Seakeeper gyro report

[jfm]

Its radical but is it scaleable down to smaller boats? And then what sort of cost would it be relative to the cost of a smaller boat? And would any production builder be willing to fit it on one of their grp hulls? How much drag would it create on a planing hull? My guess is that DMS know already that this system wont scale down which is why they're aiming it at the 30m+ market and my guess displacement steel boats only

Exactly. And in addition to all that the workings are outside, protected by several seals only one of which need fail to make for an expensive and complex repair. It's very clever thinking but it's technically risky (plus continued life of the company/spare parts risky) so you'd need to be a brave owner. All to stop forward walk, which is a tiny 1st world problem to begin with

 

[MapisM]

Its radical but is it scaleable down to smaller boats? And then what sort of cost would it be relative to the cost of a smaller boat? And would any production builder be willing to fit it on one of their grp hulls? How much drag would it create on a planing hull? My guess is that DMS know already that this system wont scale down which is why they're aiming it at the 30m+ market and my guess displacement steel boats only

Well, when it comes to what's in DMS and boatbuilders mind, your guess is as good as mine.
But fwiw, mine is much simpler: I think that at DMS they are aiming at the 30m+ market for the very same reason why also CMC aimed at superyachts first, i.e. because that's the least cost sensitive segment of the boating industry.

From a technical viewpoint, just think about it: physically, heavy displacement boats are the easier vessels to stabilize - even my old lady with her plain vanilla Naiad fins, designed 30 years ago and with zero electronic controls, was stable as a rock, under way. And it gets even easier as you get larger.
In a sense, the much higher efficiency of dual axis fins is actually wasted, when used for large D vessels...

It's the stabilization of light and smallish (say under 20m or so) P boats that is tricky.
And in that segment, even if afaik there isn't a suitable dual axis equipment available at the moment, its inherently higher efficiency, both under way and at zero speed, is bound to be a huge advantage.
It's also easy to envisage that they could be designed and placed in order to make them effectively work at speed not only as stabs, but also as lifting foils, hence ultimately improving the boat performance.
Besides, I see no logical reasons why the actuators couldn't be placed inside the hull, if that's better for reducing drag in a P boat (though there are pros also in the all-external solution), leaving only the short section of the longitudinally rotating part aligned along the hard chines, creating as little drag as with any other fins - if not less, considering that they would be in the aerated section of the water flow, as opposed to the fully submerged position of traditional fins.

Last but not least, there's another inherent advantage in dual axis design, even if afaik it has not been exploited so far by DMS (whether that's because they just didn't think of it or they had some technical difficulties, I have no clue): the possibility to combine the two rotation movements in order to minimize the "wrong" righting force of the fins, on their way back after reaching the full extension when operating at zero speed.
Which is something traditional fins are forced to live with, and can only address by delaying and/or slow down the movement - which ultimately decrease their effectiveness.

Bottom line, I don't know whether DMS is willing and capable to fully exploit their own design, offering a cost effective and reliable solution for those who can't afford 30+m ships.
In this respect, your and jfm's objections are understandable.
But I completely disagree with him when he says "all to stop forward walk", because as I already said that's the least relevant of all the advantages of dual axis design, while all others make any other fin stabs as we know them old and inefficient, in comparison.
Btw, the funny thing is that jfm surely understands that well enough to explain the reasons much better than I could, if anyone would be interested to hear them...

 

[Deleted User YDKXO]

Well, when it comes to what's in DMS and boatbuilders mind, your guess is as good as mine.

Well its clear whats in their mind if you go to their website http://www.dmsholland.com/en/. They state that the dual axis system is for yachts over 30m and their Magnus system for yachts under 30m. Having spent a load of money developing the Magnus system, I guess they're not going to damage their potential market for the Magnus system by scaling down the dual axis system. I'm sure the dual axis system is an excellent device but I suspect the biggest factor stopping sales of scaled down versions to smaller yachts will simply be cost. Just to pluck a figure completely out of the air, I would guess a scaled down version might be priced at €200k when you factor in the builders installation costs and thats just too large a proportion of the cost of a boat which might cost €1 - 2m. Gyros are probably going to come down in price with increasing competition in the market and buyers of this size of yacht are going to be asking themselves whether they need to spend such a huge amount of money on stabilisation when a gyro gives them most of what they want for a third of the price

 

[MapisM]

Well its clear whats in their mind if you go to their website http://www.dmsholland.com/en/.

