methods are quite sufficient to solve all the questions which arise regarding the influence 

 on the seagoing qualities of a ship". . . . 



We stated then that the great scientist has heavily overestimated the bearing 

 of his investigation. However, his claim provides us with a program which we shall 

 use as the backbone of the present lecture. We shall first give a short review of the 

 present status of knowledge on the seagoing properties of ships as pictured by recent 

 research work. This task is much simplified by the fact that recently in this country 

 excellent papers have been published of original as well as of synoptical character, for 

 example, by Korvin-Kroukowsky [4] and Lewis [5]. These publications are assumed 

 as known, and only short reference will be made to them. Emphasis will be laid on 

 investigations which may have escaped attention in this country although, unfortunately, 

 the present writer's attempts to procure literature were not too successful. 



We shall try to indicate some trends in the methodology of research and some 

 important results without going into details of the analysis. Secondly, the significance 

 of scientific results for future design will be discussed after having indicated sketchily 

 some shortcomings of the present state. Here again an excellent foundation is given 

 in reference 5. Beside promoting problems of design, a consistent theory of ship 

 behavior will have to furnish basic information for ship operation. The task of linking 

 explicitly design and operational problems in research, appears to present a strong 

 challenge, but is beyond the scope of this lecture. 



Finally, some ideas are developed as to future research in our field. 



Seaworthiness we define as the property of a ship to perform her duties safely 

 and well in a seaway. For a more detailed definition of seakindliness reference is made 

 to an article by Kent [7]. 



Ship theory embraces in general the application of geometry and rational 

 mechanics, especially of general mechanics and hydrodynamics, to problems presented 

 by design and operation of ships. A narrower concept of ship theory, excluding prob- 

 lems of structural strength, will be especially useful for our present review, although 

 obviously a clear-cut separation between ship dynamics and strength cannot be made, 

 problems of elastic vibrations by definition belonging to ship theory. In fact, the unity 

 of shipbuilding science is stressed at this point. 



Introduction of the concept — "ship mechanics" — as analogue to flight mechanics 

 when dealing with the behavior of a ship in a seaway, is suggested, to exclude any 

 overemphasizing of geometrical topics, a characteristic of earlier ship theory. 



When speaking about ships we have actually to deal with two different classes 

 of vessels — Archimedean and hydrodynamic, which in turn each divide into two sub- 

 classes — surface and submarine ships, and planing and hydrofoil craft. From the point 

 of view of analysis this means that we may have to create different mechanical models, 

 each of which has to embody the most important properties of the vessel in question. 

 So for the displacement vessel the appropriate hydrodynamic singularity is the source 

 (sink, doublet), while the hydrofoil is treated by the vortex concept. We must add that 

 beside ships, other floating or waterborn bodies have to be considered and should 

 profit from the activities in our field. 



If governmental stipulations [6] were completely indicative of the general trend 

 in design practice, the present speaker should confine himself to a discussion of ele- 

 mentary stability principles. Fortunately, design practice is a mental activity which 

 only to a certain extent is regulated by legal prescriptions, and the actual practical 

 contributions of ship theory in our field are more impressive than can be deduced from 

 such regulations. Especially the navies have in general displayed a more progressive 

 attitude. 



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