T&T: Active Fin Stabilizers

[Terry mann]

Does anyone have any before and after data on what speed and fuel
consumption they got a given RPM prior to installing Active Fins VS after
installation what speed and fuel consumption they got at the same RPM? There
is a price to pay in economy as you are creating drag, I would like to know
how much that price is before I make a decision on installing them.

For those slower trawler folks that have them........Are they still
effective when you are only making 6 knots speed through the water? I am
not talking about 6 knots speed over ground. The Stabilizer only knows the
speed at which they pass through the water. The lift is a function of the
speed squared and if the speed is too low to create the needed lift then you
put larger fins on. This creates more drag and less economy.

--
Terry Mann

(828)-777-7753
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[Joel Wilkins]

Don't know if they would make the data available, but when the Nordhavn 40 went from CA to Hawaii I seem to recall that they shut off the active stabilizers to conserve fuel. Perhaps a call to Jim Lishman or Nordhavn would get long term data you need.
Joel Wilkins
Miss Magoo

--
Terry Mann

(828)-777-7753
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[Ron Rogers]

Yes. My boat is 40 feet and has oversized Naiad 252s.

Ron Rogers

----- Original Message -----
From: "Terry mann" <dock...@gmail.com>
|
| For those slower trawler folks that have them........Are they still
| effective when you are only making 6 knots speed through the water? I am
| not talking about 6 knots speed over ground.

[John Ford]

That question is a bit loaded. The fins create as much resistance as the work they are asked to do.. Be off balance because of 100 gallons of extra fuel on one side the fins work hard to keep you straight. Taking a beam sea, or a healthy wind to the side, again they are working hard creating resistance so you can be straight. Also on the Tracs(I'm sure the others you can do something similar) you can tell the stabilizers how much heal will you allow, Zero(lots of resistance but you are vertical), Opt(middle ground between zero and max), and Max which allows some leaning do to wind and cuts down on the resistance. Zero Heel can have quite a penalty and I rarely use it unless I'm trying level the tanks or something. I'd say my penalty with max on in the calm waters of the bay are a quarter to half a knot depending on conditions. I typically don't turn them on unless the waves get to 2 feet or larger or we are cooking food when underway.

Again, YMMV..

John Ford
KK44007 Feisty Lady
Annapolis City Marina

[Jeffrey Siegel]

>Does anyone have any before and after data on what speed and fuel
>consumption they got a given RPM prior to installing Active Fins VS after
>installation what speed and fuel consumption they got at the same RPM?

I can guarantee that installing stabilizers will increase your fuel consumption. A lot.

I'm off the New Jersey shore in 3-4 foot straight-on-my-beam seas right now.
My wife and I are on our flybridge. She's sewing. The dog is asleep. If
I didn't have stabilizers, I wouldn't be using any fuel today.

========================
Jeffrey Siegel
M/V aCappella
DeFever 53PH
Headed toward Chesapeake Bay
Mobile phone cruising blog:
www.mvacappella.blogspot.com

[Terrence Neill]

snip

> < Does anyone have any before and after data on what speed and fuel
> consumption they got a given RPM prior to installing Active Fins VS
> after
> installation what speed and fuel consumption they got at the same
> RPM? There
> is a price to pay in economy as you are creating drag, >

> <For those slower trawler folks that have them........Are they still
> effective when you are only making 6 knots speed through the water?>

Not directly on topic, but related. We installed batwing stabilizers
on Tamarack in '04. She's a 52 foot converted seiner with a true
displacement hull form. Before installation she would roll on wet
grass with a four second period.
The batwings are fixed roll stabilizing plates attached to the keel
somewhat aft of midship...extending to within inches of the total
width of the boat and comprising a total of some sixty (60) square
feet of surface. I have forgotten the weight, but it is 5/8 steel plate.
The roll reduction underway is noticeable at idle (about 3-4 kts),
increasing to approx 70 percent at cruise (8-9 kts). There is no
effect when stopped.
The drag penalty seems to be directly related to speed (as expected)
and reaches a maximum of somewhat more than 1/2 kt. The maximum speed
obtainable at wot has been reduced to close to hull speed. I think
that the drag at the higher speeds is somewhat counteracted by
increased squatting, which on this boat with a long sloping counter
increases the wetted length by several feet.
The increase in comfort from this (totally passive) system more than
offsets the loss of speed.

