Anything good or bad about seakeeper gyros?

[Nick_H]

I've been offered a factory refurb gyro with full warranty as new, at an attractive price, and have met with an approved installer in Cannes who can fit it. I'm planning to place the order tomorrow. I've only found generally positive reviews, and I notice that Princess etc. will fit one on new boats, so they must think they're OK. Anyone heard anything to the contrary, or know someone who has one fitted? I can't realistically fit fins, so gyro seems the only option to keep my Margaux in it's glass

 

[Deleted User YDKXO]

Dunno whether this helps but I was talking to the Croatian Ferretti dealer about this very subject a few days ago and he says that his Ferretti customers who have specified gyro stabs (I think they use the Mitsubishi ones) have been very pleased with their performance. I suppose he would say that though. They seem to take a while to spin up to max rpm though (10-15mins) and a while to spin down too. I have heard one comment about noise but I can't verify that

 

[Nick_H]

Princess fitted one to a P62, bigger and heavier than my boat, and achieved 75% resonant roll reduction, so I'm confident it'll work, but less confident about reliability/teething probs etc. One downside is you have to run the genny all the time, but fortunately it's fairly quiet on the Princess.

 

[MapisM]

less confident about reliability/teething probs etc. One downside is you have to run the genny all the time, but fortunately it's fairly quiet on the Princess.

Yup, also for me reliability would be the major concern - after checking if space/location isn't a problem, which in many boats actually is.
The fact that a relatively new (I suppose) equipment already needed a complete refurbishment rings a bell in this respect, particularly if you consider that some fins stabs have a proven track record which is measurable in decades rather than years...
Otoh, I don't see the initial lag and the need to run the genset as major problems, because a) you would need the genset also with fins stabs, when used at anchor, and b) on a P boat, you would probably use them mostly in longish passages at slow speed.
Overall, on anything capable of cruising speeds in excess of 20 kts or so, gyro would probably be the first choice I would consider, if speccing a new boat. Unless I'd plan to use her almost always at slower speeds, but in that case I wouldn't go for a P hull.
And I'm saying this as an absolute fan of fin stabs, spoilt by a decade of trouble free usage.
I'd never consider anything else on a D/SD boat.
But as always, horses for courses.

 

[Nick_H]

Mapis, it's Seakeepers own R&D unit, but they have a model upgrade, so will take a new one for R&D, and rebuild the old one. All workings will be new, just re-use the case, bearers etc.

We want it mainly for at anchor, and I think gyro may be better for this purpose, though fins probably better underway. We've found a suitable location, same place Princess would fit a new one, and only minor mods req'd.

 

[jfm]

Hi Nick. A few thoughts:
1. If fitting a gyro, Seakeeper is the one to get. Despite all the marketing hype and special exclusive relationship with Ferretti blah blah, the Mitsubishi is considerably inferior technically. A crucial issue is precession. The gyro gizmo spins and is gimballed, and if you tilt it say fore-aft on the gimball, then it will induce a torque that will roll/anti roll the boat about the boat's fore-aft axis. Main issue is that the better control of the precession, the better the gyro, AOTBE. In big ship systems they use hydraulics to actually induce precession, but no leisure sytem has that yet. In Mitsubishi they don't control it at all; they merely damp it. Pretty limiting, that. In Seakeeper they have quite clever control whereby the hydrualics can slow it down, damp it, lock it (all via algroithms that have as inputs the boat's movement, captured by gyros and inclinometers in the c omputer) though not actually induce it. That's quite decent stuff, and in conclusion Seakeeper is considerable better than Mitsu, technically, imho

2. If your priority is at-anchor, then this is a good choice. The gyro is way inferior to fins underway, but at anchor it is broadly as good in principle. It needs to be installed right, with noise maangement, and you have to live with the spin-up delay time and all that (though once it is spinning you can flick it on and off to see how good it is, merely by locking/unlocking the precession tilt on the control panel), but if all that is done right then it is good kit

3. Maybe you need some come back if they dont manage the noise and it whines?

4. I was going to say be careful if buying 2nd hand but your later post allays those concerns. Remeber the tip speed of this baby is mach 1 and the rotor weighs (iirc) 150kg and the only thing between it and your kids is the casing. you plywood saloon floor aint gonna save you. But this sounds like proper refurb gear so no worries there

