Stabilizers

For those that have stabilizers. At what point in sea conditions do stabilizers become ineffective?

Wow! Loaded question! Depends on the boat, size, Hull shape, power, experience and a whole lot of other factors.

Very low speeds.

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.

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".

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.

caltexflanc said:

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".

Click to expand...

“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?

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.

menzies said:

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.

Click to expand...

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.

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.

NewbieFromNJ said:

“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?

Click to expand...

I can only think of 5: yaw, pitch, roll, heave and forward/reverse. What is #6? Sideways?

MYTraveler said:

I can only think of 5: yaw, pitch, roll, heave and forward/reverse. What is #6? Sideways?

Click to expand...

Sinking? Stabilisers can't help, best avoided ......

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.

MYTraveler said:

I can only think of 5: yaw, pitch, roll, heave and forward/reverse. What is #6? Sideways?

Click to expand...

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.

caltexflanc said:

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.

Click to expand...

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.

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.

Fletcher500 said:

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.

Click to expand...

I just heard of sway for the first time. Great. One more cause of seasickness I have to worry about.

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.
https://seakeeper.com/
Sea Gyro for Ships and Boats

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.

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.

Gordon J said:

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.

Click to expand...

I should have mentioned, 7,500+ nm in this boat. Same conclusion.

Who has room

Lepke said:

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.
https://seakeeper.com/
Sea Gyro for Ships and Boats

Click to expand...

For a stabilizer like this? I have fin stabilizers and the internal components take little room in the engine room. I would be hard-pressed on our 46 foot boat to find space for a Gyro.

caltexflanc said:

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.

Click to expand...

My experience is all with ABT, so other may vary...

Everything made since about 2009 is self-centering and self locking. And self tuning. I turn them on when I start the boat and turn them off when I shut the boat down. Otherwise they are always on, and for all intends and purposes, always help reduce roll.

As others have pointed out, if you are going really slow their effectiveness will be diminished, but for any normal forward cruising speed they are always beneficial.

NewbieFromNJ said:

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.

Click to expand...

I don't think this is correct, at least not the fin stabilizer part. We have about 25,000 miles on two different boats with ABT stabilizers and have never experienced anything by positive results in all seas, following included.

chriscritchett said:

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.

Click to expand...

$27K not including installation. I think I'll hang some buckets over the side

I suppose you could include sway, often referred to as "crabbing" in this context, but I guess I never thought of it as something that upsets one's equilibrium.

The gyros are pretty cool, especially at slow/no speed. They first gained popularity on sportfish boats for that reason (who are not about to add paravanes for a number of reasons). The ones I am familiar with all require a generator to be running, where as fins
run off a hydraulic pump from one of the engines.

Same experience

twistedtree said:

My experience is all with ABT, so other may vary...

Everything made since about 2009 is self-centering and self locking. And self tuning. I turn them on when I start the boat and turn them off when I shut the boat down. Otherwise they are always on, and for all intends and purposes, always help reduce roll.

As others have pointed out, if you are going really slow their effectiveness will be diminished, but for any normal forward cruising speed they are always beneficial.

Click to expand...

I too have abt Trac and follow same procedure. I turn the stabilizers On and off with the boat.

I am not debating which system is better, because a lot of people have fins and love them. There are positive and negatives for any system. We are having a Seakeeper installed in a 45 ft. Trawler new build, and I have not heard anything from the builder or yard regarding lack of room. They are putting in a hatch above it to allow install and improve access. A lot of these Gyros are going in on new builds these days, including retrofits on existing boats.

I went aboard the SeaKeeper Gyro test boat at the Stuart Boat Show a couple of weeks ago and was impressed. It was at the dock, and with 4 guys trying to rock the boat, once they enabled the gyro, it stopped rocking within 1.50 cycles.

The guys said most of the power goes to keep the gyro spinning, not hydraulics... I would have thought differently.

On the other hand, Tony Fleming had a gyro installed early on in Venture and removed it due to bearing noise, according to his book, Riding the Tide. I would have to assume that they have improved the technology since then, and he does not name the vendor of the ones he installed and later removed, replacing with fin stabilizers.

One of the installers said some cruisers with fin stabilizers are adding SeaKeepers to provide stabilization while at anchor.

Here’s a good read fin vs gyro:
http://www.jimmyrogersyachtbroker.com/gyro-stabilizers-and-fin-stabilizers-what-you-need-to-know/