Hopes for a new generation of electric hydrofoils — a tech with Canadian roots

Scientists in Sweden are taking a new look at hydrofoils for a new generation of fast, energy-efficient ferries. The concept has a history in Canada going back more than a century.

Researchers at Chalmers University of Technology in Sweden are doing new work studying the performance of hydrofoils. Hydrofoils are attachments to boat hulls that act as underwater wings, lifting the hull of a ship out of the water as it gains speed. Once up to speed, the craft rides solely on the submerged water wing, greatly lowering drag from the water, and allowing much higher speed. 

Hydrofoils are not a new idea, but the researchers are looking at more modern foil designs that could make passenger ferries run efficiently enough that they could run on emissions-free electric motors.

In 1919, Alexander Graham Bell's HD-4 experimental hydrofoil, powered by two aircraft engines, set a world speed record of 114 km/h while speeding across Bras d'Or Lake on Cape Breton Island. It held that speed record for almost a decade. A replica of the craft can be seen at the Alexander Graham Bell Museum in Baddeck, N.S. 

In 1968, the Canadian Navy commissioned a prototype hydrofoil, the HMCS Bras D'Or, which achieved 63 knots (117 km/h) making it the fastest non-armed naval vessel in the world at the time. The program was suspended in 1971 and the ship is now on display at the Musee Maritime du Quebec on the shores of the St. Lawrence River.

VIDEO: The Bras D'Or hydrofoil

High speed hydrofoil ferries are in use today in Russia and Europe, but the vessels and their hydrofoils are heavily built to hold the entire weight of the ships and the forces of the water. They're driven by powerful diesel or jet turbine engines to attain the high speeds.

The Swedish researchers are aiming to make ferries more environmentally friendly by utilizing electric drives and incorporating more modern lightweight carbon foils to allow them to run more efficiently. To do that, they are taking lessons from advanced racing yachts.

In 2012, the America's Cup yacht race was shocked when Team New Zealand introduced foils that enabled their boat to fly with its hull above the water at speeds unheard of in the 170 years of Cup history.

The current America's Cup boats, called the AC75 class, are marvels of exotic materials and engineering.

These high-tech boats use uniquely shaped foils that can be lowered and raised according to conditions. Only two of these single blades are needed to hold the boat above the water and skim along at 40 to 50 knots (74 to 93 km/h) and more than twice the speed of the wind. 

WATCH | America's Cup AC75 hydrofoil sailing yacht

The Swedish scientists are testing these blades for strength and performance to design larger foils for passenger ferries not so much to make them go faster but rather to enable them to rise out of the water at lower speeds to reduce drag so electric propulsion can be used.

Hydrofoils have fallen in and out of favour since they were first introduced. Alexander Graham Bell was hoping to market his HD-4 to the military, but that didn't happen and the Canadian Navy changed its priorities so nothing was built beyond the Bras D'Or. But passenger ferries are still a possibility where the century-old concept of water wings could pay off with environmental benefits.