Clipper Bulb Modification Saves Fuel

Clipper has in-house technical management of a large part of their vessels. They believe that improved performance can be achieved through innovative thinking, enabling a dynamic fleet that lives up to its full potential.

The company’s Performance Management team is continuously working on fuel efficiency and energy consumption optimization.

One such initiative was the bulbous bow and rudder bulb modifications made on a G-type 9,100 dwt multipurpose carrier, Clipper Galaxy.

The bulbous bow (bulb) is a very important part of the hull as it can potentially reduce the hull resistance considerably, or affect the resistance in a negative way. Designing the perfect bulb is delicate and the efficiency depends on the speed and loading/draught of the vessel.

In the past a bulb was usually designed and optimized to full speed and close to full load condition. However, most vessels are operated at eco-speed in part load conditions. In particular multipurpose vessels are seldom operated in full load conditions.

The bulb of Clipper Galaxy was modified during dry-dock at Lixin Shipyard in Shanghai in August 2013. The existing bulb was cut off and a new bulb with a different size and shape was fitted instead. At the same time we also designed and fitted a rudder bulb improving propeller efficiency by 2-3%.

The saving of the bulb modification alone would be above 10%, but trim optimization outweighs some of the disadvantages of the old bulb. The actual saving will also vary depending on loading and speed conditions. However, looking at the consumption before and after the modifications, as well as the current loading and speed patterns, the overall saving is around impressive 8.5% – including the rudder bulb effect.

Clipper, January 30, 2014