First Z-Tech 4500 Tug Delivered
In late December 2009, the YT 802 Valiant, first of the new series of Z-Tech 4500 Class tugs for the United States Navy Pilots operating in Puget Sound in Washington State was handed over to her eager Owners. After a shakedown period and crew training she was placed into active service in early February 2010.
This series of new tugs are being built in Tacoma, WA by J. M. Martinac Shipbuilding Ltd., who are a sub-contractor to Pacific Tugboat Services of Long Beach, Calif., the prime contractor for the delivery of the vessels to the Navy. The design was developed by Robert Allan Ltd. of Vancouver, Canada, and was adapted to the Navy Pilots' needs based on the now widely accepted Z-Tech 6000 hull form originally developed by the Designers for the Port of Singapore.
The US Navy tugs will be based in Bremerton and Bangor, Washington, and will perform ship-handling duties for the full range of US Navy surface warships and submarines. For this the tugs are equipped with an extensive array of underwater fendering, as well as the typical resilient style fenders for handling surface ships.
The Z-Tech 4500 class tugs have the following particulars:
Length, o.a. 90 ft
Beam, moulded 38.3 ft
Depth, moulded 16.5 ft
Load draft, max. 16 ft
The propulsion machinery comprises a pair of CAT 3512C, main engines, each rated 1,350 kW (1,810 bhp) at 1,600 rpm, each driving a Schottel Model SRP 1012 steering/propulsion Z-Drive units, with 2,100 mm diameter fixed pitch propellers. This combination delivered in excess of the predicted performance, providing 42 tonnes (92,500 lbs) Bollard Pull ahead, 45 tonnes (99,205 lbs.) astern, and a free-running speed of 12.4 knots on trials.
Electrical power on the tugs is delivered by a pair of R.A. Mitchell Co. diesel gen-sets with a John Deere 6068SFM75 prime mover, each rated 130 ekW at 1,800 rpm.
Deck machinery fitted includes a ship-handling hawser winch forward; JonRie Series 210 Assist winch, fitted with 180 metres 600 ft. of 175 mm line. This winch has a brake capacity of 136 tonnes (300,000 lbs), and a line pull/speed rating of nine tonnes (20,000 lbs) at 53 m/min (175 FPM).
The fendering is all rated "non-marking" for dealing with the grey hulls of warships, and was supplied by Shibata through Schuyler Fenders. The tugs are configured as "day-boats" but also provide accommodation for a crew of up to six persons. One of the unique features of the layout is the complete separation of the accommodation deckhouse from the machinery casing, a configuration designed to both provide a reasonably dry access to the accommodation spaces in the notoriously damp north-west climate, as well as to provide a significant degree of noise attenuation in the crew spaces.
