Eco Boss Cap enters production following breakthrough CFD validation
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EcoNavis Solutions has begun production of its patented Eco Boss Cap propeller hub, marking the transformation of a university-led research project into an industry-ready fuel efficiency retrofit technology.
The first unit, destined for installation on a general cargo vessel, has been cast at a foundry in China using designs optimised entirely through computational fluid dynamics (CFD). It is currently undergoing final machining ahead of factory acceptance tests.
From research to production
The Eco Boss Cap eliminates the hub vortex cavitation that causes rudder erosion, vibration, and thrust loss in conventional propulsion systems. Unlike finned boss caps, which only function optimally at narrow speed ranges, the Eco Boss Cap features a smooth, conical design with internal chambers and strategically bored holes. This configuration uses fluid pressure differences to improve flow uniformity, reducing torque while increasing thrust across a wide range of operating conditions.
The innovation began as a research project at the University of Strathclyde, led by naval architect Dr Batuhan Aktas.
“We started by identifying the failure points of existing designs,” he said. “Fin-type caps tend to generate drag outside their designed speed. We wanted to create something simpler and smarter — a passive system that could dynamically adapt without complexity or cost.”
Initial CFD simulations showed performance gains of over 3% in efficiency and reduction in propeller hub vortex cavitation. But early prototypes revealed a critical problem: some hole placements actually reduced propeller efficiency. The team returned to first principles, iterating the design using advanced parametric optimisation tools.
The breakthrough came when engineers redesigned the internal chamber to align the suction flow with stagnation pressure points, allowing the cap to draw water through its core without impeding thrust. These insights led to successful trials at a European cavitation tunnel facility, where the final design outperformed other energy-saving caps.
Performance and cost advantage
Now under exclusive licence from the University of Strathclyde, the Eco Boss Cap is cast in a single piece, requires no moving parts, and can be installed in five to six hours during a normal drydocking.
“It costs about 50% less to manufacture than typical fin-based units and is expected to achieve a return on investment in under six months for mid-sized vessels,” said Amitavo Wye, EcoNavis’s Chief Operating Officer.
Early trials showed a 3.1% improvement in propeller efficiency, a 1.1% increase in thrust, a 2% reduction in torque, and a 10% decrease in rudder cavitation. Noise was also reduced by up to 3 dB, lowering the vessel’s underwater radiated noise footprint — a key issue for ESG compliance in sensitive marine environments.
“We’ve moved from lab to foundry in less than a year,” said Dr Aktas. “And with every unit, we’re refining not just our technology, but how fast and affordably we can deliver it.”
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New tests confirm Eco Boss Cap efficiency as pilot installation planned
Home › News › New tests confirm Eco Boss Cap efficiency as pilot installat…
A second series of cavitation tests has confirmed that the Eco Boss Cap propeller hub improves fuel efficiency by up to 5% at full scale, as shipowners and propeller manufacturers express interest in the technology.
Full-scale CFD simulation of a ship operating at a design speed of 16.46 knots and turning a controllable pitch propeller with four different boss cap models found the Eco Boss Cap to be the more efficient solution, outperforming existing hubs by a factor of 2.5 or more.
According to the trials report, researchers concluded that propeller hub vortex cavitation was significantly eliminated by the holes in the Eco Boss Cap models, with vortex cavitation disappearing after interaction with the holes.
The test results mean that the simple-to-manufacture and install propeller hub can be retrofitted to large ocean-going ships as a way of contributing to shipowner ESG goals to reduce carbon emissions.
Eco Boss Cap inventor Dr Batuhan Aktas, a Chancellor’s Fellow in the Naval Architecture, Ocean and Marine Engineering Department at the University of Strathclyde, said: “Our approach to improving propeller efficiency is unique in both design and application. It diverges from traditional methods that typically use propeller hub fins to achieve similar outcomes. We are receiving a tremendous amount of industry interest.”
A key differentiating aspect of the Eco Boss Cap is the emphasis on cost-effectiveness and ease of manufacturing. Unlike conventional propeller boss cap fins (PBCF) which are complex and expensive to produce, the Eco Boss Cap offers a simpler and more economical solution without compromising on efficiency or performance.
Ship maintenance costs can also be reduced as propeller hub vortex cavitation is the primary source of rudder cavitation and damage. In addition, the Eco Boss Cap reduces underwater radiated noise and vibration levels, which impacts the migratory, mating and feeding habits of marine mammals.
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EcoNavis develops hydrodynamic energy-saving devices tailored to each vessel’s hull, propeller and rudder interaction. To assess whether Eco Boss Cap or an integrated optimisation package may be suitable for your fleet, contact the EcoNavis team.
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Eco Boss Cap validated as more efficient than existing propeller hub caps
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A revolutionary propeller hub vortex cavitation-eliminating boss cap has successfully completed validation tests at a hydrodynamic research centre in Sweden and will now undergo ship model basin trials to verify the efficiency gains on larger commercial and naval vessels.
Initial computational fluid dynamics (CFD) tests based on a typical twin-screw vessel with V-brackets and a 90 m coastal general cargo ship showed that the Eco Boss Cap increases propulsion efficiency by up to 5%, compared to conventional propeller boss caps. Tests also assessed the device against more advanced energy-efficient boss caps currently in operation, and found it to be at least 3% more efficient.
“Overall, compared to the propeller boss caps currently available, the Eco Boss Cap improved propeller efficiency by 3.1% and thrust by 1.1%, while reducing torque by 2%, rudder cavitation by 10%, and propeller-induced noise by 1–3 dB,” explained Dr Batuhan Aktas.
“The Eco Boss Cap eliminates completely propeller hub vortex cavitation, the main source of rudder erosion, and reduces associated propeller efficiency losses, which can be as much as 8%.
“Considering the investment levels required for other energy-saving devices currently in the market and the potential fuel savings, the Eco Boss Cap represents a significant advantage with a return on investment of less than six months,” he said.
How it works
The holes channelled into the Eco Boss Cap affect the high pressure in the hub vortex by redirecting the flow downstream. The resulting low-pressure swirl flows in the opposite direction to conventional hubs, behind the propeller blades, reducing propulsive drag, fuel consumption and maintenance costs.
“With shipowners grappling with new environmental legislation and emissions reporting rules, zero propeller hub vortex cavitation can help towards ESG, EEXI and CII goals, improve efficiency and reduce the costs associated with cavitation-induced rudder erosion.”
The Eco Boss Cap is reportedly less expensive than conventional propeller hub cap fins that incorporate small blades or fins to hydrodynamically deflect the water flow, as it is easier to cast and requires less material.
“What we have designed is a propeller boss cap that is 5% more efficient and costs 50% less to manufacture than current conventional propeller hubs. Considering the minimal investment required, this is a significant level of saving.”
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