First it was the Watt & Sea, now along comes the ultra-efficient eMotion rudder mounted propeller. Matt Sheahan reports on how electric engines and regeneration technology is moving yacht cruising and racing ever closer to dumping fossil fuels completely.

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The 2008 Vendee Globe saw the introduction in the IMOCA fleet of the Watt & Sea hydrogenerator. Looking more like an outboard leg without the engine body on top, these highly efficient generators were being used to provide a good deal of the power for the sophisticated navigation and communication systems without causing unnecessary drag. But more importantly for the wider sailing community, if the speed conscious racing skippers were prepared to use them, the case was made for the rest of us, even if they were travelling at two or three times the average cruiser’s velocity.

Since then the technology and the concept has been developed further and has proved extremely successful with units designed specifically for smaller race boats and cruisers. Indeed, the Volvo Ocean Race organisers have just announced that the refitted VO65 fleet will be equipped with such units as back-ups in the event of mechanical failure to the Volvo Penta engine on board. A good, green step forward but also, I guess, a delicate and tricky move given the title sponsor’s core business.

The announcement also hinted at what was really to come, stating that if all went well with the testing, the boats may well have to use the green power at times during the race.

Sailing around the world without fossil fuel

There is nothing new in going fully green around the world. Francis Joyon set the fastest time for a solo circumnavigation in 2007–08 aboard his 80ft trimaran IDEC ll which used no diesel. Shortly afterwards, Raphael Dinelli completed the 2008–09 Vendée Globe race without using any fossil fuel either.

This year Conrad Colman will be competing in the Vendee Globe aboard his IMOCA 60 100% Natural Energy, with no fossil fuel aboard too.

At the other end of the scale, production builder Hanse has unveiled an intriguing and blissfully simple idea that appears to use similar technology but in reverse and for a variety of alternative reasons.

Called the eMotion Rudder Drive, Hanse’s new system replaces the conventional propulsion system by doing away with a shaft or saildrive and builds the prop into the rudder blade.

Madness? Not at all.

Working with electric propulsion experts (and 2016 DAME Award winners) Torqeedo and steering manufacturer Jefa, the eMotion is a small electric motor and prop fitted on the trailing edge and towards the top of the rudder blade aboard the Hanse 315. The electric power means that there is no need for a shaft, just a conduit in the rudder stock through which the cables can run.

The company claims that the fully electric system means a 100kg weight saving along with no maintenance, noise or smell. But the really clever thing is that because the prop is a part of the rudder, it acts far more like an outboard motor and gives directional thrust, making the boat much more manoeuvrable. At least that’s the claim and watching the promotional videos there is little to suggest it doesn’t do just that.

In addition to the LCD readout in the throttle control that shows power consumption and range, there is also a handy smartphone app so that you can read such data remotely on board – nice.

Of course, Hanse isn’t the first to address the issue of better boat handling under power. Beneteau’s Dock and Go joystick system is an innovative combination of saildrive unit and bow thruster, but it is far more complex than Hanse’s system appears to be.

But perhaps the most intriguing bit of this development is the thought that maybe the next step might be to use the same prop to generate power when sailing, just as the Watt & Sea system does.

In the meantime, and given how important it is to include a proposal on sustainability in any modern presentation, it would appear that the sport may have taken another big step in the right direction.