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.

Wayne.B wrote:
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.

The "slosh" tunnel would need to be as big as the tanks, diameter-wise, and
a huge amount of water would be needed to have any effect whatsoever. If you
don't believe me. take an overweight friend sailing and get him to lose
weight by leaping from side to side in phase with the roll, always moving to
the "up" side. He/she would need to weigh in at around 500lbs if you can
find such a person.

If this system worked the QM2 would use it instead of spending $millions on
stabilisiers.

DP

On Sun, 30 Dec 2007 09:41:10 GMT, "Dennis Pogson"
wrote:

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

Undoubtedly not.

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.

Yes, this has been known to work, at least somewhat.

The "slosh" tunnel would need to be as big as the tanks, diameter-wise, and

Absolutely not.

a huge amount of water would be needed to have any effect whatsoever.

It does take fairly large tanks, the one big drawback to the idea.

If you
don't believe me. take an overweight friend sailing and get him to lose
weight by leaping from side to side in phase with the roll, always moving to
the "up" side. He/she would need to weigh in at around 500lbs if you can
find such a person.

I can't find a way to comment on that utter nonsense.

If this system worked the QM2 would use it instead of spending $millions on
stabilisiers.

What they have is better and they use it. This does not mean that an
arrangement of tanks cannot work at all.

Casady

DP

Richard Casady wrote:
On Sun, 30 Dec 2007 09:41:10 GMT, "Dennis Pogson"
wrote:


Wayne.B wrote:

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


Undoubtedly not.


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.


Yes, this has been known to work, at least somewhat.

The "slosh" tunnel would need to be as big as the tanks, diameter-wise, and


Absolutely not.


a huge amount of water would be needed to have any effect whatsoever.


It does take fairly large tanks, the one big drawback to the idea.


If you
don't believe me. take an overweight friend sailing and get him to lose
weight by leaping from side to side in phase with the roll, always moving to
the "up" side. He/she would need to weigh in at around 500lbs if you can
find such a person.


I can't find a way to comment on that utter nonsense.

If this system worked the QM2 would use it instead of spending $millions on
stabilisiers.


What they have is better and they use it. This does not mean that an
arrangement of tanks cannot work at all.

Casady

DP




I doubt it will work passively.
Control of the phase is most important - and won't coincide with the
roll.

Think great big powerful pumps?

On Sun, 30 Dec 2007 00:20:52 -0500, Wayne.B
wrote:

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.

I thinks its about the same principle as skyscraper passive sway
stabilizers. A moveable mass tuned to the same period as the sway
(roll) frequency, that moves out of phase with the sway or roll,
damping it. Come to think of it, there's the pendulum crankshaft
damper used in light aero engines to damp torsional vibrations - an
engine killer.

Brian Whatcott Altus OK

In article , Richard Casady wrote:
On Sun, 30 Dec 2007 09:41:10 GMT, "Dennis Pogson"
wrote:

[snip]

If this system worked the QM2 would use it instead of spending $millions on
stabilisiers.

What they have is better and they use it. This does not mean that an
arrangement of tanks cannot work at all.

Surely the water wouldn't slosh until the boat started to heel, and then
it would slosh to the lower side aggravating the situation rather than
helping it. Then, as the wave passed, and the boat was prepared to
return to upright, the water would be slow to slosh back 'up-hill' - it
would counter the mass of the keel. Wouldn't that possibly put a boat at
a potentially bad angle to the next wave?

Justin.

--
Justin C, by the sea.

In article , Roger Long wrote:
[snip]

The last ones I was involved with were on a fleet of longliners. The tanks
were tuned by adjusting the level and designed to be about 20% full. After
the vessels were in operation, they were found full to the top on all of the
vessels and they were damn near about to capsize in some loading conditions.
The less stability a vessel has, the slower the roll. The slowest roll
possible is to just lay over and stay there. The captains found that the
boat just got more and more comfortable and rolled slower and slower as they
filled the tanks. They didn't understand the dynamic and the peril they
were exposing themselves to.

Sounds like the principle that makes a metronome work as it does. With
the weight low, the beat/tick is more frequent, the low COG righting
itself almost immediately it moves away from upright. Conversely, with
the weight high up, the beat/tick is much less frequent, but the
momentum of the 'roll' carries a long way passed upright before forces
kick in to bring it back upright.

I agree, it certainly doesn't sound like something you'd want to
over-use on a boat.

Justin.

--
Justin C, by the sea.

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

On Dec 30, 4:37 am, "Roger Long" wrote:
....
The required size is a function of the vessel's stability so, if you have a
vessel with the stability I hope you have, the tanks will be huge ...

Unlike Roger, I'm not a naval architect and I don't have any
experience with this. Still, I suppose a boat with low initial
stability but with adequate stability at high angles might benefit
from smaller tanks. I can imagine a case where a ballasted sailboat
has been converted to a pure motor boat where even a few hundred
pounds of ballast in anti-roll tanks might make the boat at least as
comfortable as it was before the mast was removed. On paper, anti-
roll tanks seem like a reasonable alternative for some types of slow
speed vessels that require additional stabilization and that are
operating in somewhat protected waters. The costs are noise, weight,
difficulty of installation, reduced stability and a limited range of
effectiveness. There was a good article discussing active and passive
stability devices on smaller vessels in Professional Boat Builder in
'04.

-- Tom.

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.