5. The bearing cooling gear must be installed right. 10,000++rpm iirc!

6. I presume they will nail it to the engine bearers, which seems good idea?

7. I know you care less about underway so what follows isnt hugely important. The gyro can only produce the same antiroll torque underway as when anchorted, whereas a fin can produce way way more torque underway. A gyro can generally not compete with a fin underway. Also a gyro only roduces the anti roll torque as it precesses. Once you have reached the end of the precession angular stroke, it has to return to centre the other way. Now, at anchor that makes it like-for-like with a fin, which also has a finite angular stroke. But underway a fin has no stroke limitation. If you had an infinitely wide beam-on swell that malkes the boat tilt 30degrees for an hour, the fins can angle themsleves and hold you flat all of that hour. A gyro however can only apply a torque as it precesses, so it will run out after a couple of seconds. And worse still, the more torque it applies (ie the faster it precesses) the less time it can apply a torque for, if you get my drift. you can have a little anti roll torque for 2 seconds or a lort of torque for half a second, I mean. Now, as I say, that limitation also occurs with fins at anchor but underway this limitation completely disappears with fins becuase they act as foils and do not need to "swim" or flap. But with gyro you have this limitation underway too, and that's a big negative. So underway a fin always wins, assuming you want to be margeaux spill free in a wide variety of sea conditions

8. As everyone knows, a planing boat stiffens (much harder to alter its roll angle) once it is on the plane. That is a big issue for gyros. When you are 20kts in a big swell, your hull has some inherent anti roll property due to its stiffness when planing but it does tilt/roll somewhat towards the face of the wave. It is so stiff that a gyro will generally not have the torque to twist the hull flat again, so the hull will really do what it wants, but a bit damped by the gyros. In contrast a fin has way way more anti roll torque than a gyro, like 10x more or something like that, so even a fast stiff hull can be rolled to a flat angle by a fin and held there all day long

9. Because of the analysis in 7/8 above I completely disagree MapisM's statement that for >20kts the gyro is better choice. I find that statement completely contrary to the underlying physics and engineering. It is specifically at 20 knots, or fast speeds generally, that a gyro runs out of grunt (against the stiffness of a planing hull) and falls victim to i's own inherent physics which say it cannot produce a high torque for a long time interval. At 20knots all the physics tells you a fin will beat a gyro and anything to the contrary is marketing hype (of which there is plenty). This isn't matter of opinion, it is engineering fact. Underway, fins are different animals from at rest: they give you as much torque as you want (tilt them 10degrees at 20knots and you have 10x the torque of a gyro) for as long as you want (no stroke limitation remeber), and all you need is clever algorithms/computers to control them. But at anchor they are quite similar in performance/limitations

So, given your desire to deal with at-anchor issues, this sounds like a great plan to me, and you are buying the best designed product. Good luck and I lok forward to seeing it

Final comment: when are you around. I'm back in UK tonight but back friday. Do you want to come out to sea to try the fins? You will be amazed, seriously

 

[Nick_H]

Intuitively that all sounds right, and interesting to hear the physics behind it. In any case it's a more involved process to retro fit fin stabs, and probably therefore lot more expensive, and there's a limit to how much investment I want to make into a 7 yr old boat. Refurb gyro will cost £40k installed, which still makes sense I think.

 

[vas]

thanks for the informative (as ever) posts by you guys, I know understand there are 3 types of stabilisers:

wizzbang computer and lots of sensors regulated fins as in Match,
mechanical fins as in MapisM boat
and now
gyroscopic 10k+ rpm (!!!) in hull device as will probably be installed in Nick_H craft.

IIRC John mentioned that his setup is at 100+K GBP level, Nick just mentioned 40K GBP installed so now Mapis should put an estimate on the mech. fin options.
Or maybe there is also another type of stabs I'm not aware of and not being discussed over the last 6-8months I'm carefully following the forum?

Then my mind may rest at knowing that such systems are way out of reach (or maybe not...)

cheers

V.

 

[jfm]

Intuitively that all sounds right, and interesting to hear the physics behind it. In any case it's a more involved process to retro fit fin stabs, and probably therefore lot more expensive, and there's a limit to how much investment I want to make into a 7 yr old boat. Refurb gyro will cost £40k installed, which still makes sense I think.

