Rim motor, RAD Propulsion power new RS Electric RIB

When the world’s largest small-sailboat manufacturer decided to expand to electric boats, they chose a rim motor coupled with a RIB –  Rigid Inflatable Boat – as the best package to introduce the world to their new company.

RS Sailing made big news at BOOT Dusseldorf this January when it announced a new sister company – RS Electric Boats – devoted to boats powered by electrons instead of wind. Because of their reputation and status in the industry they knew they had to get the first boat exactly right and spent two years developing the world’s first production RIB with a fully integrated electric drive.

Most electrified RIBs are standard RIBs with an electric outboard replacing a fossil fuel motor on the transom. Of course there is absolutely nothing wrong with that – the workboat introduced by NaviWatt last year and the new Pure Watercraft outboard and Highfield RIB combination for the recreational market are both great electric options.

RS decided to do it differently, though, perhaps because their deep involvement in sailboat racing led them to look at the needs and desires of local yacht and sailing clubs for quiet, odourless coach boats to be used at regattas. Their response is the Pulse 58, which addresses those needs but also has lots of features that any boat owner can enjoy.

Editor’s Note:

The original Pulse 58 was powered by a rim drive motor form RAD Propulsion. The Pulse 58 was discontinued and replaced by the Pulse 63, which is propelled by a standard rotor/stator electric motor from RAD.

One of the key elements of the Pulse 58 as a response to coach boat usage is the rim motor and system from RAD Propulsion. A rim motor is exactly what the name suggests – its propeller blades are attached to, and driven from, the circular rim of the motor, instead of the usual set up of propellers being attached to a central hub.

rim motor showing how there is no internal hub and the propeller blades are attached to the outer rimThe rim motor is seen more commonly on large vessels where they are used as thrusters to aid in steering, or on underwater remote controlled ‘drones’. They are characteristically quieter than propeller/hub motors, and they are also less likely to get entangled with fishing line or other items – like the lines of sailboats that might be in a regatta. For this reason, and also the safety of not having open propeller blades in crowded waters, the RAD rim makes a lot of sense for RS Electric.

The RAD team’s experience in rim motors comes from their background in robotics and naval architecture, and they worked closely with the RS Sailing team on the Pulse 58. One of the features RS knew they wanted was for the motor to be retractable, for times when the Pulse would be required to venture into shallow water. It’s a fairly simple proposition with an outboard, but more complicated with an integrated motor!

Developing that ability was part of the whole process of integrating boat and motor, which touched on almost every aspect of the boat design, right down to the basics of hull shape and dimensions.

rim motor on the Pulse 58 is powered by 8 battery packs seen in the case in the hull of the boatThe tunnel hull design formed by the RIB’s tubes coupled with a long waterline give decreased low speed drag to work with the instant torque of the motor. A structurally integrated case sits deep in the hull, holding the 57 kWh battery bank and providing a low centre of gravity for stability and comfort.

Regatta and training boat use can be extremely demanding – and unpredictable – so the  Pulse’s range is at least 35 nautical miles at its maximum speed (>20knots).

The electric tilt mechanism for the retractable motor is part of the overall system controlling and monitoring the motor, power reserve, range data and plotting/navigation features. One of the important items for regatta usage is the geofencing capabilities to control security and safe use.

On the Pulse58 all of these operations are viewed and controlled through a Raymarine touch screen, but the RADLink electronics system has been designed with a proprietary transmitter that can feed data to a Garmin display or many other mainstream electronics systems.

TreeAid logo and photos of tree planting in Africa

It is sometimes a knock against electric boats that the motors may be ‘green’ but the materials in the boat don’t fit that description. The designers and builders of the Pulse58 have gone out of their way to make sure the materials used have the lightest imprint on the planet and worked with TreeAid to offset the carbon and ensure the entire build cycle process is carbon neutral.

This was made easier because the RS Sailing members of the team have worked on sailboats like the RS Aero and RS21, and were able to apply that knowledge to the Pulse58. One of the construction techniques they brought to the project is the use of bio-based infused epoxy resin, recycled PET core material and naturally sourced basalt and flax fibres that have proven themselves incredibly strong and energy absorbing.

Rim motor and RADLink data setup in 3 power ratings

The Pulse 58 is only the beginning in electric boats for both RS Electric and RAD Propulsion. The boat was planned for uses beyond coaching and will also appeal to commercial and superyacht owners who want a noise free, odour free, maintenance free smaller boat  to explore sensitive waters.

For RAD’s part, the data and software abilities in the RADLink system make it ideal for a variety of leisure boats and watercraft. A programmable safety lanyard connects directly to the RADLink and can be set so the motor matches multiple user preferences on startup. The cloud-based data analysis lets users share their location and other information through 4G and Bluetooth connectivity to the web and a mobile app and also allows for remote maintenance and updates. 

The rim motor and RADLink will be available in three sizes:  1kW for paddleboards and kayaks, 15kW for dinghies and small tenders, and 30 kW for small RIBs. They can be connected to a range of batteries from selected partners.

Exciting things are happening every day in electric boats and boating.
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One thought on “Rim motor, RAD Propulsion power new RS Electric RIB

  • April 22, 2020 at 8:03 am

    Wonder, whether the Volabo concept with alumnium cage stator could do the same… and this up to 100kW at 48VDC?!
    But anyway, a great system.


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