CHAPTER I 



INTRODUCTION 



One of the problems which faces the naval architect at an early stage in the design of 

 any new ship is the determination of the necessary horsepower to fulfill the speed require- 

 ments and to assess the effect on this power of making different choices for the size, propor- 

 tions, and fullness of the ship. 



To assist him in this problem, he will have recourse to a number ofdifferent sources 

 of data. He will have his own experience to draw upon, covering previous designs and ships 

 built to them, and, possibly, results of model tests carried out in this connection. Then 

 there are available many results of specific model tests published in various technical 

 papers and, in particular, the design data sheets published by the Society of Naval Architects 

 and Marine Engineers (SNAME).^ 



Such data, although extremely useful, suffer from the fact that they refer to a large 

 number of models which are unrelated one to the other and in which the variations in design 

 parameters are quite random. Much more valuable are the results of experiments on families 

 of models in which the different design parameters are varied systematically and, so far as 

 is possible in ship design, one at a time. Many such methodical series of model tests have 

 been carried out in the past, perhaps the best known being that due to Admiral D.W. Taylor. 

 Other such series covering different types of ships have been run by many people, ■'"'^^ 

 including one by the British Ship Research Association more or less concurrently with 

 the present Series 60 at the David Taylor Model Basin. ^^ 



The results of such tests can be expressed in design charts from which the naval 

 architect, by interpolation where necessary, can select a number of forms suitable to a partic- 

 ular problem, determine their relative resistance and propulsive qualities, and so make an 

 informed choice of the best combination of parameters to give minimum power within the 

 other limitations of the design conditions. 



Many methodical series of the past are not suitable for modern single-screw merchant 

 ship design for a variety of reasons, and although taken together they cover a large range of 

 values of the usual design parameters, they lack any overall coordinating factor. Also, some 

 doubt exists about the results in a number of the older series because of the absence of any 

 turbulence stimulation on the models. 



The need for more systematic information on the design of lines for modern, single- 

 screw ships has been recognized at the Taylor Model Basin for many years. The subject 

 was revived after the war at the meetings of the American Towing Tank Conference (ATTC) 

 and the Hydromechanics Subcommittee of SNAME held in Ann Arbor in 1948. The Society 

 agreed to sponsor the preparation of parent lines suitable for a series of single-screw 



I-l 



