Giddings and Wermter 



Table 1 

 Classification of Anti-Roll Devices 



more than the bilge keel damping. There is a small increase in hull inertia due 

 to bilge keels, but the principal effect is increased hull damping. Historically, 

 bilge keels have been discussed in the literature by White [17] and Spear [18], 

 followed by many individual model test reports on specific designs, too numer- 

 ous to mention. 



Certain fishing craft are reported to use a technique for roll reduction while 

 adrift. Booms are rigged out over each side, and lines carrying weighted 

 drogues are lowered into the water. As the boat is rolled, it tends to pull up 

 one of the drogues which provides damping, while the other drogue sinks. The 

 ubiquitous staysail is also used for roll damping by boats throughout the world. 

 There may well be other unique and homely devices used on boats in specific 

 instances. 



Anti-Rolling Fins 



Anti-rolling fins have had a relatively long history. References 59 and 60 

 are among the earliest references to this form of roll stabilization. Chadwick • 

 [13] gives a good historical view of fin stabilization, and Bell [21] discusses the 

 history of fin controls. In general, progress in fin stabilization has been char- 

 acterized by a series of inventions, each limited more by the state of the art in 

 automatic controls rather than in hydrodynamics or mechanical engineering. 

 Only within the past fifteen to twenty years has it been possible to design and 

 analyze fully automatic controllers through straightforward engineering, rather 

 than through inventive inspiration and insight. 



The current state of the art in fin stabilizers is shown by Chadwick [13], 

 DuCane [22] and Flipse [23]. The latter commendably frank reference, along 



750 