Yup, all agreed, that project/costing seems to make good sense Nick. Given the difficulty/cost of retrofitting fins and the fact your main priority is at-anchor, it looks like you have found a great solution. Looking forward to seeing the results.

And remember you will be able to defray much of the £40k investment by selling the foloppergobstoppers intot he secondaries market. The price of steel is rising every day due to China demand

 

[jfm]

thanks for the informative (as ever) posts by you guys, I know understand there are 3 types of stabilisers:

wizzbang computer and lots of sensors regulated fins as in Match,
mechanical fins as in MapisM boat
and now
gyroscopic 10k+ rpm (!!!) in hull device as will probably be installed in Nick_H craft.

IIRC John mentioned that his setup is at 100+K GBP level, Nick just mentioned 40K GBP installed so now Mapis should put an estimate on the mech. fin options.
Or maybe there is also another type of stabs I'm not aware of and not being discussed over the last 6-8months I'm carefully following the forum?

Then my mind may rest at knowing that such systems are way out of reach (or maybe not...)

cheers

V.

V, that's not exactly correct, in that MapisM's fins are not "mechanical" and are in fact hydraulically actuated based on gyros. The only differences between MapisM and Match are evolutionary rather than fundamental, being

(a) Match's Sleipner system has much fancier computer control than a 10yo system, faster/better processing, ability to adjust algortithms/parameters and all sorts via control panel and laptop, and much better hydrodynamics including proper winglets, variable fin centre, etc. Likewise, current ABT/TRAC/Naiad systmes have modern computers and stuff

(b) Match has zero-speed/at anchor function, which requires the fin to flap or "swim", rahter than merely act as a foil. This requires bigger faster hydraulics, stronger fins, better mechanical engineering generally, and of course quite different algorithms on the control side. Match has Sleipner gear, which I am really pleased with, but ABT/Trac/Naiad also have zero speed function

I'd categorise the types differently from your list. In no particular order:

1. Active gyro, where the hydrualics and control gear induce precession
2. Passive gyro where they don't
3. Fins underway
4. Fins underway plus zero speed
5. Flopper stopper
6. Water flume tanks
7. Directional control, where azipods or the sternthruster are automatically run to keep the boat nose into the swell when at anchor
8. Moving mass. I'm not aware of anyone making this commercially but there might be

A few comments, respectively, very brief, and the prices are 60-80 footers, very approximate:

1. This is big ship stuff only, not small leisure boats
2. Seakeeper best, Mitsubishi is a bit hyped. £70-100k, or £40k if a Nick H special
3. Like MapisM, though new versions have evolved
4. Like Match and MYAG's boat. £100k. IMHO the dog's bollox
5. Well known, no explanation needed, single figure £thousands, and Nick's are for sale so make him an offer!
6. Not used much now. Feadship idea 1970s-80s. Brilliant engineering and design. Two massive internal watertanks with a flume, and water swooshes side to side in the boat in antiphase with the roll. All replaced on superyachts these days with zero speed quantums and computers (ie item 4 above) etc etc
7. Not a bad idea. At anchor only. £10k maybe. Pretty limited, but occasionally not a bad idea maybe. The sole function of this gear is to keep boat pointed into the swell, in an achorage when the swell is coming sideways. Arguably not really "stabilisation" but does a job

This is high level comparison. Once you get into the detail there are many detailed differences in engineering, reliability, design, effectiveness, etc

 

[Nick_H]

OK, the deed is done and the deposit is zipping it's way electronically across the pond as I write. It'll be a few weeks to ship from US, then schedule fitting, but I'll report back on effectiveness, noise etc once it's installed

 

[jfm]

OK, the deed is done and the deposit is zipping it's way electronically across the pond as I write. It'll be a few weeks to ship from US, then schedule fitting, but I'll report back on effectiveness, noise etc once it's installed

Woohoo! Is the boat going to a yard for the job or will it be done on its berth? (So I can watch and be nosey). I expect they will have to lift out to drill seacocks for bearing cooling water so it will need a lift out for a few hours at least

 

[Nick_H]

They reckon it will be done on the berth, and may take water from an existing sea cock, but if they have to drill new ones it will go to Frejus to be lifted

 

[MapisM]

Wow, congrats! Nice to hear of another forumite joining the "stabilized boating" club. Looking forward to your reports!
And at a great price btw, considering also that a proper installation of these things is always harder when retrofitting, compared to a new build. Even more so with fins of course, but also with gyros it ain't a trivial job.

