Feature 3 | RO-RO FERRY REPORT Skarven breaks the Baltic ice
Tere is little full scale data of dedicated ice trials for ferries with azimuth propulsion. To address this, a Joint Industry Project (JIP) involving Ålands Landskapsregering, ILS Oy, Rolls Royce, BLRT Group and Lloyd’s Register (LR) studied the icebreaking Baltic ferry, Skarven. Tis is an extract of a LR’s paper delivered by senior project engineer Robert Bridges at the class society’s recent Technology Days conference in February.
S
hipping activity in cold climates has increased significantly in recent years and this has been coupled with new
operational performance of ships in ice, which may be attributed to improved ship design and technology. Te ship-ice interaction for these vessels is
a significant component of ship performance and capability in ice. Te project represents the first full scale measurements in ice on a ship fitted with controllable pitch azimuth thrusters with a complete measurement system for the hull structure, engineering systems and underwater observations. Tis valuable ice load data can be used in a multitude of ice-related projects, such as ice management icebreakers using azimuth thrusters or podded propulsion, large stern first ice class tankers, hull structural fatigue in ice for LNG and tankers, as well as ice class rule development for typical merchant vessels operating in the Baltic. Ålands Landskapsregering placed an order for the new construction of a double-
TECHNICAL PARTICULARS Skarven
Length oa ............................................65.4m Length pp ..........................................58.67m Breadth ................................................13.0m Depth .....................................................5.9m Draught ..................................................4.1m DWT ...............................................350tonnes Main propulsion .........2 x 1,800 kW Wartsila “9L20” diesels
Azimuth thrusters ..................2 x Rolls-Royce “Aquamaster US285”
Speed ........................................... 13.5knots Crew............................................................. 7 Passengers ............................................... 250 Cars ............................................................ 60
The Naval Architect April 2011
Figure 3: Von Mises stress distribution of finite element model of the aft end of Skarven with ice load applied along the waterline.
Figure 7: Bending failure of ice in the forward region of the ship
location, the Åland Islands have become the shipping hub of the Baltic Sea. Te design had to transport passengers,
cars and heavy goods traffic within the archipelago, on the same ferry year round, regardless of ice. The design therefore incorporates properties both for open water and ice. The ferry is assigned the Lloyd’s Register ice class notation 1A FS. Since the ferry is fitted with bow and
Figure 5: Aft end hull gauge arrangement.
ended icebreaking car/day passenger ferry, Skarven, which was designed by Finnish consultants, ILS Oy, and built in Lithuania at the Western Shipyard in Klaipeda, part of the BLRT Group.
The ship Te double-ended ferry operates year round in the Baltic Sea between Degerby on the island of Föglö and Svinö on the main island of Åland. Te Åland Islands are an archipelago of more than 6500 islands in the northern Baltic Sea and they form an autonomous region of Finland. Due to their
stern thrusters, measurement equipment was installed to gain data on the ship’s performance during the ice trials. The following provides a brief summary of the measurement programme. General measurements included
equipment to record weather conditions, vessel speed and heading during each trial run. Te acquisition of this data was obtained through equipment installed on the bridge. Furthermore, periodic sea temperature, ice thickness, ice type, and ice salinity were measured by ILS. Measurements were made on each of the
azimuth propulsion units when undertaking the trial runs. Measurements included engine rotational speeds, shaſt torques measured on the intermediate shaſt, azimuthing angles
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