The new 130-tonne bulbous bow, which is the protruding part of the ship just below the waterline, is much slimmer than its predecessor – the bulbous bulb – and makes the vessel less resistant to the movements of the water and thereby more efficient at sea.
Geir Fagerheim, Vice President of Fleet Management at WWL, says the new bulb is also a lot more flexible than the previous model.
“The old bulb was optimized for one specific draft,” he says. “The draft itself and the cargo onboard are constantly changing, which means it’s important to have a bulb that works well across a wide range of drafts.”
The project was initiated when operations data from the company’s performance-monitoring and analysis tool showed that the Mark IV vessels were operating on a lighter draft and lower speed than they were designed for. Designed in the late 1990s, the vessels were originally designed to carry heavy cargo such as timber products and paper pulp, cargo that is less frequent today. The new bulb is better tuned to the current cargo mix and operating speeds.
Daewoo Shipbuilding & Marine Engineering, which designed the bulb, developed 30 different design variants before reaching a conclusion together with Wilh Wilhelmsen's project management team. The selected bulb was thoroughly model-tested to verify the performance. The refitting was carried out by the IMC-Yongye repair yard in Zhoushan China within the time frame of the regular dry-docking schedule. The yard constructed a custom-made railway carriage to ensure safe movement and precise adjustment to the existing hull of the vessel.
The new bulb has shown promising performance results so far. “When comparing the vessels before and after the conversion, we clearly see an improvement in operational efficiency,” Fagerheim says. “The modification has been very successful in adapting to the current service profile of the vessels.”
Fagerheim says WWL is constantly working to improve the performance of its vessels, with both the customers and the environment in mind.
“We have quite ambitious CO2-emission targets,” he says. “We’re preparing for a future with less carbon footprint, and this initiative is one step out of many that we’re taking to move us in the right direction.”