TUG,

I've heard the rocking system described - haven't seen it in action. Simple though. The basic idea is a sealed system of a plastic tank secured to the hull on each beam (perhaps a nitro fuel tank - good variety of sizes) connected with a reversible self-priming pump (monitor pump/fuel pump maybe). Then just a simple servo control to pump fairly rapidly back & forth to rock her - about 7 to 10 degrees in 15 second cycles is about what the real one does. Remember to use a liquid medium that won't freeze - alcohol or something not too nasty/toxic in case of a spill internal or external. Water would probably be fine unless you were in really cold conditions where the ice is too thick anyway!

My own idea would be closer to the real thing where you could ballast down with external water, rock and roll, and then discharge when through the heavy ice flows. You could draw and discharge with one pump and then rock with another. Whaddaya think?

Patrick