Sec. 64.5 



SHIP-DESIGN SPECIFICATIONS 



453 



must do, the next step is to put down what the 

 owner or operator would like to have the ship do. 

 This involves listing the secondary or desirable 

 features of the specifications. These afford the 

 designer an idea of the preferences involved, and 

 the relative importance of each. As such, they 

 furnish a valuable guide in working up many 

 elements of the design. It is wise to list all features 

 of this kind, even though at first thought they 

 may seem only remotely related or distinctly 

 unrelated to the hydrodynamics of the problem. 

 A statement prepared along these lines may have 

 the form of that presented in Table 64. f. The 

 relationship of certain of these features to the 

 hydrodynamic design becomes apparent as the 

 design proceeds. 



TABLE 64.g— FEATURES NOT OTHERWISE 

 CLASSIFIED 



(49) Freedom from vibration and noise, while not a 

 must, is a most desirable end to be achieved. In any 

 case, the estimated frequencies of periodic hydro- 

 dynamic forces shall be reported to the buOder at 

 least two months before the vessel's first sea trials. 



(50) It is expected that, by the time the vessel is put into 

 service, the harbor regulations will prohibit the 

 discharge of sanitary drains into the water areas at 

 all three ports, the canal, and the fresh-water river 



(51) The maximum layover times at the three ports may 

 be assumed as follows: 



Port Amalo, 3 days; Port Bacine, 24 hours; Port 

 Correo, 2.83 days (68 hr). 



With the desirable features it is well to include 

 limitations, restrictions, and other specifications 

 of a so-called negative nature. In other words, 

 the specifications should describe clearly and 

 definitely any and all things that the ship should 

 not do or should not have. The features listed 

 under (49) and (50) of Table 64. g belong in this 

 category. 



The specifications in this stage are terminated 

 by a group of items, not conveniently classified. 

 Three of them appear in Table 64. g. 



The problem of working over these require- 

 ments until they are mutually consistent and are 

 in numerical, coefficient, or other form, ready to 

 apply to the detail design, is taken up in the 

 chapter following. 



The liquid capacity called for in these specifi- 

 cations not only permits the ship to carry liquid 

 cargo on the particular run or in the particular 

 service for which it is designed but enables it to 

 carry any other liquid cargo which may be in- 

 volved in some unexpected service of the future. 

 In the existing state of world industrialization it 

 appears that for the life of this vessel liquids 

 of some kind or other will always be useful and 

 profitable cargo. Furthermore, the provision of 

 this tankage in the after part of the hull makes it 

 possible to utilize water ballast to insure adequate 

 propeller submersion and freedom from slamming 

 and pounding when running in waves at relatively 

 light-load conditions. 



