The US Navy has awarded Canadian designer Robert Allan a contract to design a new version of the Z-Tech 4500 tug.
Four new vessels, with an option for two more, will be built by Anacortes, Washington-based Dakota Creek Industries. They will join six existing tugs based on the Z-Tech 4500 design, known as the Valiant class, operating in Japanese and Pacific Northwest waters.
While the hull form of the new vessels is largely unchanged, changes have been made to the deckhouse design to bring it in line with EPA Tier IV engine regulations, which require significantly larger exhaust emission systems. Changes will also be made to the fendering system based on feedback from crew on the existing vessels.
The new tugs will measure 27.42 m in length by 11.65 m in breadth and have a maximum draft of 4.88 m. They will be powered by Cat 3512E main engines and Schottel model 340 Z-Drive propulsion units, with a bollard pull of 40 tonnes and a free running speed of 11.7 knots.
There is provision for a crew of six, with the accommodation deckhouse separated from the machinery casing to provide dry access and noise attenuation to the crew quarters. Each tug is fitted with a telescoping gangway, stowed across the aft end of the deckhouse.
Construction of the first vessel in the order is set to begin in early 2019.