STABILISATION
Sea and waves impart six different forces on a hull, namely, heave, surge, sway, pitch, yaw and roll. Of these effects, roll is one of the most influential causes in the case of passenger discomfort
The secret is held mainly within the shape of the fins. The more up/down vertical motion re-directs the force direction, in such a way that more of it is put to good use. The concave face improves the net force angle, increasing the leverage arm around the boat’s rolling point which adds further to roll reduction.
And despite the reality of having two fins thrashing around underneath the hull, the up/down design (as opposed to a more horizontal side to side movement) was found to generate less of those inevitable side-effects of yaw and sway, which can create unpleasant motions and an unwanted ‘swimming effect’ in the water.
Proud of the impact his Vector Fins have made so far, Sleipner’s MD, Ronny Skauen, said: “The way we have seen boat usage change over the last years, and definitely this year with the Corona situation, people spend more time on their boats actually cruising, and many at slower speeds than
before, both for fuel economy as well as general comfort.
“Taking into account also the other unique benefits our Vector fins have, with much less actual drag than flat fins because of their lifting/foiling functions, together with the focus on improved fuel efficiencies, we are seeing more and more naval architects ‘getting it’ now, resulting in Vector Fins being chosen by many high-profile vessels with a clear environmental and comfort efficiency focus.”
Another fin manufacturer we talked to was SKF Marine, formerly known as Blohm + Voss Industries, whose history with fins goes back 60 years. Dedicated not just to the engineering and development of fins, but other selected areas of a yacht’s engineering needs. In their time, SKF have had installed more than 700 fin systems within boats, but that has been across different marine sectors and not solely within the leisure marine market.
SLEIPNER Sleipner Motor AS is a Norwegian technology company well known for their world leading range of Side-Power thruster systems and Vector Fin stabilisers. With the introduction of the Vector Fins, the jury of the prestigious DAME Design Award rated the innovation as the overall winner of all categories back in 2013 due to its significant leap in efficiency. The company has not been resting since and continued tirelessly to improve both software and hardware to further increase performance as well as extending the range of products. The new technology behind the Vector Fins is the next step to complete comfort at sea. The vertical concave shape of the fin creates a net force direction, both in cruising and in ‘At Anchor’ situations, so the work is more up/ down instead of side to side or almost horizontal, as flat fins work with forces parallel to the hull angle. For more details Tel: +47 69 30 00 60 or visit
www.side-power.com
From their headquarters in Hamburg, SKF Marine offer their Retractable (Type Z) and Non-Retractable (Type FZ) hydraulic Fins in a range of sizes, both for zero speed and underway and a range that is more emphasised towards larger yachts and superyachts.
An electrically driven, non-retractable
solution, Type EFZ, is currently under development and will be ready by the end of 2020 and it promises something special. The actuator is said to be silent, compact and easy to install, with stabilisers that can be locked into any position, even when switched off.
For equipment that is immersed in a salt- water environment for most of its life, its build quality and operational reliability and consistency is key. In this respect, SKF’s Rotary Vane Drive, applicable to the Type Z and FZ models, is where German engineering really shines through.
The technology provides constant maximum torque throughout the operational range and the fins themselves operate through a large working angle of up to 120° from sweep to sweep, so performance can be optimised based upon prevailing conditions. Powered by SKF’s own hydraulic control unit, it has an ECO mode for efficiency and
MOVEMENT A yacht at sea moves in six degrees of motion - simplified, it means that it is free to move up/ down, forward/backward or right/left, and its ability to rotate around its three axes. These movements are known as heave, surge, sway, pitch, yaw and roll. Graphic courtesy of Sleipner Motor.
ONBOARD | AUTUMN 2020 | 199
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