Where to locate a gyro?

[Deleted User YDKXO]

I have been thinking about fitting a Seakeeper gyro in my Ferretti 630 for a while now. One of the reasons for choosing a gyro rather than any other type of stabiliser was that I thought that on my boat there was a perfect location for it in the compartment under the bathing platform (pos 1 on the drawing below) known as the 'spoiler' in Ferrettispeak. This is a compartment designed to store a jetski and since I dont carry a jetski this spoiler is empty on my boat

Initially I approached Seakeeper Europe who inspected my boat and confirmed that the most suitable model from their range for my boat was the SK9 and further that they thought it could be fitted in the spoiler compartment. They even told me that they were aware of other Ferrettis which had been fitted with their gyros in this same location and sent me some photos of an installation in a Ferretti 53

Recently I have got prices from 2 yards for fitting a SK9, Ventura (also UK Ferretti dealer who sold me my boat) and Nemo, the south of France Seakeeper dealer. Ventura have given me a competitive price and confirmed that they would be happy to fit the SK9 in the spoiler compartment. Nemo gave me a higher price and then threw a spanner in the works. They insist that the gyro cannot be fitted in the spoiler compartment for structural reasons and must be located in the same position as Ferretti would have fitted their own ARG gyro, had it been specified, which is in pos 2 on the drawing above, just inside the engine room. The cost of doing that is much higher than putting it in the spoiler compartment because of the larger amount of work involved and in any case I dont want it there because it would take up space in the engine room and make it more difficult to get around the back of the engines. The trouble is that Nemo are a experienced Seakeeper installer and Ventura have only just started to install Seakeepers so I'm thinking I really should take notice of what Nemo said

After Nemo's statement, I asked Ventura to get approval from Ferretti for the fitment of a SK9 in the spoiler compartment but needless to say, Ferretti were unwilling to comment.

Any thoughts or comments on this?

 

[Bouba]

I would contact Seakeeper head office technical department. Once a French technician has told you something and you challenge it he will dig his heels in and claim the sky will fall in if you don't do his way.

 

[jimmy_the_builder]

Isn't the answer to this (in the absence of a definitive opinion from Ferretti) to find another 630 which has a gyro installed? Is there one?

What's the implication of Ventura being wrong? Are they prepared to warrant against the risk of stabiliser-induced structural failure?

 

[MapisM]

M, I've only just seen your post, right after emailing you on this and other matters.

But looking at the above pic, I must say that I don't like that Ventura installation on the 53' at all, for a couple of reasons:

1) I don't see any transversal reinforcements on the stringers where the SK is attached. Maybe they are just not visible in the pic, and if so, ok.
But while I believe that the stringers are more than strong enough (also in your boat) to support the sheer weight, I'd rather want to have some pretty solid cross strengthening, to support the dynamic forces that the thing can exert on the hull while operating - potentially also in heavy seas.

2) I am 90% sure that the two large openings at the bottom of the bulkhead do not exist in the stock F53, and if they were made for the SK installation, it's not something I would have wanted done on my boat!
AFAIK, in all Ferrettis the hull section under the swim platform is designed as a watertight compartment.
And it's a clever feature imho, because this way the rudders and the struts (which are the first thing potentially cracking the hull in case of grounding) are outside the main e/r. (*)
So, opening two large holes in a w/tight bulkhead isn't a clever idea in my books - makes me even wonder if that might potentially affect RCD conformity...!

Otoh, I fully agree that I wouldn't like #2 placement in your drawing either, though it would be better for weight distribution, because it would spoil an otherwise nicely accessible e/r - better than most other Ferrettis I've seen, I hasten to add!

Bottom line, having said that any choice is a compromise, with its pros and cons, I would probably give fins a thought.
Btw, looking at the drawing, even if the ideal placement for the fins and their actuators probably is in the aft part of the master cabin, it might be ok (just!) also to place them in the crew area, a better solution in more ways than one.

(*) note for Whitelighter: I'm afraid this is not true for your boat, as it wasn't for all the Ferrettis of that era, but there were other reasons behind that difference.

 

[MapisM]

Are they prepared to warrant against the risk of stabiliser-induced structural failure?

Now, that is a VERY good question.
And if - as I'm guessing - they made those bulkhead openings, it would be interesting to ask them also if they are prepared to refund a sunk boat for which the insurance refuses to respond due to their modifications....! :ambivalence:

 

[vas]

what's under the master bedroom bed?
not suggesting anything just wondering...
I'd suggest that spot only if you wanted the seakeeper working during daytime as I guess it's a bit noisy

probably bit the bullet and get it in the e/r, the issues that MM points out are fairly serious!

cheers

V.

