Stabilizers - Gyro vs Electric Fin

Saw a Humphree at the Sanctuary Cove Boat Show today. It does look pretty nice. It is 24V and can run overnight from a decent sized house bank. They can rotate 360° so they don't swim forward at anchor but instead can keep your rode in a normal downwind catenary which is important in an anchorage with other boats. Even in the US you are likely into 6 figure installed - not inexpensive!

Insequent said:

Saw a Humphree at the Sanctuary Cove Boat Show today. It does look pretty nice. It is 24V and can run overnight from a decent sized house bank.

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They seem nice.

I would bet they will come up with a 48V version/option soon. It would make sense for the bigger models, to keep the currents and wiring size more manageable.

Having started this thread, thought I would update everyone on where I landed. After doing a significant amount of research I was satisfied electric fins would work well in my application for all the reasons recently stated here recently. Stabilization at anchor was important, I already planned to have a sizable LiFePO4 house bank, and the simplicity of installation and minimal space requirement of electric fins was enticing. After finally making that decision I had NPY price out both the SeaKeeper SK6 and the recommended CMC Waveless fins. The published Waveless literature states the for a 45ft trawler the STAB20 should suffice. This install price was pretty much identical to the SK6 SeaKeeper ($750 differential) and I was ready to be a “trailblazer” and go with electric fins. Unfortunately Waveless came back and said that to provide stabilization at anchor they would recommend going one size up (STAB25), which increased the cost by 35%! That was a deal breaker. While maintenance/reliability was my biggest concern with the SeaKeeper system, for 1/3 the cost differential (SK6 to STAB25) I can buy a 5yr/4000hr extended warranty. Yes, while its not 20yrs that many get out of their hydraulic fins (maintenance/life expectancy of electric fins unknown but expected to be good) its good enough for me. Also I do like the idea of everything being inboard as most/all of my time will be spent coastal and inland cruising. I have therefore directed NPY to go with the SeaKeeper system.

SANAUH said:

The published Waveless literature states the for a 45ft trawler the STAB20 should suffice. This install price was pretty much identical to the SK6 SeaKeeper ($750 differential) and I was ready to be a “trailblazer” and go with electric fins. Unfortunately Waveless came back and said that to provide stabilization at anchor they would recommend going one size up (STAB25), which increased the cost by 35%!

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Could you share (at least) the ballpark price range you were quoted for these?

SANAUH said:

while its not 20yrs that many get out of their hydraulic fins (maintenance/life expectancy of electric fins unknown but expected to be good)

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I see no reason why they should not easily last the same, if the parts are dimensioned correctly so there is no overheating etc. At work I have come across multiple electric motors decades old and working just like new.

SANAUH said:

I have therefore directed NPY to go with the SeaKeeper system.

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Undoubtably a good choice for you, but a bummer as I would have been glad to hear first hand experience on commissioning and using the electric fin stabs!

$60K for the SK6 and STAB20. $80k for the STAB25.

SANAUH said:

$60K for the SK6 and STAB20. $80k for the STAB25.

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It says "STAB 25 is the perfect fit for yachts between 15 m (50 ft) and 24 m (80 ft)", so I presume as my boat fits that range, they would suffice for passage stabilization, but for at anchor would need to be sized up one to STAB 30 model.

They are indeed rather expensive. I would bet with time the prices might come down, or you never know in this "new normal" timeline.

I went back and reread the email exchange from a couple of months ago with the Waveless rep regarding fin sizing. Old age is creeping in and reason for needing to upsize the fins was not stabilization at anchor. It was actually stabilization at “slow” (as in trawler) speeds.

Actual response from the rep…

For the 45, the “standard” sizing would be STAB20 0.50sqm for both anchor and navigation. However, at speed below 12 knots fins (all fins, not just ours), have limited efficiency, and roll reduction performance is affected. Therefore, we have to recommend a bigger size STAB25 with 0.80sqm fins to compensate for slower speed and deliver sound performance when cruising at 8 knots. Both will work fine at anchor.

Dav said:

Actually, a motor like the one in a stabilizer would suit perfectly for steering as well - maybe implemented as a bldc motor with two independent windings and controllers fed from independent batteries, for full shared nothing class redundancy.

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Well, they seem to read this forum and it did not take them long:

https://www.cmcmarine.com/steering-systems

Instead of two identical motors they went with a main motor and smaller emergency one, each with independent power supply (230VAC and 24VDC).

