Editing Multihull (section)

==Multihull types ==
{{See also|Proa}}

=== Single-outrigger ("proa") ===
{{See also|Sakman|Walap|Wa (watercraft)}}
[[File:National Museum of Ethnology, Osaka - Single outrigger canoe (model) - Woleai Atoll in Federated States of Micronesia - Collected in 1985.jpg|thumb|Model of a ''[[Wa (watercraft)|wa]]'', a single-outrigger vessel, from [[Woleai]] in the [[National Museum of Ethnology (Japan)]]]]
A [[single-outrigger canoe]] is a canoe with a slender outrigger ("ama") attached by two or more struts ("akas"). This craft will normally be propelled by paddles. Single-outrigger canoes that use sails are usually inaccurately referred to by the name "[[proa]]". While single-outrigger canoes and proas both derive stability from the outrigger, the proa has the greater need of the outrigger to counter the heeling effect of the sail. The outrigger on a proa can either be on the lee or windward side, or in a tacking proa, interchangeable. However, more recently, proas tend to keep the outrigger either to leeward or to wind which means that instead of tacking, a "shunt" is required, whereby the bow becomes the stern, and the stern becomes the bow.

===Catamaran (twin-hull)===
{{Main|Catamaran}}
A catamaran is a vessel with twin hulls. Commercial catamarans began in 17th century England. Separate attempts at steam-powered catamarans were carried out by the middle of the 20th century. However, success required better materials and more developed hydrodynamic technologies. During the second half of the 20th century catamaran designs flourished. Catamaran configurations are used for racing, sailing, tourist and fishing boats.

The hulls of a catamaran are typically connected by a bridgedeck, although some simpler cruising catamarans<ref>Such as some [[James Wharram|Wharram]] designs</ref> simply have a trampoline stretched between the crossbeams (or "akas").<ref name="dubrovsky2001">Dubrovsky, V, Laykhovitsky, A (2001) Multi Hull Ships. Backbone Publishing Co. {{ISBN|97809644311-2-6}}</ref> Small beachable catamarans, such as the [[Hobie Cat]], also have only a trampoline between the hulls.

Catamarans derive stability from the distance between the hulls—transverse clearance—the greater this distance, the greater the stability.<ref name=Garrett>{{cite book | last = Garrett | first = Ross | title = The Symmetry of Sailing: The Physics of Sailing for Yachtsmen | publisher = Sheridan House, Inc. | date = January 1, 1996  | page = 133 | url = https://books.google.com/books?id=0VLXORumEF4C&q=catamaran&pg=PA133 | isbn = 9781574090000}}</ref> Typically, catamaran hulls are slim, although they may  flare above the waterline to give reserve buoyancy.<ref>As in all the [[Catalac catamarans|Catalac]] designs</ref> The vertical clearance between the design waterplane and the bottom of the bridge deck determines the likelihood of contact with waves. Increased vertical clearance diminishes such contact and increases [[seaworthiness]], within limits.<ref>{{Citation
 | last1 = Tuck
 | first1 = E. O.
 | last2 = Lazauskas
 | first2 = L.
 | title = Optimum Hull Spacing of a Family of Multihulls
 | journal = Applied Mathematics Department
 | publisher = The University of Adelaide
 | pages = 38
 | date = June 11, 1998
 | url = http://academic.amc.edu.au/~psahoo/Research/tl98.pdf
 | access-date = 2016-01-15
 }}{{Dead link|date=February 2021 |bot=InternetArchiveBot |fix-attempted=yes }}</ref>

The twin-hull (catamaran) design is effective in enhancing the [https://wavewalk.com/blog/fishing-kayak-stability/ stability of very small, lightweight and narrow personal boats] designed for paddling and powering with portable outboard motors. The 100 lbs (45 kg), 38 inches (96 cm) wide [https://wavewalk.com/blog/boat-skiff/ Wavewalk S4 Microskiff] catamaran is sufficiently stable to allow for three adult anglers to stand in it and fish in full confidence, and it allows for three adults to stand in it and paddle in full confidence. 

