Alright listen up. Why is this Ship’s Propeller Sculpture here?
The Ship’s Propeller Sculpture is more than just metal. It echoes a time of maritime innovation. This is a tribute to naval history.
Let’s dive into the story of the propellers from HMAS Sydney (III). These propellers weren’t just any propellers. One was three-bladed. The other was four-bladed. They sat not far from each other in the Shoalhaven. One resides at the Jervis Bay Maritime Museum. The other calls the Fleet Air Arm Museum at HMAS Albatross home.
Sailors and dockyard workers confirmed something interesting. The carriers Sydney and HMAS Melbourne had this unusual setup. Three blades graced the port shafts. Four blades powered the starboard. The reason? Vibration problems.
Back in 1938, the Royal Navy commissioned HMS Ark Royal. It was their first purpose-built aircraft carrier. More followed but these ships needed time and resources. Light Fleet Carriers emerged as an interim solution. They bridged the gap between full-sized carriers and smaller escort carriers.
The Colossus class led the way. Ships like Colossus, Glory, and Ocean filled the ranks. The Majestic class followed with HMS Majestic and Terrible. These Light Fleet Carriers were designed for a short life. Yet they exceeded expectations. They became the foundation for many countries’ Fleet Air Arms.
Both Colossus and Majestic classes shared similar engine setups. Two compartments housed the machinery. Each held two Admiralty 3-drum boilers. These fed a Parsons geared turbine. They delivered 40,000 shp to two shafts. This drove two 3-bladed propellers. The ships reached a top speed of 25 knots.
The starboard propeller shaft was longer. This difference may have caused torsional vibration. It stressed the starboard propeller shaft.
HMS Pioneer suffered an implosion during trials. This was due to the starboard propeller shaft snapping. A four-bladed unit replaced it. Subsequently all ships of the Colossus and Majestic classes got four-bladed propellers on their starboard shafts. Problems disappeared.
Twin-screw vessels usually have counter-rotating propellers. They share identical specifications. Three-bladed models were common in the Royal Navy. They provided higher speeds. Four-bladed models reduced vibration.
The three- and four-bladed combo fixed a critical design failure. It proved successful. The rest of the ships were retrofitted.
Leyland Wilkinson unearthed details from old workshop notebooks. Propellers No 2 came from J. Stone & Co. The three-bladed propeller had a 14′ 0″ diameter. Its pitch was 14′ 3″. The four-bladed propeller also had a 14′ 0″ diameter. But its pitch was 13′ 7″.
Wilkinson shared a compelling argument. In 1831, troops marched over Broughton Bridge. The bridge vibrated. It collapsed. This was due to ‘Mechanical Resonance’. The British Army then ordered troops to ‘Break Step’ on bridges.
Could the regular beating of equal propeller blades cause vibration? High propeller speeds can also cause ‘cavitation’. This happens when the propeller tries to drive water faster than it can reach the blades. Vacuum pockets form and collapse. Water slams into the blades. Change the beat and save the ship.
In July 1947, the Commonwealth Government formed the Fleet Air Arm. They acquired two Majestic class Light Fleet Carriers. HMS Terrible became HMAS Sydney. HMS Vengeance was lent to the RAN. Later HMS Melbourne was commissioned.
HMAS Sydney had an exciting career. It served in Korea. It supported forces in Vietnam. HMAS Melbourne developed a balanced fleet.
The Ship’s Propeller Sculpture reminds us of these ships. It honors the ingenuity and sacrifices of those who served. It stands as a testament to maritime history.