A Survey of Ship Motion Stabilization 



This study further attempted to compute damping assuming that the tank- 

 ship system could be described by a second order differential equation with 

 either linear or quadratic damping terms. It was indicated that while the quad- 

 ratic damping might be a reasonable representation in the vicinity of tank reso- 

 nance, damping was shown to be a much more complicated phenomenon that can 

 be treated with present knowledge. 



The results of the above as yet unpublished work of Finkel led to the design 

 of a tank system which was installed in a 1/38.1 5-scale model. Tests were con- 

 ducted in regular waves and indicated that roll would be reduced by as much as 

 55 percent in a beam sea at a speed of 7 knots, Fig. 19. These predictions could 

 not be extended to the irregular sea condition because of the nonlinearities in- 

 volved in the roll phenomenon. 



AVT-7 — Passive Tank. The AVT-7 is a planned conversion from the CVL 

 48 and is a 683 foot hull of 18,760 tons. Model tests were again conducted on a 

 1/19 scale model tank. This tank was installed below the roll axis of the ship. 

 The tank was again oscillated over the frequency range with various water depths; 

 the tank configuration is shown in Fig. 20. Tank moment versus frequency is 



45 -• 



o 



•S 35 



% 30 



I 25 



f 20 



r-l 



•§ 15 



a 



ID 

 5 



45 



90 135 



Ship Heading in Degrees- 



ISO 



Fig. 19 - Variation of maximum roll angle 

 with ship heading for a wave steepness of 1/50 



771 



