Stabilizers for Blue Angel, engineering question

[henryf]

I've only skimmed through the posts but there is clearly a great deal of passion over the subject of stabilisers. Who ever would have thought it !

An interesting topic and one I am keeping half an ear to the ground on for the future. I think we will see more boats fitted with stabilisers in the future and prices can only come down.

Am I correct in thinking that fin type stabilisers work pretty much as soon as you turn them on, whereas gyroscopic devices take a long time to get up to speed, sometimes a number of hours ?

There is clearly a lot of expertise and experience on the subject within the forum and I know who I would be contacting prior to jumping in.

For the moment it will be 2 planks and some flopper stoppers

Henry

 

[rafiki_]

I've only skimmed through the posts but there is clearly a great deal of passion over the subject of stabilisers. Who ever would have thought it !

An interesting topic and one I am keeping half an ear to the ground on for the future. I think we will see more boats fitted with stabilisers in the future and prices can only come down.

Am I correct in thinking that fin type stabilisers work pretty much as soon as you turn them on, whereas gyroscopic devices take a long time to get up to speed, sometimes a number of hours ?

There is clearly a lot of expertise and experience on the subject within the forum and I know who I would be contacting prior to jumping in.

For the moment it will be 2 planks and some flopper stoppers

Henry

Yep. The gyro's take 45 mins plus to spin up to speed. Great for packaging though, and of course add no drag to the hull, just a bit of weight.

 

[BartW]

Am I correct in thinking that fin type stabilisers work pretty much as soon as you turn them on, whereas gyroscopic devices take a long time to get up to speed, sometimes a number of hours ?

yes as Rafiki say's, startup time and the space they occupy, are the disadvantages of gyro's,
the extra drag is the disadvantage of stab's
I'm not completely sure about performance comparison, others on here know better.

In my case, I would need 2 x 1m3 space for two big expensive gyro's, while the stabs are almost invis-able inside.

NickH has a very neat gyro in his P57, both the occupied space and the budget were very good for his project.
perhaps he can tell us about the performance,

 

[Nick_H]

Start up time is 20 mins to operating revs (6,000+ RPM) and another 10 mins to max RPM (8,000 RPM).

I think it's horses for courses. Our boat usage is mostly at planing speeds in settled weather, when you don't need any kind of stabiliser, and at anchor for days at a time, when I think a gyro is better because there's no sculling action or moving parts externally. We're extremely happy with the performance of ours. For passage making in unsettled weather, i'm sure fins are better (though the gyro is still very effective), but that's not a big part of our usage, so why live with 1-2 knots of drag all of the time, for the few occasions that fins would have an advantage?

I think we were an ideal spec for a gyro, as we had a perfect space to fit one, and we were just the right size and weight to maximise the effect of a single gyro, plus we were offered a particularly good deal. Bart would need two gyros, so double the space and cost, whereas fins seem to scale up more easily and cheaply. The electric fins seem an ideal choice for the Canados.

 

[jfm]

Bart
From those bilge pictures, it all looks doable. Great news that you have such clear spaces. It looks like all the holes where pipes/cables pass through the frames are above the 80mm level, though it also looks like you will have to re-route some hoses to make room for the stab motors. Gotta say, I'm a bit surprised about the random holes in the frames: Canados just drill a hole thru a frame wherever the guy feels like it, rather than creating "services highways". No worries though, and when you re-route some of the hoses you will have the opportunity to tidy some of the spaghetti. It looks like the GRP is painted, so all that must be removed, but your yard will know that.

You gotta laugh now at all the discussion earlier in this thread about "don't remove the structural stringers". Check out bottom right corner of this picture

 

[BartW]

You gotta laugh now at all the discussion earlier in this thread about "don't remove the structural stringers". Check out bottom right corner of this picture

yes I gotta laugh now, ............ because I knew you would spot that

indeed when the bilges are open, good moment to ty up the hoses, and give the steel tubes (bilge pump tubes) a hamerite coating,
and apply a epoxy coating in the shower sink in the master cabin, to get a dry bilge
same we did in the totally refurbished crew cabin.

 

[henryf]

Thanks for that.

For some reason I had it in my mind that start up times were a lot longer with gyros.

I know you got a good deal on your package, I remember you saying at the time. If you have a convenient space then gyros are no doubt easier to fit.

I also wouldn't anticipate using stabilisers in anger, more to iron out the waves whilst at anchor although any benefit whilst underway wouldn't be a bad thing. I wonder if they encourage displacement / cheaper cruising when making longer passages?

