Twin City Liner’s new river catamaran has been designed to deal with the challenging operational conditions in which it sails. Its designer Incat Crowther explains
Central Danube Region Marketing & Development’s Twin City Liner received a new river catamaran in Q1 this year.
The low-wash round-bilge catamaran was built by Wight Shipyard Co, the shipyard’s first export order, and designed by Incat Crowther.
The vessel operates a high-speed service from Vienna to Bratislava in one hour and 15 minutes. There are three return trips per day for both commuters and tourists.
Incat Crowther technical manager Dan Mace told PST, “There are many specific considerations to operate on this route at high speed (32 knots cruise,38 knots maximum), meaning the vessel must be safe, highly manoeuvrable and reliable.”
Indeed, the River Danube presents a challenging operating environment with currents up to eight knots and water depths in the main navigation channel as low as 1.5 m.
Explaining how the design dealt with these challenges, Mr Mace said “The design is low draft (only 0.8 m at its deepest part) and hydrodynamically optimised to run at high speed in shallow waters.”
He explained that the hull has minimal wake wash and external noise emissions to minimise disturbances to other river users. As a restricted waterway, it is imperative wave wash is minimised.
“The master has excellent vision from the wheelhouse for navigating through these waters,” Mr Mace said.
Strong currents and debris
The ship’s berthing arrangements are aimed to cope with strong currents. Mr Mace said “The berthing arrangements are well thought-out to facilitate perfect crew ergonomics at the local pontoons, including stainless-steel bollards for mooring with steel wire rope. A specific anchoring system has been provided to assist berthing in very high current conditions. The anchors are stowed flush in custom pockets to prevent external contact.
“Local support to the builder and operator from Incat Crowther Europe was a key factor to successfully incorporate these specific requirements.”
The Danube can contain debris. “This required the hull construction to be very strong to withstand the unlikely occurrence of an impact with logs, while maintaining lightweight techniques to achieve high speed very efficiently. The waterjets were also fitted with inlet grids to protect from ingestion of debris,” Mr Mace explained.
Other innovative features developed to match the conditions the catamaran is sailing in include a retractable mast. Mr Mace said “This is driven by a pneumatic cylinder at the press of a button, which allows the vessel to pass under the lowest bridges on the Danube.”
Furthermore, he said, “excellent passenger vision is provided through forward and side windows, which are fitted with vents to demist and prevent fogging up in the local climate”.
The vessel uses a quad waterjet propulsion system, comprising four Rolls Royce S40-3 waterjets and four Scania DI16 076M 809kW main engines, each producing 809 kW at 2,300 rpm. Power transmission is through ZF3050D diagonal offset gearboxes and Jaure carbon shafting.
In the hulls, the enginerooms are designed to provide crews with maximum access with all machinery arranged in the same space. The enginerooms and the jet rooms are designed so the engines, generators and waterjets can be removed without slipping the vessel or damaging the superstructure or hull.
Boosting energy efficiency
The vessel has been built to be energy efficient and environmentally friendly. Mr Mace singled out that the vessel has a very low fuel burn using the efficient CFD-optimised hulls and lightweight aluminium hull structure.
“The vessel can run at the timetabled cruise speed with the four small engines at very low percentage MCR. In the event of an engine failure, the vessel can still run to the same timetable with only three engines running at less than full power,” Mr Mace said.
The vessel uses low sulphur fuel to reduce SOx emissions, and as a “forward-thinking option”, has room to install exhaust scrubbers during the life of the vessel to reduce NOx emissions.
Mr Mace summed up, “The vessel operational requirements were required to comply with DNV GL class, EU directives and local Austrian regulations. Special attention was required to ensure there was no compromise to either vessel functionality or compliance.”
Moving to the interiors of the ferry, passengers board via midship doors port and starboard and enter a main cabin capable of seating up to 182 passengers and two wheelchairs. A kiosk providing a range of snacks and refreshments is provided aft on the starboard side. On the port side toilets are provided including one for disabled customers.
Above, the upper deck is accessed from a centre staircase in the main cabin and two staircases aft on the open deck. External seating is provided for 29 passengers while aft of the elevated wheelhouse interior seating is available for 35 passengers. Being a commuter ferry as well as a cruise vessel, there will be space for 12 bicycles on the aft deck.
The vessel differs from others in the fleet as the owner required the new catamaran to have higher capacity of 250 passengers and 12 bicycles, with, Mr Mace said, improvements to passenger comfort, higher speed, high reliability, ease of maintenance and free onboard wifi. The new design features a larger Captain’s Lounge on the upper deck with comfortable first-class seating and amenities. Mr Mace said "The new Twin City Liner offers these features while maintaining a very economical operating model."
Wight shipyard is aiming to build on its first European order. Its chief executive Peter Morton told PST “Not many European yards build lightweight high-speed ferries and we are concentrating on fuel savings – that is our USP, that we are really pushing build techniques to cut weight.”
Twin City Liner managing director Dr Gerd Krämer said “With this new vessel, we will cater for projected traffic growth, achieve much better operating economies of scale, greatly reduce our environmental footprint and at the same time be able to offer a comfortable and exciting high-speed transit along this beautiful waterway.”
Builder: Wight Shipyard Co, East Cowes, Isle of Wight, United Kingdom
Designer: Incat Crowther, Sydney, Australia
Length overall: 39.99 m
Length waterline: 38.1 m
Beam: 11.40 m
Load draft: 0.8 m
Main engines: Four Scania DI16 076M marine diesel engines
Gearboxes: Four ZF 3050 D
Propulsion: Four Rolls-Royce Kamewa S40-3 waterjets