STABILISATION
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 above 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 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
fins.
In the past, stabilisation has been a choice between either underway or ‘at anchor’ performance, but with the latest fin design, we now see ‘at anchor’ results rivaling any other stabilising technology out there.
(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.
For 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
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