Roll Stabilization Tanks

On Sun, 30 Dec 2007 00:20:52 -0500, Wayne.B
<waynebatrecdotboats.TakeThisOut@hotmail.com> 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
 >> Stay informed about: Roll Stabilization Tanks 

On Dec 30, 4:37 am, "Roger Long" <stri....TakeThisOut@maine.rr.com> 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.
 >> Stay informed about: Roll Stabilization Tanks 

On Sun, 30 Dec 2007 09:41:10 GMT, "Dennis Pogson"
<dennis_nospampogson DeleteThis @ntlworld.com> 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
>
 >> Stay informed about: Roll Stabilization Tanks 

Richard Casady wrote:
> On Sun, 30 Dec 2007 09:41:10 GMT, "Dennis Pogson"
> <dennis_nospampogson.RemoveThis@ntlworld.com> 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?
 >> Stay informed about: Roll Stabilization Tanks 

"Richard Casady" <richardcasady.TakeThisOut@earthlink.net> wrote

>>> Anyone here have any experience with roll stabilization tanks -
>>> designing, building, tuning, etc. ?
>
> Undoubtedly not.

Actually, Yes.

Wayne,

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 if they
are to have more than just a slight effect on anything except conversation.
The higher they are, the better they work so retrofits are seldom practical
because the boat wasn't intended to carry that much weight so high up.
Think also about several hundred gallons of water sloshing around in a tank
without baffles (which would defeat the function) so close to your living
areas. That will make them a converstation item!

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. I designed an overflow limiter for the tanks
but they were simply taken out of service instead. The boats were marginal
on carrying capacity and they ended up needing the weight for equipment and
fish.

The motion you feel is a function both of speed of roll and angle. Reduce
either and you will experience less acceleration. Raising weight in the
vessel slows the roll period but also reduces the reserve stability and
safety if heeled to a large angle. Heel due to wind will also increase
which can effect comfort. Adding things like bilge keels which trap water
and prevent it from flowing transversely around the hull reduces the angle
of roll without changing the rolling period. Flatish, angular hull forms
also do this which is why supply boat style hull forms can be surprisingly
comfortable.

The comfort of this boat in a seaway is legendary:

http://home.maine.rr.com/rlma/Kingsbury.htm

She operates out of Portsmouth, NH where the tide and current run very hard
out of the river against the wind. If you didn't load her up with too much
topside superstructure and weight she would make about as comfortable a 47
foot trawler yacht as could be designed.

--
Roger Long
 >> Stay informed about: Roll Stabilization Tanks 

In article <4781a22f.751179765.TakeThisOut@news.east.earthlink.net>, Richard Casady wrote:
> On Sun, 30 Dec 2007 09:41:10 GMT, "Dennis Pogson"
><dennis_nospampogson.TakeThisOut@ntlworld.com> 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.
 >> Stay informed about: Roll Stabilization Tanks 

In article <4777ad47$0$10970$4c368faf@roadrunner.com>, 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.
 >> Stay informed about: Roll Stabilization Tanks 

Wayne.B <waynebatrecdotboats.RemoveThis@hotmail.com> wrote in
news:6caen3d9si90itv54uk8bdjshll1daj7pn@4ax.com:

> 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
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otnmbrd wrote:
> Wayne.B <waynebatrecdotboats RemoveThis @hotmail.com> wrote in
> news:6caen3d9si90itv54uk8bdjshll1daj7pn@4ax.com:
>
>> 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.
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On Sun, 30 Dec 2007 19:29:48 GMT, "Dennis Pogson"
<dennis_nospampogson.DeleteThis@ntlworld.com> wrote:

>maybe there IS something in this water ballasting
>after all! Perhaps it stops Mari Chai 1V from taking off and becoming a
>flying machine!

Water ballasting and water roll stabilization are two different
things.

Our boat is a Grand Banks 49 trawler displacing in the neighborhood of
60,000 lbs dry, 70,000 loaded. It has a substantial flybridge deck
located about 12 feet above the waterline, and about 12 feet wide.
Since we have frequently had a dozen people up there with no obvious
ill effects, I'm assuming we could also get away with several thousand
pounds of water, especially at anchor. The boat already has dynamic
roll stabilizers which are quite effective underway but are expensive
to maintain.

I'm aware of at least one other boat in this size range that is
successfully using water stabilization. They had their system
designed by a Naval Architect which is no doubt the right way to go
for guaranteed results. I was more interested in cobbling up
something cheap and dirty for some informal testing of the concept on
our boat. Key variables are tank size, tunnel size/shape, and
gallons/pounds of water.

Any suggestions for a starting point?
 >> Stay informed about: Roll Stabilization Tanks 

Roger Long wrote:
> "Richard Casady" <richardcasady.RemoveThis@earthlink.net> wrote
>
>>>> Anyone here have any experience with roll stabilization tanks -
>>>> designing, building, tuning, etc. ?
>> Undoubtedly not.
>
> Actually, Yes.

Roger, how does this differ from water ballasted sailboats (not that I
completely understand how THAT works either)?

--
Peggie
----------
Peggie Hall
Specializing in marine sanitation since 1987
Author "Get Rid of Boat Odors - A Guide To Marine Sanitation Systems and
Other Sources of Aggravation and Odor"
http://shop.sailboatowners.com/boat_odors/
 >> Stay informed about: Roll Stabilization Tanks 

"Wayne.B" <waynebatrecdotboats.RemoveThis@hotmail.com> 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
 >> Stay informed about: Roll Stabilization Tanks 

On Sun, 30 Dec 2007 18:01:09 -0500, "Roger Long"
<strider.TakeThisOut@maine.rr.com> 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.

Thanks, some interesting points there. Weight could largely turn out
to be a non-issue if used only at anchor or as a backup to the dynamic
stabilizer system (Naiads). It would be easy enough to pump some salt
water up into the tanks when I wanted to use them, and drain it back
out afterwards.

I was thinking of buying a couple of fiberglass dock boxes from West
Marine and cross connecting them with PVC pipes. The system could be
tuned by restricting flow or adding additional pipes. I have no idea
how to calculate optimal starting pipe size(s) however.

Just for the sake of argument, lets assume 400 total gallons and a
natural roll period of about 3 seconds. Given a 5 degree roll, most
of that water would have to flow to the downhill tank in about 1.5
seconds if I'm conceptualizing this correctly.
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