"Roger Long" wrote in
:

"Wayne.B" wrote

Any suggestions for a starting point?

Yes, start by deciding whether you are willing to invest a lot in
construction and additional weight with it's attendant increase in
fuel consumption to make things just a little better. If it's worth
it just to reduce motion by 10 - 15 percent, you can probably do
something. Most people who are bothered by motion will still think
there is nearly as much rolling as there was before. If you want to
do something significant, it will need to be huge.

The tanks in the project I was involved with were a dodge around the
MacMullen patents. They were simply rectangular boxes and worked on
the principle that the shallow wave of water rolling from one end to
the other would break, retarding it's speed. Speed was adjusted to
tune to the vessel's natural rolling period by adjusting water depth.

In the MacMullen tanks, the speed of water is regulated by either an
hourglass shape or sometimes by two pipes installed vertically at the
middle to restrict the flow. Tuning is fixed at the construction
phase requiring careful calculations.

You could build the largest tank you think the boat can handle with a
removable panel in the middle of the top. Install two pipes of 2 - 3
inches diameter between the bottom and the removable panel. Then make
larger spools of different diameters. Fill the tank half full and
then experiment by inserting different spool sizes until it seems to
work. If the MacMullen patents are still in force, they might have an
issue with this if you start selling them.

You could also just build a big rectangular tank and try different
lesser amounts of water as was done on the long liners.

Whatever you do, as you are experimenting, bear in mind that getting
the tuning such that is it in phase with the vessel's natural roll
period will increase the roll by as much as the tank is capable of
reducing it. Could be exciting. Even with properly tuned tanks, there
will occasionally be sea that creates a roll just in tune with the
tank so that the vessel will take a larger roll than it would have
without the tank.

--
Roger Long

Most "Flume" Tanks I remember were more on the lines of a "U" shape layed
on it's side (tankers being the exception). At one point they were
looking at a system for yachts which would be installed on the
"flybridge" built into the shape around the upper steering station....
this had the advantage of reducing the size due to the fact that the
higher the tank, the greater the righting moment.
I don't know if any of these were ever installed, but you would have
expected a reduction of @50% of ROLLING (note: rolling, not roll angles).
As Roger is saying, trying to design one of these systems without knowing
the basic formula's they used could lead to some catastrophic results.

One final point: If the system could have easily been designed and built
to work effectively with a minimum loss of space, ease and safety of use,
and maintenance, we'd probably see a bunch of them out there...... we
don't.

The smallest boats I remember these being put on were some buoy tenders
and Tuna Clippers (built into the ramp for the seine boat on the stern)