This is a more conventional mechanical actuator, but I would think direct driven BLDC like in the fin stablilizers would work even better and be much more responsive.

Dav said:

Well, they seem to read this forum and it did not take them long:

https://www.cmcmarine.com/steering-systems

Instead of two identical motors they went with a main motor and smaller emergency one, each with independent power supply (230VAC and 24VDC).

This is a more conventional mechanical actuator, but I would think direct driven BLDC like in the fin stablilizers would work even better and be much more responsive.

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For steering the actuator is probably fast enough that going faster won't really matter. So might as well use the actuator design that's easier to work into an existing steering system (and can be disconnected to re-gain emergency steering via another method if something fails in a way that may prevent movement).

rslifkin said:

For steering the actuator is probably fast enough that going faster won't really matter. So might as well use the actuator design that's easier to work into an existing steering system (and can be disconnected to re-gain emergency steering via another method if something fails in a way that may prevent movement).

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I agree on the speed, steering does not need to be that fast.

But conventional electromechanical actuator is much more complex system, and they have additional failure modes like stuck/stripped gears etc. A direct driven BLDC is much simpler, it has no moving parts if we don't count the bearings and it disconnects/freewheels automatically, when the brake is not engaged. Also it has the ability to soft brake, slow down the movement without locking 100%. This might be very beneficial in an emergency situation.

In addition, both steering and fins being the same unit and from same manufacturer would reduce the spares needed, and also the systems could be coupled together. Steering ie. rudder could correct fin-caused "steering" faster and also take part into the stabilization.

This is already used in many ships and called "Rudder roll stabilisation". Even more effective together with the fins.

Or even bigger bonus, the fins could very well be used as part of the steering, and also as an emergency steering mode, with fins alone.

Dav said:

I agree on the speed, steering does not need to be that fast.

But conventional electromechanical actuator is much more complex system, and they have additional failure modes like stuck/stripped gears etc. A direct driven BLDC is much simpler, it has no moving parts if we don't count the bearings and it disconnects/freewheels automatically, when the brake is not engaged. Also it has the ability to soft brake, slow down the movement without locking 100%. This might be very beneficial in an emergency situation.

In addition, both steering and fins being the same unit and from same manufacturer would reduce the spares needed, and also the systems could be coupled together. Steering ie. rudder could correct fin-caused "steering" faster and also take part into the stabilization.

This is already used in many ships and called "Rudder roll stabilisation". Even more effective together with the fins.

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That makes me think of an interesting point. You may end up with a tradeoff. The actuator type would be harder to back-drive, so it would likely use less power and make less heat (as it wouldn't need to provide as much motor torque to hold against water pushing on the rudder).



So it would be a question of whether the install in question would be designed to take advantage of the features you could implement with the faster motors or not and whether you're retrofitting an existing rudder setup where installing the faster motors may or may not be practical (vs an actuator that would likely just drop right in).

rslifkin said:

That makes me think of an interesting point. You may end up with a tradeoff. The actuator type would be harder to back-drive, so it would likely use less power and make less heat (as it wouldn't need to provide as much motor torque to hold against water pushing on the rudder).

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These direct driven high torque motors usually have a integrated, but separate magnetic braking device, so that the no-speed torque does not need to be held actively and thus consumes very little torque/power. Maybe a separate positive locking pin would also be a good addition, like they have in the hydraulic fins usually.

Maybe this is where we could leave a place for (electro)hydraulics, for braking it is an excellent choice

Of course this combining of roll stabilization and steering is not mine nor novel:

https://core.ac.uk/download/pdf/36699844.pdf

But it would just make so much sense. One supplier for all the fin actuation, one set of spares, one combined integrated system and ability to use fins smartly together, and in emergency to use the fins available, without loosing either 100% of the steering or stabilization.

Actually, it seems none of these electric stabilizers is (yet) direct driven.

Waveless units have a small epicycloidal reducer pancaked next to the motor, and other manufacturers seem to have somewhat similar setup:

https://www.praxis-automation.nl/products/electric-fin-stabilizer

https://www.naiad.com/wp-content/uploads/2021/09/Product-Flyer-Electric-Fin-Stabilizers.pdf

And I would think Humpree has similar reducer as well.

SANAUH said:

$60K for the SK6 and STAB20. $80k for the STAB25.

