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December 09, 2013

Seakeeper Gyros: Archenemy of Seasickness

Seakeeper units take out the roll.

There is no perfect hull design. Every boat since the very first dugout canoe rolls a bit and has room to improve. The user/designer always seeks to enhance everything about his or her boat, especially the ride. Over the centuries, boatbuilders designed, developed and improved on an untold number of hull designs for many different applications. The one thing that boatbuilders and those who go out to sea have not been able to control is the weather — and the wind and seas that come with it.

Every once in a while, someone comes across an improvement that makes a difference, but the size of hulls has probably been the biggest advancement to affect a boat’s ride. The bigger the vessel, the more comfortable it tends to be at sea. However, some very clever guys took the proven anti-roll and anti-vibration aspects of gyro technology and made them work on recreational boats.

The guys at Seakeeper made an incredible impact when they launched their stabilizing system, which is meant to take the roll movement out of a boat in heavy seas. The company has enjoyed great success in not only the recreational sport-fishing and yachting marketplace but also the commercial and military industries. Seakeeper’s technology represents a novel use for an advanced piece of gear known as a “control moment gyro.”

Using the basic principals of gyro-dynamics, the Seakeeper system exerts strong forces to right the boat when it is in a rolling state, counteracting movement caused by the sea. The neat thing is that the Seakeeper system does this without the large external foils previously used to help stabilize boats.

The protruding, fin-style stabilizers are optimized to operate at a certain cruising speed and are fit to match the fin size with that speed. So although they may help reduce roll at cruising speed, they have little or no effect when the boat is sitting still, lying too or while trolling.

How They Work

Any aerial footage you see in a movie or on TV was likely shot with a camera mounted on a gyro to stabilize the camera and remove vibration from the aircraft, typically a helicopter. The gyro helps keep the camera level and counteracts any abrupt movements made by the aircraft, offering a smooth and steady shot. The gyro keeps the camera balanced by spinning at a high rate of speed to create stable and clear shots.

Using the same principals of stabilization, Seakeeper manufactures a compact unit that looks like an orb. Inside the round metal housing, a heavy flywheel spins in a near vacuum, which eliminates air friction and reduces weight and the amount of power needed to keep the wheel spinning. The vacuum allows the flywheel to gain the necessary speed to counteract any roll the boat is experiencing.

Reducing onboard roll with a gyro is a function of several factors, including displacement, transverse (side-to-side) metacentric height, hull damping, and operating speed and heading in the given sea conditions. The gyro controller manipulates the active hydraulic brake to make sure the gyro’s torque is maximized regardless of hull characteristics or operating conditions.

Seakeeper units are self-contained, can be placed off centerline and have no appendages. Because the unit uses torque to counteract roll, it does not have to be located on the centerline, but it should not be located forward in high-speed boats because of increased G forces as the boat rides the seas. But there are always compromises; wherever the unit is placed, something else must be moved or eliminated, in most cases fuel.

The ideal location for mounting and placement is under the cockpit deck or, if the boat is large enough, in the engine or pump room. However, in order to place it in either space, you will sacrifice fuel capacity or access. In a new build, options can be planned for optimum install, but in a refit, things get slightly more difficult but not impossible.

The installer or boatbuilder is responsible for designing and fabricating the foundations where the main support “saddle beams” of the unit are attached to the boat. Typically, attaching the unit to the main stingers or a similar setup is ideal. The unit must be mounted and attached to the boat properly, so that the inherent loads from the gyro can be transferred to the hull structure. Following recommended protocols makes this process much easier, as there are over 1,200 units in service in all types of vessels.

The gyro unit runs at an incredibly high speed that requires the gyro bearings and motor drive box to be cooled by a closed glycol cooling loop. That closed system is in turn cooled by raw water through a heat exchanger with minimum volume flow rate specifications. The main gyro control and motor drive boxes should not be mounted in spaces that exceed temperatures of 140 degrees.

The Seakeeper’s electrical requirements are modest as both the M8000 and M26000 models require just 3kW of power. A typical 55-footer using a Model 8000 requires a single phase 30A, 185-230VAC either 50 or 60 Hz service for the motor-drive box and 10A 24VDC service for the gyro control box, so you need both AC and DC power to operate the unit. A small display user interface is all that’s required to start, operate, monitor and shutdown the unit.

Seakeeper utilizes the latest motion sensors and processors to control the unit and its function. Despite being intricate pieces of machinery, these units are simple to operate. The units have complex algorithms and formulas programmed into their computer brains, allowing for optimum results. Unattended operation is the norm and made possible through smart technology components, such as sensors, alarms and automatic shutdowns. Sensors measure critical operating functions, such as bearing temperature, motor and drive temperatures, vacuum pressure, gimbal angle, brake pressure, and ship motion.

The gyro controller gathers sensor values and alarm information, and the information is sent to the user interface display. The sensors can lock the brake and shut down the motor drive when a fault or alarm is triggered. All faults and alarms are saved in the operating history of the controller’s memory and are available for recall by service techs if service or repairs are needed. The units have built-in safety factors that automatically lock the gyro so that it will not generate excessive anti-roll torque loads when there is a fault or alarm, such as loss of electrical power or brake pressure. The operator can also lock the brake from the user interface keypad or by shutting off power at the motor drive box or gyro control box.

These Seakeeper units have made many folks happy and continue to impress even the most hardened old salts. Many owners and captains have told me how impressed they are with their Seakeeper, as the units have reduced cases of the dreaded mal de mer, allowing passengers to enjoy a smoother ride and experience a much better night’s sleep on a stable boat while on the hook.

There’s no question a Seakeeper unit could change your boating experience for the better. Seakeeper manufactures a finely engineered, well-executed, robust piece of machinery that does the incredible task of calming the seas — and it does so successfully. If you haven’t yet done so, you need to take a ride on a Seakeeper-equipped boat, preferably in real sea conditions; they are impressive. For more information visit seakeeper.com.