SEAKEEPER The Seakeeper 1 is designed to eliminate up to 95% of boat roll on vessel 23-30 feet (7-9 meters) or up to ~ 5.5 tons. With a fresh, new look, the Seakeeper 1 is completely contained with no part of the sphere hanging below the point of installation. With a height of only 15.68”, deck installation beneath a seat is easier than ever. With a totally unique flywheel and smaller envelope, the Seakeeper 1 can start stabilising in record time – just 15 minutes. A control keypad, called the ConnectBox, is directly on top of the unit. But, the Seakeeper can be controlled from the helm, or directly from the unit itself. The unit is completely hoseless and a self-contained single cylinder active control is engineered for enhanced performance and reliability. For more details visit www.seakeeper.com


create lift, referred to as the Magnus Effect. Instead of protruding at a 90-degree right angle to the hull, these can be raked back for less resistance at higher cruising speeds. A secondary benefit is a back and forth action, which, when deployed correctly, gives stability at zero speeds, yet without creating the ‘swimming’ effect of slowly paddling the hull in a forward or backwards direction.


Another emerging system is from Hull Vane, who have developed a patented static, wing- shaped appendage, or underwater spoiler, fixed across the full width of the hull at the rear.


Said to be particularly effective against hull pitching and slamming, the wing is designed for displacement and semi-displacement hulls, effectively converting stern wave energy into forward thrust, the benefits claim to be reduced resistance from between 5% and 25%, higher top speed, better fuel economy and less noise on the aft decks.


Hull Vane also offer an active version of this system, namely their Dynamic Hull Vane®, said to raise performance levels even further. Developed in partnership with Naiad Dynamics, the system is governed by


Roll is exacerbated by the boat’s own inertia energy, the effect of which makes a boat roll even more than the angle of the wave itself. The result is large movements of the head in the form of sudden accelerations from side to side Fin Stabilisers


a Ride Control System using actuators to vary the angle of attack of the appendage, thereby increasing the damping and reducing the pitch motions by 30% to 45%.


For fully planning vessels operating in both recreational and professional markets, Foil Assist by Hull Vane® consists of a passive, mid-ship mounted wing under the bottom, which carries a significant portion of the displacement and therefore dampens the pitch excitation when sailing fast through waves.


By taking this load on the more deeply submerged wing, rather than on the running surface, means that waves have less influence, as the orbital motion of waves decreases with depth. Using the car analogy, Hull Vane® claims it feels more like active suspension has been added to the yacht creating a much smoother ride.


Lastly, Interceptors are active & intelligent trim tabs that offer speedy responses to reduce slamming, and, to a lesser extent, reduce roll, but their total effect is the least on offer from those other solutions we have discussed here. In some cases, Interceptors can be integrated with fins and rudders - the net effect promising stability across a wider range of on-water scenarios.


One of the most well-known, (but relatively young as stabiliser manufacturers go), is 112 year old Sleipner Motor, whose elegant and aesthetically pleasing Vector Fins caused quite a stir back in 2013, when the design scooped the coveted overall DAME Award for marine equipment design and innovation. The patented design, with its distinctive, concave face, curved sides and winglets on the bottom edge, proved that with proper hydrodynamic input, and a lot of R&D and real-time testing, a significant jump in roll reduction was achievable, compared to equivalent size ‘traditional’ flat-fin designs. Sleipner claim their Vector Fins can offer the same level of performance, or often that much better, yet from comparably smaller fin sizes. This means less drag and therefore less fuel consumption.


Reduced internals meant there was less power required for what was already a smaller fin size in the first place. And because everything was smaller, it gave installers and boat builders more scope to physically locate the fins in their most optimal position on the hull. In the event that a more compromised hull position was the only option available, less un-wanted ‘side-effects’ meant this design was also the most forgiving.


198 | AUTUMN 2020 | ONBOARD


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