Gyro stabilizers

[Deleted User YDKXO]

I can confirm that I have been offered the same deal by Mr Karlsen. For me a discount of 15% makes a MC2 40 €25000 cheaper than a SK9 when you also take account of the extra shipping cost and duty for importing the SK9. That is enough for me to seriously consider the MC2 and I have also asked Mr Karlsen to confirm installation costs in my boat so that I can make a direct comparison

The only concern I have about the MC2 is its weight which is 200kg more than the SK9. That means I would be placing an extra 3/4t of weight at the back of my boat which I feel has to effect the performance

 

[MapisM]

The only concern I have about the MC2 is its weight which is 200kg more than the SK9. That means I would be placing an extra 3/4t of weight at the back of my boat which I feel has to effect the performance

Good point, but if the additional weight astern and far from the CoG (which I agree is far from ideal, in principle) is going to have any meaningful effect on the boat performance, that's bound to happen already with the almost 600Kg (IIRC) of the SK9...
And on a 35kts boat like yours, even a 1kt loss (not that I would expect it, mind) isn't such a big deal anyway!

Otoh, in such (relatively) exposed and salty environment, I'd rather a simpler and hopefully stronger equipment, if given the choice.

Good luck anyway for the project, and if by chance at any stage you think you could use a direct contact in IT, I would gladly try to help.
Not that I ever met anybody at Item Mare, but I did get in touch with the Quick technical assistance manager once for the remote of my passerelle - and fwiw, he has been very helpful.

 

[Deleted User YDKXO]

Good point, but if the additional weight astern and far from the CoG (which I agree is far from ideal, in principle) is going to have any meaningful effect on the boat performance, that's bound to happen already with the almost 600Kg (IIRC) of the SK9...

Probably you're right but I'm always concerned about putting more weight aft particularly on my boat with the very heavy MAN engines on V drives already well aft. On the other hand Ferretti say you can have both a tender on the bathing platform and a jetski underneath which must mean they considered at least 600kg of extra weight aft when designing the hull plus of course the 630 can be fitted with the ARG gyro installed albeit fitted at the aft end of the engine room. But even on my boat which has no ARG gyro and a relatively light tender, she needs a lot of trim tab down in the 15-25kt range to optimise speed

Btw its not a project yet. I'm still not 100% sure that I will fit a gyro but I'm closer!

Thanks for the offer of help

 

[jfm]

Mike, just for idle research, let me know if you're in antibes next few weeks and want to see a fins retrofit project. I just waved goodbye this afternoon to the truck taking a full set of fins and ancillaries to France for my brother's boat, and I will fly down tomorrow to meet it. The boat is being hauled out this Friday for the retrofit and it will take 3 weeks ( with some other refit tasks).

 

[Bouba]

Mike, just for idle research, let me know if you're in antibes next few weeks and want to see a fins retrofit project. I just waved goodbye this afternoon to the truck taking a full set of fins and ancillaries to France for my brother's boat, and I will fly down tomorrow to meet it. The boat is being hauled out this Friday for the retrofit and it will take 3 weeks ( with some other refit tasks).

Is your brother's boat steel? I ask as this as grp boats can need reinforcing for fins and there would be a cost difference

 

[Deleted User YDKXO]

Mike, just for idle research, let me know if you're in antibes next few weeks and want to see a fins retrofit project. I just waved goodbye this afternoon to the truck taking a full set of fins and ancillaries to France for my brother's boat, and I will fly down tomorrow to meet it. The boat is being hauled out this Friday for the retrofit and it will take 3 weeks ( with some other refit tasks).

Thanks jfm I would be interested in seeing that. I guess these are Sleipner fins?

 

[jfm]

Thanks jfm I would be interested in seeing that. I guess these are Sleipner fins?

Yep sleipner. The 1.05m2 fins with the tiller arm actuators, and electro pack for generator use at anchor. Exact same as in my boat.

 

[jfm]

Is your brother's boat steel? I ask as this as grp boats can need reinforcing for fins and there would be a cost difference

Aquastar 74, grp. Will need reinforcing (extra layup) like any grp boat. Piece of cake. :encouragement:

 

[Bouba]

I have a question for all of the uber lucky forumites who have stabilisers either fins or spins.
When they are on do they affect steering? Especially close quarters for example getting into a tricky berth, do they fight you or assist you or don't you notice?

 

[A&K]

We have a Sq58 with a Seakeeper installed. I am convinced that the gyro impacts the movement of the boat when we're mooring. Usually the engines really move the stern round to moor, I don't think this happens so much with the gyro engaged. So whenever we start to moor now we disengage the gyro. It's just a push of a button on the seakeeper.

Nickh and JFM will be along in a minute to tell you this is complete nonsense and I just use this as an excuse when I make a mess of mooring...

 

[Nick_H]

Nickh and JFM will be along in a minute to tell you this is complete nonsense and I just use this as an excuse when I make a mess of mooring...

