Quartet of Robert Allan Ltd.’s new RAstar 2700 Class escort tugs for Rimorchiatori Napoli of Naples

October 30, 2007

Further establishing the popularity of their tug designs in Italian waters, Robert Allan Ltd. is pleased to announce that their Client, Rimorchiatori Napoli of Naples have recently placed an order with Cantieri San Marco of La Spezia, Italy for four new RAstar 2700 Class ASD Escort tugs. These powerful, compact tugs are the first of a new class of ship-handling/escort tugs developed by Robert Allan Ltd., Naval Architects of Vancouver, B.C. for the unique demands of this Client.

As in many other compact tugs, the major design challenge here was to put all the Owner’s operational requirements, and in particular a very high specification for indirect towing performance, together with a high-standard of accommodation for six crew into a compact and attractive package which offered good ship-handling and escort towing capabilities. Under the direction of Project Manager, Mike Fitzpatrick, these objectives have been well-fulfilled.

These new tugs will be used in the coastal ports of southern Italy served by the Owners. They are to be built to RINA Class notation “(C), Coastal Area Re, Towing, Aut UMS, Fire-Fighting Ship 1 with Water Spray, Salvage, TPF”, reflecting the multiplicity of its duties.

The demands for a very high indirect performance as well as a reasonably high speed in such a short vessel led the Owner to approve a recommended set of model-scale tests, which were performed at Vienna Model Basin, under the guidance of Offshore Research Ltd. of Vancouver acting on behalf of Robert Allan Ltd. These tests included free-running speeds ahead and astern, Bollard Pull verification, and the complete suite of indirect steering and braking tests. It is a very welcome addition to the lexicon of tug performance data when a unique new design such as this can be subjected to this scope of behaviour verification before the construction is committed. As a RAstar Series design, the hull form incorporates the unique sponsoned shape developed by Robert Allan Ltd. to maximize indirect steering forces as well as to provide maximum sea-keeping capability. This hull form has now been well-proven in both model and full scale tests on a wide range of tug sizes to provide far superior performance than a conventional vertical-sided design. New designs which purport to provide a high degree of offshore performance, but which are simply wider versions of what has been the previous standard, have simply missed the point. The RAstar designs can demonstrate roll motions and roll accelerations which are less than one-half off the typical tug design.

Particulars of the RAstar 2700 Class tugs are as follows:

Propulsion comprises a pair of Wartsila 6L26 A2 diesel engines, each rated 2,040 kW at 1,000 rpm, and each driving a Lips model CS250-S/WN-K Z-drive with a 2,600 mm diameter controllable pitch propeller through a straight line hollow steel shafting system. This combination will deliver a minimum Bollard Pull of 70 tonnes ahead, 67 tonnes astern, and provide a free running speed in excess of 13 knots, the latter amply demonstrated in the model tests, a significant achievement for a tug of what can only be described as “chunky” proportions!

The RAstar 2700 Class tugs are outfitted for a crew of six persons, in very comfortable, modern and well-equipped quarters, as illustrated in the accompanying General Arrangement drawing. The Master and Chief Engineer each have private en-suite lavatory facilities. A high standard of noise abatement treatments are specified throughout, including resilient mounting of the main engines.

The main hawser winch is a double drum, hydraulic winch supplied by Romagnoli, with capacity for 2 x 200 metres of high-strength synthetic towline. Aft towing will be provided by a radial-arm tow-hook and a cruciform towbitt which incorporates a hydraulic capstan. The heavy-duty bow-staple is the first of a unique new T-RAx design developed by Robert Allan Ltd. to provide equal indirect line forces in both port and starboard directions when working from either double or split type winch drums.

Electrical power is provided by a pair of diesel gen-sets, each rated 180 kW, and a small harbour gen-set is provided for dockside operations to minimize both noise and emissions.

The tugs have a full Fi-Fi 1 rating in accordance with Class notation requirements. The fire pumps are driven from the front end of the main engines through a Kumera gearbox, which also drives the main hydraulic pumps, powering the winch.

Construction of the new RAstar 2700 Class tugs has just commenced, with delivery of the first vessel anticipated late in 2008.

For more information on any of the design services offered by Robert Allan Ltd., please contact us.