Superyacht stabilisation

Some stabilisation solutions have ‘bridged the gap’ between zero-speed and cruising speed performance, so it was time for Adam Fiander to take a closer look

Having returned from a fantastic few days at the MetsTrade show in Amsterdam back in November, there were two product sectors that made a big impression on me.

The first was how much design creativity and investment is being poured into zero-emission propulsion, and the so called, Next Generation Propulsion Zone was a fascinating showcase of some 20 new ideas and initiatives for electric, hybrid and alternative fuel propulsion, with the cast-iron certainty of exciting times ahead.

The other burgeoning product sector centred around METS was for roll reduction and stabilising technology, with new and existing companies offering alternative and innovative ideas, including reworked and reimagined versions of existing fin/gyro technology.

The main contenders, gyros and fins, still dominate across leisure and commercial marine, notwithstanding a few exceptions, the commonly held perception is that gyros remain the better option for reducing roll at very slow speeds and ‘at anchor’ situations, compared to fins. But some manufacturers are disputing those traditionally held views, through improved versions of existing technology (mainly fins), and results gained from alternative products starting to break through. Referring to fins, I was fortunate to join a press trip to Sleipner’s head-office and production facility recently in Fredrikstad, Norway, to find out more about their latest, 3rd generation Vector Fins™. Instead of having a flat-face profile, Vector Fins™ have an elegantly curved, upswept profile that increases the vertical force component, creating a ‘merger’ of both horizontal and vertical forces for the desired net effect.

The design works well in the 12m to 50ft size range, and you only need to glance at Sleipner’s long list of boat-builder customers to discover that must be true.

The most significant difference is the outline shape, with a new cut-away section at the back of the face, allowing for an even wider arc of movement when flapping backward and forwards.

This new ‘paired-back’ design is said to be more energy efficient and allows for a wider arc of movement. The second difference is an even more pronounced curvature of the face, further improving the force direction and giving an even better drag to lift ratio than before. During the press trip we were invited onboard Sleipner’s Fairline 65 test boat, one of only a few boats that have the new 3rd Gen fins installed. Roll motion sensors have been fitted, so we could plot and record the ‘fins on / fins off’ effects over given periods of time.

Conditions in early November were far from ideal, horrible, in fact, for most people, but perfect for testing stability products!

Harsh, cold, windy conditions in the Norway’s Skagerrak, with up to 1m average wave height, meant the boat was rolling and pitching quite a lot, as we motored out from Fredrikstad harbour to find open water to switch-on and test the fins.

Cruising at 15 knots or so underway, with quite a lot of motion, we throttled back to a standing still position, at which point the motion became even more severe, with crockery & glasses banging and rattling in cupboards, it was nigh-on impossible to stand, let alone walk.

To put this into context, no ‘normal’ skipper would contemplate stopping in these conditions, so we motored back in to find a somewhat more realistic place (although still lumpy) to test the fins. At which point we switched them on and after about a minute or so – while waiting for the system sensors and algorithms to settle the hull – the motion became considerably that much more bearable, and the significant ‘before and after’ effect was clearly evidenced and greatly appreciated by everyone onboard.

Looking at the roll stats for average degrees of roll angle, we witnessed improvements from 1.78 degrees (fins off) to 0.25 degrees (fins on) – not bad at all, with the difference being seen in the smiling faces of everyone onboard, proving how important stability on boats has now become.

Sleipner’s Product Communication Manager, Thomas Skauen, summarised when he said: “In the past, stabilisation has been a choice between either underway or ‘at anchor’ performance, but with our latest fin design, we now see ‘at anchor’ results rivalling any other stabilising technology out there, meaning there is finally a system that can deliver top end efficiency both underway and ‘at anchor’.” As the roll degree stats graph below shows.

Where Sleipner specialise solely in fins for stabilisation, Dynamic Marine Systems (DMS Holland) are impartial to which system they supply, and it’s more a case of which one is best suited to which particular boat.

DMS anti-roll, for example, are dual-axis fins that rotate while underway and make a flapping motion at zero speed, offering stabilising forces in multi-direction scenarios, and a good example of how fins are potentially bridging the gap between zero speed and high-speed performance.

