Inverted bow

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M/Y A cruising at Sorrento, Italy in 2012. A (ship) at Sorrent 2012 3.jpg
M/Y A cruising at Sorrento, Italy in 2012.
SMS Viribus Unitis, a dreadnought type ship with inverted bow, flagship of the Austro-Hungarian navy in 1912. Vu1912.JPG
SMS Viribus Unitis , a dreadnought type ship with inverted bow, flagship of the Austro-Hungarian navy in 1912.

In ship design, an inverted bow (occasionally also referred to as reverse bow) is a ship's or large boat's bow whose farthest forward point is not at the top. The result may somewhat resemble a submarine's bow. Inverted bows maximize the length of waterline and hence the hull speed, and often have better hydrodynamic drag than ordinary bows. On the other hand, they have very little reserve buoyancy and tend to dive under waves instead of piercing or going over them.

Contents

Inverted bows were popular on battleships and large cruisers in the early 20th century. They fell out of favour, as they were very 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 hull design.

Well intervention vessel Sarah with X-Bow. Well intervention vessel Sarah.JPG
Well intervention vessel Sarah with X-Bow.

Ulstein X-Bow

The Ulstein X-Bow (or just X-BOW) is an inverted ship's bow designed by Ulstein Group to improve handling in rough seas, and to lower fuel consumption by causing less hydrodynamic drag. [1] It is shaped somewhat like a submarine's bow. [2]

Bourbon Orca anchor tug, shown in 2012, was the first ship built with an Ulstein X-Bow in 2006. Bourbon Orca in Stavanger 2012.jpg
Bourbon Orca anchor tug, shown in 2012, was the first ship built with an Ulstein X-Bow in 2006.
Norwegian offshore support vessel Siem Moxie. Siem Moxie ship R01.jpg
Norwegian offshore support vessel Siem Moxie.
USS Zumwalt (DDG-1000), lead ship of her class, after floating out of drydock in 2013. USS Zumwalt (DDG-1000) at night.jpg
USS Zumwalt (DDG-1000), lead ship of her class, after floating out of drydock in 2013.

The MV Bourbon Orca , design AX104, is an Ulstein A-Series anchor handling tug supply vessel (AHTS) built for Bourbon Offshore Norway, the Norwegian division of the French Groupe Bourbon, [3] and was the first ship built with the Ulstein X-bow in 2006. She was awarded Ship of the Year 2006, both by Skipsrevyen [4] 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. [5] 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, [6] and Lindblad Expeditions also ordered two such expedition cruise vessels. [7]

The number of X-BOW vessels contracted and or delivered reached the 100 mark in 2017. [8] Later developments from the X-BOW are the X-STERN [9] and TWIN X-STERN [10] hull line designs.

Zumwalt-class destroyer

The bow of the Zumwalt-class stealth guided missile destroyer for the United States Navy is also inverted. It has a wave-piercing tumblehome hull form whose sides slope inward above the waterline. [11]

See also

Related Research Articles

<span class="mw-page-title-main">Hull (watercraft)</span> Watertight buoyant body of a ship or boat

A hull is the watertight body of a ship, boat, submarine, or flying boat. The hull may open at the top, or it may be fully or partially covered with a deck. Atop the deck may be a deckhouse and other superstructures, such as a funnel, derrick, or mast. The line where the hull meets the water surface is called the waterline.

<span class="mw-page-title-main">Multihull</span> Ship or boat with more than one hull

A multihull is a boat or ship with more than one hull, whereas a vessel with a single hull is a monohull. The most common multihulls are catamarans, and trimarans. There are other types, with four or more hulls, but such examples are very rare and tend to be specialised for particular functions.

<span class="mw-page-title-main">Yacht</span> Recreational boat or ship

A yacht is a sail- or motor-propelled watercraft made for pleasure, cruising, or racing. There is no standard definition, though the term generally applies to vessels with a cabin intended for overnight use. To be termed a yacht, as opposed to a boat, such a pleasure vessel is likely to be at least 33 feet (10 m) in length and may have been judged to have good aesthetic qualities.

<span class="mw-page-title-main">Catamaran</span> Watercraft with two parallel hulls of equal size

A catamaran is a watercraft with two parallel hulls of equal size. The distance between a catamaran's hulls imparts resistance to rolling and overturning. Catamarans typically have less hull volume, smaller displacement, and shallower draft (draught) than monohulls of comparable length. The two hulls combined also often have a smaller hydrodynamic resistance than comparable monohulls, requiring less propulsive power from either sails or motors. The catamaran's wider stance on the water can reduce both heeling and wave-induced motion, as compared with a monohull, and can give reduced wakes.

<span class="mw-page-title-main">Anchor handling tug supply vessel</span> Type of 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 as supply transports.

<span class="mw-page-title-main">Small-waterplane-area twin hull</span> Ship configuration with submerged twin-hulls

A small waterplane area twin hull, better known by the acronym SWATH, is a catamaran design that minimizes hull cross section area at the sea's surface. Minimizing the ship's volume near the surface area of the sea, where wave energy is located, minimizes a vessel's response to sea state, even in high seas and at high speeds. The bulk of the displacement necessary to keep the ship afloat is located beneath the waves, where it is less affected by wave action. Wave excitation drops exponentially as depth increases, so wave action normally does not affect a submerged submarine at all. Placing the majority of a ship's displacement under the waves is similar in concept to creating a ship that rides atop twin submarines.

<span class="mw-page-title-main">Capsizing</span> Action where a vessel turns on to its side or is upside down

Capsizing or keeling over occurs when a boat or ship is rolled on its side or further by wave action, instability or wind force beyond the angle of positive static stability or it is upside down in the water. The act of recovering a vessel from a capsize is called righting. Capsize may result from broaching, knockdown, loss of stability due to cargo shifting or flooding, or in high speed boats, from turning too fast.

<span class="mw-page-title-main">Incat</span> Manufacturer of large high-speed craft catamarans

Incat Tasmania is an Australian manufacturer of high-speed craft (HSC) catamaran ferries. Its greatest success has been with large, sea going passenger and vehicle ferries, but it has also built military transports and since 2015 it has built smaller river and bay ferries. Based in Derwent Park, a suburb of Hobart, Tasmania, Australia, it was founded by Bob Clifford.

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-trough dimension (height) increases as well. When hull speed is exceeded, a vessel in displacement mode will appear to be climbing up the back of its bow wave.

<span class="mw-page-title-main">Bulbous bow</span> Protruding bulb at the front of a ship

A bulbous bow is a streamlined flaring or protruding bulb at the bow of a ship just below the waterline. The flare or bulb modifies the way the water flows around the hull, reducing drag and thus increasing speed, range, fuel efficiency, and stability. Large ships with bulbous bows generally have twelve to fifteen percent better fuel efficiency than similar vessels without them. A bulbous bow also increases the buoyancy of the forward part and hence reduces the pitching of the ship to a small degree.

<span class="mw-page-title-main">Bow (watercraft)</span> Forward part of the hull of a ship

The bow is the forward part of the hull of a ship or boat, the point that is usually most forward when the vessel is underway. The aft end of the boat is the stern.

<span class="mw-page-title-main">Waterline length</span> Size of a ship

A vessel's length at the waterline is the length of a ship or boat at the level where it sits in the water. The LWL will be shorter than the length of the boat overall as most boats have bows and stern protrusions that make the LOA greater than the LWL. As a ship becomes more loaded, it will sit lower in the water and its ambient waterline length may change; but the registered L.W.L is measured from a default load condition.

<span class="mw-page-title-main">Tumblehome</span> Design element of ships and automobiles

Tumblehome is a term describing a hull which grows narrower above the waterline than its beam. The opposite of tumblehome is flare.

<span class="mw-page-title-main">Ulstein Group</span>

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 are located in the town of Ulsteinvik in the municipality of Ulstein in Møre og Romsdal county, Norway, an important area for the Norwegian maritime cluster, and with subsidiaries in several other countries. The group also includes companies working with power & control systems, engineering, site follow-up and aftermarket services. The company has also been engaged in shipping.

