A Survey of Ship Motion Stabilization 



Fig. 24 - Conaparison of roll angle envelopes 



The application of stabilizer fins to this class of ship is the first since 

 those previously reported on GYATT, COMPASS ISLAND and OBSERVATION 

 ISLAND [31]. The apparent success of all installations would seem to indicate 

 that more attention should be given to this area of stabilization. It should be 

 mentioned that the tests presently under discussion were conducted at a ship 

 speed of above 20 knots. There appears to be an obvious advantage to using ac- 

 tive fin roll stabilizers on high speed ships. 



Current Studies. Under sponsorship of the David Taylor Model Basin, the 

 Southwest Research Institute is conducting a continuing study of ship roll stabi- 

 lization tanks [44,45]. This program provides for four related studies: (a) The- 

 oretical tank damping characteristics; (b) experimental tank damping character- 

 istics; (c) extended theory of ship-tank systems; and (d) application to design. 



After progressing in phase (a) and (b) for a period of time it became appar- 

 ent that the study was hampered by a lack of a physical understanding of the 

 tank fluid behavior. Finkel also discovered this in his work on ARIS-3 as did 

 Motora and Lalangas [41]. To illustrate the point, Fig. 25 shows comparisons 

 of several experimental approaches. The lack of agreement is startling. Addi- 

 tional experimentation is indicated and a nonlinear model must be discovered. 



Pitch Stabilization 



Pitch stabilization has received a moderate degree of attention in recent 

 years in both theoretical and experimental studies but as yet these studies have 

 not resulted in a successful full scale installation. The problems of reducing 

 pitch are quite different from those of roll stabilization. Pitch is already con- 

 siderably dampened by the ship's hull. This of course means that large forces 



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