===Trimaran (double-outrigger)===
{{Main|Trimaran}}
[[File:LoeReal 60 foot Waterworld trimaran (cropped).jpg|thumb|A 60' trimaran with high aspect fractional Bermuda rig]]
A trimaran (or double-outrigger) is a vessel with two outrigger floats attached on either side of a main hull by a crossbeam, wing, or other form of superstructure. They are derived from traditional double-outrigger vessels of maritime Southeast Asia.<ref name="Mahdi1999"/><ref name="Doran1981"/><ref name="Beheim"/> Despite not being traditionally Polynesian,<ref name="Hornell1932"/><ref name="Doran1974"/> western trimarans use traditional [[Polynesians|Polynesian]] terms for the hull ([[Vaka (sailing)|''vaka'']]), the floats ([[Ama (sailing)|''ama'']]), and connectors ([[Aka (sailing)|''aka'']]).<ref>{{Cite book|last=White, Chris.|title=The cruising multihull|date=1997|publisher=International Marine|isbn=0-07-069868-6|location=Camden, Me.|pages=45|oclc=39033104}}</ref> The word ''trimaran'' is a portmanteau of ''tri'' and ''(cata)maran'',<ref>Collins English Dictionary – 2007 – Harper Collins – {{ISBN|978-0-00-780072-8}}</ref> a term that is thought to have been coined by [[Victor Tchetchet]], a pioneering modern multihull designer, born in [[Ukraine]] (at that time part of the [[Russian Empire]]).<ref name="mm2">{{cite web|title=Victor Tchetchet|url=http://www.multihull-maven.com/Designers/Victor_Tchetchet|publisher=Multihull Maven|access-date=2021-02-02|archive-date=2014-12-15|archive-url=https://web.archive.org/web/20141215013524/http://www.multihull-maven.com/Designers/Victor_Tchetchet|url-status=live}}</ref>

Some trimaran configurations use the outlying hulls to enhance stability and allow for shallow draft, examples include the experimental ship [[RV Triton]]<ref>{{cite web |url=http://www.customs.gov.au/webdata/resources/files/FS_Triton.pdf |title=Northern Patrol Vessel ACV Triton Fact Sheet Australian Customs Service |access-date=2019-03-22 |archive-date=2012-02-27 |archive-url=https://web.archive.org/web/20120227223623/http://www.customs.gov.au/webdata/resources/files/FS_Triton.pdf |url-status=live }}</ref>  and the [[USS Independence (LCS-2)|''Independence'']] class of [[littoral combat ships]] (US).<ref>{{cite web|url=http://www.navy.mil/navydata/fact_display.asp?cid=4200&tid=1650&ct=4|title=US Navy Fact File: Littoral Combat Ship Class – LCS|publisher=US Navy|access-date=14 March 2015|archive-date=2 March 2015|archive-url=https://web.archive.org/web/20150302070526/http://www.navy.mil/navydata/fact_display.asp?cid=4200&tid=1650&ct=4|url-status=dead}}</ref>

===Four and five hulls===

Some multihulls with four (quadrimaran) or five (pentamaran) hulls have been proposed; few have been built.<ref name="qf">{{cite journal|journal=Sage|title=Quadrimaran Ferries - High Speed with Shallow Draft|author=William Hockberger|publisher=Transportation Research Board Annual Meeting|year=2007|doi=10.3141/2033-01|s2cid=109720261}}</ref>  In 2018 a Swiss entrepreneur sought funding<ref>{{Cite web|url=http://www.yacht.de/aktuell/panorama/ein-quadrimaran-fuer-saubere-meere/a116062.html|title=Ein Quadrimaran für saubere Meere|last=Müller|first=Kristina|date=January 3, 2018|website=Yacht Magazin|language=de|access-date=2019-03-22|archive-date=2019-03-22|archive-url=https://web.archive.org/web/20190322151011/https://www.yacht.de/aktuell/panorama/ein-quadrimaran-fuer-saubere-meere/a116062.html|url-status=dead}}</ref> to build a sail-driven quadrimaran called ''Manta'' that would use solar power to scoop plastic from the ocean.<ref>{{Cite web|url=https://www.blick.ch/news/schweiz/erfindungen-mit-einem-quadrimaran-will-ein-schweizer-plastik-aus-dem-meer-holen-id8240306.html|title=Mit einem Quadrimaran will Schweizer Plastik aus Meer holen|last=Staff|date=2018-04-11|website=Blick|language=de|access-date=2019-03-22|archive-date=2019-03-22|archive-url=https://web.archive.org/web/20190322151000/https://www.blick.ch/news/schweiz/erfindungen-mit-einem-quadrimaran-will-ein-schweizer-plastik-aus-dem-meer-holen-id8240306.html|url-status=live}}</ref> ''Manta'' was still under development as of the end of 2023.<ref>{{Cite web |title=The SeaCleaners {{!}} The SeaCleaners in action: retrospective 2023 |url=https://www.theseacleaners.org/news/the-seacleaners-in-action-retrospective-2023/ |access-date=2024-02-01 |website=The SeaCleaners |language=en-GB |archive-date=2024-02-01 |archive-url=https://web.archive.org/web/20240201081345/https://www.theseacleaners.org/news/the-seacleaners-in-action-retrospective-2023/ |url-status=live }}</ref> A French manufacturer, Tera-4,  produces motor quadrimarans which use aerodynamic lift between the four hulls to promote planing and reduce power consumption.<ref>{{Cite web|url=http://www.actunautique.com/2017/04/tera-4-signe-la-vente-de-son-tout-premier-quadrimaran.html|title=Tera-4 signe la vente de son tout premier quadrimaran|date=April 10, 2017|website=ActuNautique.com|language=fr|access-date=2019-03-22|archive-date=2019-03-22|archive-url=https://web.archive.org/web/20190322151003/http://www.actunautique.com/2017/04/tera-4-signe-la-vente-de-son-tout-premier-quadrimaran.html|url-status=live}}</ref>

