Below are Frequently Asked Questions (FAQ) about the Seakeeper Gyro. If you have a question in a specific area of interest, go to the list of questions below that are organized by specific areas and click on your specific question. If you want to browse the entire list of questions, just scroll down to find the question of interest.
General Questions
How does the gyro work?
The Seakeeper product is a "Control Moment Gyro" or CMG and employs the physics of gyro-dynamics. The unit has a heavy flywheel that spins at high speed in a near vacuum, thus virtually eliminating air friction and allowing weight and power consumption to be greatly reduced. The angular momentum of this flywheel produces a gyroscopic torque which exerts a powerful righting torque that counteracts any boat roll. The unit also includes an active control mechanism which optimizes the gyro’s performance over a wide range of sea states. For a more detailed explanation see the Theory of Operation section.
How does the Seakeeper gyro compare to the Mitsubishi MSM gyro?
The Mitsubishi MSM control moment gyro (CMG) applies the same principles of gyro-dynamics as the Seakeeper gyro, but the application is much less sophisticated, and therefore, less useful and effective.
The most important difference is that the Mitsubishi gyro spins its flywheel at ambient air pressure, which because of air friction, limits flywheel speed and requires substantial electrical power to overcome that friction. The Seakeeper Gyro, by contrast, spins its flywheel in a near vacuum. The result is that air friction is eliminated, thus greatly reducing power consumption and allowing a faster turning, lighter flywheel that reduces weight.
For example, the Mitsubishi MSM-4000 has an output of 5,000 Newton meter seconds (N-m-s is the fundamental measure of CMG output), weighs 700 kg, and requires 3kW of power at steady state. By comparison, the Seakeeper 7000 Gyro has an output of 7,000 N-m-s, weighs 455 kg and requires 1.5 kW of power at steady state, resulting in the Seakeeper unit being almost 2½ times more effective by weight and nearly 3 times more effective by power.
In addition, the two devices are controlled differently, resulting in substantial differences in effectiveness. The Mitsubishi gyro is regulated by a passive damper, which requires that it be “tuned” to one optimum point of wave energy. Conversely, the Seakeeper product is actively controlled by state of the art motion sensors and processors, with the result that the full output of the gyro is available in the lowest and highest sea states, resulting in much greater effectiveness over a range of conditions.
Finally, the Seakeeper vacuum containment provides a durability advantage because it isolates the most critical components (flywheel motor and bearings) from salt air and other contaminants entirely -- a unique advantage for a marine product.
Despite these advantages, the Seakeeper Model 7000 gyro stabilizer is about two-thirds the cost (per Nms) of the Mitsubishi MSM-4000.
It should also be noted that there is a difference in philosophy between Mitsubishi and Seakeeper, probably rooted in the difference in the relative effectiveness of the products. Mitsubishi’s recommended sizing (by N-m-s) of its gyros to boat size is about 1/3 of what we would advise. Our goal is to virtually eliminate boat roll as opposed to the Mitsubishi approach of achieving some roll reduction.
How does the Seakeeper gyro compare to fin-based roll stabilization systems?
Because of there drag at speed, fin systems are not suitable for planing hulls. Fin systems are speed dependent, always balancing fin size with projected cruising speed, so as to create minimum drag for desired performance. The result is that at zero speed they have no effect (except on very large yachts with long roll periods), and at less than cruising speed, performance drops off sharply. In contrast, the Seakeeper Gyro remains fully effective from zero speed right through planing speeds, including the roughest conditions when the boat has to slow down. Because the gyro requires no protrusions from the hull, it is not subject to snagging seaweed, damage from grounding, or impact from floating debris.
What is the advantage of spinning the gyro in a near vacuum?
Until the Seakeeper Gyro, air friction was the limiting factor on how fast the flywheel could be spun, driving up flywheel weight and power requirements. The Seakeeper Gyro spins three times faster than comparable products, cutting flywheel weight by two-thirds and halving power requirements. Moreover, because the critical components (flywheel bearings and motor) are sealed for life in a near vacuum containment, they are forever isolated from the marine environment. In addition, cooling requirements are less, both because there is less heat and it is easier to dissipate. For more details on this, see the Why Use a Vacuum section.
