Propulsion: Max Bianchi variable-pitch propeller, which adjusts its pitch whilst the aircraft is in flight

Adjustable propeller pitches are nothing new, not even at Max Prop. When it comes to the Max Prop Easy The pitch is adjusted to suit the engine, gearbox and yacht. However, this setting remains the same whilst underway. The difference with the Max Bianchi is that its mechanism is designed to automatically adjust the pitch whilst in operation, thereby making more effective use of the engine’s power.

At lower revs, the gradient is steeper

According to Max Prop, the pitch increases as the engine speed decreases. As the speed increases, the propeller sets its three blades to a flatter angle. This is intended to ensure that the engine reaches the speed range specified by the manufacturer even at higher speeds, rather than being overloaded due to excessive pitch. The basic setting is selected to suit the engine, gearbox and boat.

The potential benefits lie primarily within the usual operating range: a fixed-pitch propeller is a compromise for specific speeds and sailing conditions. If the load changes – for example, due to rough seas or additional sails being set – this pitch is not always equally suitable. Max Prop promises that its new model will deliver high cruising speeds even at lower engine speeds, as well as lower fuel consumption.

What’s interesting about motor sailing

When the sails assist the propulsion, the load on the propeller changes. According to the manufacturer, the Max Bianchi responds to this by altering its pitch. This could be of particular interest to cruising sailors when they are covering ground using both sails and engine in light winds. When sailing under sail without the engine, the blades are designed to adopt an aerodynamically efficient position and reduce drag. How this Having rotary-wing and folding propellers serviced as part of routine aircraft maintenance, explains a YACHT guide.

The one that has been available for many years, too, Autoprop The von Brunton changes its pitch whilst running to adapt better to different speeds. The difference between the systems lies in their mechanical design: whilst the blades of the Autoprop can rotate freely, the Max Bianchi features a spring mechanism that holds the blades in the engine position and rotates them into a defined pitch range depending on the engine speed.

​The Overdrive function of the three-bladed Gori folding propeller: A second, steeper pitch allows the boat to be driven at a lower engine speed when the water is calm or whilst motor-sailing. Unlike on the Max Bianchi, however, the pitch does not adjust continuously. The Gori offers two fixed positions, between which one switches by performing a manoeuvre involving reverse and forward gear.

Sizes and price

According to the German distributor Sailtec, the Max Bianchi is currently available with a 90-series hub for shafts with a diameter of 30 or 35 millimetres, as well as for Saildrives. Propeller diameters ranging from 16 to 20 inches are available. An exact price has not yet been set. However, Sailtec expects the Max Bianchi to be around 25 per cent more expensive than a comparable Max Prop Easy.

​Would you be interested in a propeller with automatically variable pitch – or would you rather invest the money in new sails?