In reply to previous comments:

virtuvas,
sorry but I can't give you a cost estimate of my stabs. They were fitted during build, and the boat was specced by her first owner.
But as jfm correctly explained, they're just an older generation of the current fin stabs, whose mechanical and hydraulic components aren't much different, really. So, it's easy to guess that they were a rather expensive option also 15 years ago.
Anyway, the question remains academic, because I don't think any builder is now offering plain vanilla systems (gyroscope controlled, hydraulically actuated) anymore. Actually, I'm skeptic that through number crunching of many other parameters aside from the actual hull roll - which only a very responsive gyroscope can sense, anyway - the system can perform much better. But these days, you can find a CPU even in washing machines, so I suppose you can expect the same also when you spend one hundred grand...!

Btw, I recently made a brief test of my stabs at anchor, because I couldn't think of any logical reason why they shouldn't be somewhat effective also at zero speed (something my stabs are not designed for). And guess what, they worked!?!
More about that later. I was thinking to report these results, together with a short clip, in the previous jfm thread.

jfm,
just for the records, you forgot the magnus effect stabs in your categorization.
Not that they're widely known/used, but since you mentioned also moving mass...

That aside, I agree with all your very well made explanations.
All of them, including the part where you disagree with myself (!), because the rationale behind my previous suggestion was actually very different from the one you disagree with.
I didn't say that when cruising at 20+ kts gyros are better.
I said that if I would spec a new boat thinking to use her frequently at 20+ kts, gyros would be my first choice.
In fact, I'm perfectly aware of the limitations which you accurately (as always) summarised, but my train of thoughts is that:
a) on a pleasure boat, I wouldn't cruise at 20+ kts unless the sea conditions allow me to do that in comfort;
b) in such conditions, at 20+ kts the stabs are pretty useless, and I would neither turn on gyros nor fins;
c) as a consequence, I'd rather NOT have a turned off stab system which adds drag (whose negative effect on performance and fuel burn increases exponentially with speed) and increases the risk of major damages in the not so unlikely event of hitting some flotsam, particularly at high speed.

Otoh, for cruising in huge seas (which necessarily means at slow speed), I also said that I wouldn't consider anything else than fins stabs.
In other words, by horses for courses, what I meant is that the concept of "best of both words", which is sometimes used to describe stabilised P boats, is also yet another form of marketing hype, neither better nor worse than the others which you correctly criticised.
It's always a matter of compromises, and imho the one Nick is going for is the best for his boat, assuming that he still wants to use her also at the cruising speeds she's designed for.
If/when he will see the light and decide to stick to slow cruising style, it won't be a matter of choosing another type of stabs, but rather another type of hull, to start with.

 

[nimbusgb]

Blimey. After reading that I don't know why you lot don't just go and buy a piece of land!

Stabilising the boat at anchor with a 150 kg flywheel spinning at 10 000 rpm plus! The energy in that ( 20 mJ? ) is like a small bomb! It's a boat for gawds sake!

If you hate the motion of the ocean so much just buy a caravan!

 

[Lozzer]

NickH

Sorry for the late reply but only just found your thread.

A couple of comments from someone that used these units for a season on a brad new 78 Squadron last year..

1, Original software was somewhat hit and miss. SK were putting together new setup, never saw it arrive as I left the boat.
2, Noise is a big issue. We had two units and when running they were VERY noisy. No chance for crew to sleep with them whilst operating.
3, Start and stopping them takes a while. To spin up I recall them taking about 45 mins to be fully active. As JFM mentioned there is a significant amount of weight that has to be shifted at 10,000 RPM. Stopping them is also an issue. Once all that energy is moving it can take up to 4 hours to stop. All the time they need to be fed by cool water fed via the 240v water pump so you have to have the genny or shore power running.
4, Space, these are big units, yo are looking at the size of a small washing machine pretty much.