What is the advantage of active control?
Unlike passive control, which must be optimized for a particular level of wave energy, active control permits the gyro to exert its full torque over a range of sea states. A passively controlled gyro must be turned off in the roughest conditions to keep from damaging itself, whereas the Seakeeper Gyro can continue to operate when it is most needed. The Seakeeper Gyro’s processor control allows for protective auto shut down in event of a fault, and provides self-diagnostics using an ordinary lap top computer. For more details on this, see the Why Use Active Control section.
What maintenance needs to be done on the gyro?
The gyro is designed to require minimal maintenance. Most of the critical parts operate in a sealed environment. Vacuum level and hydraulic brake seals should be periodically inspected per the operating manual provided with the unit.
Can I operate the gyro dockside?
The gyro can be operated dockside utilizing boat generator power or shore power.
Can I run the gyro from my batteries using an inverter?
The gyro should not be operated on boat batteries via an inverter since in most boats there is insufficient battery capacity to operate the gyro for any reasonable length of time. The gyro should only be operated from generator power or shore power.
Will the gyro operation disturb my auto-pilot?
The gyro operation will not disturb your boat’s auto-pilot and in fact will make it easier for the auto-pilot to do its job since it will reduce boat roll which reduces roll induced yaw.
Why is the gyro shaped like a sphere?
The sphere shape minimizes the size and weight of the unit while also providing an optimal mechanical coupling path to the hull for the righting torque.
What materials are used to construct the gyro?
The flywheel is a single piece, high strength steel forging and each piece undergoes several levels of inspection and tests to ensure it meets out design requirements. Aluminum is used for most other components to reduce weight and provide good heat transfer for cooling.
Why hasn’t this been done before?
Gyro stabilizers have been used for many years but because of their size, weight, and power consumption were restricted to application in larger vessels. Seakeeper’s use of modern technologies to spin the flywheel in a near vacuum and provide active electronic control now allows this gyro stabilization capability to be economically and practically applied in smaller, modern boats.
Commercial Questions
What is the price of the gyro?
For pricing on the Model 7000 Gyro Stabilizer, please submit a Request for Quote (RFQ) form by clicking here.
Where can I buy a Seakeeper gyro?
To buy a gyro now, go to the Buy section.
Do you have any dealers?
Seakeeper is currently developing an authorized network of dealers, distributors and installers. Please check back periodically or send an email to Notify to get automatic email notification of additions to our network.
What is the warranty on the gyro?
The gyro has a two year warranty from the date of manufacture. The warranty covers all parts and labor.
Sizing Questions
What size gyro do I need for my boat?
Sizing depends on the objective of the boat owner. The Seakeeper gyro with its vacuum technology and active control makes it practical, for the first time, to virtually eliminate boat roll in any reasonable condition. Because prior roll attenuation gyros do not use these technologies, space, weight and power constraints have limited them to “Stability at Anchor”, meaning that effective stabilization is limited to low sea states. While we recommend the higher level of stabilization where possible, we recognize that “Stability at Anchor” may meet the needs of many yachtsmen while still enjoying the benefits of Seakeeper technology.
A single Seakeeper Gyro system will provide excellent roll reduction for a boat of approximately 35,000 to 55,000 lb full load displacement. Boats with higher displacements will require multiple gyro systems to insure good roll reduction.
See the Sizing section for more detailed sizing information and our Sizing Wizard.
Can I use multiple gyros on one boat?
Multiple gyros can be used on one boat. See the Sizing section.
Product Specifications
How much power does the gyro require?
The gyro requires 3kW (14 Amps) at 230 VAC 50/60 Hz during flywheel spin up. The power requirement drops to 1.5 kW (7 Amps) when the flywheel has reached operating speed. See detailed electrical requirements in the Product Spec section.
How much does the gyro weigh?
The gyro units weights 455 kg or 1000 lbs.
How much noise does the gyro make?
Gyro noise has been measured under steady state conditions (no wave load) in Seakeeper's lab and in our 43 ft Viking test boat. The steady state noise is typically in the range of 70-80 dB unweighted. As the frequencies emitting the highest sound pressures are low (like other marine machinery), it is recommended that the gyro be installed in a machinery space that is treated with soundproofing. If the gyro stabilizer is located outside a machinery space, soundproofing is required to eliminate low frequency (approximately 160 Hz) noise from entering living spaces.