An aside re: roll tanks - we considered them but gave up when we were
unable to locate any statistical info on the boat...no lines or any
of the stability data are known to exist, and producing them seemed
to be just one obstacle too many. These kinds of data are essential
to the design of effective roll tanks.

Terry
Tamarack

[Ron Rogers]

How do you keep the area between the hull and the wings clean and bottom
painted?

Ron Rogers

----- Original Message -----
From: "Terrence Neill" <tsn...@centurytel.net>

| The batwings are fixed roll stabilizing plates attached to the keel
| somewhat aft of midship...extending to within inches of the total
| width of the boat and comprising a total of some sixty (60) square
| feet of surface. I have forgotten the weight, but it is 5/8 steel plate.

[Dave Cooper]

Terry wrote: An aside re: roll tanks - we considered them but gave up when

we were unable to locate any statistical info on the boat...no lines or any

of the stability data are known to exist, and producing them seemed to be
just one obstacle too many. These kinds of data are essential
to the design of effective roll tanks.>

In order to properly design these tanks for a boat you do need this data. I
too didn't have anything on Swan Song.

It took my wife and I one day to take about 75 data points of the hull
offsets and do the inclination tests all in the water. A bit of a PTA but
certainly not a deal breaker for us in going forward with our tank.

As a side benefit of doing this we have ended up with a nice 3 D model of
the hull that we are working on to do the topsides. Once it is all do we can
watch her on the computer screen and rotate her around. Want a new paint job
or stripe? Bingo it's there. Take a look at what she'd look like ;-)

Cheers

Dave & Nancy
Swan Song

[Dave Bullis]

I installed West Mar active fin stabilizers on my 47 Defever last winter and
kept careful records of fuel consumption from the season before and after
installation. I found zero impact to fuel consumption from the stabilizers.

Dave Bullis
Facing West
47 Defever RPH

[Terrence Neill]

Now that this topic has been masticated pretty thoroughly, it should
be noted that the big gorilla in stabilization (Naiad) has for some
years sold equipment which it claims will counteract roll while
anchored.
Naiad is a big company, and they're marketing it. Since they're still
in business I assume it's not smoke.

See http://www.naiad.com/2003-09SAFlyer.pdf

I like the roll (flume) tank notion. I like passive systems. But for
some boats (especially large ones), maybe the Naiad system would be
sensible.

Terry
Tamarack

[Dave Cooper]

<Terry wrote: I like the roll (flume) tank notion. I like passive systems.

But for some boats (especially large ones), maybe the Naiad system would be

sensible.>

I am aware of the Naiad zero speed product. A couple of the mega yachts that
frequent the BVI have them and they do work well according to the captains
I've talked to. OTH, these systems cost a lot more than the normal fins and
require operation of the genset all the time as they are not driven off the
engine. SO if you wanted to use a smaller version on a trawler you'd need to
run the genset whenever you wanted to use the fins underway or at anchor.
Not the option I'd like to use on Swan Song

The big "gorilla" in stabilization is the Flume Company. They deal with many
of the cruise ships and merchant marine fleet.

There is much promise in the gyro's from MHI in Japan if they can solve the
cost, heat and power requirement issues.

The rudder wag system works on fast ships but doesn't scale down well and
requires the boats structure to be built in from the early design phase.

Trim tab stabilizers are slowly beginning to come on the market but again
they are expensive and only work in a limited design envelope.

Paravanes we all know the plus and minus's of.

