Let is see how hydraulic power unit are performing in lifting keel and foil systems on sailing yatchs.

A chance discovery during a sailing charter in Brittany turned into an engineering story worth telling. Andrea, Hydronit’s CEO and a lifelong sailing enthusiast, chartered a sailing yacht last spring from a shipyard in Brittany — a region known for high-performance racing and cruising sailboat construction. Walking through the technical compartment before setting off, he recognized something bolted to the bulkhead: a compact hydraulic power unit built in Varedo, Italy — one of his own company’s.

It’s a coincidence, but not really a surprise. Lifting keels and foils are among the most mechanically demanding systems on a modern sailing yacht, and behind most of them there’s a hydraulic power unit doing the heavy lifting — often literally.

Why lifting keels and foils need hydraulic power

A lifting keel has to move a heavy ballasted structure vertically inside a narrow keel box, against gravity and against the hydrodynamic loads generated by the boat’s motion through water. A foil, whether a lifting daggerboard-style foil or a canting/rotating foil arm, has to be positioned with precision, hold that position reliably under load, and often reposition quickly for trimming.

Both tasks share the same underlying requirement: high force in a very small, weight-sensitive space, the core business of hydrualic power unit.

Electric linear actuators struggle to deliver that force density. Manual or mechanical winch systems can’t match the control or repeatability required.

Hydraulics remains the technology able to combine:

• High force output relative to actuator size
• Precise, controllable speed in both directions
• The ability to hold a load in position without continuous power draw, via pilot-operated check valves
• Synchronization between multiple cylinders, when a keel or twin-foil system needs to move as one
• Built-in redundancy on canting systems, where the load typically runs through two cylinders so the system can still be operated, in a reduced mode, if one side is out of service
• Position feedback, through sensors or angle indicators, so the operator knows the actual keel or foil position rather than inferring it

Hydronit’s marine range already covers both categories of vessel. Gangways, hydraulic tender platforms, and tender cranes are common ground between motor yachts and sailing yachts — the loads and installation logic are similar enough that the same product architecture applies to both. Lifting keels, foils, and rigging adjustment systems (backstay tensioners, mast rotation, and similar) are where sailing yachts diverge: applications with no real motor ( yacht equivalent, built around the same underlying hydraulic engineering) high force in a small footprint, precise directional control, and the ability to hold a load in position without continuous power draw, applied to a more demanding problem.

What hydraulic power unit has to deliver for lifting keel

On a sailing yacht, space and weight are never abstract concerns — every kilogram and every liter of enclosed volume has a direct effect on performance. A hydraulic power unit destined for a keel box or foil compartment has to meet several constraints at once:

• Compact — fitting inside tight, irregularly shaped technical compartments without blocking access to other systems
• Corrosion-resistant — surviving a marine environment of salt spray, humidity, and condensation over years of service
• Customizable — matched to the boat’s specific cylinder bore, stroke, and control logic, since no two keel or foil systems are identical
• Easy to maintain — accessible for service in a compartment that’s rarely convenient to reach
• Cost-effective — justified within a yacht’s overall build budget
• Lightweight — every kilogram matters, especially on performance-oriented boats
• Reliable — failure of a keel or foil actuation system at sea is not an option

These are the same design priorities behind Hydronit’s Compact and Micro Series hydraulic power units. The manifold blocks are machined from die-cast aluminum, a construction method refined over more than two decades of production, and the connecting bars are made from lead-free aluminum, which holds up better against marine corrosion than standard alloys. The modular architecture means a unit can be configured around a specific cylinder and control requirement rather than forcing the application to adapt to a fixed product — and Hydronit’s online 3D configurator lets that customization happen without a long design cycle.

There’s no standard configuration for these installations, each one is customized around the boat. Boat size is the main driver of the choice: smaller sailing yachts tend to be served by the Micro Series, while larger keel and foil loads move into Compact Series territory. Power and voltage options matter just as much for onboard installations, where 12V, 24V, and 48V DC systems are the norm. Across both series, these marine units run up to 25 l/min in flow and up to 370 bar in working pressure, sized case by case to the specific cylinder bore, stroke, and load rather than pulled off a fixed spec sheet.

One more detail matters more at sea than almost anywhere else: what happens if the system leaks. Hydronit’s Matrol BI, a biodegradable hydraulic fluid developed with Novamont, was designed for exactly this kind of risk — reducing the environmental impact of a hydraulic system operating in direct proximity to open water.

Lifting keel with Hydronit

A lifting keel or a foil doesn’t move on its own. Somewhere inside the hull, a compact hydraulic power unit is doing the quiet, unglamorous job of generating and controlling force in a space barely big enough to hold it – reliably, for years, without much attention from anyone.

Andrea’s discovery on that chartered yacht wasn’t really about coincidence. It was a reminder that when an application genuinely needs compact, reliable, corrosion-resistant hydraulic power, the engineering conversation tends to lead to the same place.

Explore the Compact and Micro Series range, call our experts for design the best hydraulic power unit for your own application.