Candela’s Hydrofoil Boats are, Quite Literally, Taking Off

Electric cars have, surprisingly quickly, become de riguer on European streets. Electric boats, on the other hand, are still relatively uncommon. However, Swedish company Candela is looking to change that.

“Candela’s mission is to speed up this shift to electric boats,” CEO Gustav Hasselskog tells Auto Futures. “Our craft can match internal combustion engine (ICE) boats in terms of speed and range but are superior in all other respects.”

How has it managed that? By using hydrofoils.

Ice Creams and Flying Boats

Candela’s CEO Gustav Hasselskog

A hydrofoil, if you aren’t up on your maritime nomenclature, performs the same function as an aeroplane wing – but underwater.

As the boat’s speed increases, the hydrofoil literally pushes the hull out of the water which, to the untrained eye, could give the impression that the boat is flying. As a result, hydrofoil boats create significantly less drag and can reach higher speeds while using less energy.

“In 2013, I worked as CEO of a chemicals company, had a summer house in the Stockholm archipelago, where I had a V8 powered American Bertram powerboat,” says Hasselskog. “On hot days, I used to drive to the local fuel dock/grocery store to buy ice cream for my sons. The 20-minute trip would cost €50 in gasoline money and €5 worth of ice cream. This made me realize that something was horrendously wrong with the energy consumption of conventional boats.”

And so, rather than telling his children that the regular ice cream sorties were simply too pricey, Hasselskog decided to fix the problem.

“I dug into the maths of planning hulls,” he says, “and I concluded that a conventional 25-foot hull uses 15 times more energy at 20 knots than a family car – so electrifying a conventional hull wouldn’t work, not even with the best lithium-ion batteries.”

By his reckoning, a regular electric boat would be out of charge after just 30 minutes and, rather than making his sons swim the remainder of the trip, ice creams in hand, he decided to build a better boat.

The Candela C-7 hydrofoil

“My conclusion was that in order to make a long-range and high-speed electric boat, one must reduce the boat’s energy consumption,” he says. “Our solution is to use hydrofoils that lift the hull above the water.”

The result was the Candela C-7 and C-8 boats.

“They use 80-85% less energy at high speeds than traditional fast motorboats, allowing for long-range at speeds of 20 plus knots,” explains Hasselskog. “They don’t slam into waves, they are absolutely quiet, need very little maintenance, and are 95% cheaper to operate. Also, they don’t create any wake. They’re simply better boats. Once you’ve driven one, it’s hard to go back to conventional ICE craft!”

Speed and Inefficiency

At this point, you’d be forgiven for thinking that Candela’s boats are simply regular boats with hydrofoils. However, as Hasselskog explains, there’s far more going on beneath the surface.

“We have a main foil amidships, and a stabilising aft foil, which is connected to our Candela C-POD drive unit.”

While it might not be as eye-catching as the hydrofoil, the C-POD drive unit is just as important to the C-7 and C-8’s operation.

Candela’s C-POD electric motor and propeller

“The C-POD motor is unique in the sense that the motors – two inline driving counter-rotating propellers – are under the water, directly driving the propellers,” says Hasselskog. “There are no losses from gears. It makes the C-POD the most efficient marine drivetrain.”

It also means that the boats are remarkably quiet. Traditional ICE boats can, according to Candela, be as loud as 100 decibels – that’s as loud as a motorbike or a jackhammer, for example.

There is “no rattling, no squeaking, absolutely no noise, even at 30 knots,” says Hasselskog.

The fact that the C-POD motors are underwater hides a lot of the noise, but the torpedo-shaped propellers aren’t just about being quiet.

“Making the very compact energy-dense electric motors – the diameter is 11 cm – was quite hard. But having abundant cooling from the flow of seawater solved the biggest challenge in electric motor design, which is heat,” explains Hasselskog.

Being submerged, the rotors must have a very small diameter to reduce drag. But, in order to achieve the same speeds as traditional boats, Candela had to increase the RPM of the blades while lowering the motor’s torque in order to increase the power density. By splitting the load over two propellers, they can spin at a faster rate, without generating the same level of noise and inefficiency as traditional rotors.

A High Watermark?

All this begs the question, why are all boats using hydrofoils, smart underwater propellers, and electric motors?

Hydrofoils have traditionally been associated with extra complexity and, as a result, extra maintenance and increased cost. Several Soviet-made hydrofoils are still in civil and military use in modern Russia, for example, but most other countries have chosen to remove them from service.

One major concern for traditional hydrofoils is marine growth – basically when seaweed, moss, algae, and barnacles become attached to the hull of a boat. If something became stuck to the hydrofoil, it would have a massive impact on efficiency and speed.

Candela, fortunately, thinks it has solved the problem. “In our new C-8 the foils are retractable above the waterline, meaning no growth,” says Hasselskog.

The upcoming Candela C-8

And, while Candela’s boats aren’t cheap, the new C-8 starts at €290,000 plus VAT, the company’s more than 100 orders make it “one of, if not the best-selling €300,000 boat in Europe,” according to Hasselskog.

“And we’ve got interest from 45 cities, entities and urban developers for our commercial craft,” continues Hasselskog. Those commercial craft include the P-12 water taxi and P-30 ferry.

The Candela P-12 water taxi

The P-30, according to Hasselskog will bring “considerably faster travel times” and promises to more than half the travel time on its route from the Ekerö suburbs to central Stockholm from 55 minutes down to 25, compared to the conventional ferry or a combination between bus and metro.

The Candela P-30 ferry

This is because the P-30 is “able to go faster in no-wake zones and it has higher cruise speed – 25-28 knots versus 18 knots or so for the conventional ferries,” according to Hasselskog.

So, what’s next for Candela and electric boats?

Reservations are open for the C-8 boat and the P-30 ferry is due to launch this year, with commercial operations beginning in 2023.

“Although the efficiency benefits of hydrofoils are less pronounced on really big ships. But all coastal passenger transports up to 300 passengers can be electrified using hydrofoils,” says Hasselskog.

“I think that 10 years from now, the most common new boat will be an electric hydrofoil craft. The benefits are so many, that conventional craft will have a hard time competing.”

It’s certainly a compelling vision for the future of waterborne transportation, even if most of the boars aren’t in the water at all.