What is a Hydrofoil Supported Catamaran (HySuCat): A patented hybrid catamaran hull consisting of asymmetrical sponsons and unique bow design, incorporating a special hydrofoil system with more than a thousand vessels produced globally; ranging in size from 5 m to 65 m.
Why Use Foils: Hydrofoil-supported catamarans achieve their efficiency by lifting a significant portion of the vessel’s mass onto the foils at planing speeds, which partially or even fully removes the hull from the water. This principle is grounded in the lift-to-drag ratio (L/D):
Hydrofoils typically have an L/D ratio of 20:1, meaning for every unit of drag, they generate 20 units of lift. In contrast, a typical planing hull has an L/D ratio of about 5:1, making the hydrofoil four times more efficient at carrying load than the hull itself.
The higher L/D ratio of hydrofoils means that, from a resistance perspective, it is advantageous to carry as much load on the foils as possible and minimize the hull’s contact with water. This reduces hydrodynamic drag and increases overall vessel efficienct.
Modern foiling sail craft can lift the hull completely out of the water, achieving the most hydrodynamically efficient solution by relying almost entirely on the foils for support.
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However, keeping the hull partially in the water offers three distinct advantages:
: With the hull still in contact with the water, standard inboard and outboard engines can be used in their proven, conventional configurations. This avoids the need for specialized propulsion systems that are required when the hull is fully lifted out of the water.
: The hull’s contact with the water provides passive stability in both pitch and roll. When the hull or foils are partially submerged, changes in submergence automatically create righting moments. For example, if the vessel rolls to one side, more of the foil or hull enters the water on that side, increasing lift and generating a stabilizing force. This natural feedback helps maintain stability without active control systems.
: The depth of submergence of the hydrofoils or hull determines the amount of lift generated. As the vessel heaves down, more foil enters the water, increasing lift and pushing the vessel back up; if the vessel rises, less foil is submerged, reducing lift. This self-regulating effect controls the vessel’s attitude and lift without relying on external mechanical or electrical adjustments to the foils, making the system robust and economical to produce.
These features together make partially submerged hull and foil designs attractive for vessels seeking a balance of efficiency, stability, and simplicity in construction and operation.
The performance advantages of hydrofoils are substantial and well-documented across thousands of watercraft, offering transformative improvements in performance, comfort, and efficiency:
: Hydrofoils lift the hull above the water, allowing vessels to “run on the crests” and act as a shock absorber. This results in a much smoother ride in short, choppy, or confused seas. Compared to conventional catamarans or deep-V monohulls, hydrofoil vessels experience up to a 50% reduction in pitch, heave, and vertical accelerations at the center of gravity and further aft, virtually eliminating slamming even at high speeds in rough conditions.
: At planing speeds (typically from 12 knots), hydrofoils can reduce resistance by up to 30% compared to traditional symmetrical catamarans or deep-V hulls. This translates to higher achievable speeds and significantly lower power requirements, often resulting in a 30% reduction in fuel consumption at these speeds.
: As the hull is lifted out of the water, the vessel’s lateral area decreases, enabling tighter turning circles and allowing the boat to lean into turns like a monohull. This is a notable improvement over symmetrical catamarans, which often have unusual handling characteristics. Hydrofoil-supported boats can perform tight turns in waves without instability.
: When stationary or fishing in swell, hydrofoils dampen hull motion, reducing the need for additional stabilizing devices such as flooding keels or gyroscopes, which are often required on offshore monohulls.
: Hydrofoil catamarans feature unique bow designs that provide greater dynamic lift, eliminating tendencies to weave, broach, or capsize—risks that are more pronounced in conventional powercats under these conditions. Even when airborne over swells at high speed, re-entry is smooth, as the foils help disperse impact forces.
: While operating in submerged mode, hydrofoils provide a nearly constant lifting force at cruising speeds, regardless of depth. This keeps the hull in a stable vertical position, minimizing the impact of waves and acting as a vertical damper. The result is enhanced seakeeping and a more comfortable ride for passengers and crew.
: By lifting the hull above the water, hydrofoils drastically reduce hydrodynamic drag, enabling higher speeds and better fuel efficiency—key advantages for both recreational and commercial vessels.
In summary, hydrofoils deliver a smoother, faster, more efficient, and more stable ride than conventional hull designs, especially in challenging sea conditions. These benefits have been proven on thousands of vessels worldwide and are driving increased adoption in both recreational and commercial marine sectors