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So ultimately you compare a SK6 to a STAB20. Not really a fair comparison. All the reasons the STAB25 was called for also would call for a SK9, which is over $90k. I hope it works out for you but Seakeeper is notorious for undersizing and for owners wishing they'd gone one size larger.

BandB said:

So ultimately you compare a SK6 to a STAB20. Not really a fair comparison. All the reasons the STAB25 was called for also would call for a SK9, which is over $90k. I hope it works out for you but Seakeeper is notorious for undersizing and for owners wishing they'd gone one size larger.

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Correct sizing is quite important. I can see a business quoting towards the minimum requirement to avoid losing customer to a competitor.

My boat is 50' and 30 tonnes. The yard sized the Naiad's at 7 sq ft fins to give reasonable performance at slow speeds (6 kn), so that at normal cruise (8-9 kn) they would perform well. And they have. In 9 years they have only been overwhelmed a couple of times - shallow water strong wind against outgoing tides generating steep closely spaced waves. Change of heading got back to it being manageable.

The STAB 20 has only 5.4 sq ft fins. I can see that as being iffy. The STAB25 can have fin sizes from 7 - 8.6 sq ft. They would be my choice, but of course its the OP's money and not mine!

Last time I was in a major boatyard here I was told there were a lot of Seakeeper's coming out of boats. At the time I thought it was due to reliability and maintenance issues, but undersizing and a resultant poor bang-for-the buck outcome might be a factor also. I'd suggest the OP do more research if possible before installing an SK6, simply on the basis of it likely being too small.

BandB said:

So ultimately you compare a SK6 to a STAB20. Not really a fair comparison. All the reasons the STAB25 was called for also would call for a SK9, which is over $90k. I hope it works out for you but Seakeeper is notorious for undersizing and for owners wishing they'd gone one size larger.

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Except for Seakeepers aren’t dependent on boat speed to produce their stabilizing effect. So the reasons the fins needed upsizing may not apply to the SK.

guy with a boat said:

Except for Seakeepers aren’t dependent on boat speed to produce their stabilizing effect. So the reasons the fins needed upsizing may not apply to the SK.

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I'm just saying a lot of disappointed Seakeeper owners over undersizing. Salesmen seem to love to undersize to reduce the price and make the sale. Everyone with experience that I know recommends one size larger than Seakeeper's website and charts.

And just to add, others selling stabilizers do the same as do anchor manufacturers and thruster sales persons and others. Common practice to sell based on price.

I have a Hobie 360 kayak for fly fishing. Your legs drive two nearly horizontal paddles that can also aliase which can steer you as effectively as the sledge and rudder.
Wonder if for displacement boats such a system driven by the new electric motors would work. No need for thrusters at all. Nor other appendages if you so choose. On the Hobie the paddles kick back without damage and reset when you go forward again.
Just thinking outside the box.

We have a SeaKeeper 5 on a NT42. Installed a decade ago. Works fine. Wonder if that 5 year policy was necessary.

mvweebles said:

Website shows mostly larger, fast boats such as a Sunseeker. Compact design would really benefit small boats such as mine (hydraulic tank takes up a fair amount of space). Any sense if there are electric actuated fins that scale down? When I replaced mine, Wesmar and Naiad were the only options.

I would also think installation would be less expensive, especially on a smaller boat that frequently does not have a PTO of the generator or engine.

Peter

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A friend removed his hydraulic stabilizers and put the electric Humphree on. Now has an all electric boat. Stabilizers, windlasses, and thrusters.

We have a 25t 2010 4800 Navigator Pilothouse. She has 21kWh 48V LiFePO4 bank paired with a 10kW Victron inverter setup backed up with a 10kW genset. Since we are an all electric boat and have relatively limited mechanical space, we’ve selected the Electric CMC Waveless Stab 20.

The kit is $55k (with dual helm screens) and we are expecting another $20k in installation.

The extremely low wattage draw (at speed or zero motion), small footprint, track record on larger vessels, minimal moving wear parts, and non-proprietary electric motors from the industrial robotics industry all played a role in our decision.

My experience of reaping significant benefits by being an educated early adopter gives us a great deal of confidence in this solution. Much like the shade I received implementing LiFePO4, which is rapidly transforming how we power vessels, I see electric motors making new hydraulic fin stabilizer implementations a thing of the past, in the bit so distant future.

We’ll keep y’all up to date on the refit and results.

