The watchword is to stabilize. Until a few years ago, only megayachts had appendages that came out of the hull and dampened unwanted movements. Today, however, many systems are available to offer the advantages of a stabilizer even to those who have a 10-meter boat. Especially the so-called zero- speed solutions that work even at berth. Or those that (much less onerously) dampen movements and adjust speed when sailing.
Among gyro stabilizers, those made by Seakeeper are maybe the best known. They have a rotating part kept under vacuum to increase the rotation speed, thus reducing the necessary mass. The basic model, the Seakeeper2 (rpm: 9000; torque: 5.2 kNm; weight/mass: 188 kg, price 19 thousand euros) is suitable for 8-meter boats up to 8 tons; the biggest model, the Seakeeper 35 (rev/rpm: 5150; torque: 73 kNm; weight/mass: 1778 kg; price around 200 thousand euros), instead, is designed for yachts over 85 feet.
The MC2X line includes nine models of stabilizers from the MC2X5 model (rpm: 4800; torque: 5.5 kNm; weight / mass: 265 kg, price around 17,500 euros) to the MC2X56 (rpm: 3500; torque: 56 kNm; weight/mass: 1400 kg; price …). The flywheel rotation system is on a horizontal axis instead of a vertical one. This is why bearings suffer less friction and maintain lower temperatures, thus not requiring water cooling.
Even the Japanese company brings its expertise to smaller vessels with the ARG 50T / 65T model (rpm: 4200; torque: 5.0 kNm; weight / mass: 234 kg, price around 15.500, 11.600 €) designed for boats from 7 to 10 tons. Among its peculiarities, the battery-based operation with direct current. The largest model of gyroscopic stabilizers of this company is the ARG 375 (rpm: 3250; torque: 37.5 kNm; weight / mass: 910 kg; price: na).
www.samos.it / www.antirollinggyro.com
Zipwake’s interceptors automatically correct speed by reducing roll and pitch. In addition to the comfort on board, they also improve the fuel efficiency of the boat. Suitable for boats from 20 feet , they can be connected to a single electronic control unit managed by a digital control panel with an integrated gyroscope that automatically sends the impulse to the interceptors to correct speed.
Price starts from 2,000 euros.
They are probably the most popular interceptors. They work actively and automatically to reduce pitch, roll and trim on semi-planing or 25-foot planing boats. They offer the coordinated turn function (Automatic Turn Control), with which they intervene on the turning angle in maneuver to reduce the turning radius and limit lateral accelerations to the benefit of comfort.
The system uses the Magnus effect (read in the text). It combines lightness and immediate functionality (it is totally operational even when it is switched on) typical of a fin with a reduced increase in hydrodynamic friction (if it is switched off, it can also be installed inside the hull). It guarantees three possibilities of use – Zero Speed; Cruising, between 4 and 14 knots;
and Rake, at above 14 knots.
Among the most affordable stabilizers, gyroscopic ones are become increasingly more popular. Like a spinning top, they use their quick spin to keep balance around the rotation axis. You only have to install (no matter where, the gyroscope works even if it is mounted on the fly bridge) a rotating mass, whose size varies according to the boat displacement. When the boat starts rolling, the mass moves in such a way as to keep its rotation axis stable, effectively dampening the roll.
Compared to fin systems, rolling resistance decreases because they have no immersed parts. Easier to install, they are more compact and suitable even for 8-meter boats.
However, to be efficient, the gyroscope must reach its normal rotation speed (Spool-up): this means that it takes about 30 minutes to be operational (in this phase, consumption is higher than normal us). The same time, if not twice, is needed for total shutdown (Spool-down). The disavantage lies in the additional weight (a few hundred kg per ton) and the idea of having a mass of such dimensions constantly moving on board.
The third possible option to stabilize your boat is the Magnus effect: a rotating cylinder, immersed in moving water, will tend to move from the side (down or up) where its rotation and the movement of the water have an opposite direction. If the boat is at anchor, the system works just as long as the cylinder is moving. Less expensive and heavier than gyroscopes, these systems always have immersed parts, but about a tenth of a fin providing the same thrust.
IT DEPENDS ON WEIGHT
The size of the stabilizer should be calculated according to the anti-roll torque it delivers, ie the force with which it tends to straighten the boat. Expressed in kiloNewton meters, this means that you need a 5 kNm stabilizer for a boat of about seven tons; a 6.5 kNm stabilizer if the tons become 10 kNm and up to 130 tons of displacement if the kNm produced are 120.
From a user interface point of view, the situation is fairly equal for the various manufacturers since they all have a digital control panel directly on the machine and, often, there is also an app you can download on your smartphone or connected device to manage and monitor the whole system.