will become from 30 March 2023.


Innovative hull design for more fuel-efficient vessels

Ulstein has developed a hull line design for the fore and aft of ships that reduces fuel consumption and emissions while improving operability and comfort.


Windea Jules Verne. Ulstein/Marius Ertesvåg

Most ocean vessels still run on fossil fuels, accounting for over 1 000 million metric tons of global greenhouse gas emissions annually. Despite incentives for more environment-friendly vessels, international shipping emissions have increased by 9.6 per cent from 2012 to 2018. More radical measures must be taken if the industry is to achieve the IMO target of a 50 per cent reduction in annual emissions by 2050.

Moreover, conventional ship design has not focused on environmental concerns, leaving room for improvement in operational efficiency and power consumption.

Hull line designs for smarter, greener ships

Ulstein’s X-BOW® and X-STERN® hull line designs for ocean vessels improve operability and comfort and reduce wave-making resistance, decreasing fuel consumption and emissions.

Launched in 2005, X-BOW is the reverse of a conventional bow, leaning backwards instead of forwards. An X-BOW vessel cleaves the waves, reducing noise and vibration. It can sail faster and consume less fuel in high waves. X-BOW has been used in over 100 vessels of various types, including offshore vessels, walk-to-work service operation vessels (W2W SOVs), and expedition cruise vessels.

Applying these same principles to the ship’s aft, Ulstein created X-STERN in 2015. All X-STERN deliveries so far have been W2W SOVs. SOVs operate stern first 70 per cent of the time when at an offshore wind farm. While a vessel with a traditional transom stern will experience slamming when operating stern first, slamming is avoided with an X-STERN vessel, resulting in better operational flexibility and reduced power consumption. With less pitch motion, personnel can work under safer conditions and get better rest.


The X-BOW expedition cruise vessel National Geographic Endurance, a 2020 delivery from Ulstein.

Ulstein/Marius Ertesvåg

Concrete benefits

Tank tests have shown that the X-BOW feature reduces propulsion power demand by 6 to 8 per cent, resulting in substantial fuel savings. Similarly, it lowers speed losses in waves, resulting in higher average transit speeds and fewer problems meeting sailing schedules.

The X-BOW also increases a vessel’s cargo capacity by 4 to 10 per cent compared with a conventional bow design of equal length, beam and depth, boosting the vessel’s revenue-generating capability.

Both X-BOW and X-STERN vessels improve crew comfort and safety considerably compared with conventional vessels.

Market potential

Companies that rely on ocean vessels are under pressure to reduce their environmental footprint. In addition to the IMO target , the European Parliament has voted for similar reductions.

Moreover, demand for greener vessels for offshore wind farms is expected to increase with the growth of the offshore wind market, which is projected to reach USD 1 trillion by 2040.

Ulstein Group is a large group of shipbuilding, ship design and supporting companies. Founded in 1917, it is one of Norway’s largest shipbuilders.


The X-BOW/X-STERN W2W SOV vessel Acta Centaurus performing services for offshore wind farms.

Flying Focus

Do you want to contact this company?

Register for free and connect

Create an account



Osnesvegen 118, 6065 ULSTEINVIK, Norway

+47 70 00 80 00

At a glance

  • Innovative bow and stern designs

  • Improved fuel efficiency, operability and safety

  • Lower emissions and higher profitability



Advancing the Sustainable Development Goals