On a positive side when they worked they were good. We used them pretty much all the time. In fact I recall have them running in Palma harbour to take out a slight swell. No sleep for the crew but hey ho. At anchor with little people you can be relaxed in knowing that they wont get side swiped swimming to close to a fin. They also worked well when doing 20 knots in a 2.5 - 3m quarterly sea.

In short I probably would keep the money in the bank if it were me but each to their own. A big plus point will be that it will differentiate your boat when you come to sell it in the future and I am sure that JFM and others would agree with me on that.

By the way, I thought that SK were a good company, always responded promptly and accurately to issues that we had. If I had to install gyro it would be SK.

Good luck with your project.

 

[jfm]

Interesting stuff Lozzer. I hadn't appreciated the run-on thing. What I've learnt from your post is that if you have them on in an anchorage in a breezy afternoon, then the wind drops in the evening and the sea goes flat, you cannot just turn them off. You need to keep the genset running to run the pumps for the bearing cooling for another 3 hours. I'd hate that - I like to turn the gensets off in the evening and have peace and quiet (all my refrigeration can be inverter powered so unless I'm cooking or have airco I do not need gensets). Thanks

 

[jfm]

1, Original software was somewhat hit and miss. SK were putting together new setup, never saw it arrive as I left the boat.

Interesting Lozzer. It's a double edged sword though. You could have Mitsubishi gyros on a Ferretti and they hardly have any software becuase they dont do much to control the precession. In contrast, the better SK product has active control of the precession (though it doesn't induce it as I said above) which gives better stabisation but of course needs more complex software and control, which means inevitalby there will be some trial and error and "customer testing" of software

 

[jfm]

I'm skeptic that through number crunching of many other parameters aside from the actual hull roll - which only a very responsive gyroscope can sense, anyway - the system can perform much better.

I don't think that's right Mapis. The motherboard in my stabs controller has perhaps 20 processoers on it and it measures about 300mm square and is 7 layers. That's a load of computing power. It has much faster/higher resolution gyros and inclimometers than what was on the market 10 years ago. Electronics have moved on by several orders of magnitude in 10 years. The speed of the calculations is way higher now and timing is everything in stabs

I didn't say that when cruising at 20+ kts gyros are better.
I said that if I would spec a new boat thinking to use her frequently at 20+ kts, gyros would be my first choice.

I'm struggling with your logic. Fins are better but you'd spec gyros???

a) on a pleasure boat, I wouldn't cruise at 20+ kts unless the sea conditions allow me to do that in comfort;
b) in such conditions, at 20+ kts the stabs are pretty useless, and I would neither turn on gyros nor fins;
c) as a consequence, I'd rather NOT have a turned off stab system which adds drag

MapisM, you have to come out on my boat some time. All what you have written there is so wrong - you have never exoerienced good stabs in a fast boat in big seas. I have been out in genuinely huge seas in my boat, several metres of swell and steep wave faces with breaking crests. Stuff you would never choose to go out in normally. YOU DO NOT TURN THE STABS OFF! I am amazed by your comment that you'd turn them off. Gyros would be useless of course, because of the stroke limitation of the precession. But powerful fins have an amazing amount of never-ending anti-roll ability at 12 kts plus, and at 20kts they are awesome. The stabs create what feel like pure magic. The boat rises up the (scary) wave faces (beam on) perfectly horizontally, no roll. Nothing rattles in the cupboards; no drawers fly open. It is a quite magical experience, and I can do 22-23 kts in this stuff. You get covered in spray of course. Jack Haines, JTB, Hurricane, have been out with me on those conditions and I have been out in worse since that trip (the day San Lorenzo came out in a F7, in particular, was much worse). I'm not kidding Mapis, it is truly wonderful stuff and some time we need to get you to try it and I assure you that you will then retract what you have written above

To be clear, all this (as you well know) is for beam seas and quartering seas. I would not choose to go out in 2-3m steep faced waves on the bow.

 

[Lozzer]

JFM

For sure i think that SK are better than Mitsubishi. The software will inevitably have glitches that will iron out over releases. SK very good at keeping in touch.

I am currently assisting someone in the purchase of a new yacht and gyros are not on the list, fins all the way.

The ability to turn the fin stabs off is key point for me. Also added advantage of fins on sizeable boats you get the benefit of hydraulic anchor winches and thrusters.

Hope you have had a good season thus far.