The first US-built Rotortug, carrying the name ‘Trident’ and first in a series of three has been delivered to Seabulk Towing of Ft Lauderdale, Florida.

The story of the Rotortug has been an interesting one and worth a brief look at including some significant dates in the history of a tug that gains its uniqueness from the propulsion arrangement of two azimuthing thrusters mounted forward and one aft in a triangular configuration.

The design dates back to 1998 with deliveries of the first four. RT Pioneer, RT Innovation, RT Spirit and RT Magic were constructed in Spain (the last completed at Padmos shipyard in the Netherlands) and were RT 75-32 models denoting a length of 32m and bollard pull of 75 tonnes. It was a further seven years before the next deliveries after which production gradually increased as the portfolio of various lengths and bollard pulls expanded meeting specific requirements and potential markets.

A wide range of models are available ranging from the ART 10-15 which as well as being a trainer adapted to simulate the behaviour of full-sized Rotortugs, is offered as a tug in its own right, albeit with a length of 15m and bollard pull of 10 tons. At the top end of the range is the ART 100-42 marketed as an infield support vessel, most recent examples of which are the three for KT Marine Services for operation at Shell’s Prelude floating LNG facility off northwest Australia (see MJ January 2017).

Rotortug BV now has an exclusive design contract with Robert Allan Ltd allowing the former to concentrate on development and marketing of the Rotortug. Other notable deliveries include the Damen-built RT Evolution and RT Innovation which employ hybrid technology (following earlier retrofitting of the RT 80-32 RT Adriaan with hybrid propulsion). An impending delivery promising to be an important milestone for the Rotortug project is SD Tempest for UK-based Serco Marine Services especially adapted to support the Royal Navy’s two new aircraft carriers at Portsmouth naval base.

Returning to the ART 80-98US Trident, construction of this first US-built Rotortug was entrusted to Master Boat Builders of Bayou La Batre, Alabama with Robert Allan Ltd stating: "These tugs will truly raise the bar for ship-handling operations in US waters."

Main characteristics (quoted in imperial measures) are: length overall 98’-6”, beam moulded overall 43’-6”, depth moulded 15’-7”, draught maximum 18’-9”. Tank capacities include: fuel oil 52,000 US gal, potable water 5,000 US gal and foam 4,200 US gal.

Main machinery comprises three Caterpillar 3512C diesels each rated 1,911bhp at 1,600rpm driving Schottel SRP 1012 fixed-pitch Z-drive units. Auxiliary machinery includes two diesel gensets each rated at 150ekW.

Deck machinery includes a Jonrie Series 230 ship-assist hawser winch forward and Jonrie Series 500 combination towing/hawser winch aft allowing escort operations over both bow and stern.

High standard accommodation is provided for a crew of six with the master’s and chief engineer’s cabins located in the deckhouse and two double-berth crew cabins on the lower accommodation deck. The deckhouse is also home to a mess/lounge area and fully-equipped galley.

A row of cylindrical shiphandling fenders are fitted forward at main deck level with ‘W’ block fenders arranged below. Two rows of hollow ‘D’ fender provide protection at main deck and forecastle level with similar fendering at the stern and ‘W’ block fenders beneath. A combination of hollow ‘D’ fenders are fitted around the stern and below the waterline for submarine-handling operations.

Master Boat Builders has been in business since 1979, specialising in work boats including for the offshore oil and gas industry and fishing vessels. Seabulk Towing is a subsidiary of Seacor Holdings Inc and is involved in ship-assist operations along the Gulf coast and south eastern seaboard port system from Cape Canaveral Florida to Port Arthur Texas. Seacor itself controls a diverse range of offshore and general shipping service interests including, well-known in European waters, Windcat Workboats.

By Peter Barker