A Survey of Ship Motion Stabilization 



Table 2 

 Comparison of a U-Tube Analogy with Theory 



r/B 



a;(U-tube) 

 a>(Lamb) 







.90 



.04 



.916 



.06 



.916 



.08 



.861 



.09 

 .762 



1.0 

 



Active Internal Systems 



This paper will not elaborate on moving weight or gyroscope systems. It 

 can be said that moving weights have an attraction due to the possible high den- 

 sity of such an installation. It may be that the effective density of a moving 

 weight system, after including the volume needed for the operating machinery, 

 necessary to move the weights and safety devices, would be about the same as 

 that for a tank system. The additional property of a solid weight system that 

 there is no loss in hydrostatic stability when at rest is also attractive. How- 

 ever, there is no active research or development known to the authors in this 

 field. Reference 35, besides being interesting reading, contains a good discus- 

 sion of the first successful moving weight installation. 



Gyroscopes, both passive and active have been installed in many ships in 

 the past. References 36 and 37 discuss early installations. The dynamics of 

 both types of gyroscopes are analyzed by Diemel [38]. Their great weight and 

 the engineering difficulties of highly loaded bearings have limited their accept- 

 ance. The most recent installations of gyrostabilizers was in POLARIS subma- 

 rines, where they performed well enough, but changes in operational concepts 

 caused their removal. 



Recent Applications 



A limited number of naval installations have been completed or studied 

 since the recent paper by Vasta, et al. [31]. These have usually all been in an 

 area requiring stabilized gun, launching, or search platforms. Oceanographic 

 research ships have all been considered for the installation of passive tank sys- 

 tems in recent years. 



The recent studies conducted on passive anti-roll tanks and active anti-roll 

 fins will be discussed. The results of full scale trials and/or model tests will 

 be presented. 



Interpretation of full scale tests requires care. To quote Pierson [39], 

 "The surface of the sea is a mess." This complicates the roll records. It is 

 rare that the statistical properties of the sea remain static long enough to com- 

 plete the schedule of trials necessary for a good evaluation. The trial analysis 

 therefore demands a good deal of judgment on the part of both the analyzers and 

 the readers, especially without good measurements of sea conditions. 



USNS ELTANIN- Passive Tanks. The USNS ELTANIN (TAK 270) was con- 

 verted from a cargo ship to a scientific research ship of 3330 tons displacement. 



755 



