Vari Pitch Propeller
Looking somewhat battered and bruised by her fishing days with Ross Fisheries, pictured below is a view of the Ross Revenge single vari pitch propeller whilst dry docked in Solares, Santander - Spain, during the Radio Caroline fit out in 1983.
At the time of build in 1960, the Freyr and her three sisters were all fitted with single vari pitch propellers. Whilst the cost of vari pitch compared to fixed pitch propellers is considerably more expensive, the benefits of manouvreablilty far outweighed the cost. If you have watched the videos of the Vikingur and Mai, in our Freyr RE1 History Section, you will have seen the ease of how these huge supertrawlers were docked by incorporating vari pitch into the build.
Vari Pitch PrinciplesTo get a better understanding of how the vari pitch propeller (VPP) operates you first need to understand the principles of the fixed pitch propeller. If you have ever looked at propeller blades you will have noticed that they are slightly angled. With the ship put into forward motion, and with the prop shaft turning in a clockwise direction, forward propulsion is achieved. All good so far - but what if the ship needed to go into reverse ?
To achieve reverse motion this would entail the ships engineers shutting down the engine and restarting in reverse. As you can see from the ships starting procedure, detailed throughout our Engine Room section, this was not a practical solution.
With a vari pitch propeller there is no need for shutting down and restarting the engine as the pitch of the propeller blades is operated hydraulically, via a Vulkan Coupling, remotely from the Bridge. The video below shows VPP in action.
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