 

[Portofino]

Adding to whats allready been said agreeing with JTB and MapishM --the bathing flatform locker idea in that pic looks daft
Perhsps on the 53 -no other options ?
Apart from the inherent torsonal strength issues or lack of as the numbers increase in the 63 ,what about the water tightness of the actual door /lid ?
Going fwds if that door seal leaks on a bumpy -splashy down wind /beamy sea of say 4-5 hour --you are gonna arrive and find everything in there dowsed in sea water (not lake water ) .
I don,t like the opening too that MapishM has highlighted --but I,am coming from a 3 water tight bulkhead -cum- compartment boat piont of view .I would be upset if engineers left my boat (after an install) with a gaping hole like that .
What would happen if the catches of the lid were not properly secured of faulty and in a big sea or wha ever a wave lashed up and lifted the hatch ?

I think it needs to inside warm n dry on somthing a bit more solid near the centre .
Crew cabin -knock about the locker and bed --reshape resize ?
Or under the mid cabin bed --on the basis nobody will be sleeping when under way or if at anchor ( Geny running ) -sunbathing up top some where .

E room obvious place


Ps how are the side windows doing --any further with quotes /works ..?

 

[petem]

Those bulkhead openings must be original, surely? Not that I like them either.

 

[Whitelighter]

Yep, I know where my rudders are and they are well forward if the stern at the rear end of the boat (rather than the spoiler locker)

 

[Nick_H]

Those bulkhead openings must be original, surely? Not that I like them either.

They're certainly nothing to do with the gyro, which is wholly contained in the centre section between the stringers.

Mike, it's a tough one. I don't think the forces at play are actually that large, so my gut feel is that the spoiler location would be fine, but of course you're looking for something far more concrete than my gut feel!

I agree that you can't just ignore Nemo's advice, they have retro-fitted far more gyros than anyone else in Europe. How about asking a surveyor to calculate the forces and comment on the risk? I also like mapism's idea of transverse reinforcing of the stringers prior to fitting the gyro. If there is a strength issue with placing the gyro a metre or two further back on the same stringers, it can surely only be the increased torsional effect due to the twisting load being further from the fixed point (the gyro), so transverse reinforcement would help i'd have thought, although you may need to reinforce further forward, at the point where Nemo suggest fitting the gyro. I think it would need proper calcs and design though, so would require engineering input.

The other option is to try to get more detail from Nemo. Thierry is usually a helpful guy but of course he wont want to spend a lot of time helping you design an installation for someone else to do. I assume you've told him about the price difference and he can't bridge the gap? I know they're very busy, especially right now just before the season, so he probably doesn't need to be cutting prices.

The only other port of call I can think of is Seakeeper themselves. They obviously want to sell you a unit, so maybe they would do some calcs for you, if you could get hold of any hull drawings for the F630?

 

[[2068]]

I think I'd be checking that the section of the hull containing the "spoiler" was built equally as strongly as the section forward of the bulkhead, in particular, whatever it is that the stringers are attached to at the very end of the stern ... is it as strong as the bulkhead in front of it?

Once you are satisfied about that there won't be any minor issues with the rear section of the hull being twisted off, or filling up with water then being twisted off, you then need to think about the positioning of the weight.
A jetski weighs maybe 250kg?
You'll be putting something like two jetskis right at the stern, which might not help with trim underway.

.

 

[BartW]

..........what about the water tightness of the actual door /lid ?
Going fwds if that door seal leaks on a bumpy -splashy down wind /beamy sea of say 4-5 hour --you are gonna arrive and find everything in there dowsed in sea water (not lake water ) .
.
What would happen if the catches of the lid were not properly secured of faulty and in a big sea or wha ever a wave lashed up and lifted the hatch ?

+1,
particularly the foldeable hatch !?
one day, some seawater will get in,
The Volvo Penta D3's in our Karnic absolutely didn't like that, (You don't want to know about all the issues we had with them)
and I guess that the electronics / wires and connections on a seakeaper don't like that either

my choice would be fins as you know.

 

[MapisM]

Those bulkhead openings must be original, surely? Not that I like them either.

Well, I said 90% sure that they aren't, not 100%. But I inspected several F53 during my search, and I never noticed them, while they are the first thing which grabbed my attention in the above pic.
And fwiw, I agree with N_H who can't see what they have to do with the gyro: I can't either.
Otoh, if I'm right in thinking that they aren't original, it's even more puzzling to think of another reason (other than the gyro installation), to make them...

 

[MapisM]

Yep, I know where my rudders are and they are well forward if the stern at the rear end of the boat (rather than the spoiler locker)

Yup. But still, the stern hull section is a watertight compartment anyway, also in your boat.
In a sense, even more so than in later Ferrettis, 'cause in yours it's a completely separate mould, so instead of "just" a bulkhead between that section and the e/r, you have the even more solid main hull mould.
Fwiw, I would have understood MUCH more any structural restrictions suggesting the #2 placement instead of #1 in a boat like yours (or a 165/175/185).
But in a 53/57/630 etc., I can't see any structural differences: CoG and exposure to moisture, yes, they are different.
Otoh, the hull mould and its stringers are AFAIK exactly the same, either side of the aft e/r bulkhead...