It wouldn't be on the P50, not enough space to fit them but something a bit larger. In an ideal world with them already fitted. I know John has made the point on a number of occasions that it's one of the few things you can add to a boat which genuinely raises value or at absolute worst an incentive to purchase.

Henry

 

[jfm]

Henry I'd definitely agree with Nick that it is horses for courses. The single gyro in Nick's p57 fits beautifully into the lazz and doesn't really impact the space on the boat. On Bart's boat or mine, you'd have 2 gyros possibly up at chine level not down in the V, and the space eating seems much worse.

Also if your main concern is at-anchor then gyros are great. They're great underway too, until you get to very big seas where they run out of angular stroke (on the precession motion), a limitation that never applies to fins while underway. Personally I want the stabs for big seas and therefore fins suit me

The spool up time is a non issue. You just flick them on before you begin all the untying mallarkey when you leave port. It used to be the case that spool down time was a problem because the bearings need seawater cooling and some installs had 230v pumps, meaning you couldn't flick the genset off in the evening till the thing stopped spinning, but Nick has 24v pump which cures this problem

I've been out in Nick's boat in a swell and the effectiveness of the things is very apparent as you flick them on/off with the dashboard switch. It's a massive improvement. (Sorry if telling you how to suck eggs but even though the thing is spinning at a zillion rpm you can still flick it on/off becuase it's the precession not the rotor spin that you flick off, and the precession is controlled or locked using hydraulic rams on the Seakeeper unit)

T'other thing to remember is that not all gyros are the same. The Seakeeper is superior to the Mitsubishi ARG (that's the one fitted exclusively to Ferretti group boats). Seakeeper control the precession actively using hydraulics controlled by complex algorithms and a stab computer, whereas Mitsubishi merely damp the precession

 

[Nick_H]

All agreed, though as a point of minor detail the 8000 series doesn't need cooling water during spin down, they just reccommend you leave the pump running while you moor up, then switch everything off.

 

[MapisM]

There may be nothing underhand about any of this...

LOL, why do I find it "interesting that your mind ran straight to that"?
Of course that's not what jfm meant!

 

[MapisM]

I was genuinely saying Sleipner is a bunch of engineers intended as a compliment to them, nothing else, and it was your imagination only that added the CMC=marketeers point).

Of course it was. In fact, I even qualified that as just a funny feeling, because I saw your answer coming, after your previous backpedalling.
But my imagination is guilty as charged only for the equation, not for the use of the adjective.
In fact, when you qualify someone as being something "and not something else", your message is actually meant to stress the latter, rather than the first.
That's pretty much the ABC of communication, regardless of the language.
So, why do you think it's important to underline that at Sleipner they are NOT marketeers? Nobody ever hinted that they are.
If it wasn't meant as a comparison with CMC (and you'll forgive my imagination for the mistake, in the context of this thread...), who else do you think are "just marketeers" in this industry, and why? Trac? Naiad?
Just curious.

my "negative" comments on CMC have only been to cut through the BS like heat being generated only in gearboxes and my reservations about their small fin sizes, the two points obviously being potentially linked.

Ok, this is a more interesting point, because it brings us back to the real content of this thread.
You constantly suggested that CMC might use smaller fins for any given hull size, if compared to hydr. stabs builders, in order to minimise the heat dissipation problems that in your opinion they "must" have.
And in turn, since this is a sort of compromise made for technical reasons, the stabilization effectiveness just can't be the as good as with bigger fins.
Now, that sounds to me much more as a sort of conspiracy theory, rather than an engineering consideration, for at least a couple of reasons:

1) if bigger fins are by definition better, why don't you think of fitting even bigger ones on M2?
You mentioned that in some conditions the 1sqm fins on M1 reached their max excursion, which proves that the stabilization wasn't so effective, after all.
Or that it could have been better, anyway.

2) If bigger fins would lead to overheating or to any other problems with CMC stabs, it's pretty obvious that these problems could not be cured by a bigger/heavier hull. Quite the opposite, in fact: if the motors would overheat with 1sqm fins on say a Sq78, a bigger and much heavier boat is bound to emphasize the problem.
So, I collected a few numbers to try and make a comparison based on actual installations.
In all these boats (except yours, of course), the very same type of CMC motors are used, with fins ranging from 0.8 to 1.4 sqm.
The 0.8 sqm fins are used in the SL82, which is the boat nearer to yours (though a bit bigger and heavier), whilst the 1.4 sqm fins are fitted on a boat (Benetti 93) whose displacement is more than DOUBLE of a Sq78.
Now, can you explain me in layman's term how their reason for not fitting 1sqm fins on the SL82 could have anything to see with overheating or whatever, when the same equipment is used to drive 1.4 sqm fins on the Benetti???