<span class="mw-page-title-main">Wave-piercing hull</span> Hull with fine bow with reduced reserve buoyancy

A wave-piercing boat hull has a very fine bow, with reduced buoyancy in the forward portions. When a wave is encountered, the lack of buoyancy means the hull pierces through the water rather than riding over the top, resulting in a smoother ride than traditional designs, and in diminished mechanical stress on the vessel. It also reduces a boat's wave-making resistance.

<span class="mw-page-title-main">Wave-making resistance</span> Energy of moving water away from a hull

Wave-making resistance is a form of drag that affects surface watercraft, such as boats and ships, and reflects the energy required to push the water out of the way of the hull. This energy goes into creating the wave.

<span class="mw-page-title-main">Draft (hull)</span> Depth of a vessel below its waterline

The draft or draught of a ship is a determined depth of the vessel below the waterline, measured vertically to its hull's lowest—its propellers, or keel, or other reference point. Draft varies according to the loaded condition of the ship. A deeper draft means the ship will have greater vertical depth below the waterline. Draft is used in under keel clearance calculations, where the draft is calculated with the available depth of water to ensure the ship can navigate safely, without grounding. Navigators can determine their draught by calculation or by visual observation.

AHTS <i>Bourbon Dolphin</i> Anchor handling tug supply vessel of Bourbon Offshore Norway

AHTSBourbon Dolphin was an anchor handling tug supply vessel of Bourbon Offshore Norway. The ship capsized off the coast of Shetland on April 12, 2007, and sank three days later while preparations were being made to tow her to shore.

<span class="mw-page-title-main">Sailing yacht</span> Private sailing vessel with overnight accommodations

A sailing yacht, is a leisure craft that uses sails as its primary means of propulsion. A yacht may be a sail or power vessel used for pleasure, cruising, or racing. There is no standard definition, so the term applies here to sailing vessels that have a cabin with amenities that accommodate overnight use. To be termed a "yacht", as opposed to a "boat", such a vessel is likely to be at least 33 feet (10 m) in length and have been judged to have good aesthetic qualities. Sailboats that do not accommodate overnight use or are smaller than 30 feet (9.1 m) are not universally called yachts. Sailing yachts in excess of 130 feet (40 m) are generally considered to be superyachts.

<i>Horizon Arctic</i> Deep sea operations support ship

Horizon Arctic is an anchor handling tug supply vessel (AHTS) completed in 2016 by Vard Group at its Brattvåg shipyard as Bourbon Arctic for Bourbon Offshore Norway AS, part of the Marseille-based Bourbon group. As of 2023, it is operated by Horizon Maritime of Canada. Under Horizon, it served as the surface support vessel for the Titan submersible during its 2021 and 2022 survey expeditions to the wreck of the Titanic, conducted by OceanGate.

References

  1. Five (TV channel) television program Megastructures , 12.45 to 1.45 pm Friday 29 January 2010
  2. "X-Bow: Innovating an old industry — The Hand & Eye". www.thehandandeye.com. Archived from the original on 2015-09-26.
  3. Ship Of The Year 2006. Archived 2015-01-28 at the Wayback Machine Accessed: 24 January 2015.
  4. http://ulstein.com/news/2006/2006-ahts-bourbon-orca-ship-of-the-year Archived 2021-05-14 at the Wayback Machine 2006: AHTS Bourbon Orca - Ship of the Year
  5. A series of four Ulstein designed inverted bow PSV vessels page 16-17 Bourbon (company), 24 June 2010. Accessed: 11 March 2011.
  6. "SunStone, China group to build 4+6 expedition cruise ships in Shanghai". 17 March 2017.
  7. "It's official: Lindblad inks 1 + 2 newbuild deal with Ulstein". 7 November 2017.
  8. "X-BOW cracks the 100 vessels mark". www.offshorewindindustry.com/ 16 January 2016. Accessed: 7 July 2022.
  9. "X-Stern®". 16 March 2020.
  10. "Two sterns provide fuel savings and maximum manoeuvrability". Archived from the original on 2022-06-28. Retrieved 2022-07-07.
  11. "Full Page Reload". IEEE Spectrum: Technology, Engineering, and Science News. 31 July 2013. Retrieved 2020-11-10.