In ship design, an inverted bow (occasionally also referred to as ''reverse bow'') is a ship's or large boat's bow whose furthest forward point is not at the top. The result may somewhat resemble a

submarine A submarine (often shortened to sub) is a watercraft capable of independent operation underwater. (It differs from a submersible, which has more limited underwater capability.) The term "submarine" is also sometimes used historically or infor ...

's bow. Inverted bows maximize the length of waterline and hence the

hull speed Hull speed or displacement speed is the speed at which the wavelength of a vessel's bow wave is equal to the waterline length of the vessel. As boat speed increases from rest, the wavelength of the bow wave increases, and usually its crest-to- ...

, and often have better

hydrodynamic drag In fluid dynamics, drag, sometimes referred to as fluid resistance, is a force acting opposite to the direction of motion of any object moving with respect to a surrounding fluid. This can exist between two fluid layers, two solid surfaces, or b ...

than ordinary bows. On the other hand, they have very little reserve

buoyancy Buoyancy (), or upthrust, is the force exerted by a fluid opposing the weight of a partially or fully immersed object (which may be also be a parcel of fluid). In a column of fluid, pressure increases with depth as a result of the weight of t ...

and tend to dive under waves instead of piercing or going over them. Inverted bows were popular on battleships and large cruisers in the early 20th century. They fell out of favour, as they were extremely wet at high speeds and in heavy seas, but have made a comeback on modern ship design.

Examples

Motor Yacht "A"

The 390 ft luxury motor yacht M/Y "A" has an inverted bow, along with a

tumblehome Tumblehome or tumble home is the narrowing of a Hull (watercraft), hull above the waterline, giving less beam (nautical), beam at the level of the main deck. The opposite of tumblehome is flare (ship), flare. A small amount of tumblehome is nor ...

hull design. Well intervention vessel Sarah

Ulstein X-Bow

The Ulstein X-Bow (or just X-BOW) is an inverted ship's bow designed by

Ulstein Group Ulstein Group is a group of companies focusing on various marine-related industries, but is mainly known for its shipbuilding and ship design activities. The largest unit is ''Ulstein Verft AS''. The company's head office and primary operations ar ...

to improve handling in rough seas, and to lower fuel consumption by causing less

. It is shaped somewhat like a

's bow.

The MV
Bourbon Orca
', design AX104, is an Ulstein A-Series

anchor handling tug supply vessel Anchor Handling Tug Supply (AHTS) vessels are mainly built to handle anchors for oil rigs, tow them to location, and use them to secure the rigs in place. AHTS vessels sometimes also serve as Emergency Response and Rescue Vessels (ERRVs) and a ...

(AHTS) built for Bourbon Offshore Norway, the Norwegian division of the French

Groupe Bourbon A group is a military unit or a military formation that is most often associated with military aviation. Air and aviation groups The terms group and wing differ significantly from one country to another, as well as between different branches o ...

, and was the first ship built with the Ulstein X-bow in 2006. She was awarded Ship of the Year 2006, both by Skipsrevyen and Offshore Support Journal. In 2007, the Bourbon Orca design model was included in the London Science Museum's display of innovative technology. The vessel's operator claims that the design achieves higher speed and a calmer motion in head, rough seas. Originally developed for offshore oil and gas vessels, the design has entered new segments such as yachts, cruise vessels, offshore wind and fisheries. In 2017, a US cruise company ordered the first four X-BOW cruise ships for arctic ice conditions, and Lindblad Expeditions also ordered two such expedition cruise vessels. The number of X-BOW vessels contracted and or delivered reached the 100 mark in 2017. Later developments from the X-BOW are the X-STERN and TWIN X-STERN hull line designs.

Zumwalt-class destroyer

The bow of the stealth guided missile destroyer for the

United States Navy The United States Navy (USN) is the naval warfare, maritime military branch, service branch of the United States Department of Defense. It is the world's most powerful navy with the largest Displacement (ship), displacement, at 4.5 millio ...

is also inverted. It has a wave-piercing

hull form whose sides slope inward above the waterline.

References

Ulstein delivers second wind service vessel

External links

X-BOWUlstein GroupUlstein Group History book

pdf 'Bourbon Orca'
{{DEFAULTSORT:X-Bow (Shipbuilding) Shipbuilding