What controls (operator panel) does the gyro have?
The gyro has a display and keypad that are mounted in the bridge. The display provides gyro status and diagnostic information. The keypad allows the operator to turn the flywheel motor on/off and it allows the gyro system to be enabled/disabled. See the diagrams Product Specs section.
How much heat does the gyro produce?
The gyro produces approximately 1.5-2 kW of heat during normal operation. The majority of this heat is absorbed by the cooling loop.
Installation Questions
Where does the gyro have to be located in the boat?
From a theoretical perspective, the Gyro Stabilizer can be located anywhere in the boat hull as long as sufficient structural coupling can be provided to transmit the gyro's righting torque safely and reliably to the hull structure. From a practical perspective, Seakeeper strongly recommends that the Gyro Stabilizer be installed aft of amidships to minimize vertical accelerations due to wave impacts. If the Gyro Stabilizer experiences vertical acceleration exceeding ± 1G about a 1 G mean due to gravity, the Gyro Controller will shut down the Gyro Stabilizer to protect the flywheel bearings. Proper operation of the Gyro Stabilizer when mounted forward of amidships cannot be guaranteed by Seakeeper.
How much space does the gyro require?
The 7000 gyro fits within a cubic envelope of 977 mm × 778 mm × 671mm (38.5” × 30.7” × 26.5”). The mounting saddles are on 870 mm (34.25”) centers. See detailed dimensional drawings in the Installation section.
What is required to install the gyro?
Installation of the gyro requires roughly the same level of complexity and effort as installing a generator. A key component of the installation is the design and construction of the mounting stringers which must be capable of safely transferring the gyros torques to the hull structure. Other major installation considerations are the mounting and electrical wiring of the drive box and control box. Wiring also must be installed between the control box and the key/display control unit mounted on the bridge. Finally, a source of seawater must be plumbed to the heat exchanger. For more detailed information, see the Installation section.
Who can install a Seakeeper gyro?
Any competent boat yard, but the structural foundation should be reviewed or designed by a professional engineer to ensure it will safely transfer the gyro loads to the main hull structure.
How is the gyro integrated into the ship’s systems e.g. hydraulic, electronics, etc?
The only connection between the gyro and other boat systems is for 220 VAC power, 12 or 24 VDC power, and cooling fluid. The keypad and display, which mount on the bridge, are independent of other ship’s systems and only connect to the gyro system. See the Connection Information section for more details.
Does the gyro need cooling?
The gyro system requires 8 liters (2.1 gal.) per minute of continuous raw water be provided to the heat exchanger. See the Connection Information section for more details. Filtering the raw water is also necessary to ensure proper flow.
What are the structural requirements for installing the gyro?
The gyro foundation saddle beams should be attached to stringers using an adhesive bonding agent. The stringers and bonding agent must be capable of reliably and effectively transmitting the gyro’s torques to the hull structure through an infinite number of fully reversing load cycles. See the Installation section for more details.
What adhesive should be used to attach the Gyro Stabilizer to the hull's stringer system?
The boat builder or installer is responsible for selecting the structural adhesive to secure the Gyro Stabilizer's aluminum saddle bearings to the boat’s GRP hull beams. The calculated shear stress in the structural adhesive between the saddles and the hull foundation beams for the above loads and 100% structural contact is 2.3 MPa (337 psi). Seakeeper recommends that the builder or installer use a structural adhesive with a minimum shear strength of 13.8 MPa (2000 psi) to provide a Factor of Safety of 6 (Margin of Safety of 5). Additionally, it is strongly suggested that the builder or installer test the compatibility of his structural adhesive with cast A356 T6 aluminum (the saddle beam material) and their GRP hull materials by laying up joints and doing mechanical property tests. This is standard practice in many yards when they have to adhesively bond two materials that they are not familiar with. Because bond strength and choice of adhesive can vary depending on the type of GRP hull material, Seakeeper cannot make specific adhesive recommendations. However for reference, we have used Pro-set 176/276 http://www.prosetepoxy.com/adhesive_techdata.html.
