- 

 pelling machinery as far aft as practicable in the 

 ABC design are augmented by moving the exhaust 

 fan or smoke discharge aft with it, where the gas 

 may be projected upward through one or two 

 tall, slender stacks. 



The superstructure for housing the passengers 

 and the public spaces is a unit placed well aft to 

 clear the forward deck for the handling of package 

 cargo and to be close to the pitching axis. The 

 derrick posts forward are to be in pairs, so it 

 appears logical and architecturally consistent to 

 carry this scheme aft by mounting two tall 

 inlet-and-exhaust-air shafts over the superstruc- 

 ture and placing two steeple-type smoke stacks 

 well aft, one over each steam generator. An 

 estimate of the extent of the turbulent region 

 over the ship is sketched in Fig. 68. M with a 

 moderate true wind of 25 kt from ahead, on the 

 basis of H. G. Acker's estimate that the thickness 

 of the turbulent zone over the top of the super- 

 structure is of the order of 0.8 the height of a 

 stepped-front superstructure above the main hull. 

 Combined with a ship speed of 20 kt, the relative- 

 wind velocity is 45 kt, or about 76 fps. 



The stack gases from each of two modern 

 8,500-horse steam generators should require a 



,. - — ;j.^ Estimated Upper Limit of Turbulent and Eddv/inq Flo 

 Combustion ..'-'^"*%. - / "Tf 



GQsesp ■ Exhaust -^'r] ^^ ^IL 



circular outlet not more than 3.0 ft in diameter 

 for a gas velocity S of the order of 55 to 75 ft 

 per sec [MacMillan, D. C, SNAME, 1946, p. 68; 

 Sharp, G. G., SNAME, 1947, p. 465; SuUivan, 

 E. K., and Scarborough, W. G., SNAME, 1952, 

 pp. 488-490]. The top of each stack casing could 

 then have a width of say 3.5 or 4.0 ft with a 

 fore-and-aft length of 5 ft. This leaves room for a 

 safety-valve escape pipe and for a damper and 

 its mechanism to keep the stack-gas velocity 

 high at reduced powers, as when running in the 

 Port Amalo canal and the river below Port Correo. 

 To give the structure rigidity without the use of 

 heavy scantlings or stays, the bottom width is 

 of the order of 5 ft. The bottom length is increased 

 to some 8 ft to give the profile the appearance of 

 sturdiness. The aft edge is raked downward and aft 

 like the transom profile. The streamlined casing, 

 in the form of a round-cornered rectangle at the 

 top, converts to a square-cornered rectangular 

 shape just above the fidley. This is to provide a 

 rigid foundation where the ends and sides of the 

 stack casing attach to the transverse beams and 

 fore-and-aft carlines directly below them. 



If it were considered that an underwater smoke 

 discharge, into the — Ap region of the separation 

 zone, along the lower edge of the transom, could 

 be worked out in the course of the design of the 

 vessel, the position of the steam generators well 

 aft would lend itself admirably to this arrange- 

 ment. 



"Necessity, if not reason, has provided another flourish. 

 Large steamships now e.xpel their waste gases through 

 giant chimneys surmounted by all manner of strange 

 devices. To prevent these unpleasant vapours obstinately 

 returning to spotless decks below, invention has run riot 

 in providing amusing, if not always elegant or effective, 

 headgear for funnels. Angels' wings, admirals' caps, 

 upturned pudding bowls, skeleton triplanes — all of these 

 and other fancies now proudly sail the oceans in the cause 

 of science and clean decks. What shall we see tomorrow? 

 Perhaps someone may get rid of those obnoxious fumes 

 somewhere else? Why not through the stern?" [SBSR, 

 1 Apr 1954, p. 401]. 



Some excellent comments relative to the dis- 

 posal of the products of combustion, made by 



Not Less Than 0.8 hg 



Fig. 68.M EsTI^LA.TED Air-Flow Pattern Over the ABC Ship 