 

[[2068]]

Otoh, the hull mould and its stringers are AFAIK exactly the same, either side of the aft e/r bulkhead...

I think you need to take into account where the stringers "terminate" as well.
So even if the hull underneath is the same, then putting it on stringers that are between two structural bulkheads will be different to putting it on the same stringers that are attached to a structural bulkhead at one end, and a thinner panel at the other.

 

[MapisM]

I'm not sure to see your point, FP.
In #2 placement (Ferretti standard), the stringers are attached to the bulkhead but are "open" on the other side, up to the front e/r bulkhead, which is far away.
In #1, the stringers are attached to exactly the same bulkhead on one end, BUT on the other end (and very close) there is the hull stern section, which is as strong as it gets...

 

[[2068]]

I'm not sure to see your point, FP.
In #2 placement (Ferretti standard), the stringers are attached to the bulkhead but are "open" on the other side, up to the front e/r bulkhead, which is far away.
In #1, the stringers are attached to exactly the same bulkhead on one end, BUT on the other end (and very close) there is the hull stern section, which is as strong as it gets...

My point is that the E/R bulkhead and the hull in-between is doing "something" in terms of preventing the stringers from twisting, despite being far away.

I'm unsure what is at the the extreme stern end of that "spoiler" cavity. If that section is built to the same specs as the the rest of the hull, and the rearmost panel is structural, then great. But if that section is built more lightly, and the rearmost panel thin, then not so good.

And in any case, it doesn't address the issue of hanging another 550kg right at the back of the boat!
Is there any chance it could go underneath the berth in the main cabin?

The SeaKeeper website quotes 18,810 Nm of torques available for anti-rolling at rated rpm.
That sounds like a fair amount of force to me, applied over quite a small area.

.

 

[jfm]

As you know I would prefer fins and the 0.8msq sleipners under crew space or aft of master cabin would be uber feasible because they have very low profile actuators. These are what we fitted a year ago to my brothers Silver Dee, on same quai as your boat and you're welcome to look at them. But I appreciate the benefits of gyros too, and don't wish to turn this into a gyro v fin debate so will stick to your gyro scenario

I wouldn't give up on using the jet ski locker.

1. The bulkhead holes in the picture are a red herring. They are not necessary, you wouldn't cut them, so your locker would remain as water tight as it is now

2 structurally I would be amazed if Nemo are right. The forces here are up and down on the two stringers that the gyro needs to sit on, and those stringers are or would be made big enough, and would be between the transom abaft and the bulkhead in front. It would need to be looked at but it is verging on implausible for memo to say they can't deal with the gyro's forces. Quick maths: sk9 does 19000 nm of torque. It happen to be 1m wide. So at max effort one stringer is seeing a downward load (ballpark) of one tonne and the other an upward pull of one tonne. Really, that isn't like building the Golden Gate Bridge. I just dont see any problem in beefing up those two stringers to take those sorts of quite modest loads

3. Water tightness of the hatch lid is an issue. I can't say for sure without seeing it. You need to be sure this is ok. I would think that a good rubber seal and perhaps some extra (monitor marine-ish) latches would do the job but I'm only keyboard engineering here. In addition I would (a) build the stringers up to the sk9 is high (b) fit a local bilge pump and alarm if needed (c) spray the bottom part of the sk9 in waxoyl when installed. I think that could be ok with some regular checks and wiping clean

Mike I'm trying to be practical here. It's easy for posters to say it should be in e/r or master cabin and in perfect world that is true but the cost/effort/ cutting and shuttting/spoiling the e/r, etc etc etc to achieve that are massive. You would face Nemo's wrath if you use the jet ski locker but there are worse things in life. I would want to know who Ventura are subcontracting to because they won't be doing it themselves but there must be plenty of good installers they can use and this is not rocket science

But before final decision make sure you are happy to reject fins. Electric gives easy install if you have the height to accommodate the actuator motors and don't mind the unpleasant noise. Hydraulic means moderately more complex install but uber low profile actuators and quieter. Either is awesome underway, much better than gyro in big seas, and say 90% as good as gyro at anchor ( and like night and day compared with having no stabilisation). Apologies for mentioning fins - don't wish to make this a gyro v fin thread but seems slightly relevant to your circs. Quite happy if you say you 100% don't want to consider fins.

 

[jfm]

The SeaKeeper website quotes 18,810 Nm of torques available for anti-rolling at rated rpm.
That sounds like quite a lot of force to me, applied over a fairly small area.

It's worth doing the maths. The forces are not huge and are well within what FRP stringers of quite modest size can deal with. Maths is more important here than intuition imho.

 

[[2068]]

I could well be wrong, but in the static case ...

18,810Nm of torque would generate a force of 37,620N at a point 0.5m out from the center, where the stringers are.
Shared between two stringers = 18,810N on each
Which is approximately 2 tonnes on each

Either way ... it's still "more than a jetski".