VARIABLE PITCH PROPS

A normal fixed propeller is designed for propelling the boat and not for generating power as with a hydrogenerator. However, Oceanvolt’s DAME awardwinning Servoprop saildrive, suitable for monohulls and multihulls from 35-90ft LOA, features a variable pitch prop that combines a high efficiency saildrive with a powerful hydro-generator. With its unique ability to rotate its propeller blades through more than 180°, Servoprop’s control software adjusts the pitch of the propeller blades to automatically optimise all hydro-generation and propulsion needs.

Oceanvolt claims that a normal fixed propeller generates less than half the power of Servoprop, which it states can produce more than 1kw at 6-8 knots, and 5kw at 10 knots. It also estimates a 30% increase in forward propulsion, +100% in reverse, and +300% in hydrogeneration mode.

Renowned marine propeller supplier, Bruntons, has also launched its Autoprop Eco*star, designed specifically to propel the rapidly growing number of hybrid and pure electric craft, both motor and sail.

Autoprops are highly efficient because of their ability to auto-pitch depending on engine speed and sea conditions, in order to provide optimum thrust at all times. But with electric propulsion the advantages provided by the new Eco*star propellers are further extended.

Electric motors provide a constant torque from zero to maximum rpm. Using its auto-pitching ability, the Eco*star can match its own efficiency curve with that of the electric motor, resulting in more boat speed with less energy.

Eco*star can spin when under sail allowing the motor to become a generator for recharging the batteries.