Propellers

Gloriana’s alternative propulsion – Bruntons Autoprops.

Posted June 11, 2012, 12:49 p.m.
Gloriana’s alternative propulsion – Bruntons Autoprops. Whenever the Queen’s row barge Gloriana is seen with Her Majesty on board it is expected that a team of rowers will provide the motive power; however it’s not her only form of propulsion. For some considerable time the naval architects and engineers at Bruntons Propellers have been keeping a secret; without her rowers Gloriana is propelled by a pair of Bruntons Autoprop propellers. The reason for choosing Autoprops is not hard to understand. Firstly, when Gloriana is powered by her rowers they want the vessel to produce as little drag as possible. Using Autoprops in these circumstances is similar to the reasons for using them on a sailing yacht. The blades feather, and propeller drag, compared with fixed bladed propellers, is reduced by up to 85%. The second reason however made Autoprops almost compulsory. The power on Gloriana is provided by two 7.5kw electric motors which deliver their power through saildrive legs, and there is probably nothing more efficient at delivering the power of electric motors, than Autoprops. Unlike most other propellers Autoprops provide a high level of propulsion efficiency across the rev range of an engine, thanks to the ability of the blades to adjust their pitch relative to the engine revolutions. This ability is as evident with electric motors as it is with diesel or petrol power and is one of the main reasons why Autoprops are rapidly being adopted by many electrically driven vessel operators. The propellers on ‘Gloriana’ are based on Bruntons existing APS-H20 model but the propeller hubs where custom designed to provide the modified profile required to blend in with the saildrive legs; these have a smaller diameter than those normally fitted to sailing yachts. Working with Gloriana’s designers, who provided 3d models of the hull together with resistance calculations, and the manufacturers of the saildrive legs themselves, Bruntons team came up with a modified hub design that ensured excellent water flow to the propellers. Adrian Miles, Bruntons Managing Director is obviously delighted with his company’s involvement. “This has not been the most difficult project we have worked on but has certainly been the one which has been the most satisfying to be a part of. We are very pleased to hear that during trials under electric power Gloriana’sperformance exceeded expectations. Autoprop was given a Queens Award for Technical Achievement in 1999 and we are delighted the relationship with Her Majesty is continuing”.
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