Fig. 1
The Jetfoil can travel comfortably at speeds to nearly 50 knots in moderate waves thanks, in part to servohydraulics.

Digital Electrohydraulics Helps Calm the Seas

Electrohydraulics technology smooths high-speed water travel.

If you get seasick easily, a boat is the last place you want to be—especially a fast one. Strangely enough, though, hydraulics could be your best friend if the next boat you board is equipped with the right technology, like the one shown here. This is the Jetfoil, a 122-ft long hydrofoil—a boat with a submerged structure that lifts the boat’s hull above the water’s surface at elevated speeds. The foils produce dramatically less drag than the hull plowing through the water. This improves fuel economy, allows higher speed, and smooths out the ride because the boat is much less subjected to wave action. These fully-submerged foils enable the Jetfoil to ride the waves at 48 knots at Sea State Code 4 (moderate waves).

Fig. 2

TEZ digital servoproportional valves provide the rapid response needed to operate the Jetfoil’s fins for steering and ride stabilization.

But there’s more to the Jetfoil than just hydrofoils. An underwater stabilizing system (actuated by Atos electrohydraulic servoactuators) helps control roll, pitch and direction, thus maximizing the comfort of the queasiest landlubber. The bow foils control stability (pitching) by lifting and lowering the vessel through precise longitudinal regulations; the stern foils trim the ship motions (rolling); and the vertical movement (heaving) as the ship travels. TEZ digital servoproportional valves from Atos operate the fins and steer motion with accuracy and fast response time.

Meanwhile, an Atos onboard axis controller manages closed-loop position and force. These components are interfaced through a fieldbus to the hydrofoils’ electronic system and to the shipboard sensors: inclinometer, gyroscope, and accelerometers.

Fig. 3

This stainless steel cylinder has spherical end bearings to prevent binding when its rod extends and retracts during high-speed travel.

The hydraulic power unit, ISO 6020-1 stainless steel servocylinders, and manifolds blocks are RINA-certified for marine applications. The same technology can be applied to other applications commercial, pleasure, and luxury watercraft. For example, variable-pitch propellers can use the digital proportional valves control the axial rotation of blades, improving vessel maneuverability, and fuel economy. Likewise, roll-stabilization systems: the electronic sensors, controls, and hydraulic components can be used with underwater fins for anti-roll torque devices that generate a counteracting moment to eliminate a vessel’s tendency to roll, thereby improving comfort and safety.

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