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Old 01-26-2018, 05:05 PM   #1
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Stabilizers

For those that have stabilizers. At what point in sea conditions do stabilizers become ineffective?
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Old 01-26-2018, 05:13 PM   #2
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Wow! Loaded question! Depends on the boat, size, Hull shape, power, experience and a whole lot of other factors.
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Old 01-26-2018, 05:19 PM   #3
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Very low speeds.
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Old 01-26-2018, 05:40 PM   #4
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Is your question for active or passive stabilizers? Naiad (hydraulic type fin) which I consider active or paravanes. In either case, head seas or following seas they aren't much help. Paravanes will work at any speed with beam seas.
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Old 01-26-2018, 05:50 PM   #5
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Remember stabilizers affect only one of the four motions of a boat: roll.

In addition to the necessary and well asked questions above, define "ineffective".
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Old 01-26-2018, 06:00 PM   #6
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My Naiads switch off when below 4 kn, via a GPS SOG input. Head or following seas they continue to work fine in terms of roll elimination, but they do nothing for fore & aft pitching.

In shallow water with strong wind that is opposing a strong tidal flow then things get interesting. Basically short period very steep waves on the beam can overwhelm the Naiads. Bearing off to say 45° means roll is manageable, but pitching can become annoying.

Once you have had modern active fins you would never have another boat without them.
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Old 01-26-2018, 07:06 PM   #7
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Remember stabilizers affect only one of the four motions of a boat: roll.

In addition to the necessary and well asked questions above, define "ineffective".


“Ineffective” in the sense that they no longer work and might as well be turned off.
PS I thought there were 6 motions of a boat?
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Old 01-26-2018, 07:17 PM   #8
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If you read the operating instructions for Naiads you will find that in conditions where you have a following sea which is outpacing your vessel you MUST turn them off.

If you think about how they work, if the wave is passing under you the stabilization will work against you with some very dangerous results.
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Old 01-26-2018, 07:21 PM   #9
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If you read the operating instructions for Naiads you will find that in conditions where you have a following sea which is outpacing your vessel you MUST turn them off.

If you think about how they work, if the wave is passing under you the stabilization will work against you with some very dangerous results.
That's only true in severe following sea. Normally you just adjust the roll period sensitivity. I've never encountered seas bad enough to have to turn them off. What does happen is that the autopilot gets a workout trying to maintain heading.
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Old 01-26-2018, 07:27 PM   #10
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I have never been in sea conditions in which my 9sf Wesmars were not effective to hugely reduce roll, but inherent in their design, they do virtually nothing to reduce pitch. So far, the worse the seas, the more effective they are. Unlike Niads, my Wesmars don't shut themselves off at low speeds. When I forget to shut them off, I am quickly reminded when the stabilizers screw up my the boat's tracking while backing. I generally run my boat between 8 and 10 knots. From what I can tell, the stabilizers are equally effective throughout that range. At higher speeds, their effect seems less pronounced.
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Old 01-26-2018, 07:30 PM   #11
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“Ineffective” in the sense that they no longer work and might as well be turned off.
PS I thought there were 6 motions of a boat?
I can only think of 5: yaw, pitch, roll, heave and forward/reverse. What is #6? Sideways?
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Old 01-26-2018, 07:31 PM   #12
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I can only think of 5: yaw, pitch, roll, heave and forward/reverse. What is #6? Sideways?
Sinking? Stabilisers can't help, best avoided ......
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Old 01-26-2018, 07:55 PM   #13
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I was just referring to motions acting on the boat while underway. Sorry for the confusion.

I don't recall the bit about following seas in the Naiad manual. I operated in some wicked following seas and never had such an issue. Maybe not wicked enough?

One thing I do, as reinforced by two excellent techs is that they should never be turned off when underway. At the very least, centered.

The slower the boat the bigger the fins have to be. So there's a big variant right there affecting the OP question.
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Old 01-26-2018, 08:04 PM   #14
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Originally Posted by MYTraveler View Post
I can only think of 5: yaw, pitch, roll, heave and forward/reverse. What is #6? Sideways?


To be honest as a learner I did not know there were more than two. Googled and found heave, sway, surge, roll, pitch and yaw.
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Old 01-26-2018, 08:10 PM   #15
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I was just referring to motions acting on the boat while underway. Sorry for the confusion.

I don't recall the bit about following seas in the Naiad manual. I operated in some wicked following seas and never had such an issue. Maybe not wicked enough?

One thing I do, as reinforced by two excellent techs is that they should never be turned off when underway. At the very least, centered.

The slower the boat the bigger the fins have to be. So there's a big variant right there affecting the OP question.


Somewhat familiar with the pros and cons of conventional vs the gyro stabilizers. Appears a severe following sea may be a pro got gyros and a con for the conventional. Not sure how the paravanes would fit in here.
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Old 01-26-2018, 08:10 PM   #16
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I read a good quote awhile back, that I believe came from this website. “I never met anybody with stabilizers, who wish they didn’t have them”.

Pitch and roll where the only two in my vocabulary until now.
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Old 01-26-2018, 08:36 PM   #17
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I read a good quote awhile back, that I believe came from this website. “I never met anybody with stabilizers, who wish they didn’t have them”.

Pitch and roll where the only two in my vocabulary until now.
I just heard of sway for the first time. Great. One more cause of seasickness I have to worry about.
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Old 01-26-2018, 09:46 PM   #18
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Large gyro stabilizers work in most conditions. They are internal and the spinning mass counteracts roll with gyroscopic torque. It's not necessary to be moving for the gyro to stop the roll. No thru the hull outside fins, etc. Work on boats 10 tons and up. Maybe smaller.
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Old 01-26-2018, 10:01 PM   #19
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Was waiting for this to show up. Coming on strong in most markets, even for ~30’ boats now. Not cheap, but no active stabilizers are. Have seen a lot of skeptics be really impressed by gyros.
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Old 01-26-2018, 10:05 PM   #20
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Cant think of any...

We have about 2000 miles on our boat, and I am currently in the Bahamas. I have not yet encountered any sea state where the stabilizers did not help. But I also have to say that I doubt I would be in seas where I would have to question their effectiveness.
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