Playful in front of the Bourbon Front photo Christian Remoy

Surfing on top of the waves

The X-BOW® is somewhat the reverse of a conventional bow, leaning backwards instead of forwards. An X-BOW vessel cleaves the waves, significantly reducing slamming and vibration. This allows it to sail faster than a conventional bow would allow and it is more comfortable for the people on board. 
With reduced resistance comes reduced fuel consumption. 

Published
09 March 2020
Updated
18 February 2026
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Less shaking, it also means less vibration, less noise and less splashing

Arnkjell Brandal
First Master of 'Bourbon Orca'

First impressions

The X-BOW® was developed by the team at Ulstein Design & Solutions AS and has greatly improved crew comfort.

The ship owner, having seen an early sketch, challenged us to present some realistic ideas for a vessel with a backwards-sloping bow. This instigated a dedicated effort. Bourbon Offshore Norway was convinced by the bow design because it would eliminate slamming, keep up speed in head sea and protect the fore-deck area from green sea and spray, while simultaneously improving comfort and rest for crews in transit.

CEO Gunvor Ulstein, Ulstein Group

Arnkjell Brandal was the first officer to command the anchor-handling tug supply vessel Bourbon Orca from 2006 until May 2015. This seafarer, used to traditional bows, tells us of his first impressions:

Less shaking, it also means less vibration, less noise and less splashing.

Captain on the first X-BOW vessel, Arnkjell Brandal

It was like a shock, paradoxically. This vessel was nothing like what I had experienced before! Traction situations in head seas were much more comfortable. There was no slamming and, therefore no loss of speed. We could easily tow without the high dynamic tension variations experienced with traditional bow forms in bad weather conditions. And in transit in head seas, we kept high speed, floating on top of the waves, with a substantial reduction in heave movements and stamping, 

says Brandal. He adds;

Due to a favourable combination of diesel electric propulsion, azimuths and the X-BOW, the Bourbon Orca has a proven record of up to 50% less fuel consumption in typical anchor handling operations than conventional anchor handling vessels.

Bourbon Orca was contracted by Bourbon Offshore Norway in 2005 as the first X-BOW vessel. She was delivered by Ulstein Verft in 2006.

Bourbon Orca towing the Voyageur Spirit

Norwegian shipbuilding traditions

While some have compared them to Viking ships, others say the X-BOW vessels resemble spaceships, taking the crew into space rather than over the seven seas. Due to her organic lines, the shipowner gave the first X-BOW vessel the name 'Orca'.

The Kvalsund ship found at Sunnmøre was built around 700 AD. Together with the Oseberg ship from approximately 800 AD and the Knarr from around 1,000 AD, the latter two were built in the Viking age. These ships have bow shapes resembling the ULSTEIN X-BOW.

After approximately 1,000 AD, the Viking bow design disappeared from Norwegian shipbuilding:
Upon entering the 12th and 13th centuries, a ship with straighter stem and stern posts, the jekte, makes its entry, says Per Weddegjerde, who is responsible for the boat collection at the Sunnmøre Museum in Ålesund, Norway.

Skilled shipbuilders and mariners

Did they understand what made a boat seaworthy and speed-efficient a thousand years ago?

"There is a lot we do not know about shipbuilding during the Viking era and before, but we do believe the Vikings were good craftsmen. They were skilled shipbuilders and mariners with knowledge and experience going back generations."

Per Weddegjerde says the lines of today’s X-BOW vessels from Ulstein are similar to those of the old boats in the museum’s collection but stresses that the new ships are something altogether different.

The Metric System's winner concept of the next 100 krone note, showing the Gokstad viking ship and the X-BOW hull line design from Ulstein.

Protected

He believes there were several reasons why the old Norwegian mariners wanted boats with an aesthetic bow shape.

I do not know exactly why they chose this bow shape, but one would imagine that the tall lines in the bow provided protection against arrows and spears during battle as well as a buffer against wind, storms and sea spray, says Weddegjerde. He holds a skipper’s license and was once a fisherman.

I have no problem seeing that the ULSTEIN X-BOW is a hull shape that provides good seakeeping characteristics and steady running in head sea. The shape takes a bit of getting used to; but once people see that these are good sea boats, they will probably come to like the shape, says Weddegjerde reflectively.

Playful in front of the Bourbon Front photo Christian Remoy

This interview with Per Weddegjerde was conducted in 2006 when the first X-BOW vessel was delivered. Ten years later, the number of X-BOW vessel designs sold exceeded 100.

Below is a mobile phone film dating from 2007, showing the first X-BOW vessel, the AHTS ’Bourbon Orca’, on her way from Mongstad to the North Sea. Keeping a speed of 13 knots, she passes between two vessels that have reduced their speed to 8 knots due to heavy seas.

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Testing of the first X-BOW vessel, the hull of 'Bourbon Orca', at Marintek, Trondheim. Photo: Tony Hall
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Model test of first ULSTEIN X-BOW® - New bow type results in extremely good seakeeping qualities

ULSTEIN X-BOW® public announcement in April 2005: 
"When the model of the ULSTEIN AX104 anchor handling vessel with the newly developed ULSTEIN X-BOW™ was placed in the water of the drag basin at Marintek in Trondheim early in February, you could have cut the suspense with a knife. Everyone wanted to know how the hull, with its completely new bow design, would move through waves. Researchers at Marintek expressed a great deal of interest prior to the test, but warned that a sea with high wave heights could follow the vessel’s side up over the bow and impact the bridge deck. These warnings were shown to be baseless."

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2005: X-BOW® - Norwegian Engineering Feat of the Year

After the launch of the ULSTEIN X-BOW® concept in 2005, the bow has received, or been nominated for, a number of Innovation Awards. The first was the Norwegian Engineering Feat of the Year from the magazine “Teknisk Ukeblad” in 2005.

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