• Yacht

Ever-Lasting Bearings Keep World's Largest Sloop Ever-Ready for Charter

Mirabella V equipped with COMPAC birds eye view

One of the projects Canada’s Thordon Bearings is most proud to be associated with is that of the Mirabella V, which has been operating the company’s SXL and COMPAC bearings continually for more than 15 years.

The M5, formerly named Mirabella V, designed by Ron Holland Design, was built by VT Shipbuilding of Woolston, UK in 2003. The 77m flybridge sloop, with a beam of 14.8m (48.5 ft) and a height of 88.5m (290.3 ft) to the top of the carbon mast, remains the largest single-masted sailing vessel ever built.

The single-mast sloop rig was chosen in order to maximise sailing performance in all wind conditions.  M5 was commissioned by US Yachtsman Joe Vittoria and built for luxury yacht charters, offering equivalent facilities to those of a similarly-sized motoryacht. The stability of the sailboat is said to make it more sea-kindly than a motor vessel, which enhances passenger comfort. The high-aspect sail configuration has achieved a good sailing speed potential, and M5 regularly achieves over 19 knots in comfort

Such a tall mast has to be balanced by a heavy deep keel, and maximum draught with the keel in its sailing position is 10.2m (33.5 ft). To allow M5 to enter harbours such as her original home port of Palm Beach, Florida, naval architect John Stott of The Ron Holland Design team specified a lifting keel, weighing 150 tonnes. This was chosen rather than the swing keels normally specified in similar large sailing yacht applications. The keel is raised by powerful hydraulic cylinders, and when fully retracted the draught is reduced to 4m (13.1 ft).

Support pads for the keel had to be capable of carrying high loads and offer good wear resistance, as well as being as quiet as possible in operation. During design team member John Stott’s research into composite bearing materials he discovered Thordon. And working in conjunction with Thordon’s Chief Designer, he specified the company’s SXL pads for the lateral guides, and for the front and back guides, which also function as location ram bearings for the keel locking arrangement, Thordon SXL TRAXL bearings with Thorseals were chosen.

The Thordon inventory is completed by water-lubricated COMPAC propeller shaft bearings for the motor propulsion plant, which were specified by propeller supplier Rolls-Royce Kamewa.

Coinciding with the change of name, the yacht underwent a comprehensive refit at Pendennis Shipyard in Falmouth, UK, in 2013. Work included replacement of MTU main engines with higher-power 1300 bhp Caterpillar units, a new electrical system, redesigned interior, an extended stern and conventional transom to accommodate a carbon cup float plane. A lighter ballast keel arrangement was achieved due to use of lighter carbon fibre standing rigging.

During the DNV 10-year survey which was undertaken at the same time, the Thordon bearings were all found to be in excellent condition, and they remain fully serviceable five years on, with a total of 15 years’ service.

George Morrison, Thordon’s Regional Manager, said: “The SXL lateral lifting keel guides have proven capable of withstanding the high forces and have shown excellent wear resistance, while the SXL TRAXL bearings have proved highly capable of withstanding high operating pressures and able to absorb impact loads. The Thorseal self-lubricating polymer material has been shown to reduce cylinder wear, while noise is minimised when the keel lifting mechanism is in operation. This is because there is no metal-on-metal contact.”

When the vessel was launched in 2003, Thordon’s scope of supply helped towards M5 breaking new technological barriers. It continues to do so, ensuring the sloop was sea-worthy during her 2016/2017 circumnavigation.