The ULSTEIN X-BOW®, the inverted bow concept, redefined marine engineering. The bow concept was launched in 2005, together with the first shipbuilding contract, and gained immediate interest from shipowners. The X-BOW hull line design has been tried in all weather conditions.

The X-BOW (and later, the X-STERN) is one of ULSTEIN's main contributions to maritime history. X-BOW vessels are being built at shipyards on many continents. Currently, more than 100 vessels with this bow concept are being constructed or in operational work around the world.

The X-BOW introduces the gentle displacer; a tapered fore ship shape with a different volume distribution as well as sectional angles, resulting in a wave piercing effect at small wave heights, and also reduces pitching and bow impact loads in bigger seas. When comparing fore ship volumes with more conventional, bulbous bow shapes, the X-BOW has more displacement volume starting from the waterline.

The experience is quite amazing. I cannot imagine myself ever travelling with a conventional bow vessel again in winter time. Captain of the AHTS 'Bourbon Orca​'

While a traditional bow vessel rises on the waves and then drops violently onto the surface of the water, an X-BOW vessel, less subject to the vertical motions induced by the waves, continues on course more smoothly, while maintaining its speed. And because it uses less fuel to get through the waves, it also helps to save energy

Key benefits

Improved power efficiency

The bow shape reduces pitch/heave accelerations and speed loss in waves, which renders higher transit speed or reduced power consumption possible. This improves fuel efficiency and reduces emissions to air.

Increased comfort

The bow shape eliminates slamming and bow impact, thereby reducing noise and vibration. This leads to a more comfortable workplace and more effective rest time for the crew.

Safety & less damage

The bow shape gives a soft entry in waves, thus reducing spray and icing. The likelihood of extreme weather damage to the forebody is reduced.

Accepts anything the sea throws at it

The X-BOW is in its element in the more harsh environments, but is not any worse in lower weather conditions. The benefit is the security for the crew and ship that the bow can accept anything the sea throws at it. This becomes stories, remembered and told by the crew on these vessels, and this is where the X-BOW design excels. 

From a HSE point of view, reduced accelerations and slamming fores mean less wear and tear on people and equipment. The X-BOW has very little spray, so the deck remains dry behind. It takes very little water on deck to start being a hazard, or simply a nuisance.

X-BOW - how it started

​When times are tough, it is still possible to nurture and grow good ideas. That’s the story behind the ULSTEIN X-BOW® hull line design, which upon its introduction in 2005 literally turned the image of the ship’s bow upside down.

The development of the X-BOW

Shipbuilders with a sense of the aesthetic

While some have compared them to viking ships, others say the X-BOW vessels resemble space ships, taking the crew out into the space rather than over the seven seas. The first X-BOW vessel was given the name 'Orca' after a name competition at the shipowner's office, a tribute to the vessel's organic shape.

Organic lines

Simplified shipbuilding

When presenting the X-BOW® design in 2005, the designers claimed that these vessels would be easier and less resource intensive to build. In 2006, this statement was tested in reality through the construction of an X-BOW® hull at Maritim Ltd: "It was easier to build the backward-sloping bow than a conventional bow."

Simplified shipbuilding


When new hull designs are undergoing tank tests, a scale model must endure various waves and wave length conditions. We have performed model tests and comparative model tests for X-BOW hulls and bulbous bows in areas such as supply, seismic, offshore construction, drill, short-sea and anchor handling tug supply.


Videos about the X-BOW®: