Hull Vane: A Wing With Benefits

COURTESY HULL VANE

The Dutch navy’s patrol boat HNLMS Groningen in dry dock reveals the attached Hull Vane.

Typically, military ships are designed and built for specific missions, not to curb their carbon footprint. However, if the Dutch navy serves as an example, that is about to change. Earlier this year the patrol vessel HNLMS Groningen was fitted with a so-called Hull Vane and sea-trialed extensively in the North Sea, the Caribbean, and during two Atlantic crossings, with results that warrant notice. Depending on vessel type, design, and speed, efficiency gains can reach up to 25%, according to Hull Vane, the Dutch company that developed this appendage about a decade ago (see Professional Boatbuilder No. 154, page 16) as a spinoff from research originally conducted for the America’s Cup.

In essence a lift-generating wing similar to those used between the hulls of foil-assisted catamarans that span most or all of a vessel’s beam, the Hull Vane is instead installed on monohulls, mounted under the stern. It is not a new concept, though. Similar kinds of devices, called Hydralift skegs, have been in use on oceangoing barges for decades to make them track better when towed and reduce fuel consumption on the tugs. Hull Vane detailed the hydrodynamic benefits of its wing:

LiftUsing a lift-generating profile, the wing converts part of the stern wave’s energy into forward thrust. Because the lift force is angled forward, it has a forward-pointing horizontal component that adds wave energy to the vessel’s propulsion. In shallow water, vertical lift reduces the squatting effect, thus boosting top speed.

Wake suppressionA wing-shaped profile creates an accelerated flow of water across its upper surface, which leaves behind a zone of low pressure to interact with the wake and suppress energy-sapping stern waves (similar to the bulbous bow reducing the bow wave). Because there is a direct correlation between a ship’s wave pattern and the power required for propulsion, suppression of the stern wave reduces fuel consumption, noise levels, and disturbance, making the wing a useful asset for military vessels because it reduces detectability by drones, satellites, and aircraft.

Trim correctionThe wing helps keep the vessel on an even keel throughout its speed range, so naval architects can design vessels for minimal trim variations.

Pitch dampeningHorizontal wings also mitigate pitching motion, which reduces wave resistance. That in turn improves crew comfort and stability for landing helicopters on deck or for launching and retrieving small craft via a slipway on the stern. When rough seas cause significant pitching, the Hull Vane generates a “pumping effect” that adds to forward thrust.

COURTESY HULL VANE

The wing’s curved shape on the outside added complexity to production.

The wing was patented in The Netherlands and is installed on more than 60 vessels. The project for the Dutch navy discussed here was financed and led by Military Innovation by Doing (MIND) and the Innovation Centre of Commando Material and IT (COMMIT). “We tested the hull vane on our Holland-class patrol vessels, which are almost halfway through their life cycle, with the target to reduce CO2 emissions,” a press release quoted Richard van Dijk, Captain Lieutenant Commander at COMMIT. “During sea trials, a 16% fuel reduction at 17.5 knots and 10% across the full usage profile [was measured], because of the hull vane.” Based on the use profile of a patrol vessel that travels long distances at fairly constant speeds, van Dijk claimed that a reduction of 300,000 tons of CO2 emissions per year is possible. “It is important to be less dependent on fossil fuels and maintain the same employability of the vessel. With less resistance, it has a higher top speed with the same fuel consumption, so the range is extended.”

The product also is available for yachts and superyachts (which were among the early adopters, see below) and commercial ships. Hull Vane declined to share the approximate cost for R&D and manufacturing but confirmed that these wings can be produced in aluminum and carbon fiber, in addition to steel, which was used for the Groningen’s 11m (36) wing.

COURTESY HULL VANE

Steel plates were CNC-cut, then shaped with the help of hydraulic presses to make the curved parts connecting the wing’s ends to the outer struts. High-load parts were cast in steel.

The initial analysis of that project used computational fluid dynamics (CFD), which forecast a reduction of fuel consumption and CO2 emissions between 10% and 16%, depending on speed. Model testing at the MARIN Research Institute to assess performance in waves and impact on maneuverability supported the CFD results, so the project moved to engineering. Finite element modeling determined the fatigue, strength, and vibration properties of the wing, which comprises 250 components, all with unique ID numbers. In construction, steel plates were CNC-cut and shaped with the help of hydraulic presses to make the curved parts connecting the wing’s ends to the outer struts, while high-load parts were cast in steel. Cross-connections were machined for precise fit before the wing was assembled and welded in a building jig, which also helped maintain the prescribed shape despite heat deformation during welding. For a smooth finish that resists marine growth, the wing was sandblasted and hard-coated. See the video.

While the Hull Vane will be marketed to other navies and government agencies, the device found use on large private motoryachts early on. There’s the 42m (138Alive, launched by Heesen Yachts in 2014. Hull Vane claims that the wing reduces resistance to achieve fuel savings of 20.4% and 23.2% at speeds of 12 knots and 14.5 knots, respectively. It also allowed for a reduction in engine size (twin V-12s instead of V-16s) and helped increase maximum range from 3,250 nm to 4,000 nm. Another example is the 34m (111.5) motoryacht Lady Lene, built by the Van der Valk yard in 2021. Combined with her fast displacement hull and wave-piercing bow, its Hull Vane is credited with contributing to fuel savings from 12.5% at 11 knots to 1% at the top speed of 18 knots.

Hull Vane BV, Nude 46, 6702 DM Wageningen, The Netherlands, tel. +31 (0)317 425818

—D.L.