LOL, their website shows (pretty much by definition) what they want us to believe - not necessarily what's in their mind...
Regardless, if I should bet which between those two systems could potentially become the best solution for P boats in a not so distant future, I'd put my money on dual axis fins in a heartbeat.
But as I said, whether DMS will be capable to fully exploit its potential, that's anybody's guess.

Btw, the fact that none of their competitors came up with a similar solution so far is obviously just due to patent restrictions, no matter what else they can pretend: anyone who should argue that the dual axis design is not inherently superior to traditional fins, either knows nothing of basic physic principles (which are obviously very well known and understood by all of DMS competitors), or is lying to defend some vested interest.

Ref.costs, I honestly struggle to see any major reasons why a properly engineered and optimised dual axis equipment should cost so much more than traditional fins.
Yes, there must be two sets of actuators for each fin rather than just one, but that alone doesn't imply a double production cost. It's also true that there are more seals involved, but also that ain't rocket science...
Anyhow, I bow to your vast knowledge on similar stuff in the industrial field. If you really think that a dual axis system sized for a 60' boat couldn't be sold for less that 200k Eur or so, well, I can't imagine why (having in mind the ballpark cost of "normal" fins), but I take your word for it.
Of course, at that price level, neither boaters nor builders would consider it.

And frankly, I agree with you that nowadays a gyro is overall the better compromise for fast(ish) P boats.
In fact, in any P boat capable of 30+ kts, I also would go for a gyro, also if given the choice upon build, and not just for retrofitting.
After all, for those who rank comfort while under way as their highest priority, when all is said and done, a P boat is a wrong choice regardless of how the hull is stabilized, because even if rolling is the single major factor affecting onboard comfort, roll stabilization alone is nowhere near enough to make a rough sea passage a pleasant, rather than an annoying experience...

 

[Deleted User YDKXO]

Ref.costs, I honestly struggle to see any major reasons why a properly engineered and optimised dual axis equipment should cost so much more than traditional fins.
Yes, there must be two sets of actuators for each fin rather than just one, but that alone doesn't imply a double production cost. It's also true that there are more seals involved, but also that ain't rocket science...
Anyhow, I bow to your vast knowledge on similar stuff in the industrial field. If you really think that a dual axis system sized for a 60' boat couldn't be sold for less that 200k Eur or so, well, I can't imagine why (having in mind the ballpark cost of "normal" fins), but I take your word for it.
Of course, at that price level, neither boaters nor builders would consider it.

None of it is rocket science but a dual axis fin system is always going to cost more than a single axis fin system. OK lets say a dual axis fin system for a €1.5m 60' P boat costs €150k, a single axis fin system €100k and a gyro €60k. How many buyers are going to specify the dual axis system? Very few if any I would suggest. Yes I suppose there might be a small market for a dual axis fin system in the 60' D boat market but even in that market, the cost will be a major consideration

 

[Portofino]

Nobodies mentioned drag or extra drag of fins in or around 60 ftr ? Planning boat .
I would think over a certain speed your guess is a good as mine planning , sticking something even hydrodynamic into the water is not gonna help speed , load or EGT ., and of course your wallet at the pumps .
Some builders went to great lengths to lift the rudders up as much as the helmsman could cope .
For example this boat a gyro is a no brainier ,
https://imgur.com/gallery/i1DHe

 

[MapisM]

I would think over a certain speed your guess is a good as mine planning , sticking something even hydrodynamic into the water is not gonna help speed , load or EGT ., and of course your wallet at the pumps.

That actually depends, to some extent.
Sure, any submerged appendix adds drag in principle, which in turn affects negatively the boat performance.
But think about hydrofoils: the principle is that by lifting the hull completely above water, the dramatic wet surface reduction more than compensate the foils drag, eventually allowing the boat to go faster when "flying" on foils, for any given power.
Now, true hydrofoil hulls are not a viable proposition for pleasure boats, for all sort of reasons.
But dual axis fins, by sticking fins outside the hull while under way, could definitely contribute to hull lifting, which is bound to affect positively speed/load/fuel burn.
If you ask whether this effect can be relevant enough to more than compensate the additional drag, I don't know what the real world answer is. I wouldn't be surprised if it would be yes, though.
And in comparison with the negligible impact on lift of traditional fins, dual axis ones can only be much better, anyway.

 

[MapisM]

OK lets say a dual axis fin system for a €1.5m 60' P boat costs €150k, a single axis fin system €100k and a gyro €60k. How many buyers are going to specify the dual axis system? Very few if any I would suggest.

Assuming those numbers, yep, I agree.
As I said, on a 60' P boat, I'd rather have a gyro than traditional fins even at the same cost... :encouragement: