With the exceptional facilities available to them at the Portchester yard the company have focussed considerable effort on extending their steel product range to cover both the multipurpose pontoon work vessel and conventional tug/workboats. This latest vessel follows hard on the heels of the smaller but similar 15m tug/workboat Farset of Belfast now working successfully in Northern Ireland ( Maritime Journal July 2003).

Prince Rock is the first vessel to be built to the new VT Halmatic WB18 design. The tug is intended for towage, mooring, and general harbour duties in the port of Plymouth, replacing the smaller existing tug/workboat Plym Echo . A larger, more powerful tug has been made necessary by the increasing size of ships using the privately owned Victoria and Cattedown Wharves, as clients seek to maximise their operational efficiency.

Prince Rock will be able to meet those requirements, and in addition will provide escort duties for product tankers shipping over 1 million tonnes of refinde oil products through the port each year. The increased bollard pull and the compact size make the new tug ideally suited to local conditions.

Prince Rock has a welded steel, double chine, hull with an overall length of 18.87m, a breadth of 6.56m and an approximate draft of 2.50m in the full load condition.

Scantlings and construction conform generally with Lloyds Register of Shipping Rules for the Classification of 'Special Service Craft' and the vessel complies with the requirements of the MCA Workboat Code Category 2 - allowing operation up to 60 miles from a safe haven. The vessel displaces approximately 100 tonnes in the full load condition. Dedicated internal tanks are capable of accommodating 20,000 litres of diesel fuel and 1,100 litres of fresh water.

Construction was carried out using pre-cut steel components produced in Holland by Centraalstaal. The hull incorporates a semi-raised foredeck and the underwater hull form affords an uninterrupted water flow to the twin-screw propulsion system. Bottom, side and transom plating is 10mm thick and a 20mm sheerstrake is located at gunwale level. The superstructure is an all steel structure, arranged on a single deck with a small, unprotected, flying bridge. Moulded rubber bow fendering, supplied by Fendercare, has a large surface area and a central knee extending down to the waterline. Additional fendering, in the form of neatly secured vehicle tyres, is provided around the sides and aft quarters.

Two fixed nozzles from Kort Propulsion Ltd form an integral part of the stern structure and were supplied complete with mounting structures and pre-aligned "Y" brackets. Kort also supplied the stern gear and twin Kaplan type, bronze, four blade propellers. Two Cummins KTA 19M4, 6 cylinder, turbo-charged and after cooled, main engines, are each rated at 700bhp (522bkW) at 2100 rev/min MCR. Power is transmitted to the propellers via Twin Disc MG5170-DC gearboxes with a reduction ratio of 6.53:1. Main engine cooling is effected by a Kort 'Gridcooler' keel-cooling system and a dry exhaust system incorporates Halyard silencers, mounted in the engineroom, and outlets above the wheelhouse roof.

A pair of, semi-balanced, plate rudders are actuated by a Kobelt power-assisted steering system, with a single central wheel in the wheelhouse and a 'jog-lever' on the flying bridge console.

Helm indicators are fitted at both control positions. Hydraulic power for the steering gear is provided by a pump driven by the port main engine. Final performance trials had not been completed at the time of writing but a bollard pull of over 18 tonnes is anticipated and a free running speed of 10 knots.

Electrical power aboard Prince Rock is supplied by a single Onan model 22.5 MDKAF diesel driven generator set with a continuous rating of 22.5kW at 1500rev/min. The generator is located in the after end of the engine room and enclosed in an acoustic cabinet. Controls and instrumentation for the set are situated in the wheelhouse.

The tug is fitted with a fire fighting system comprising a single Hydrodiesel EL 367 water/foam fire monitor located on the after end of the wheelhouse roof. Water is supplied to the monitor at 100m 3per hour by a Cleghorn Waring fire pump driven from the forward end of the starboard main engine via a declutchable belt drive.

Prince Rock has a large clear working deck aft, with a Britannia quick release towing hook mounted on a set of 'H' bitts situated immediately behind the superstructure. The hook can be released manually from within the wheelhouse and has a safe working load of 20 tonnes.

Located neatly beneath the towing bitts is a hydraulically operated Spencer Carter bridle (gob) winch with a line pull of 3 tonnes (on the first layer) and a maximum brake load of 6 tonnes. The latter is used in conjunction with a suitably positioned gob eye on the after deck.

Hydraulic power for the winch is supplied by a pump mounted on the starboard main engine.

Other deck equipment includes a hand-operated windlass on the foredeck to handle the single 40kg high holding power anchor and its 80m of short link chain, the usual mooring posts and life saving equipment. A chain locker located in the forepeak is fitted with a GRP drainage bow to prevent contact between the chain and hull structure.

Lifesaving equipment includes a 'Jasons Cradle' man-overboard recovery system, a 'Halmatic Matesaver' recovery pole and the usual mandatory items.

A spacious wheelhouse has a single control position at the forward end with good all round vision for the tug master through a total of 12 windows.

The forward windows are angled steeply outwards, giving the vessel a distinctive 'style'. An overhead window is provided on both sides at the forward end of the roof. Controls and instrumentation have been kept simple with the majority of engine and propulsion system instruments located on a central console at the control position.

Engine and gearbox controls are combined in a single 'twin-lever' installation.

A nautical and communications equipment package includes a Simrad RFC35 fluxgate compass complete with an IS15 display and a Simrad CA40 navigational system. The later comprises a single10 inch TFT display with combined inputs from the radar, DGPS, chart-plotter and echosounder.

A Simrad RD68 Marine VHF radio with DSC is installed at the control position, with a repeater on the flying bridge.

A Raymarine (RAY 430) talkback system incorporates two external speakers, one forward and one aft.

Accommodation below decks is fitted out to a high standard with two single cabins, a galley, sanitary spaces for WC and shower, and useful storage areas. The accommodation and wheelhouse are well insulated with mineral wool slabs or spray foam insulation and lined using materials and components from BD Systems. Alto Mondopave flooring is used in the wheelhouse and access to the accommodation is by means of an internal companionway at the forward port side. The engineroom can also be accessed internally from the accommodation via a watertight door.