Ditto convention active fins

We went thru all of these systems, and maybe a couple of others that I can't
remember right now, when looking at one for Swan Song's stabilization
system.

We chose Don Bass' stabilization tank and it works for us. It may not for
you nor may not even be suitable for your boat if it has marginal stability
anyway. Only a full analysis by Don or other marine design professional can
make that call.

Again YMMV and I am only trying to let folks know our experience with
something different in the stabilization arena that works for us on our boat
in the sea conditions we have encountered to date. Hell, we may find
ourselves upside down in a big sea someday again and get to say..."gee I
wish we had gone with active fins so we'd have something to hold onto
instead of this slippery bottom" ;-)

Cheers
Dave
Swan Song

[Pete Drez]

Have a question for those who have active fin stabilizers on their current
boat in operational condition. Question: Would you prefer to have your boat
without the stabilizers?

We have active fin stabilizers and would not own a boat without them. As for
the drag, the loss of a fractional knot, the use of a little more diesel, etc,
a look at the forest rather than using a microscope on a single tree may be in
order. If you have active fin stabilizers, or are considering them, you have
already spent a good amount of money on a boat. Then you have/will have handed
over a $35K plus for stabilizers, either as an install or in the price of the
boat. And we are debating the cost of a couple of gallons of diesel fuel in
each tank full for a significant improvement in cruising comfort. Excuse me, I
have to go get the boat ready for departure today for a week cruise, and yes,
the stabilizers will be on and they are welcome to the power they need to
operate.

Pete

[Dave Cooper]

<Pete wrote: And we are debating the cost of a couple of gallons of diesel

fuel in each tank full for a significant improvement in cruising comfort.
Excuse me, I have to go get the boat ready for departure today for a week
cruise, and yes, the stabilizers will be on and they are welcome to the
power they need to operate.>

Heavens Pete, I don't think anyone, I know I certainly haven't, has
suggested removing or not using whatever kind of stabilizers you currently
have installed. Once the commitment has been made to a particular type of
unit then the money has been spent. Use them and enjoy the reduced roll :-)

I'm only suggesting that there is one more type of stabilization system that
people may want to look at before they make the investment. In doing so they
should look at all the cost involved. Not just initial purchase,
installation or operational cost but total lifetime costs.

OTH, if you have plenty of $$$ then go with the MHI gyro's. There's nothing
better on the market for absolute stability but for Swan Song and our budget
we just couldn't swing it. $150K plus the ongoing cost to run a dedicated
20KW genset and an additional 16K BTU Air conditioner to keep it cool ;-)

We took a simple and effective way for us. We too never leave the dock
without our tank "turned on"...as a matter of fact it's always "on" ;-) Swan
Song was a rolly lady and now she's a well mannered comfortable one all the
time.

YMMV

Dave
Swan Song

[Carl H. Martin]

Dave,
I have found the information you have shared on the stability tank very
interesting. Before your posts regarding Swansong I had never heard of
them.

I have a small boat with a full displacement soft chine hull. At 30' she is
obviously too small for fins & while paravanes are an option they are a
hassle & would not solve 2 big problems, rolling at anchor & rolling caused
by wakes in channels. I would think that if a boat meets the stability
requirements the physics of the stability tank would not be limited by boat
size. What do you think?

Carl Martin
Scout 30

----- Original Message -----
From: "Dave Cooper" <swan...@gmn-usa.com>
To: <trawlers-an...@lists.samurai.com>
Sent: Saturday, October 14, 2006 9:58 AM
Subject: Re: T&T: Active Fin Stabilizers

[Steven Dubnoff]

A very good article on stabilization options by Michael Kasten can be
found here:

http://www.kastenmarine.com/roll_attenuation.htm

My guess is that 50+ feet is where tanks become practical.

Best,

Steve

Steve Dubnoff
1966 Willard Pilothouse
www.mvnereid.com
sdub...@circlesys.com