Anyone in the towage industry who doubted the likely success of the unique triple unit ‘ Rotor Tug’ design when it was first introduced by Ton Kooren of Kotug in 1999, must surely be having second thoughts.
Within that first year a fleet of four highly versatile Rotor Tugs entered service in the Netherlands and Germany
This quartet of identical 31.63m, extremely well equipped vessels, had engines producing 6,300 bhp and a bollard pull of 78 tons. In addition to carrying out routine ship handling duties at their home ports, tugs from this small group have been involved in many high profile towage operations around the coast of Europe and offshore.
Although the towage industry greeted this innovative triple unit tractor design with great interest, orders from other owners were slow to materialise, but recent completions and orders confirm that the Rotor Tug has come of age. Four additional tugs have now been added the Kotug fleet, orders for eight more vessels have been placed by other operators and prospects for more orders and future development of the triple unit tractor concept are very good.
KST BV, formerly trading as Kooren Shipbuilding and Trading, recently announced contracts with Unterweser Reederei GmbH of Bremen, Germany for the construction of a further pair of new Rotor tugs of the RT80-28 design. The vessels, known originally as the RT80-r, are expected to have a bollard pull in excess of 83 tons. With an overall length of only 28m, they will be powered by three ABC 8DZC engines, rated at 1,760 kW each, driving a Schottel SRP 1215CP fully azimuthing propulsion unit. The tugs will also be equipped with FiFi 1, classed by Germanischer Lloyds, and operate under the German flag. In common with other recent orders and deliveries, both tugs will be constructed at the ASL Shipyard Pte Ltd in Singapore with delivery scheduled for 2010. This order follows a similar contract for two tugs placed earlier in the year with deliveries due between December 2008 and February 2009.
KST is currently finishing the construction of three similar vessels ordered by Bugsier Reederei GmbH of Hamburg, Germany and one similar vessel for an investment company in Southern Europe. Once these vessels have been completed in the last quarter of this year and the first of 2008, ASL will begin construction of the first two Rotor Tugs for Unterweser Reederei.
Associate company Kotug recently christened the final two of a quartet of Rotor Tugs completed by ASL and now in use in Europe. Named RT 'Antonie' and RT 'Zoe', the tugs are now on station in Bremerhaven and Hamburg respectively, replacing earlier less powerful vessels. Identical tugs of the RT 60 type, they have main engines generating a total of 5,465 bhp and a bollard pull of 68/70 tons.
The company is also close to signing shipbuilding contracts for the construction of four more Rotor Tugs to a design designated the RT80-32. This is a 32m vessel with a bollard pull of 80 tons minimum.
A promising development is the new RT 110E design, developed by KST in conjunction with Canadian naval architect Robert Allan of Robert Allan Ltd. Although the performance of the Rotor Tug concept is now well proven, a decision was made by KST to develop a new generation, high performance, Rotor Tug with a bollard pull of over 100 tons and enhanced escort and offshore capability. The aim is to achieve that added performance without sacrificing any of the handling characteristics of the original Rotor Tug concept. Among the objectives to be addressed were the capability to apply significant forces in extreme situations when escorting, towing, shiphandling or salvage and reduce the cost of tug services by using fewer tugs for the same operation, resulting in less crew and maintenance, etc. The decision to ask Robert Allan to participate in the new design process was made on the grounds of his impressive track record in developing powerful terminal tugs and his innovative approach to hull design in that field.
The resulting design specified a triple unit tractor of 37m in length overall, with a maximum breadth of 14m and a design draft of 4m. Three Schottel SRP 1515 CP propulsion units were specified, powered by Caterpillar 3516B main engines of 2,000 kW (2,717 bhp) each. In order to enable the tug to produce the required steering forces on the indirect towing, escort mode of operation, a sizable skeg is fitted aft of the single propulsion unit beneath the stern. The skeg incorporates a large retractable panel intended to be used during indirect towing operations but retracted when not required to ensure that the unique side stepping ability of the Rotor Tug is not impeded.
Comprehensive computer modelling and an extensive tank testing programme was conducted by Force Technology in Copenhagen. The results confirmed that the final design will achieve a free running speed of 14 knots, the ability to side step at up to 6 knots, generate steering forces of 165 tons (while meeting the DNV escort notation criteria) and produce good seakeeping characteristics going ahead or astern. The new RT 110E design will also include a large working deck aft capable of transporting 100 tons of deck cargo, a hold to carry 500m of protective boom on two reels, and crew accommodation to the highest standards. At the time of writing no firm orders had been placed but KST are adamant that negotiations are taking place.