I wouldn't dream of doing that (because if I do, you might tell everyone about my boat handling in Sanary-sur-Mer last year! )

 

[BartW]

I have a question for all of the uber lucky forumites who have stabilisers either fins or spins.
When they are on do they affect steering? Especially close quarters for example getting into a tricky berth, do they fight you or assist you or don't you notice?

fins;
When one of the gear's goes over Neutral; the fins automatically switch from "navigation" mode to stabilisation off, fins fixed in "center" position.
and stay there until you re-engage the system.
so you don't notice any effect during manouvring

 

[Deleted User YDKXO]

Yep sleipner. The 1.05m2 fins with the tiller arm actuators, and electro pack for generator use at anchor. Exact same as in my boat.

Thanks. Who's doing the installation if you don't mind me asking? Wasn't your brothers's boat already fitted with stabs or do I remember incorrectly?

 

[wakeup]

Has anyone looked at this product in detail. Seems to be for smaller '10 tonne' boats

http://www.nauticexpo.com/prod/orbit-gyro/product-68316-500710.html?token=105595e19e0a269326053d5d6f935628cc330484#utm_medium=email&utm_source=insight&utm_campaign=4-equipment-21-02-2017&utm_content=photo&utm_term=PRODUCT_highlight

 

[MapisM]

When they are on do they affect steering?

I've cruised with a fin stabilized boat since 2000 (and coming to think of it, I guess I'm the asylum member with the longest experience on this - but happy to be corrected if anyone had a stabilized boat also in the previous millenium!), so I can safely confirm you that the short answer to your question is yes.
But, and it's a big but, the way they affect steering is in terms of reducing the need for corrections, rather than the opposite.

A proper answer requires a bit of foreword: when talking of roll stabilization, what you are mostly interested in are the effects in rough seas.
Not because stabs are totally useless in an almost calm sea, but when the effort required to cancel the roll is very low, also any side-effects is bound to be irrelevant.
Which btw is the reason why stabs are useless when maneuvering, to the point that modern systems switch keep them automatically centered as BartW said, hence making them irrelevant.
Maneuvering is quite simply a non-issue, and also accepting what A&K said about his gyro behaviour (which is something for which I struggle to think of any logical justification, but I take his word for it, also because my gyros experience is very limited) it still is just a matter of pushing a button to disengage the system, as he said - again, a non-issue.
Another scenario which is unaffected by your question is the stabilization at anchor, when obviously steering is inactive and irrelevant.

Now, back to stabilization under way, and particularly in rough stuff.
The 3 degrees of motion that affect any hull are roll, pitch, and yaw.
With the additional complication that all of them work at the same time, making the actual boat motion a tricky combination.
For sake of simplification and (hopefully) better understanding, let's consider them separately:

1) roll as such does not change the boat heading, so doesn't demand rudder corrections to keep the boat on her course.
With fin stabs, the fins are longitudinally placed as close as possible to the position where their action does not induce any yaw, but only creates a roll motion - obviously opposite to the one created by the sea motion, but what is relevant here is that they are yaw-neutral, so to speak. Exactly the opposite of bow and stern thrusters, in other words.
This means that a pure roll motion (which, remember, does not require rudder corrections) is contrasted by stabs in a way that does not require rudder corrections, too.
Bottom line, there is no difference in terms of course-keeping between a theoretical boat affected by roll motion alone, and the same boat stabilized.

2) pitch is easy, because that's a type of motion for which there's nothing stabilizers can do (leaving aside multiple fin systems used on some ships - and even those, can actually just soften the pitching a bit, surely not eliminate it).
And pitching alone - similarly to roll - does not affect steering, so we are now talking of a motion that is irrelevant to both steering and stabilizers, and we can forget it altogether.

3) yaw is the real culprit, and it's because of yaw motion that in rough sea any boat requires constant steering corrections to keep a straight course.
I'm not explaining this because I assume it's intuitive enough.
Otoh, I said that stabs do not create a yaw motion, which in turn means that they can not correct/reduce one, so the conclusion of this brief analysis of the three motion when considered alone should be that the answer to your initial question is no.

Otoh, the answer is yes because a stabilized monohull, which rolls much less than the same hull without stabs, remains closer to its ideal asset on the water surface (i.e. very close to zero listing), instead of cruising most of the time listed either side.
In turn, this makes the hull less sensible to yaw motions (particularly when yaw is combined with pitching, as it's normally the case.), therefore requiring less steering corrections to keep a steady track.

Unfortunately, it is very difficult to give an easily understandable explanation of that, and TBH I'm not aware of how the physics involved can explain this scientifically, though I'm sure that some sort of scientific explanation must exist.
Anyhow, what really matters is that the difference exists, and it can be very relevant.
I read about that already a quarter of a century ago, well before buying a stabilized boat, but trust me, you wouldn't believe how high the difference can be till you are out there in some rough beam seas, with the autopilot on, and you try switching on and off the stabs: aside from the rolling difference, which is obviously night and day, you can immediately see on the a/p that the steering corrections are reduced/increased depending on whether the stabs are on/off.
And I'm not talking of 4 degrees corrections reduced to 3 or whatever - I'm talking of changing the boat behavior radically, from rudders constantly working hard from port to stbd, 20 degrees or more, to moving much more gently and slowly, 6 to 8 degrees max either side..!

