Scott wrote: The discussion of Active Fins and Paravanes got me thinking about Dave Coopers anti roll tanks. I don't recall hearing how they work? All I can envision is a series of baffles that somehow keep the water out of phase with the boat rolling, something like a bunch of kids running around doing exercises during a Romper Room session on TV.> Funny you should mention them. Nancy actually got the idea as she was the Miss Nancy of Romper Room on ABC.......uh oh the Do Bees are out of the closet now!!!! The "Magic Mirror" shows, in its simplest form, the tank is baffled and runs athawtship. The quantity of water, the location of the baffles and the interspacing of them are the basic dimensions that give the tank its performance. These factors are derived by the roll period of the boat, its stability, its natural roll decay period and a few 100 other inputs A few passes thru Dr. Bass's modeling programs and out comes the design for a particular boat. Hopefully you, or the NA, have worked with him so the tank that is designed has a place to fit. It can be curved, it can have a pinched middle it can have fat ends it can be taller or shorter, fatter or wider....you get the picture. Now have all my friends ......... As always YMMV........ Dave & Nancy Swan Song Roughwater 58 Caribbean Cruise '07