This is from Ulstein's webpage.
X-BOW®
Principal characteristics
- A novel hull shape, with a redistributed foreship volume and substantially reduced flare
- A raised foreship, which normally incorporates accommodations
- Patented internationally by Ulstein
Optimised hull shape
The shape of the hull has been optimised with a view to high top speeds, low resistance and reduced fuel consumption. Great emphasis is placed on the crew’s comfort and safety during work and rest periods.
Comfort
- Elimination of slamming and bow impact
- Soft entry in waves
- Low acceleration levels
- Reduced vibration levels
- Available crew rest time increased
- Safer workplace due to smoother motions
Environment
- Significantly more energy efficient shape in waves
- Higher transit speed
- Reduced power consumption
- Improved fuel efficiency
- Increased operational time
- Increased schedule keeping
Inverted bow
- Larger and higher volume distribution
- Less spray
- Slender hull lines
- Safer workplace due to increased protection provided by hull
X-BOW® versus conventional bow
X-BOW® is a backward-sloping bow that starts at the extreme front of the vessel. This allows for the sharpest possible bow shape.
Result: A continuous and sharp bow shape, which smoothly divides both waves and calm water. Increased volume above and up front allows the vessel to efficiently respond to large waves.
A conventional bow has a forward-sloping bow shape that starts at the extreme front of the vessel and drops down and back. The actual start of the bow at the waterline is moved back, and the bow shape at the start of the waterline is less sharp.
Result: A bow that pushes the waves down and forward, - this absorption of energy slows the vessel.
Comparison testing - offshore vessels
The photos above show comparison testing of equivalent offshore vessels with the
X-BOW® versus a conventional bow. The wave height is 2.8 metres, with a wave period of 10.5 seconds and a speed of 15 knots.
The photo to the left shows the
X-BOW® vessel. With a sharp hull shape, there is no spray and there´s a soft entry into the waves. As the waves are parted efficiently, wave energy transfer is minimised. This means that speed losses are reduced. The photo to the right shows the conventional bow vessel. The waves and speed are the same, but there is spray generation, high bow impact and slamming, and a blunt hull shape. The waves are pushed forward, and wave energy is moved against the hull. This makes for greater speed losses.
Fuel consumption
Comparison study of short sea container vessels with
X-BOW® versus a conventional bow in conditions expected in service has been performed. With a design speed of 18 knots, the results show 7-16% fuel reduction, depending on ship speed and sea state.
Speed loss in waves
The attainable speed in waves and the speed loss in waves of a vessel with an
X-BOW® compared to a vessel with conventional bow: The trend indicates that the
X-BOW® has a significant speed advantage in sea states most probable on a North Atlantic trade route. Waves in the North Atlantic are expected to be above 2.5 metres 74% of the time, and
X-BOW® vessels have an average improvement of 19% in the 2.5-10.0 metre wave height range.
source:
http://www.ulsteingroup.com/Kunder/u...m_2,18,2,2,2,0