Guide: Stabilizing systems

Why do you need a stabilizing system on your boat? 

Picture this: you're on a boat, and suddenly the wind picks up, and the seas become rough. The vessel starts to sway back and forth, and you feel like you're on a rollercoaster ride. The next thing you know, you're feeling queasy and wishing you were on solid ground. 

We've all been there, and we can all agree that it's not a pleasant experience. But the effects of an unstable boat go beyond seasickness. Imagine plates and cups flying around the cabin, passengers struggling to move around the ship, and crew members risking their safety to keep everything under control. It's not just uncomfortable; it's dangerous. That's why having a reliable stabilizing system on board is crucial for any vessel, whether it's a luxury yacht or a workboat. It's the key to a smooth and safe ride, even in the most challenging conditions.

Designing ships that can handle the challenges of roll reduction is a complex task. Rolling is one of the most challenging issues faced by ships at sea, and addressing this issue requires advanced technological solutions. Naval architects are at the forefront of this challenge, using cutting-edge technology to study wave motions around the ship's hull and develop designs that minimize the impact of rolling, providing a comfortable and safe voyage for passengers and crew alike.

For workboats that operate under rough conditions, an active stabilizing system can make the difference between getting the job done safely or not done at all. A stabilized vessel significantly improves the safety and comfort of the seamen as the boat roll is almost eliminated, both underway and at anchor.

Different methods of stabilization

Marine stabilization systems have become big business. Today, you can choose between several providers, using various methods to decrease roll. Roll motion stabilization can be achieved in conventional ships by changing the form of the hull. Reduction in roll amplitudes is also possible by other means. Broadly, we classify stabilization systems into two categories:

Passive systems: No separate power source or special control system is required. Examples of passive systems are the bilge keel, anti-rolling tanks (passive), fixed fins, and passive moving weight systems.

Active systems: When the opposing roll is produced by moving masses or control surfaces using power like active fins, anti-rolling tanks (active), active moving weight, and the gyroscope.

On this page, we will primarily focus on active systems. Depending on the planned use and type of boat, there are mainly three methods you can choose between active tanks, gyro stabilizers, and active fin stabilizers.

When designing a new yacht, we recommend thinking carefully through the advantages and disadvantages of the various options when choosing technology. Start by asking yourself these questions:

• Where will the boat be sailing? The Mediterranean Sea, Caribbean, The North Sea or under conditions demanding an entirely different technology?
   
• What is the primary use of the boat? Is it intended for use in challenging working conditions, observing whales, leisurely cruising around the Greek islands or angling in the waters beyond the Norwegian coastline?
   
• Hull design. Is the hull designed for high speed or displacement?
   
• Usage. Will the ship be used for traveling long distances at a steady speed, for trolling, or mainly to lie still by anchor?
   
• Budget. What is my budget for stabilizer systems?

A brief overview of active systems

Active tanks

Due to their bulky construction and costly assembly, they are mainly used on large bulk carriers, tankers, and LNG carriers. In active rolling tanks, the movement of the water is controlled by pumps or by the air pressure above the water surface. When the water is forced against the power of the waves, it provides stability. Active tank stabilizers can leave an efficiency of 80 percent or more in motion stabilization, depending on the system's sophistication. However, it requires so much onboard space that it will not apply to the vessels we focus on.
applicable to the vessels we focus on. 

Gyro stabilizers

Gyro stabilizers can be installed in smaller boats and are commonly used in larger ships and carriers. Large boats may require more than one gyro stabilizer. Gyro stabilizers utilize the physical laws of precession to counteract sea motions. The gyro spins and tilts fore and aft as the boat rolls, creating a torque that reduces roll. The first large ship with gyro stabilizers was the USS Henderson, completed in 1917, which had two 25-ton and nine-foot diameter flywheels.

Active fins 

Active fins are fitted outside the hull. Sensing the rolling motion of the ship, a gyro sensor sends a signal to the actuating system. This causes the fins to move in a direction that counteracts the roll. The bigger the boat and the longer the lever between the center of gravity and the fin, the more power it gives. The active fins get stronger the bigger and wider the boat is. Fin stabilizers are vastly more efficient at higher velocities, while they lose effectiveness when the ship travels at minimum speed. At low speed or anchor, stabilization-solutions include actively-controlled fins. The first use of fin stabilizers on a ship was on a Japanese cruise liner in 1933.

The video below shows active fins and their impact on the hull's movement in 0,5-1 meter high waves at zero speed:

Which stabilizer system is the right choice for you?

It ultimately depends on your preferences and intended use. Both active fins and gyro stabilizers have their pros and cons.

When at anchor, both technologies offer a similar effect on reducing roll and sway. However, active fins may cause some noise from the anchor chain and have a slight impact on moving the boat forward under very light wind conditions due to their flapping/swimming motion. On the other hand, gyro stabilizers may create noise pollution onboard due to their high-speed spinning below deck.

The startup time for gyro stabilizers can take 30-45 minutes before delivering full effect, while active fins are active immediately after being switched on. Repairing submerged fins can be more challenging, resulting in increased repair costs. In contrast, the gyro stabilizer is located safely inside the hull, reducing the risk of damage. However, servicing the gyro stabilizer may require taking the whole gyro-wheel out, depending on the manufacturer's construction.

