otnmbrd wrote:
Wayne.B wrote in
:

Anyone here have any experience with roll stabilization tanks -
designing, building, tuning, etc. ?

I'm talking about passive roll stabilization using port and starboard
water tanks connected by a "slosh" tunnel. If sized properly the
water sloshing between the tanks will be out of phase with the roll
period and dampen the motion, even at anchor.

Basically what you're talking about are "Flume" Stabilizers.
John J. McMullen (the company) was at one time the principal designer.
You might try going to them to see if they are still using them and if
there have been any advances.
No pumps are needed, other than for filling and installation; high
up is generally better for better results; you generally need to be
aware of stability (waddahey, you're basically making "free surface"
work for you in a positive way; the system works the same at all
speeds, but EG you have to roll for the system to work (sometimes
that first roll can be a doozy)..... etc.

otn

Googling for "water ballasted yachts" brings up a whole plethora of stuff,
including forum discussions. The consensus seems to be that the roll period
is too short to move a volume of water that would make any difference to
lateral stability, and pumping requires a huge amount of energy.

The pendulum-like swinging bulb keels fitted to the Open 60 and other
derivatives seem to provide much more resistance to heeling than any water
ballast gadgetry, increasing the resistance to heeling by as much as 55%,
according to one guy. This, plus the double-rudder (fore and aft), and
massive dagger boards either side, seem to provide much more stability than
moving water around inside the hull.

This said, the all carbon fibre 140 foot super-maxi, Mari Cha IV, was
launched in August 2003, the yacht weighs just 50 tonnes, and has a canting
keel with a 10 ton bulb, which can be swung + / - 40 degrees; and a water
ballast system.

Since she did the west-to-east crossing of the north Atlantic in 6 days
shortly after her launch, maybe there IS something in this water ballasting
after all! Perhaps it stops Mari Chai 1V from taking off and becoming a
flying machine!

Dennis.