Kaplan 3B & 4B Propellers


The Austral Kaplan style propeller is the major part of a complete ducted propeller system. This specially designed propeller is mounted within a venturi shaped nozzle which for highly loaded applications can develop substantially greater thrust than open or free propellers.

Using this system the bollard pull (i.e. thrust) of trawlers and the like can increase by 25 to 35% while harbour tugs can typically increase 30 to 50% as compared to open propellers. In fact when a nozzle of correct geometric design is combined with an Austral Kaplan propeller, it can mean the same bollard pull could be achieved with a smaller engine providing substantial running cost savings.

Conventional propellers have the blade face generation at 90 degrees to centre axis whereas the raked design has blades which are tilted at an angle to the centre axis. Austral now produces Kaplan propellers with aft rake, basically the centre of the blade at the tip is approximately in line with the rear face of the propeller hub. This aft rake design normally means a larger diameter propeller can be fitted because of greater aperture available toward rear of boat.

Design Features and Advantages:

  • Improved steering and manoeuvrability
  • Raked models available
  • Cast in Nibral and Manganese Bronze
  • Reduced vibration and noise
  • Individually pitchometer checked
  • Statically balanced
  • Bollard pull increased 25 to 50%
  • Substantial fuel savings