The use of very small, powerful, azimuthing stern drive (ASD) tugs in the southern hemisphere continues to spread. One of the latest and most impressive vessels in this category has now entered service with MacKenzie''s Tug Services in Port of Esperance, Western Australia.
Named Cape Pasley, the new tug with it's greater bollard pull was required to meet the needs of larger ships of up to 150,000dwt Panamax due to use the port. The company were keen to meet this demand without the need to build a much larger vessel and looked to the Canadian naval architect AG Mcllwain and their Tiger Sun design for a remedy.
Built by Structural Marine of Henderson, the tug's vital statistics are stunning with an overall length of 21.7m, a beam of 10.7m and draft of 4.6m.
The sturdy welded steel hull is shaped like a shallow disk and has no fixed skegs.
Substantial bulwarks and rubbing bands are heavily fendered to enable Cape Pasley to perform well in the push-pull mode, without fear of damage.
Shiphandling is carried out over the bow from a single drum towing winch supplied by the builders. The tug has internal tanks for 40,000 litres of fuel and 2,000 litres of fresh water.
Cape Pasley is powered by two Deutz T8D620 V-16 diesels, each with a continuous maximum rating of 1,864 kW (2533bhp) at 1800rev/min. Power is transmitted to a pair of Rolls Royce Ulstein 1650H fully azimuthing propulsion units.
The units incorporate an integral slipping clutch, automatically giving precise control of propeller speed at low revolutions, and twin steering pumps to give optimum steering response. This propulsion system enables the compact little tug to produce a bollard pull of 66.2 tonnes and maximum free running speed of 12.7 knots at MCR. A speed of 7.8 knots is given as the maximum speed moving sideways and a rate of turn through 360º in seven seconds.
The fully air-conditioned wheelhouse is a composite structure of aluminium and steel, flexibly mounted on a relatively simple deckhouse. Vision from the wheelhouse is reported to be excellent and the entire vessel virtually free from vibration.
Cape Pasley is designed to be operated by two men but Mackenzie's currently work the vessel with a crew of three.