PS: glad to stand corrected if my memory didn't serve me right on M1/2 speed and full load displacement.
Actually, not so much the first, but the latter is quite relevant in this context.
But for some reason, on FL website only the dry weight is published.

 

[BartW]

So, I collected a few numbers to try and make a comparison based on actual installations.

imo it makes sense to include WLL and
beam at WL in your table
because these are more appropriate then LOA and max beam,
LOA can vary a lot due to the big difference in swimplatform sizes,


fe.
WLL from BA is 19m
WLL from SL72 is 19m
and I believe that Sq78 is not far off, not sure though
WLL from SL82 is 21m !

Beam at WL from BA is 4,4m
Beam at WL from SL72 is 4,8m (important difference, compared to BA)
Beam at WL from SQ78 don't know

 

[MapisM]

imo it makes sense to include WLL and beam at WL in your table

Agreed 100%, B.
But unfortunately, those numbers aren't so easily available.
It's particularly the beam at WL that is almost never included in the specs, though it's reasonable to assume that it's somewhat in proportion with the max beam, at least for the same hull types.
In fact, for SD and D hulls, the beam at WL is typically closer to the max beam than with P hulls.
Otoh, for the Benetti (which is the only full D hull of the lot), I could find neither the WLL nor the max beam at WL.
I would guess that the latter is massive anyway, probably very close to her max beam.
And also the WLL is surely closer to the LOA than in the other boats, also because she has a bulbous bow.
Anyway, I updated the previous table at least with the WLL numbers which I could find.
Glad to complete it with anything else you might be able to collect!

 

[jfm]

Mapism I'm afraid I've lost the will to live with this, ref post 291. There is so much in terms of incorrect premises in there that it would take too much typing ( on iPhone; travelling in US ATM) and its not benefitting the thread. Happy to agree to disagree

 

[jfm]

imo it makes sense to include WLL and
beam at WL in your table
because these are more appropriate then LOA and max beam,
LOA can vary a lot due to the big difference in swimplatform sizes,


fe.
WLL from BA is 19m
WLL from SL72 is 19m
and I believe that Sq78 is not far off, not sure though
WLL from SL82 is 21m !

Beam at WL from BA is 4,4m
Beam at WL from SL72 is 4,8m (important difference, compared to BA)
Beam at WL from SQ78 don't know

Bart I will try to get you WLB FOR SQ78 to complete that data

 

[jfm]

imo it makes sense to include WLL and
beam at WL in your table
because these are more appropriate then LOA and max beam,
LOA can vary a lot due to the big difference in swimplatform sizes,


fe.
WLL from BA is 19m
WLL from SL72 is 19m
and I believe that Sq78 is not far off, not sure though
WLL from SL82 is 21m !

Beam at WL from BA is 4,4m
Beam at WL from SL72 is 4,8m (important difference, compared to BA)
Beam at WL from SQ78 don't know

Bart I will try to get you WLB FOR SQ78 to complete that data

 

[henryf]

I also agree the tone of the thread has gone a bit sour.

Trying to move forward - surely it isn't just beam at the waterline which determines how much stabilisation power is required. The height of the boat, particularly the height of the mass of the boat, the centre of gravity.

If I put 20 big blokes on the flybridge of my boat the pendulum effect would be significant. We're they all standing on the hull along it's centreline their influence would be less. In fact they would be helping the boat to stay upright because they were under the centre of gravity.

In reality choosing the correct stabilisers is probably a bit of a black art. How "hard" the fins "hit" the water will be dependent on speed as well as size, how well they time their movement crucial. I'm not sure you can assume all stabilisers are equal in these departments. And before I get accused of siding with one manufacturer or another remember I have the benefit of zero knowledge & zero experience

All I can say is what ever the 140,000 tonne Independence of the seas uses is pretty effective in a storm battered Mediteranian. That's the only stabiliser experience I have

Henry

 

[MarkNL]

hi Bart,

My first post, I have read the thread on rebuild and fins installation (almost) from the start.

I have been selling smaller US built console boats in France and Italy (Boston Whaler at the start, Sailfish now) since almost 10 years. When in serious trouble, I have had great help from a surveyor in Toulon... I dont know if your analysis and naval architects questions are still open, if so, please check him out, it's an official approved french surveyor of dutch origin who lives in Toulon (jan.verbeek@wanadoo.fr). Might be helpful.

If you want feedback on the Wesmar system, please try Pierre Marechal at Arie De Boom service yard in la Napoule (pierre@ariedeboom.com). French name, but belgian origin, speaks dutch. I know Wesmar is a hydraulic system, it might be too large/complicated. They have done retrofits on numerous vessels and are a great team to work with.

Good luck,

Mark

 

[Portofino]

I,d have thought it pretty obvious if your fin can move/ respond faster ,then it can be smaller to achieve same effect all else being equal
Hydraulics may be " Flintstone " tech ? In comparison
i have to say -Italian boat builders and super car builders are driven ( excuse the pun ) by high tech .

lifted this from CMC site looks credible makes sence and adds up IMO

Stabilis Electra is the world’s unique revolutionary system offered by CMC Marine to overcome the problem of limited dynamics of a hydraulic actuator.

Stabilis Electra uses a new generation of drive to move a fin stabilizer connected to an electrical brushless motor with a permanent magnet.

Thanks to its faster response and lower power absorption the Stabilis Electra is the perfect system for the stabilization at anchor of yachts starting from 18 metres.

Stabilis Electra, covered by EU patent n. 2172394, makes CMC Marine the unique company able to produce an electrical stabilization system
FEATURESSE40SE60SE100SE160FinsGallery
Why Electrical?
The market’s demand for new yachts generation* is oriented towards faster vessels and bigger livable volumes. Those hull parameters affect directly the ship seaworthiness, even on reduced sea state. The demand for an efficient stabilization at anchor is no longer an optional but it’s becoming more and more a must. It’s easy understandable that, to be efficient, the stabilizers system must react faster than the induced roll, as well as the forces generated by the fin movements have to be well phased with the ship roll angles. The idea behind the use of an electrical drive instead of a hydraulic one, comes from the aim to offer a system with a higher dynamic and a more accurate response, so to satisfy the new market’s needs.

In the electrical system, the actuation speed is higher and can reach at least 80°/sec, while for a traditional hydraulic actuator it is rarely more than 60°/sec. When at anchor, the fin acceleration/deceleration phases are better controlled thanks to the lower inertia of the electrical drive. The fin position, controlled with greater accuracy and smoothness, combined with an advanced sophisticated control regulator, results in a better cruise comfort.

Thanks to its adaptability the new electrical drive can be the solution for a wider range of yachts, either planning or displacement hull. Fin size can be reduced, since the same (comparable) amount of roll reduction can be obtained with a smaller fin area, which leads to a gain of energy due to the reduced hydrodynamic resistance of appendages.
Stabilis Electra Range
Model SE40 SE60 SE80 SE100 SE120 SE160 SE200
Standard Fin
Size (sqm)
* 0,40 * 1,00 * 1,60 * 1,80 * 2,30 * 3,00 * * - *
* 0,60 * 1,20 * 1,80 * 2,00 * 2,50 * 3,30 * 3,60
* 0,80 * 1,40 * 2,00 * 2,30 * 2,75 * 3,60 * 3,90
* 1,00 * * - * * * - * * 2,50 * * - * * * - * * 4,20*
Main characteristics
Improved dynamic
Accurate response
Low volume
Low weight
Low power absorption
No hydraulics on board
Use of advanced industrial Components

Main Advantages
Maximum efficiency
50% less electrical power consumption
More electrical power available for other onboard users
Compact unit dimensions
Easier installation
Cables no pipes
Reduced fin size
Low drag effects
More advanced electronic regulator
More comfort even at anchor mode
Drastic noise reduction
Maintenance reduced to a minimum
Longer components lifetime

 

[rafiki_]

Portofino, at the risk of falling into a similar trap as earlier on this thread, there is no reason why a hydraulic system is inherently slower than electrical, in fact there are many reasons why hydraulics should be more responsive than an electric system, all to do with stored energy, ram and piston design etc. An electric system will need some sort of gearbox, which will increase inertia, above that of a well designed hydraulic system. An electric system could benefit from a really good sensing and control protocol, but so can a hydraulic device. This just smacks of using a bit of technobabble for marketing BS IMHO