Smooth Swath ferries
01 Oct 2004
Two SWATH (Small Waterplane Area Twin Hull) vessels, designed by BMT Nigel Gee and Associates, a subsidiary of British Maritime Technology (BMT), and built in Holland at the Vlissingen yard of the Damen Shipyards Group for the Province of Zeeland, entered
service in April this year.
Designed to offer a smooth ride on the choppy waters of the Western Schelde, Nigel Gee?s SWATH design sets new standards for quietness, safety and comfort. Due to its small waterplane area and submerged torpedo-like hulls, the vessel is able to
minimise the effect of surface wave motions to reduce the risk of passenger seasickness or weather cancellations.
Named Prinses Maxima and Prins Willem-Alexander, the two vessels are operated by BBA Fast Ferries, part of the Connex Group, and ply the four mile route between Breskens and Vlissingen in Holland. They replace a now defunct car ferry service following the recent opening of a new tunnel under the Schelde estuary. Up to 181 passengers (including up to five disabled people), 75 bikes or 50 bikes and 20 mopeds will be transported on each vessel on the 20 minute route across the Western Schelde up to 34 times per day.
Constructed out of high tensile steel and aluminium, the ferries are designed to last for a 30 year lifespan and be able to operate in extreme weather conditions, winds, waves and current. Sea keeping model tank tests were carried out at the MARIN institute. The motion damping systems was provided by Maritime Dynamics, and consists of four active stabilising fins positioned fore and aft on each of the floaters controlled by a motion sensing system. The fins are positioned inboard on the floaters, reducing the likelihood of damage when coming alongside the jetty. Even in a wind force of 8 to 9, it is claimed that the new ferries give a stable and comfortable ride.
Redundant propulsion and control
The propulsion system was designed in close co-operation with the yard, owners and its representatives. The main parameters called for a high degree of reliability and redundancy, low-noise and vibration levels, installation flexibility and a total control with efficient power distribution/management of on-board circuits and/or diesel engine load. Only a diesel electric plant was deemed to be able to meet this brief.
The diesel electric propulsion system is based on two MTU 12V 4000 diesel engines, driving a Bakker Sliedrecht electric propulsion system comprising generators and electric propulsion motors turning two fixed pitch propellers and giving a service speed of 15 knots.
Each of the Bakker systems comprises of two low-speed Indar AC double rotor propulsion motors in one housing, each with a power of 1,320 kW with incorporated thrust bearing. To save weight and space a system was chosen using brushless AC/DC generators. Power is generated by 2 AvK brushless main generators each with a 1,585 kVA output and two auxiliary generators for the boardnet supply. The main propulsion system is powered and controlled by four Bakker tailor-made AC frequency inverters in modular design which, in combination with the system, provide optimum availability. The installations were delivered turnkey, including consoles and cabling.
A Monitoring, Automation and Alarm System was installed to manage the propulsion and power generation system. It will allow a close watch to be kept on the various systems onboard including the propulsion, power generation, motor drives, bilge levels, ballast systems, tanks and ventilation. n
