Fin stabilizers are appendages strategically positioned outside the hull in the hull envelope, below the waterline. They are designed in shape and movement to generate lift or downforces that reduce the roll of a vessel. A vessel typically rolls sideways, and the fins oscillate, using opposing movements to negate the roll and stabilize the vessel. The fins are powered either hydraulically, electrically, or pneumatically through a mechanism known as a hull unit, inside the vessel, typically at the turn of the bilge. The stabilizer system is activated by a master controller that directs the power required and the movement of the fins through an algorithm and various motion sensors. Naval Architecture is a discipline that plays a major role in the design, sizing, power, and placement of marine stabilizers.

Zero Speed™ Stabilization was a feature brought to market by Quantum Marine Stabilizers in 2000. Slow or zero speed is when a vessel is the most vulnerable to movement or rolling. Adding Zero Speed™ capabilities revolutionized the yachting industry, helping thousands of people who had previously suffered from seasickness.

All about Yacht Stabilization in 2023

What is a yacht stabilizer?

In general terms, yacht stabilizers are fins or rotors mounted beneath the waterline, positioned typically amidships, laterally from the hull to reduce the roll of the vessel. There are several types of stabilizers, whereby some are active (with movement underwater) and some are passive (fix, with no movement underwater).

How do yacht stabilization systems work?

Active fin stabilizers, in zero speed mode, use a paddling motion with an opposing force between port and starboard to generate lift. The roll reducing movements are initiated by a custom control system which uses specific algorithms, along with either an electric or hydraulic power source, to maintain proper stabilization.

What are the types of stabilizers used on yachts?

Overall, there are two different types of yacht stabilization systems, which we will explore in the following paragraphs.

Passive yacht stabilization systems

A passive system does not require a separate power source, nor does it need a unique control system. Examples of passive stabilization systems and their key elements include the bilge keel, passive anti-rolling tanks, passive moving weight systems, and fixed fins. With this report, we will only touch on the two most common, bilge keels and anti-roll tanks.

Bilge Keels

Bilge Keels are one of the most widely-used passive stabilizers. They consist of a bulb plate, fitted externally, that is welded on a flat bar located at the turn of the bilge. Bilge Keels work by forcing the water to move with the ship, creating turbulence and reducing motion. The damping effect is greater as the speed increases and less effective at zero or slow speeds.

Passive Anti-Roll Tanks

The shape and size of the internal baffles allow the liquid inside to slosh from side to side in response to the roll motion of the ship. The various phases of the roll moments on a yacht, along with the sloshing tank liquid, will reduce the roll motion of the vessel.

Active yacht stabilization systems

An active system uses power to produce a moving mass or control surface that provides an opposing roll. Examples of active stabilization systems and their key elements include active fins, active anti-rolling tanks, active moving weight systems, and the gyroscope. With this report, we will only touch on the two most common, active fins and gyroscopes.

Active Fins

Active fins are able to detect the rolling of a vessel through a roll sensor that will then transmit the roll angle and roll velocity to the main controller for processing. Using the yacht’s roll characteristics and the customized algorithms, the main controller sends the appropriate response to counteract the roll with the optimal fin movement and the necessary hydraulic pressure.

Overall, active fins may deliver up to a 90% roll reduction, ensuring onboard comfort and safety while enhancing the vessel’s resale value. Zero Speed™ technology was introduced in 2000 by the innovators at Quantum Marine Stabilizers. This enhancement represented an enormous step in stabilizer technology, setting new expectations and comfort levels that were unprecedented.

Gyroscope (Gyro Stabilizer)

The first use of a fin stabilizer dates back to 1933 with a Japanese cruise liner. Stabilizer gyroscopes go back even earlier to the late 1800’s, but the hydrodynamic roll stabilizer was favored due to the lower cost and lighter weight.

Basically, gyro stabilizers operate within a vacuum-enclosed sphere. Inside the sphere is a steel flywheel that spins at a rate of 9,750 rpm. When a vessel encounters a roll, the gyro movement is fore and aft (processes) to negate the roll of vessel from port to starboard. Though there are no appendages with a gyro, they can take 45 – 60 minutes to “ramp up,” and they are less effective in underway mode. Additionally, they are heavy and can be difficult to service.

What is zero speed stabilization?

Zero Speed™ was introduced by Quantum Marine Stabilizers in 2000. Vessels tend to be most vulnerable or susceptible to rolling at slow or zero speeds. Quantum developed an active paddling system, generating lift that proved to be groundbreaking for the industry.

How do hydraulics work to power a marine stabilizer?

Many stabilizer systems, especially in the larger boat market 50m+, are powered by hydraulics. Electrical energy is converted to fluid energy (hydraulics) under pressure using pumps creating pressure and valves to control the flow. In other words, the hydraulic energy is converted into mechanical energy that drives the movement of the cylinders. The cylinders are connected to the fin by a shaft that extends from inside the vessel, typically at the turn of the bilge, through the hull, and under the waterline. The fin is directed to move per the control algorithms and conditions.

Which stabilization system is right for which yacht?

“It is not just about the length, but about the requirements, specifications, and how the vessel is intended to be used. An 85m, for example, could use different stabilizer options or a combination of stabilizers. The analysis may find that a MAGLift™ or an XT™ will be well suited for the requirements of the vessel. The next question is, are you going to Monaco or the Antarctic? How many people do you want to take with you? How long do you want to be at sea? What is the comfort level you are looking for? “

John Allen, CEO of Quantum Marine Stabilizers

Though there are many options to consider when analyzing the best stabilizer solution for your needs, it is NOT an “off-the-shelf” item.

Yacht stabilization falls under the domain of naval architecture as there are many calculations and relevant data points to assimilate, such as hydrostatic characteristics:

• Natural roll period
• Vessel speed
• Metacentric height (GM)
• Displacement
• Beam
• Sea state requirements

Naval Architects in the past and today use adaptive and variant design. In other words, using an existing stable design as a starting point and then making revisions as needed. This ensures a successful design versus starting from scratch and taking on new risks. In addition to that practice, Computational Fluid Dynamics (CFD), ship model testing, and advancements in hydrodynamics and structure interaction have been added to the toolbox, offering greater precision to the process of specifying a stabilizer system. Keep in mind that the stabilizer supplier, the shipyard, and an experienced naval architect are excellent resources to help in determining the optimal system, the appropriate size and proper power are best suited for your needs.

The large number of elements involved (naval architecture, hydrodynamics, seakeeping studies, and performance requirements) result in a complex problem for which the solution is necessarily vessel-specific, as no two yachts share the same combination of the above factors.

Do you want to find out more about how yacht stabilization works?

Contact Quantum’s team of marine stabilization experts today