Flapping up and down creates lift and minimises the unwanted ‘swimming effect,’ sometimes caused by single axis fins. Installations are mainly suited to large yachts and superyachts, and the fins can also retract against the hull, making them suitable for large sailing yacht use as well.

If you can’t decide which system to use, DMS all in one, might solve your problem because these smaller fins are placed at the very aft end of the boat, relatively close to the surface, offering stability at zero speed (up and down flapping), cruising speed (rotating motion) and higher speed stability, where they can be folded in 180-degrees, to act like inboard trim tabs, with anti- roll and anti-sway capability thrown in.

DMS HOLLANDFor low-speed displacement vessels, trawlers, and such like, operating anywhere up to 12 knots, DMS MagnusMaster creates an imbalance of pressure either above or below the rotating tube, depending upon the direction of spin.

The force-direction can be switched in an instant to counteract roll, and, like most good ideas, it’s beautifully simple, with tubes that can auto-retract and park themselves neatly parallel to the hull at anything above 12knots, (at which point the magnus effect no longer increases).

Apart from space, weight and cost considerations, there’s nothing preventing a customer from installing a combination of systems, if that is what it takes.

And if your existing hydraulic fin system is perhaps old, but still mechanically sound, DMS Universal will reinvigorate the performance completely, by retaining the existing hardware, but replacing the old operating system with new software / new stability algorithms that will make you think you’ve spent far more budget than you actually have.

DMS Sales Manager, Tim Kehoe, told me: “In many instances you realise there’s ‘no one type fits all option’ and we know that gyros really deliver at zero speed/at anchor, the problem is as boat speed increases you see that performance drop off and you’re looking for another solution to carry you through. Rather than compromise and suffer the sick-inducing consequences, you enter the territory of combination solutions where you opt to reconsider the budget and go for the best of the best for each situation.

“We aim to provide the best possible solution from what we have available, and before proposing a system, the overriding question we ask is ‘where do you want to be stabilised’ – in terms of is it more at anchor, when cruising, at high speed or low speed? And the answer largely depends upon what type of boat the customer has and how they want to use it.”

When it comes to history and provenance, the ‘granddaddy’ of marine stabilisation has got to be Naiad Dynamics, who can trace their roots back over 100 years, through a series of mergers and acquisitions to the point where they are today. Major OEM’s who exclusively or routinely specify Naiad stabilising equipment include, among others, San Lorenzo, Damen/Amels, Ferretti, Marlow, CRN, Heesen, Benetti, Westport, Royal Hakvoort, Baglietto, Turquoise, Navetta and many others.

In addition to leisure marine, Naiad’s extensive workboat and military expertise requires a level of knowledge and understanding of stability few companies could replicate, in particular, for unusual hull types with niche purposes in mind.

Naiad Dynamics“What sets us apart is our ability to provide motion control solutions for practically any type of hull from monohulls, catamarans and trimarans to advanced forms such as SWATH, SLICE, and even air cushion vessels,” says Naiad’s Charles Egan.

“Commercial crew-transfer vessels require life-saving levels of stability when crews are exchanging from offshore windfarms or drilling platforms. Likewise, when navies need to extend the operational effectiveness of vessels, they must ensure crews and ship personnel are as comfortable and as free from nausea as possible, often in sea conditions where no leisure marine vessel would ever be seen.”

When quizzed about how some of today’s technology is ‘bridging the gap’ between zero speed, slow speed and cruising speed stability, Charles said: “Simply put, fins are the one system that can provide very good roll control while at rest, as well as underway, and our systems have the benefit of lower installed weight and volume, as well as lower through-life cost of ownership.”

Maximising comfort onboard and the overall experience of charter guests, especially those new to the world of chartering is paramount and with an ever more informed pool of superyacht owners or potential owners entering the market, these stabilising solutions are under pressure to deliver comfort and to enhance the overall experience of being on a superyacht.

We expect to see even more solutions hitting the market over the coming years as more superyacht builders look to add these solutions as a ‘normal’ feature on a wider range of yachts.

There’s nothing for it, I must be getting old because I can still recall the days of popping stugeron tablets, while eating plenty of ginger biscuits and keeping my eyes fixed upon the horizon – folklore that is probably best consigned to the history books, or the next time my yachtie friends and I visit the pub.