X-STERN®

The X-STERN introduces the documented X-BOW® effect to the aft ship. The sloping, higher stern allows for a sharp stern shape in which the transom plate is replaced by a pointed aft. Some of the benefits are: Improved safety for crew and equipment, increased flexibility in operations and reduced fuel consumption.

The X-STERN® is inspired by the X-BOW®, and the first deliveries (2016/2017) were two service operation vessels for the offshore wind industry.

For vessels where the best possible operational characteristics are vital, the Captain’s first choice will be to place the X-STERN towards the weather instead of the bow. When placing the stern towards the weather, the X-STERN has a major effect on the vessel’s capabilities and flexibility. Stern first, the vessel will be less influenced by weather, and pitch motion and wave drift will be reduced. The work deck aft is enclosed, with no sea on deck or ice build-up and increased safety for crew, passengers, cargo and equipment. Deeper drafts increase the benefits.

The advantages include:

Reduced pitch motion and increased operational window when placing stern to weather (weather vaning).
Up to 50% less propulsion power required with stern to weather vs bow to weather
Significant reduction in wave response and slamming. Stern is quartering seas, which decreases accelerations and improves comfort
Safer workplace due to sheltered aft deck and high freeboard, less probablility of green water on deck
Reduction in resistance in calm water and waves by up to 28%
The option to sail astern and with up to 60% reduction in power consumption
Massive reduction in trim and draft sensitivity

"The X-STERN met all our expectations. It is amazing to see a vessel going backwards in bad weather without slamming and having spray on deck."
'Windea La Cour', BS Offshore

'With the stern towards the weather, we experience absolutely no slamming and vibrations, not even when we are in transfer, and people love it.' Matthias, DP operator, Windea La Cour

X-STERN feedback

The X-STERN is the X-BOW® effect implemented in the aft ship. While the traditional transom plate causes slamming and vibrations when the vessel is backing, the pointed X-STERN has no such effect. The softer motions are energy saving and increase comfort and safety.

X-STERN feedback

Improved positioning

The X-STERN pointed shape improves positioning capabilities compared to stern designs with a flat transom plate.

Reduced weather dependency

Improved motion characteristics widens the operational window.

Fuel efficiency

Vessels can operate in a wider sector with the same power consumption. Reduced fuel emissions improves the vessel's footprint.

X-BOW® and X-STERN: Studies, documentation and experiences

TWIN X-STERN for walk-to-work services

Is a bow really a necessity for large ships? A heightened stern, the TWIN X-STERN, can operate either way, thus facilitating on-site DP positioning. This idea was nominated for the Innovation of the Year Award at the OSJ Conference 2016.

TWIN X-STERN®

X-BOW®

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 most weather conditions.

X-BOW®