A SURVEY OF SHIP MOTION STABILIZATION 



Alfred J. Giddings 

 Bureau of Ships 

 Washington, B.C. 



and 



Raymond Wermter 



David Taylor Model Basin 



Washington, D.C. 



ABSTRACT 



A brief historical review of significant developments in stabilization is 

 presented. Some recent investigations in roll are discussed followed 

 by a survey of the progress and potentialities of pitch stabilization. 

 The important differences between pitch and roll stabilization are ex- 

 amined, and the reasons for the greater difficulty of the former are 

 discussed. Since pitching, relative to rolling is not a sharply tuned 

 resonant phenomenon, large magnitude moments are needed to develop 

 appreciable effects. Model test results are presented to indicate the 

 degree of stabilization possible and the vibration problem associated 

 with bow fin installations is examined. The effects of configuration, 

 platform area and aspect ratio are also mentioned. 



INTRODUCTION 



Stabilization of ship motions can be considered in a very broad sense, or in 

 a narrow sense. In the broadest sense, consideration should be given to static 

 stability, motion amplitude and controllability in each of the six degrees of free- 

 dom of rigid body ship motions. A more narrow view might consider only the 

 limiting or prevention of one of the motions. It is the aim of this paper to strike 

 a middle ground, recognizing that there are significant and undesirable motions 

 in all six degrees of freedom, but expanding only on those of particular interest. 



It is advisable to define what is meant by "stabilization" in this paper. By 

 this is meant the deliberate limiting of a ship motion caused by waves, which 

 motion is otherwise stable. With this definition, automatic steering of a direc- 

 tionally unstable ship, or of a stable ship in calm waters are only of passing in- 

 terest while the more obvious cases of pitch and roll "stabilization" in a seaway 

 are of definite interest. 



A cursory examination of the literature on ship motions and stabilization 

 reveals some interesting trends. The principal interest of those writing on 



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