Gyro stabilizers do not require protrusions from the hull, making them less susceptible to damage from grounding or floating debris. Fins, conversely, can correct small steady/static heels or lists due to beam winds, off-center weight, or extended period rolls running downwind, thanks to their ability to apply a steady lift force under the hull while the vessel is in motion. Gyros cannot supply constant forces, making them unable to correct a heel or list angle over longer periods.

The power impulse of a gyro stabilizer is firmly defined, while the force from active fins is an exponential result of speed (V^2). This means that fins have very high power at high speeds. Additionally, modern actuator systems for fins have a low built height, allowing you to spread the gear around the boat. In contrast, gyro stabilizers come as one big box, which can be space-demanding.

Real stories from happy boaters: Vector Fins™ in action

The best way to understand the benefits of a stabilizer system is to hear from those who have already experienced them. We've gathered a range of testimonials from boat owners and captains who have installed stabilizer systems on their vessels, and the feedback is overwhelmingly positive. From smoother rides in rough seas to improved comfort and safety for passengers and crew, these systems have proven to be game-changers for those who spend significant time at sea. In this section, we'll share some of these testimonials to give you a sense of what it's like to have a stabilizer system onboard.

A game-changer for luxury yachts

John Maxey, the owner of the luxurious Fairline Squadron 78, faced significant challenges with stability and comfort on his vessel, especially during rough sea conditions. To tackle this issue, he installed Vector Fins™ stabilizers from Sleipner. The results were impressive, with the system significantly improving his boat's stability and comfort. In the video below, John shares his experience:

The efficient solution for smaller boats

Captain Richard Kennedy of Anna J explains how Vector Fins™ has revolutionized roll reduction by providing more efficient stabilization with reduced side effects. Learn how Vector fins™ has become the go-to choice for smaller boats seeking an ideal solution for cruising and anchor stabilization in the video below:

The versatile solution

According to professional yacht broker Jimmy Rogers, fin stabilizers are versatile, handling both cruising and at-anchor use. The size of the fins determines the "at-anchor" stabilization force. Larger fins provide higher stabilization force but create more drag, resulting in higher fuel consumption, which can be a decisive factor for most boat owners. Larger fins can also make it more challenging to install the internal components in an optimal position, resulting in negative side effects like causing yaw and sway. Thus, most fast boats today compromise on fin size, resulting in insufficient stabilization for some owners. 

Read his full article summarizing the pros and cons of fins and gyros here. 

Installation and planning of a stabilizer system 

When planning to install stabilizers, it is essential to consider the hull's design and ensure it can handle the additional load and strain. Softening the hull to comply with the minimum stabilizer requirements can provide greater freedom and a more fuel-friendly hull.

The smaller fins can achieve the same stabilization force as bigger flat fin systems while reducing the internal component size, resulting in more efficient stabilization and reduced fuel consumption.

Overall, the choice between active fins and gyro stabilizers depends on personal preferences and specific needs. However, Sleipner's Vector Fins™ offer a superior solution for smaller, fast boats with their improved efficiency and reduced side effects, providing better stability and comfort for all types of cruising and anchoring situations.

What is the cost of a functional stabilizer system?

The price of installing a stabilizer system on a boat can vary based on factors such as whether the boat is new or used, as well as the design characteristics of the vessel. Typically, the cost of a stabilizer system ranges from 2-4 percent of the boat's total cost. For a new 70-foot motor yacht, the complete installation of a stabilizer system could cost around GBP 70,000. Active fin systems have a smaller price range than gyros, as gyros weigh four times more than active fins, requiring hull strengthening and space for the two-ton gyro box.

It's worth noting that fins are generally not installed on boats smaller than 50 feet, while gyros can be fitted into vessels as small as 30 feet. Both systems can be retrofitted into a motor yacht, making it a smart investment for a proud boat owner who would rather install a stabilizer system on their ten-year-old vessel than buy a new one. The direct benefits of a stabilizer system are clear in terms of comfort and safety aboard, allowing usage of the vessel that would have otherwise remained docked. A stabilization system can be a wise financial investment for workboats, charter boats, and other vessels generating income by the hour. Furthermore, having a good stabilization system onboard can give a significant advantage in the market when selling or buying a secondhand vessel.

At Sleipner, we offer advice based on your specific needs. Our preferred product, Vector Fins™, provides highly effective roll reduction both at anchor and underway.

There may be compromises when choosing a stabilizer system, but we strive to provide you with the best possible foundation for making that decision.

Talk to a stabilizer expert

If you're still unsure which stabilizer system best fits your vessel, consider talking to a stabilizer expert. They can help assess your needs and recommend the most suitable system for your boat. With years of experience and knowledge of the latest technology, they can guide you through the process of choosing and installing the right stabilizer system.

Our team of experts is always available to answer any questions. Contact us today to learn more about our Vector Fins™ and how they can improve the stability and performance of your vessel. Our resellers are also available worldwide to help you find the perfect solution for your needs. Don't let unwanted motion keep you from enjoying your time on the water. Invest in a stabilizer system and experience the comfort and safety it provides.