But hang on, where is the cool splash? Where is the angry whirr of the petrol motor?
Such might be the thought process of a rider on the WaveFlyer, the “world’s first electric hydrofoil jet-ski”. Instead of smashing doggedly through the waves, the personal watercraft is designed to ‘fly’ serenely about a foot above the surface.
Described as “an entirely new way of experiencing the water” by Australian company Electro.Aero, which is partnered with the University of Western Australia (UWA) and lithium producer Galaxy Resources on the project, the WaveFlyer appears similar to a conventional jet-ski while stationary in the water. When it gets going, however, it rises up using its actively stabilised hydrofoil propulsion system. Lithium-ion batteries rated 2kWh reportedly power the craft with two riders for more than 30 minutes, compared to maybe more than two hours using petrol.
Electro.Aero calls the craft “smooth, stable and efficient” but a promotional video appears to show it wobbling slightly while travelling and it is not clear how fast it is moving. The clip also shows it going up and down with little sustained ‘flight’.
“It’s a curious, weird thing,” says Professor Sandy Day, marine hydrodynamics expert from the University of Strathclyde. UWA and its partners have not revealed extensive details, but Day says it likely uses twin T-foils to rise up – wing-like structures shaped like inverted underwater Ts, rather than commonly used Vs.
“A T-foil set-up has much less drag but the downside is the loss of stability. There is no intrinsic stability from this,” says Day. The efficiency advantages are clear and mean faster travel or the same speeds using less energy, however. “That bit is not very controversial… the real challenge is height control, particularly in waves.”
Controlling a hydrofoil craft becomes “an order of magnitude more difficult” in wavy conditions, he says. Waves can confuse height sensors, tricking the system into thinking it is lower down than it is and triggering an attempted increase in altitude. Any lag in this process could lead to the jet-ski “heaving up and down,” says Day, with waves and the flight control exacerbating the issue.
Other issues might arise – the developers’ assertion that lifting riders up will make the craft safer is not necessarily watertight, for example, while hydrofoils could also pose a risk to wildlife or swimmers.
Day says he is nonetheless “not surprised” to see something like the WaveFlyer thanks to material advances. “Carbon fibre has enabled people to build these foils that they couldn’t do 20 years ago,” he says.
Electric propulsion will reduce pollution. WaveFlyer’s eco-friendly credentials could open up the use of recreational lakes that were previously restricted to fossil-fuel vehicles, says Professor Thomas Braunl of the UWA. There could be “tremendous commercial potential,” he claims.
With people’s propensity to show off at the beach, he could well be right.
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