FOIL POWER’S POTENTIAL BUILDS ON DECADES OF DEVELOPMENT

Former The Motorship deputy editor Paul Gunton recalls his first encounter with wave foils and explores what happened next

Four decades ago, in August 1983, The Motorship described a novel propulsion device that converted wave energy into forward motion. Our report was picked up by The Financial Times newspaper and by the BBC, which followed in our footsteps and visited its inventor, Einar Jakobsen, at his purpose-built model tanks in a former barn, located a few miles north of Oslo.

Mr Jakobsen’s demonstration for the BBC’s Tomorrow’s World programme can still be found on YouTube.

His invention, which he had patented in 1977, involved a horizontal foil mounted at the base of a strut that could be attached to the bow or stern of a vessel. As the hull pitches in waves, the foil glides forward on both its downward and upward strokes, drawing the craft forward, both with and against the waves, the video confirms. The footage also shows a 7.5m yacht fitted with the device reaching 6kts in choppy waters.

Norway’s state broadcaster NRK also featured the technology. Its report – also available on YouTube – opens with a reporter sitting on a small catamaran and pushing a vertical pole up and down. It is connected to a submerged foil and the craft moves forward at an impressive rate.

Taken together, the two videos provide vivid demonstrations of his invention’s potential to both extract natural energy or absorb mechanical power and use them to deliver propulsive force.

Mr Jakobsen was not alone in experimenting with foil propulsion. In 1982 Hitachi Shipbuilding Co conducted a conceptual study of wave powered boats while, in the same year, Japan’s Tokai University was working on a similar concept, which it called ‘wave devouring propulsion’.

Nor was he the first to realise this means of using wave energy: literature on the topic mentions Herman Linden who, in 1895, was working at the Naples Zoological Station when he noticed how a boat was affected by passing waves and explored how this could be harnessed to move it forward. He subsequently built a prototype craft, Autonaut, with horizontal foils fitted below its bow and stern.

It is pictured in a detailed history of foil power on the environmental engineering website Bluebird Earth Concepts (www.bluebird-electric.net; look for ‘Wave powered boats and ships’ in its index), which mentions other early pioneers and includes a photograph of an unknown Californian inventor holding a foil-powered model in 1935. It also refers to an article in 1950 about an Australian wave-powered boat concept and includes a link to a 1966 patent application (granted in 1970) by a Canadian sculptor, painter and inventor Joseph Gause, for a “Flexible fin propulsion system and vessels incorporating same”.

He fitted three pairs of fins to a 10.4m boat, Gausefin I, which the magazine Mechanix Illustrated reported in 1972 had reached 5mph during a demonstration for Canadian Government officials.

Mr Gause’s foils were flexible but rigidly fixed; what made Mr Jakobsen’s concept notable was that his foils were rigid but spring-loaded – a “milestone in the development of wave-powered boats”, according to a 2013 paper for the Third International Symposium on Marine Propulsors. It was written by Eirik Bøckmann and Sverre Steen, then of the Department of Marine Technology at the Norwegian University of Science and Technology.

Their paper focused on the effect of a fixed foil on a ship’s propulsion and motions and found that it reduced heave and pitch significantly and that maximum thrust was obtained with the foil slightly ahead of the bow for wavelengths equal to or longer than the ship’s length.

Dr Bøckmann’s subsequent PhD thesis was also about wave power for ships and he went on to found the company

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Wavefoil in 2016, which produces retractable bow foils that “give significant fuel savings, reduced motions and a more comfortable experience at sea”, he says on LinkedIn. Dr Steen is now head of the university’s marine technology department.

Learning From Nature

Our 1983 article referred to mathematical modelling of the hydrodynamics of unsteady hydrofoil propulsion, carried out by Prof Johannes Lunde at Sweden’s Chalmers University. He considered the merits of a variety of foil shapes and found that curved leading and trailing edges would give better performance than a rectangular foil; “the similarity with the tails of fast-swimming fish did not escape his notice”, we reported.

Such creatures have vertical tails, which they use in the same way as a powered foil. Cetaceans, on the other hand, have horizontal tails and research in 1989 at the Memorial University of Newfoundland found that they do benefit from wave energy. Bluebird Earth Concepts mentions a paper that looked at an immature fin whale and found that – in a fullydeveloped seaway at a low swimming speed and in following seas – it obtained a third of its propulsive power in this way.

Research into foils as propulsion units has continued. In the early 2000s, for example, Rolls-Royce Marine – since taken over by Kongsberg Marine – explored their potential for a number of years, led by its then director of research and technology, Rune Garen. Interviewed for the company’s publication Vision in 2005, he said that “we have much to learn from nature”. For example, a pike can accelerate at 8-12g, which “makes animal locomotion a very interesting field of study.”

His remarks came in a discussion about how ship propulsion technology might develop over the following 20-30 years and predicted that “oscillating propulsors may well challenge today’s rotating ones.” Now, nearly 20 years later, he told The Motorship that although foils are not part of Kongsberg’s portfolio – where he is senior vice-president for business concepts – understanding nature is still vital “in order to become better at [tackling] the energy conservation issue.”

Current Development

Other companies are actively exploring foil propulsion within an EU-funded three-year project, SeaTech, which is due to end this year. Its seven partners – coordinated by Wärtsilä –set out to develop “two symbiotic ship engine and propulsion innovations that when combined, could lead to a 30% reduction in fuel consumption,” according to background notes on the project’s website.

One of those innovations is aimed at reducing engine emissions; the other is “a biomimetic [inspired by nature] dynamic wing mounted at the bow of the ship to augment propulsion in moderate and heavy sea conditions.” By capturing wave energy, the notes explain, “extra thrust is produced and ship motions are dampened.”

One of those involved is Dr James Bowker, a senior research fellow in engineering and physical sciences at the University of Southampton – one of the SeaTech partner organisations. In a lecture to the local branch of the Royal Institution of Naval Architects in December 2022, he described foil propulsion as “a proven concept” for small craft and that SeaTech’s mission was to look at its application to ships of around 100m length.

From tank tests using a 2m scale model of a 100m bulk carrier, he reported a reduction in delivered engine power in waves of up to 50% – depending on their wavelength – as a result of using the foil, along with average reductions of 10% in heave and 20% in pitch. There is a link to a YouTube video of his presentation from the project website.

Although the technology and sophisticated analysis techniques he described were not available to Herman Linden in the 1890s, the foil arrangement used in Dr Bowker’s tests would look familiar to him. After 130 years, his time may have finally come.

8 Dr Eirik Bøckmann identified a need for hull optimisation for ‘whale tail’ foils to improve performance further during early stage tests at Norway’s NTNU in 2013