 

[MapisM]

Wasn't your brothers's boat already fitted with stabs or do I remember incorrectly?

No, you don't.
SD2 already had some non-zero speed fins, but unfortunately (you can guess why I know that! ) upgrading from non-STAR to STAR fins is almost as expensive as fitting a whole new equipment.
On top of that, jfm explained in this post that they are also moving the fins positions, due to a (rather amazing, I must say) build mistake.
I am mentioning this because it's a remarkable exception to what I said in point 1 of my previous post ref fin stabs not creating any yaw motion: if Aquastar placed the fins more astern than they should have been, of course that can create a yaw motion, making the boat "fishtail", if I may steal the expression jfm used, which I think is pretty effective.
But of course, that ain't an inherent problem of fin stabs per se, just of their incorrect placement.

 

[Portofino]

Just to add a bit of balance to all this stabs stuff , are we manly referring to either round bilge D speeders or top heavey Planers whereby a bit of stab fin or "spin" eases the ride ?
Some sort of 220 V is needed either Geny or cobbled together inverter + extra large alternator when running the main engines .
@anchor Geny or short burst of extra consumable batts + inverter = hassle in my book .

It's just a most MoBo ers have a reasonably fast planning boat whereby the hull stability is optimal @ planing speeds .
Most P boats have a range of P Speed ,from say 16-18 knots to 40 or more if Anerson driven .
So in a chop planing boats can get up and start to scythe through ,depending on the hull shape ,deepness of the Vee or deadrise ,the faster and smother it becomes .
Additionally with 1/2 decent weather forecasting ,plan around a blow up ( if up wind ) or hold fast and catch up tomorrow ?

Personally each to there own of course ,but after 12 years in the med I don,t feel I ve missed out not having stabs in a leisure boat -emphasise on the leisure side just feels a waste of money to me .

Sell it to me ps ?

 

[jfm]

Yep to all that Mapis M - except that, more theoretically than noticeably, gyros induce yaw. At the split second during the precession that the axis of the gyro spin is vertical (ie the mid point of the precession cycle) there is no yaw torque, only anti-roll torque. But as the gyro moves past the vertical, there is a yaw torque induced as the thing continues to precess. Now, this is not too noticeable because a boat's yaw stiffness is much higher than its roll stiffness, and the autopilot would correct, but for sure the yaw toque occurs. That's why gyros are built so that they only precess +/- 30-45 degrees. Beyond that they create too little roll torgue and too much yaw torque. But as I say this is a bit theoretical in terms of feel when driving a motor boat

 

[jfm]

Just to add a bit of balance to all this stabs stuff , are we manly referring to either round bilge D speeders or top heavey Planers whereby a bit of stab fin or "spin" eases the ride ?
Some sort of 220 V is needed either Geny or cobbled together inverter + extra large alternator when running the main engines .
@anchor Geny or short burst of extra consumable batts + inverter = hassle in my book .

It's just a most MoBo ers have a reasonably fast planning boat whereby the hull stability is optimal @ planing speeds .
Most P boats have a range of P Speed ,from say 16-18 knots to 40 or more if Anerson driven .
So in a chop planing boats can get up and start to scythe through ,depending on the hull shape ,deepness of the Vee or deadrise ,the faster and smother it becomes .
Additionally with 1/2 decent weather forecasting ,plan around a blow up ( if up wind ) or hold fast and catch up tomorrow ?

Personally each to there own of course ,but after 12 years in the med I don,t feel I ve missed out not having stabs in a leisure boat -emphasise on the leisure side just feels a waste of money to me .

Sell it to me ps ?

If you're wanting to go a long way in a big beam sea then you need stabs for comfort. Even in a low COG boat like itama, indeed even in a flat tea tray, the "dynamic stability" of the hull will merely keep your hull flat to the wave surface, not flat to the horizon, yet what you want for comfort is flat to the horizon.

I agree with you that in plenty of sea conditions stabilisers are a mere luxury and not necessary, but that defines a powerboat to begin with doesn't it?

 

[jfm]

Thanks. Who's doing the installation if you don't mind me asking? Wasn't your brothers's boat already fitted with stabs or do I remember incorrectly?

Installation is being done mostly by team of shipwrights flown and driven in from Scotland. We like them! With bit of help from me and my father, mostly making tea. He bought the stabilisers direct from sleipner in Norway - shipped in a couple of big crates. Easy stuff really. Work is being done at Bleumer's yard; lift out is tomorrow am. Deserves a thread!

Yep the boat had koopnautic fin stabs but they are just such pathetically poor engineering you cant wait to throw them in a skip. They are not zero speed. And they are mounted too far aft by Aquastar, so they induce fishtailing yaw torque.

All this was factored in to the economics when he bought the boat. Cost of changing them is same as cost of installing new, as MapisM says above. nothing at all is re-useable from the old system, because it is junk