The 2-blade folding prop has been available with a composite hub since 2017. Now the Danish manufacturer Flexofold is following suit and is also offering the larger 3-blade version in this combination. As usual, the blades are made from nickel-aluminium bronze, while the hub is made from a composite material. The use of plastic at this point makes the entire propeller three to four kilograms lighter. In terms of thrust and manoeuvrability, the composite variants are in no way inferior to the bronze models. According to the manufacturer, the lower weight even has advantages for boats with electric drives.
In addition, the blades are completely electrically insulated from the rest of the prop by the plastic hub, and galvanic corrosion between the blades and the saildrive cannot occur. The bolts are dimensioned for blades up to 20 inches. The 3-blade 18'' by 13'' LH model as a composite folding propeller costs 2,698 euros.
Advantages and care of folding propellers
In contrast to conventional propellers, a folding propeller moves into a favourable position when the engine is off, thus reducing the resistance and load on the shaft. This means that the gearbox does not suffer when the gear is engaged and there is hardly any wear on other components. The ship is also quiet.
Another advantage is that the ship sails faster due to the lower resistance of the propeller. Depending on the type of propeller and ship, up to 1.5 knots of additional speed can be achieved. This can make a considerable difference, for example a 60 nautical mile journey can take just 10 hours instead of 12. This makes it possible to reach a destination in daylight.
To enjoy these benefits, a folding or rotary blade propeller requires some care. The moving parts must be lubricated regularly and the surfaces must be protected against corrosion and fouling so that they function smoothly and for a long time.
