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LS

Leonard Stern

Tue, Apr 14, 2020 2:09 AM

Keep in mind that placing rolling tanks on the fly-bridge will drastically change the center of gravity. Trawlers are usually designed with specific CofG. and low down
A better place would be in the engine room if you have space.Whatever you decide get an opinion from a nautical architect so you do not mess up the GofG.May I remind you of Boeing ????

Just my 2 cents FWIW.
Leonard Stern, INDIFFERENCE

Keep in mind that placing rolling tanks on the fly-bridge will drastically change the center of gravity. Trawlers are usually designed with specific CofG. and low down A better place would be in the engine room if you have space.Whatever you decide get an opinion from a nautical architect so you do not mess up the GofG.May I remind you of Boeing ???? Just my 2 cents FWIW. Leonard Stern, INDIFFERENCE

DC

Dave Cooper

Tue, Apr 14, 2020 6:45 PM

Many factors have to go into the design of an Anti Roll Tank, aka ART.
The designer of the tank needs the design hull form, the CoG, the
stability, the roll period, the roll attenuation, plus some variables like
the desired location of the tank, the space that the tank can occupy. All
to stuff into his computer modeling software.
The higher the tank is the less water required, aka weight, it takes to do
its job.

A few of the spec's we gave the designer, Dr Bass, for Swan Song were:
Roll Period: 4.1 seconds
Roll attenuation: 25 seconds
Stability: 1500 lbs on the rail 3 degrees of list.Swan Song is heavy, 50
tons, and very stiff especially for a full displacement hull we have 20000
lbs of ballast.
Preferred tank location: top of the pilothouse 12' X 4' space
Hull design: a few pages of our taking the hull dimensions while Swan Song
was in the water...a whole book worth of how to and the data ;-)

So the final design is a 12' X 4' by 16" high tank. 7 L shaped baffes 16"
high with a 1" spacing 18" from each end. That's it.

We fabricated the tank in the British Virgin Islands of 1" NidaCore so that
the tank itself is light...about 150 lbs.

Again that was 15 years ago, still in top nick and many 10's of thousands
of miles of smooth passagemaking under her keel :-)

Dave
Swan Song
Custom Roughwater 58 North Sea
Lying in FT myer Yacht Basin

On Mon, Apr 13, 2020 at 10:10 PM Leonard Stern via Trawlers-and-Trawlering <
trawlers@lists.trawlering.com> wrote:

Keep in mind that placing rolling tanks on the fly-bridge will drastically
change the center of gravity. Trawlers are usually designed with specific
CofG. and low down
A better place would be in the engine room if you have space.Whatever you
decide get an opinion from a nautical architect so you do not mess up the
GofG.May I remind you of Boeing ????

Just my 2 cents FWIW.
Leonard Stern, INDIFFERENCE

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Many factors have to go into the design of an Anti Roll Tank, aka ART. The designer of the tank needs the design hull form, the CoG, the stability, the roll period, the roll attenuation, plus some variables like the desired location of the tank, the space that the tank can occupy. All to stuff into his computer modeling software. The higher the tank is the less water required, aka weight, it takes to do its job. A few of the spec's we gave the designer, Dr Bass, for Swan Song were: Roll Period: 4.1 seconds Roll attenuation: 25 seconds Stability: 1500 lbs on the rail 3 degrees of list.Swan Song is heavy, 50 tons, and very stiff especially for a full displacement hull we have 20000 lbs of ballast. Preferred tank location: top of the pilothouse 12' X 4' space Hull design: a few pages of our taking the hull dimensions while Swan Song was in the water...a whole book worth of how to and the data ;-) So the final design is a 12' X 4' by 16" high tank. 7 L shaped baffes 16" high with a 1" spacing 18" from each end. That's it. We fabricated the tank in the British Virgin Islands of 1" NidaCore so that the tank itself is light...about 150 lbs. Again that was 15 years ago, still in top nick and many 10's of thousands of miles of smooth passagemaking under her keel :-) Dave Swan Song Custom Roughwater 58 North Sea Lying in FT myer Yacht Basin On Mon, Apr 13, 2020 at 10:10 PM Leonard Stern via Trawlers-and-Trawlering < trawlers@lists.trawlering.com> wrote: > Keep in mind that placing rolling tanks on the fly-bridge will drastically > change the center of gravity. Trawlers are usually designed with specific > CofG. and low down > A better place would be in the engine room if you have space.Whatever you > decide get an opinion from a nautical architect so you do not mess up the > GofG.May I remind you of Boeing ???? > > Just my 2 cents FWIW. > Leonard Stern, INDIFFERENCE > _______________________________________________ > http://lists.trawlering.com/mailman/listinfo/trawlers_lists.trawlering.com > > To unsubscribe or modify your subscription options (get password, change > email address, etc) go to: > http://lists.trawlering.com/mailman/listinfo/trawlers_lists.trawlering.com > Trawlers & Trawlering and T&T are trademarks of Water World > Productions. Unauthorized use is prohibited. >

MM

Mike Miles

Tue, Apr 14, 2020 9:02 PM

Did I calculate the amount of water correctly? I make it 2 tons. Must be
quite a strong wheelhouse! I do like the idea of this simple solution to
anti rolling. Much less hassle than floppers, underwater wings or
gyroscopes. Nothing to go wrong and no maintenance.

On 14/04/2020 19:45, Dave Cooper via Trawlers-and-Trawlering wrote: