Fleming 58 video

[Portofino]

We tested our boat in similar sea conditions off the Porquerolles this year. The gyro was at its most effective with the boat stationary just lying beam on to the sea which are conditions which would normally have any boat rolling like a pig. In fact my SWMBO was able to stand on the flybridge sunpad without bracing herself which was testament to the effect of the gyro. But what was noticeable was that as soon as we started to make way the effect of the gyro was reduced and she was not able to stand unsupported and as I said in another thread, by 10kts, the effect was negligible

This makes me wonder whether, instead of fins which as you say are very much more effective the faster you go, whether D or slow SD boats would actually be better stabilised with a large gyro rather than fins

Just to be clear it’s roll or side ways tipping you are talking about .
Pitching ,by which I mean going up and down hill like a fairground roll a coaster on waves then both stabiliser systems can,t help there .Wives stud on sun pads will fall over

Bit like anti roll bars or active air suspension on a car , fine round corners , keeping it flat but no use on a series of speed bumps or mini hills , like waves really .
So in the 4 planes - - Left n right that’s roll and tipping up and down - pitch on a wave the stabs only work in 1/2 of the potential axis of movement ?
Is that correct ?

 

[Zing]

Agree, not a proper engineering solution but the other side of the coin is that the hyd cylinder will act faster in one direction than the other, albeit, as you say, with less force. Just wondering but how much does speed of fin actuation affects stabilisation?

The port cylinder will be pushing and the starboard cylinder pulling, so one side of the boat is acting faster when the other is acting slower and one side is pulling stronger when the other is pulling less strongly. The average speed and pull of the cylinders should be equal during operation.

This is assuming flow and pressure regulation is not present, which may well be incorrect. If it is, then it is equal anyway.

Written without any study of any manual/drawing, so happy to be corrected.

 

[Deleted User YDKXO]

Just to be clear it’s roll or side ways tipping you are talking about .

Yup, stabilisers are useless for correcting pitch

 

[jfm]

The port cylinder will be pushing and the starboard cylinder pulling, so one side of the boat is acting faster when the other is acting slower and one side is pulling stronger when the other is pulling less strongly. The average speed and pull of the cylinders should be equal during operation.

No. There is one cylinder per actuator, and as I said the actuators are not handed. So both are pushing, or both are pulling. It's not the case than one pulls and the other pushes.

 

[jfm]

Wives stud ...

Deleted User is his wife's stud

 

[Zing]

No. There is one cylinder per actuator, and as I said the actuators are not handed. So both are pushing, or both are pulling. It's not the case than one pulls and the other pushes.

How foolish of them. They missed a trick there. It should be possible for a pressure/flow control system to balance them though, or they just oversize to suit the requirements of the weak side. Not ideal if that's what they do.

 

[Piers]

How foolish of them. They missed a trick there. It should be possible for a pressure/flow control system to balance them though, or they just oversize to suit the requirements of the weak side. Not ideal if that's what they do.

I seem to have lost the plot here. Can you explain the argument to me, please?

 

[Zing]

I seem to have lost the plot here. Can you explain the argument to me, please?

According to jfm your stabilisers are powered by a single double acting hydraulic cylinder, which are not handed, i.e. they are identical units port and stbd. In a double acting cylinder the piston rod occupies part of the bore of the cylinder, but only on the retract side. This means the cylinder will have less power on that side, but will move faster. It is unbalanced. If they handed the units then the imbalance on one side would have been matched by a counterbalance on the other side, but they don't it seems.

They could still balance them with controls such as flow and pressure control valves. If they don't do that then it will mean they have to size the cylinders and pumps to be slightly oversized and for response rates to be slightly different port compared to starboard. Not a disaster, probably not noticeable I'll bet, just not so elegant, but more reliable than in having extra controls.

Handing would seem best, but probably not done to save what is likely to be only a little cost.

 

[Piers]

According to jfm your stabilisers are powered by a single double acting hydraulic cylinder, which are not handed, i.e. they are identical units port and stbd. In a double acting cylinder the piston rod occupies part of the bore of the cylinder, but only on the retract side. This means the cylinder will have less power on that side, but will move faster. It is unbalanced. If they handed the units then the imbalance on one side would have been matched by a counterbalance on the other side, but they don't it seems.

They could still balance them with controls such as flow and pressure control valves. If they don't do that then it will mean they have to size the cylinders and pumps to be slightly oversized and for response rates to be slightly different port compared to starboard. Not a disaster, probably not noticeable I'll bet, just not so elegant, but more reliable than in having extra controls.

Handing would seem best, but probably not done to save what is likely to be only a little cost.

Thanks Zing. Really interesting, and grist to the mill in my future enquiries about potential upgrades either to bigger fins or a complete change as JFM has recommended.

Gum sucking and pencil and paper and budgets seem to call.

 

[Deleted User YDKXO]

Deleted User is his wife's stud

Not sure about that after 26yrs

 

[Deleted User YDKXO]

Handing would seem best, but probably not done to save what is likely to be only a little cost.

Agree. Its borderline bizarre not to hand a rotary actuator like this as the cost would be negligible within the overall cost of the system. I can only think that this is an engineering decision not a cost decision. I guess they believe that the force developed on the rod side of the cylinder generates more than enough torque than will ever be needed in any situation so specifying a non-handed double acting cylinder won't affect the performance of the fins?

 

[jfm]

This makes me wonder whether, instead of fins which as you say are very much more effective the faster you go, whether D or slow SD boats would actually be better stabilised with a large gyro rather than fins

No way. It is correct than fins work less well as speed reduces, aotbe, so in a D boat you must size them knowing that Vmax is 10kts.

But once fins are sized correctly they perform far far better than gyros in a big sea. Problem with gyro is that it can only apply an antiroll toque on the hull for a very limited amount of time, like 1-1.5 seconds. After that it stops doing any stabilisation whatsoever. Absolutely nil. You have to wait till the boat is rolled in the opposite direction by the wave action. In contrast, a fin can apply a constant antiroll torque to the hull all day long, till you run out of diesel. There is no time limit. Now, in a big beam sea, and even more in a big quartering sea, the rolls are big and they last several seconds. Much more than 1.5 seconds. That's when gyros are useless and fins are 100x better.

Totally different story at zero speed, where gyro has the inherent advantage (when comparing a correctly sized gyro with correctly sized fins).

 

[Zing]

Agree. Its borderline bizarre not to hand a rotary actuator like this as the cost would be negligible within the overall cost of the system. I can only think that this is an engineering decision not a cost decision. I guess they believe that the force developed on the rod side of the cylinder generates more than enough torque than will ever be needed in any situation so specifying a non-handed double acting cylinder won't affect the performance of the fins?

Not handing will increase cost in so far as sizing of pumps and cylinders will increase slightly to ensure adequate power to compensate, but it will save cost too in having fewer parts and larger production batches. Sometimes decisions like this are not clear cut. It could even come from a management edict to minimise skus.

 

[jfm]

How foolish of them. They missed a trick there. It should be possible for a pressure/flow control system to balance them though, or they just oversize to suit the requirements of the weak side. Not ideal if that's what they do.

Yup, exactly.
If you were to examine these units you would be very unlikely to call them oversized!
Ok for moderate weather of course, but when you reach stabilisation limits this weakness of Trac (and others who pull the same trick) shows. First world problem I admit, but this is a first world discussion.

 

[jfm]

minimise skus.

Yup. Mind you, they're always sold in pairs. And if they put 2 cylinders on each actuator and just build them strong, they'd have one sku not two

 

[jfm]

Gum sucking and pencil and paper and budgets seem to call.

Piers, I live on an island to your SW these days. Castle quay. One winter Saturday morning I'll invite myself over for a coffee and look in your e/room and chew the fat about replacing fins.
The fin hardware is in the ballpark of £45k. Vat free in gsy obviously. Installation is 2guys x 1 week say £6000 ball park. Actuators will have similar footprint to existing, and lower profile. Plus haul out cost. Those numbers are very ball park. The whole thing isn't difficult.

 

[MapisM]

Thanks Zing. Really interesting, and grist to the mill in my future enquiries about potential upgrades either to bigger fins or a complete change as JFM has recommended.

Gum sucking and pencil and paper and budgets seem to call.

Piers, fwiw I must disagree with most of jfm diagnosis and also with Zing concerns about what's wrong with your ABT stabs - if anything. I'm just afraid that it'll take a while to explain the reasons, so bear with me if you are interested.

I'll start from Deleted User question about... "whether D or slow SD boats would actually be better stabilised with a large gyro rather than fins", because it's relevant to the debate.
Jfm already answered that in his post #172, and I fully agree with everything he said there, but there's more.
Another crucial point is that D hulls, by their nature, have a longer natural rolling period (and a lower initial stability) when compared to hard chine hulls, AOTBE.
In other words, they offer little resistance to rolling, but the bright side of it is that it doesn't take a lot of force to contrast their motion. It's rather a matter of calibrating just as much righting force as necessary (i.e., the fins angle), and apply it for as long as the waves require.
Which is precisely what fins are good at, as opposed to gyros, for all the reasons already explained by jfm.
As a result, in my old D boat (which is a couple of feet shorter than yours, but with a tad higher displacement), her 6 square feet fins driven by a Naiad equipment designed more than a quarter of a century ago never struggled to keep her straight, at any speed above 5 knots or so.
Otoh, I don't think they could be equally effective at the same speed, in a P or SD boat of the same size.

Secondly, the single cylinder with not handed actuator levers: now, that's a massive red herring, if I've ever seen one.
Btw, I have a funny feeling that jfm is actually well aware of that, considering that right after mentioning this as a potential issue, he called it hair splitting...
In fact, saying that with such equipment there's "more hydraulic force to stop the boat rolling" to one side is like saying that since rudders are driven by a single cylinder, the boat can steer more/better to one side...
Truth is, the one and only real issue is that both actuators and fins must be sized according to what the hull requires - nothing else.
Fwiw, the archaic Naiad on my old boat, which are also driven by a single cylinder with non-handed actuators, still do their job just perfectly, and her new owner would be right in replacing them only if interested in zero speed stabilization (which he isn't).
Other than that, it would be a total waste of money.

Bottom line, Piers, if while cruising in rough seas your stabs frequently reach their max angle, and even then they can't stop the boat from rolling, my bet is that Fleming just used some slightly undersized fins.
Based on my experience with 6 sqft, I would think that for your boat it would be appropriate to go one step larger, for the reasons I mentioned in my previous reply to the point raised by Deleted User.
In ABT range, that means 7.5 sqft.
Is that the size of your fins, or do you have the 6?
Besides, I would expect your actuators to be the 250 model.
And if so, it's good for handling up to 9sqft fins, so you have an easy and unexpensive upgrade path available, before replacing a perfectly good equipment - unless you are also interested in stabilization at rest, of course.
But mind, on top of requiring the genset running, STAR also means several new bits to place somewhere onboard: VFD, electric motor driven hydraulic pump, compensation tank...
...you pays your money, etc! :encouragement:

 

[Piers]

Piers, fwiw I must disagree with most of jfm diagnosis and also with Zing concerns about what's wrong with your ABT stabs - if anything. I'm just afraid that it'll take a while to explain the reasons, so bear with me if you are interested.

I'll start from Deleted User question about... "whether D or slow SD boats would actually be better stabilised with a large gyro rather than fins", because it's relevant to the debate.
Jfm already answered that in his post #172, and I fully agree with everything he said there, but there's more.
Another crucial point is that D hulls, by their nature, have a longer natural rolling period (and a lower initial stability) when compared to hard chine hulls, AOTBE.
In other words, they offer little resistance to rolling, but the bright side of it is that it doesn't take a lot of force to contrast their motion. It's rather a matter of calibrating just as much righting force as necessary (i.e., the fins angle), and apply it for as long as the waves require.
Which is precisely what fins are good at, as opposed to gyros, for all the reasons already explained by jfm.
As a result, in my old D boat (which is a couple of feet shorter than yours, but with a tad higher displacement), her 6 square feet fins driven by a Naiad equipment designed more than a quarter of a century ago never struggled to keep her straight, at any speed above 5 knots or so.
Otoh, I don't think they could be equally effective at the same speed, in a P or SD boat of the same size.

Secondly, the single cylinder with not handed actuator levers: now, that's a massive red herring, if I've ever seen one.
Btw, I have a funny feeling that jfm is actually well aware of that, considering that right after mentioning this as a potential issue, he called it hair splitting...
In fact, saying that with such equipment there's "more hydraulic force to stop the boat rolling" to one side is like saying that since rudders are driven by a single cylinder, the boat can steer more/better to one side...
Truth is, the one and only real issue is that both actuators and fins must be sized according to what the hull requires - nothing else.
Fwiw, the archaic Naiad on my old boat, which are also driven by a single cylinder with non-handed actuators, still do their job just perfectly, and her new owner would be right in replacing them only if interested in zero speed stabilization (which he isn't).
Other than that, it would be a total waste of money.

Bottom line, Piers, if while cruising in rough seas your stabs frequently reach their max angle, and even then they can't stop the boat from rolling, my bet is that Fleming just used some slightly undersized fins.
Based on my experience with 6 sqft, I would think that for your boat it would be appropriate to go one step larger, for the reasons I mentioned in my previous reply to the point raised by Deleted User.
In ABT range, that means 7.5 sqft.
Is that the size of your fins, or do you have the 6?
Besides, I would expect your actuators to be the 250 model.
And if so, it's good for handling up to 9sqft fins, so you have an easy and unexpensive upgrade path available, before replacing a perfectly good equipment - unless you are also interested in stabilization at rest, of course.
But mind, on top of requiring the genset running, STAR also means several new bits to place somewhere onboard: VFD, electric motor driven hydraulic pump, compensation tank...
...you pays your money, etc! :encouragement:

This is becoming more and more interesting. Thank you for taking the time to write this missive. Play d'eau stabs are model 220 but nowhere can I find the fin size, so I've asked the question. Mind you, Fleming fails to answer many questions I ask claiming they've 'lost the records.' Hmmm. So if Fleming doesn't know, I'll find my B&Q 'value' measure when she's next out of the water.

You raise another point about maximum deflection. There are seas when this certainly happens and we've often commented that maybe bigger fins would be a solution, but never taken it further. Maybe now is the time.

So, I'll start by asking Fleming. If no good, I'll measure (http://abttrac.com/sites/default/files/ABT-TRAC 220 Stabilizer.pdf). Meanwhile, I'll ask ABT if fitting larger fins requires a change to any of the control parameters.

This has been a good and really helpful thread. Thank you. I feel an MBY Our Boats article coming on for next year....

 

[MapisM]

You raise another point about maximum deflection. There are seas when this certainly happens

Pretty much as I suspected.
Normally, the worse situation for this to happen at D speed are stern quartering seas, in a long and high-ish swell.
This can make the boat corkscrewing, with a combination of pitching and veeery slow rolling,
In such conditions, whenever you see that the fins are both at their opposite max angle, and they stay there for a while, but in spite of this the boat is still listing a bit (I'm using "listing" because the motion is so slow to be more akin to a constant listing - either side, for several seconds - rather than a rolling), then the only possible improvements can only come from a larger fin surface.
No way round that. The type of actuators behind the scene, be it single, double cylinder or electric, have ZERO relevance in this situation, as well as their speed.

Apropos, for the records, I forgot to mention that even my very old Naiad must have some kind of flow/pressure control, as Zing envisaged, because their motion speed is variable.
In fact it's evident, while seeing the stabs working, that the fins rotation speed changes depending on the sea state.
But I don't think that Naiad designed this feature (as well as ABT did, I would guess) in order to compensate the different cylinder behavior in push/pull movement - though this can also be a by product, so to speak.
It's just something inherently necessary to grant a smooth roll cancellation, which is what stabilization systems are all about.

Ref. the fins installed in your boat, don't you have an ABT report released upon commissioning? The fins size should be included in such document...
Anyway, of course you can check whether you have 6 or 7.5 sqft fins just by measuring their length (or height) and cross-checking that with the ABT sheet which you linked.
But if you've got the 220 actuators, I'd expect the fins to be 6 sqft, and if so, the easy peasy upgrade to 7.5 sqft fins (which is the max that 220 actuators can handle) should give a meaningful improvement in extreme conditions.

 

[MapisM]

Piers, I just checked a database of technical files which I collected back in the days when I dealt with ORY (which also used ABT stabs), and I found a PDF of their installation manual, which you might wish to have a look at.
Just pm me your mailbox if you are interested, and I'll send it to you! :encouragement: