CHAPTER 64 



Formulation of the Design Specifications 

 Involving Hydrodynamics 



64.1 General 44G 



04.2 The First Task of the Designer 446 



64.3 Statement of the Principal Design Require- 



ments 446 



04.4 Absolute Size as a Factor in Maneuvering 



Requirements 452 



64.5 Tabulation of the Secondary Requirements . 452 



64.1 General. The hydrodynamic design pro- 

 ject carried through this part of the book involves 

 a combination passenger and cargo vessel, because 

 the requirements for such a craft are relatively 

 severe. This vessel is intended to travel between 

 the hypothetical cities of Port Amalo, Port 

 Bacine, and Port Correo, leading to the simple 

 project name ABC Design. 



Any working example of this kind is but one of 

 a multitude which can be presented to a marine 

 architect. Chap. 76 in this part therefore discusses 

 variations from big-ship rules, applying to the 

 design of special hull forms and special-purpose 

 craft. It considers only the problems pecuhar to 

 the majority of special designs and not treated 

 adequately or at all in the ABC design. 



In an effort to cover the hydrodynamic design 

 field for small craft as well as for large ships, 

 Chap. 77 contains a working example of a design 

 for a motor tender for the ABC ship. 



64.2 The First Task of the Designer. Com- 

 plete success in a design project is only achieved 

 after careful formulation of the purposes and aims 

 of the project. Once formulated, these aims are 

 kept continually in view and constantly in mind. 

 There is no better way of doing this than to write 

 them on paper, to look at them frequently, and 

 to think about them all the time. 



It is considered in many quarters that a ship 

 owner or operator can be relied upon to formulate 

 his own requirements and that these will suffice 

 for the design of the ship. He, however, is taking 

 only his view of the picture, whereas the designer 

 must look at it from many angles. Furthermore, 

 the owner is often so famiUar with his own 

 requirements that it does not occur to him to 

 pass them on to the designer as pecuUarities. 

 The designer must think of the right questions to 

 ask, then ask plenty of them, interpret offhand 



comments, and perhaps find out for himself by 

 riding on and watching the operation of a similar 

 vessel [Simpson, D. S., SNAME, 1951, p. 558]. 

 This is why the designer must in effect prepare 

 his own picture and plan to survey it from all 

 angles. 



Setting down the ends to be achieved is often 

 not as simple and straightforward a task as 

 appears at first sight. Some designers are fortunate 

 enough to come by it naturally but most have to 

 learn it the hard way, and without any good text 

 or adequate reference works available for study. 



This chapter is by no means a course in writing 

 specifications but aU the simple rules involved in 

 preparing the hydrodynamic and related features 

 of a ship specification are set down here, supple- 

 mented by a few of the more complicated but 

 equally necessary rules. It covers the development 

 of fairly complete specifications for the general 

 and the hydrodynamic features of the ABC ship 

 design which is to be prepared as the illustrative 

 example. 



It is not possible to work up a set of coherent 

 design requirements by neglecting or omitting 

 any considerations whatever of hydrostatics, meta- 

 centric stabiUty, strength, engineering, cargo 

 handUng, and accommodations such as passenger 

 quarters and crew's berthing and messing. How- 

 ever, only enough of the foregoing features are 

 brought in to make the design specifications hold 

 together, with major accent on those features 

 having to do with hydrodynamics and ship 

 motions. 



64.3 Statement of the Principal Design Re- 

 quirements. Even though they may already have 

 been partially or completely drafted by someone 

 else, it is ^vise for the designer to restate the 

 design requirements in his own language. When 

 properly worded, these emphasize the limitations 



446 



