Preface 



I 



wo niethcids of prepiiring this mono- 

 graph were originally discusseil by I'anel 11-7 (Seakeeping 

 Characteristics) of the Hydrodynamics Committee of 

 SNAME: a composite work in which various sections 

 would be written by experts in the respective fields, and 

 a general sur\'ey conducted by one person. The latter 

 method was decided upon as more likely to produce a 

 logically coherent and compact presentation.' 



It was realized that ship behavior in a complex seaway 

 is not .yet sufficiently luiderstood to permit writing a 

 definiti\'e textbook. The objective of the monogra])h 

 was then defined as the preparation of the critical f>um- 

 mary of the existing state of the art, in order to assist in 

 planning of further research. The scope of the monograph 

 was to be the entire field of ship responses to seas, start- 

 ing with the definition of the seaway and ending with 

 the loads imposed by the seaway on a ship's structure. 

 Consultation of the author with the Monograph Ad- 

 visory Committee resulted in the following di\ision of 

 the subject matter into chapters: 



1 Seaway 



2 Ilydrodynamic Forces 



3 Ship Motions 



4 Resistance and Lo.ss of Speed in Waves 



5 Djaiamic and H.ydrodynamic Loads on a Ship's 

 Structure. 



Broadly speaking, the interests of the two sponsoring 

 bodies haxe been different. The Seakee])ing Charac- 

 teristics Panel has been interested in ship motions 

 (amplitudes, accelerations), wetness, slamming, and 

 .steering, inasmuch as these affect the .safe .speed of a 

 ship in adverse weather conditions. The Connnittee 

 on Ship Structural Design has been interested primarily 

 in the loads affecting the structural integrity, including 

 the transient loads with which a ship's elastic response 

 is invoh'cd. Both interests were to be kept in mind 

 throughout the development of the monograph. The 

 exposition was limited, however, to the definition of 

 external hydrodynamic loads and of accelerations causing 

 dynamic or inertial loads. It has been expected that 



' Thi.s i)olif.\- was subseqiientl\' modified in regard to section 8 

 of the first chapter and Section 3 of the third one. These sections 

 are coni-erned with the application of mathematical statistics to 

 the description of sea waves and shijj motions caused \>y them. 

 The Monograph Advisory Committee decided that the chapters 

 written l)_\- the original author slioiild lie rewritten by a sjiecialist 

 in this field. j\h-. Wilbur Marks of the David TaylorMotlel Basin 

 undertook this task. \Miile he broadly followed the original 

 author's plan, he modified the e\i)osition so that it no longer con- 

 forms to the jiolicy and ob.ieetives of the other parts of the mono- 

 graph; the critical attitude anil emphasis on the shortcomings of 

 the existing knowledge were replaced by a smooth informative 

 description. 



tidditional projects would be orgainzeil for the examina- 

 tion of ship .stresses or, more generally, of ship structiu'al 

 responses to these loads. It was intended, ne\'erthele.ss, 

 to include in C-hapter 5 a brief outline of the methods 

 available for computing the transient response to the 

 time-dependent load application occtiiring in a complex 

 seawa^'. 



The jiresent work is aimed solely at the beha\'ior of 

 surface-displacement ships. Although a large amoiuit 

 of material can be applied to submarines, planing-type 

 craft recjuire a different approach :ind are definitely ex- 

 cluded. 



In research iilanning, either by the investigators them- 

 s('l\-es or by sponsoring Ijodies, the first reiniirement is to 

 estaljlish the cxifstinci state of the art, and the second 

 (e(iually importtuit) is to understand the shortcomings 

 of the exi.sting knowledge. These two requirements 

 determined the style of presentation in the present 

 monograph. An efl'ort was made to present the basic 

 principles and the current state of the art as factually, 

 ciuantitatively and completely as possible within the 

 limitations set by time availal)le and a reasonable size 

 of the monograph. However, the monograph was to be 

 only a sununary, and it has not been possible to treat all 

 subjects exhaustively. The treatment of each subject 

 was intended to be in the nature of an introduction and a 

 ginde to existing literattu'e. Preparation of an exten- 

 sive bibliography, therefore, formed an important part 

 of the work. Certain reviewers of the early draft 

 criticized this plan because the references listed have 

 been difficidt to obtain. The author solved this diffi- 

 culty in his own work by relying on microfilm copies. 

 The New York Public Liijrary- has an amazingly com- 

 plete collection of technical literature and furiushes 

 excellent microfilming and photostatic service. Micro- 

 filming service is also available from the Library of Con- 

 gress, Washington, D.C. 



The references have been made as precise and complete 

 as possible. The introductory outlines to each subject 

 and the bibliography are intended to serve as a basis for 

 further dex-eloijment by readers. In order to stimulate 

 this de\'elopment, great emphasis has been placed upon 

 the shortcomings of the existing knowledge.^ In this 

 connection it should be said that the stated opinions are 

 the author's own, and the sponsoring bodies bear no 



-Fifth Avenue at 42nd Street, New York, N. Y. Attention: 

 Photographic Service. 



' In view of this polic.v, the author wishes to apologize in advance 

 to the many authors whose works are reviewed here in what may 

 appear as an unfavorable light. Exposition of shortcomings is the 

 basic thread of this work. 