Jpmelliott said:

We have a 25t 2010 4800 Navigator Pilothouse. She has 21kWh 48V LiFePO4 bank paired with a 10kW Victron inverter setup backed up with a 10kW genset. Since we are an all electric boat and have relatively limited mechanical space, we’ve selected the Electric CMC Waveless Stab 20.

The kit is $55k (with dual helm screens) and we are expecting another $20k in installation.

The extremely low wattage draw (at speed or zero motion), small footprint, track record on larger vessels, minimal moving wear parts, and non-proprietary electric motors from the industrial robotics industry all played a role in our decision.

My experience of reaping significant benefits by being an educated early adopter gives us a great deal of confidence in this solution. Much like the shade I received implementing LiFePO4, which is rapidly transforming how we power vessels, I see electric motors making new hydraulic fin stabilizer implementations a thing of the past, in the bit so distant future.

We’ll keep y’all up to date on the refit and results.

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Thanks for the info. I have not heard of this brand, but am definitely interested. Like you we are also going as much electric as possible and most stabilizers are very power hungry.
So am really curious to find out what your experience will be. The installation price seems low, but would be great if they will do it for that price. I already had a quote for Humphree of 120.000 euro just for installing them. That was a bit over the top.

So looking forward to your story !

Hippocampus said:

We have a SeaKeeper 5 on a NT42. Installed a decade ago. Works fine. Wonder if that 5 year policy was necessary.

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I was told (by a captain of a super yacht) that the main problem with the seakeeper are the bearings. Apparently they need to be changed if you use the boat heavily, like a live aboard. And the cost of changing the bearings seems to be immense.
Is that true in your opinion or do you think that is just a marina myth ?

Mambo42 said:

Thanks for the info. I have not heard of this brand, but am definitely interested. Like you we are also going as much electric as possible and most stabilizers are very power hungry.
So am really curious to find out what your experience will be. The installation price seems low, but would be great if they will do it for that price. I already had a quote for Humphree of 120.000 euro just for installing them. That was a bit over the top.

So looking forward to your story !

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I briefly looked at Humphree however, being currently limited to a 24VDC system, was eliminated since our main house LiFePO4 bank is 48VDC inverting to 120/240VAC. That put CMC Waveless on our short list. I really like the 240VAC power factor as it keeps the current below 10A.

As to total power consumption, the option we’re going with is 0-1kW underway and 0-2kW at anchor. Since the fins are only active during roll, the average power consumption is .1kW underway and .25kW at anchor. That’s 60hrs on the hook, with our 21kWh bank.

In practice, we recharge every morning from our genset, for a couple hours, and then run off of our inverter the rest of the day.

Problem with the internal bearings is the device needs to be removed from the boat and the vacuum broken. The actual replacement isn’t the issue. Had the thing gone over by a certified tech and had several phone conversations with SeaKeeper. After a decade it’s at 25% of the time before that service is likely to be needed.
We don’t use it every time. Of course you plan ahead for weather so decide then if it’s needed. Have turned it on mid transit after my at least twice a day routine of reassessing the weather. It does eat the zinc in the heat exchanger but their cheap and can be done in ten minutes inside the boat. Figure doing bearings is less frequent than seals on fins. More money and longer time of use of the device. However during that time you can use the boat. It just won’t be stabilized.
To my mind if long ocean passage go with Humphrees. If coastal or skinny water SeaKeeper. If both Magnus Master. This assumes FD or SD hull of 40-60’.

The Waveless Stab look interesting from a couple of angles. It looks to me like the install is significantly less costly, if you look at the recent threads installing hydraulic ones the hydraulic installation by itself was a lot of time (and space). Very little space required inside the hull. The are also "shaftless", I wonder what the safety fuse is when you strike something?

We installed our Waveless STAB 20 electric fin system 3 weeks ago. 17 hours underway and 174 hours in anchor mode (zero speed). Very pleased. Power consumption is nominal ~100 Watts underway and 135W average at zero speed. We have 21kWh of LiFePO4 so, we can go days on end without recharging.

We’ve experienced a couple outings with 30knt sustained and 45knt gusts. 5 ft trailing seas used to be absolute punishment on our 2010 48’ Navigator (especially with her tall bridge hardtop). No longer. It is absolutely surreal how flat she rides.

The 180 degree fin rotation at anchor stops her from walking up on the rode. A very elegant solution in our early assessment.