The only specialised marine publication in Oceania that focuses on the maritime industry, from super yachts to small craft to large commercial ships, including coastal shipping, tugs, tow boats, barges, ferries, tourist, sport-fishing craft
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The heads Galley and crew's mess are of mild steel running in oil-lubricated bronze bushes driving twin 1494mm-diameter four-bladed manganese bronze propellers with a blade skew of 20 degrees. Engine and gearbox control is by a three-station ZF controller with one MC2000 and two 760 control heads. The propulsion train is remarkably free of vibration both ahead and astern and at all speed ranges, giving a no-load service speed of 10.5 knots. For crew comfort the wheelhouse and accommodation floors are of a floating type. The main engines are mounted on LO-REZ BR4LS spring- type vibration isolators. They have a high load capacity, incorporating safe limits stops and neoprene dampers to prevent excessive vertical or rocking motion of isolated machinery. The exhaust piping and mufflers are also resiliently mounted, all resulting in very good noise control. Electrical power is generated by two Cummins generator sets. One genset, a 6B-CP80DM/5, rated 80kW 380 volts 50Hz keel- cooled and with electric start is for general on-board power, while the other, larger genset, a keel-cooled and air-started 6C-CP136DM/5, rated 136kW 380 volts 50Hz supplies the power to drive the towing winch. Because of her intended use in the sub-tropical waters of Australia's northern and eastern coast, airconditioning of the wheelhouse and accommodation areas was essential. Ocean Breeze uses a chilled water system, with keel-cooled chiller units in the engineroom, along with stainless steel air handlers in the living areas and wheelhouse. Although her propulsion is by twin screws through conventional drives, the PT May stands out from her predecessors of similar size with a number of clever design features. They include individual steerable quartz nozzles, making her perform more like a Z-drive ship-handling tractor tug than a traditional working towboat. "By utilising independent steerable nozzles, the tug has exceptional manoeuverability," Lance said during her sea trials. "This includes being able to move sideways, which is a step ahead from most standard twin-screw tugs. The nozzles are top-hung and have 35 degrees of steerage to port and starboard, taking a total of 12 seconds lock-to- lock. The steering gear is manufactured by ShipCo with TQM autopilot and electronic steering levers. Three steering stations are provided: one in the wheelhouse, one on the flybridge and one at the winch station. The amount of grunt this little workhorse delivers from 900kW is most impressive. During trials on the bollard pull she comfortably delivered 17 tonnes pull ahead, with a couple of sneaky tonnes still up her sleeve if you want to get serious with the hammer down in an emergency. MARINE ELECTRONICS SPECIALISTS Proud suppliers and installers of electronics equipment to the PT May • Design and specifi cation • Supply of all leading brands • Installation – commercial and recreational vessels • Service and repairs 225 Lower Port Road, Whangarei Ph: (09) 438 4644 Email: info@steelcom.co.nz 8 Professional Skipper September/October 2011 The impressive bit was the 14 tonnes she pulled with relative ease astern, once again reinforcing the value of the nozzles and directional thrust. "With 1200hp giving a bollard pull of 17 tonnes ahead and 14 tonnes astern, this makes for a very powerful and lively vessel that can be used to best advantage with fingertip control," said Lance. Not only is she very nimble in confined spaces when traveling, but also the steering is by one nozzle only and she remains very positive to the helm. The PT May's fendering system was also designed and made in-house by ShipCo, with a 1.1m-wide sweep of double-loop tyre fendering 500mm deep around the bow and extending to the for'ard shoulders. This fendering has very good energy- absorbing characteristics together with good holding ability. Aft of this is a section of aircraft tyres 1m in diameter and 500mm wide, secured to the hull without chains by way of steel rims. Aft of this again are two rows of variegated single-cut tyre fenders suitable for the hard knocks that inevitably happen. The towing winch is electrically driven using a 37kW electric motor via an ABB variable-speed drive, also designed and built by ShipCo. The company is building an international reputation for designing and constructing tough tow winches. The drum diameter is 610mm, and the capacity is 550m of 32mm diameter wire in six layers. A level winding system has been installed to ensure the drum packs tight with no riding turns that may weaken the wire. Controlled emergency quick release is provided at speeds of 48m to 88m per minute, although to meet Australian rules, a 35 tonne SWL rotating-type hook with hydraulic quick release has been installed. Clearly, the Australian authorities have not come up to speed with the safety value of towing off a modern tow winch incorporating the new controlled release system. Even in an emergency it still provides the ability to regain control without dumping the tow. VIP.S83