Sec. 64.3 



SHIP-DESIGN SPECIFICATIONS 



447 



and conditions imposed by the owner or operator. 

 The latter may have overlooked certain features, 

 seemingly unimportant in appearance but vitally 

 essential in design, in his version of the specifica- 

 tions. The ship designer must, moreover, be 

 prepared to present to the ship owner-operator 

 adequate engineering data upon which the latter 

 can make certain design choices within his 

 province. The data and facts are to be collected, 

 developed, and presented by the designer in the 

 form of clear, concise digests, setting forth the 

 advantages and disadvantages, the premiums and 

 the penalties associated with each choice. The 

 owner-operator can then feel that he is making 

 logical, intelligent selections from a reasonable 

 number of design alternatives. 



For instance, can the designer build up a case 

 for wide bilge or roll-resisting keels forward that 

 project beyond the side at the designed waterline, 

 on the basis of augmented roll- and pitch-quench- 

 ing characteristics? Will the owner-operator 

 accept a projection of the rudder beyond the 

 extreme stern overhang for the sake of improved 

 flow to the propeller and reduction of vibration? 



One's views as to what features of the ship are 

 important and controlling often depend upon his 

 position in the overall setup. A limitation on 

 length, for example, may be only an expression of 

 well-hardened opinion on the part of an operator 

 who thinks that it should be possible to get 

 everything he wants in a ship of a certain size. 

 It may be, on the other hand, a vital restriction 

 to the designer if he is endeavoring to squeeze 

 out a small margin of speed or power. 



The salient features of a muddled and verbose 

 specification may need to be brought out so as to 

 keep them alive and vivid before a designing staff. 

 These and other reasons may well justify the 

 extra time spent on highhghting essentials and 

 generally reworking the specifications furnished 

 by someone else. 



The guiding principle in the preparation or 

 revision of design requirements, first, last, and 

 always, is to keep the language direct, straight- 

 forward, and simple. Stress the specific but 

 informal treatment. Start off by setting down, in 

 plain language and short words, just what the 

 ship is required to do; just what mission it is to 

 fulfill. A ship which ultimately does not carry 

 out its appointed mission is to be reckoned not a 

 success, no matter how efficiently it may meet one 

 or more secondary requirements. 



The combination passenger and cargo vessel for 



the Port Amalo — Port Bacine — Port Correo route 

 was selected as one hkely to present the most 

 varied and numerous ship-design problems for 

 consideration in this part of the book. The mission 

 of a hypothetical vessel of this type, operating in 

 an imaginary part of the world, is rather easily 

 roughed out. The result is given in Table 64.a. 

 This mission, as with the requirements to follow, 

 is intended to emphasize the size, form, power, 

 speed, and other design features having to do 

 primarily with hydrodynamics. It would be 

 amplified considerably when considering the ship 

 as a whole. 



TABLE 64.a — Partial Design Specifications for a 

 Combination Passenger and Cargo Vessel 



MISSION 

 The vessel described in these speciiications is intended 

 to be used for: 



(1) The transportation of passengers to and from Port 

 Amalo, Port Bacine, and Port Correo, making the 

 outbound trip from Port Amalo in that order and 

 the homeward trip in reverse order 



(2) The transportation of liquid bulk cargo from Port 

 Correo to Port Amalo, and of high-class package 

 cargo back and forth between Port Amalo, Port 

 Bacine, and Port Correo.* 



The service to be rendered requires: 



(3) The safe and comfortable transportation of the 

 passengers on a rigid, year-round schedule, established 

 well in advance, regardless of local and seasonal 

 weather conditions 



(4) The storage and transportation of the high-class 

 package cargo safe from damage by the elements or 

 from violent and jerky ship motion 



(5) Performance of the required transportation as 

 efficiently and economically as the present state of 

 the art permits 



(6) Safe and rapid handling and berthing of the vessel 

 under its own power at Ports Bacine and Correo. 



*The "liquid bulk cargo" mentioned in (2) preceding is not 

 necessarily composed of heavy oil or its products. However, 

 G. A. Veres has recently (1955) proposed the carrying of 

 passengers on high-speed tankers [SBSR, 23 Jun 1955, 

 p. 797; 7 Jul 1955, p. 5]. 



The next step is to write out the principal duties 

 which the ship is to fulfill, and the principal 

 requirements which must be met. If there are 

 compulsory or mandatory limitations, include 

 them by all means. Do not clutter up these major 

 features of the specifications with details of lesser 

 importance, or with superlatives intended to 

 emphasize them. 



The first items to set down are those involving 



