Engineering Boats for Seakeepers

On a recent sea trial, the owner of a Weaver 43 fishing boat pointed out how resolutely his vessel held a course against a quartering head sea once its Seakeeper gyroscopic stabilizer spooled up. Indeed, the boat’s feel was uncanny.

Waves be damned, it was going where he pointed it, urged on by its 550 hp Cummins QSB 6.7L diesel. The experience made us think about how the boat’s structure withstood the combined pressures of the Seakeeper, the powertrain, and the Chesapeake Bay water through which we were traveling. There were multiple forces working on the four bolts holding the Seakeeper in its bed, as well as the hull structures of which the bed was part.

So, how do a naval architect, an engineer and a boatbuilder spread out those forces so the Seakeeper doesn’t simply rip itself loose in the boat’s bilge? We asked our friend Lou Codega, a naval architect perhaps best known for designing Regulator Boats. “The gyro guys are very good at giving us the loads in multiple axes,” Codega says. “And you have to design for all of them at once. They’re huge, massive forces—big numbers, hundreds or thousands of pounds.”

In fact, the Seakeeper 1, the company’s smallest model designed for center-consoles ranging from 23 to 30 feet in length, can produce forces of up to 1,515 pounds in the vertical direction, 2,248 pounds in the longitudinal direction, and 1,697 pounds in the lateral direction at each of the four mounts, according to the installation manual. Think about what that means in terms of holding down equivalent masses, like multiple NFL nose guards or a 300 hp outboard motor. “You have to engineer the hull structure to spread those forces properly,” Codega points out. The gyro mounts need to be tied into longitudinal stringers and transverse members, he says.

We also asked Chris Gratz, engineering director at Pursuit Boats, how his company ties in Seakeepers. “Pursuit engineers placement from the start by fully integrating the Seakeeper into the structure,” Gratz says. “We design interior spaces to accommodate the gyro, but avoid crowding features like fuel capacity or genset size. We optimize the center of gravity (COG) for the Seakeeper,” he explains.

Pursuit also distributes the gyro’s righting moment throughout the hull in the original design. “It goes onto a powder-coated, high-strength alloy cradle fastened to the boat’s stringer grid, which has a beefed-up laminate schedule to maintain longitudinal integrity while distributing the Seakeeper’s loads,” Gratz says. The fasteners are stainless-steel bolts tapped into brass plates encapsulated within the grid to prevent corrosion, and Pursuit bonds the cradle to the grid with methacrylate adhesive. The cradle also preserves access for service.

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A Seakeeper (or any other brand of gyro) can work to deliver a rock-steady ride. But you can’t just bolt it down and walk away. Placing and fastening it takes as much care as working out the engine beds for an inboard or the transom braces for an outboard. A gyro on the loose could ruin your whole day—and boat. And the forces a gyro exerts to counteract the waves can also be destructive if the design and build of the boat are not accounted for.

The Steady Touch

Seakeeper gyrostabilizers are straightforward to operate. Just press the power button and wait about 40 minutes. (Spool-up times vary.) After spool-up, it’s ready to stabilize.

Beyond powering up and activating stabilization, there are a number of other monitoring, maintenance and operational features you can access via Seakeeper’s touchscreen helm display. Examples include finding the number of hours run, adjusting the rpm to save power, and locating the electrical power required to stabilize. Naturally, basics like the day/night toggle, display brightness and language are easily selected. 

We spent four days operating a Seakeeper 3 installed aboard a Formula 387 Center Console. It was watertight and easy to operate. We appreciated the large, intuitive icons that serve as buttons on the touchscreen. The screen proved easy to read in varied light conditions.

The 5-inch display comes standard with most Seakeeper models. The Seakeeper 1 features a ConnectBox control panel mounted on the unit. For other models, if a second display unit is desired, or a compatible MFD is not installed, an extra 5-inch display costs $2,060.

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