Thruster upgrade improves Croatian ferry’s seakeeping

The successful modernisation of the propulsion system demonstrates that in some cases existing vessels can meet the challenges posed by new operational profiles without the expense of new thrusters. 

Earlier this year, the Croatian ferry Krk operated by Croatia’s state-owned Jadrolinija shipping company was retrofitted to cater for a new route with stronger winds and currents. The shipping company opted to replace the Krk’s existing thrusters’ open propellers with new optimised propellers and VarioDuct SDV45 nozzles supplied by SCHOTTEL. The thruster upgrade was scheduled to fit around the vessel’s planned maintenance cycle.

The entire retrofit process took place during the annual lay days between seasons. The thrusters were dismounted and reinstalled in Croatia by SCHOTTEL partner Alfa Marine. The conversion work on the thrusters themselves was carried out at the SCHOTTEL service workshop in Spay, Germany. By overhauling the existing thrusters, including the transportation costs to Germany, instead of purchasing new ones, the project was delivered with a cost saving of around 50 percent. 

The results of the Krk’s modernisation exceed all of Jadrolinija’s expectations. The ferry is responding more accurately to steering manoeuvres and the autopilot makes fewer corrections thanks to the much-increased course-keeping stability. Hydrodynamical analyses from SCHOTTEL predicted the now realized top speed of 13 knots and various other advantages gained from using the SDV45 nozzle. In addition to the vessel’s increased course-keeping stability, the new nozzles also ensure smoother operation of the thrusters. Due to the much-improved thrust and performance values of the Krk, Jadrolinija is now able to tighten the ferry’s schedule.