Design concepts for vessels with two pair of outriggers have been referred to as pentamarans. The design concept comprises a narrow, long hull that cuts through waves. The outriggers then provide the stability that such a narrow hull needs. While the aft sponsons act as trimaran sponsons do, the front sponsons do not touch the water normally; only if the ship rolls to one side do they provide added buoyancy to correct the roll.<ref>{{Cite web|url=http://www.marinetalk.com/articles-marine-companies/art/Five-Hulls-Make-Ships-Faster-64639T.html|title=Five Hulls Make Ships Faster|date=June 21, 1999|website=marinetalk.com|access-date=2019-03-09|archive-date=2018-12-25|archive-url=https://web.archive.org/web/20181225125613/http://www.marinetalk.com/articles-marine-companies/art/Five-Hulls-Make-Ships-Faster-64639T.html|url-status=usurped}}</ref><ref>{{Cite news|url=http://news.bbc.co.uk/2/hi/science/nature/1703904.stm|title=In the ocean fast lane|date=December 11, 2001|work=BBC News|access-date=2019-03-09|language=en-GB|archive-date=2019-03-22|archive-url=https://web.archive.org/web/20190322115813/http://news.bbc.co.uk/2/hi/science/nature/1703904.stm|url-status=live}}</ref> [[BMT Limited|BMT Group]], a shipbuilding and engineering company in the [[United Kingdom|UK]], has proposed a fast [[cargo ship]] and a [[yacht]] using this kind of hull.<ref>{{Cite web|url=https://newatlas.com/project-veloce-130-metre-40-knot-pentamaran-super-yacht/9934/|title=Project Veloce - 130 metre 40 knot Pentamaran Super Yacht|last=Martin|first=Jack|date=September 4, 2008|website=newatlas.com|language=en|access-date=2019-03-09|archive-date=2019-02-20|archive-url=https://web.archive.org/web/20190220062819/https://newatlas.com/project-veloce-130-metre-40-knot-pentamaran-super-yacht/9934/|url-status=live}}</ref><ref>{{Cite news|url=http://news.bbc.co.uk/2/hi/technology/4503686.stm|title=Ships power into faster future|date=December 7, 2005|work=BBC News|access-date=2019-03-09|language=en-GB|archive-date=2019-02-25|archive-url=https://web.archive.org/web/20190225063754/http://news.bbc.co.uk/2/hi/technology/4503686.stm|url-status=live}}</ref>

===SWATH multihulls===
[[File:SWATH waterline.svg|right|thumb|A narrow waterline distinguishes a SWATH ship from a conventional [[catamaran]]]]
Multihull designs may have hull [[Beam (nautical)|beams]] that are slimmer at the water surface ("waterplane") than underwater. This arrangement allows good wave-piercing, while keeping a buoyant hydrodynamic hull beneath the waterplane. In a catamaran configuration this is called a [[Small-waterplane-area twin hull|small waterplane area twin hull]], or SWATH.<ref>{{cite book|url=https://books.google.com/books?id=8o_wCgAAQBAJ&q=SWATH&pg=PA230|title=Design Principles of Ships and Marine Structures|last=Misra|first=Suresh Chandra|date=2015|publisher=CRC Press|isbn=9781482254471|pages=474}}</ref> While SWATHs are stable in rough seas, they have the drawbacks, compared with other catamarans, of having a deeper draft, being more sensitive to loading, and requiring more power because of their  higher underwater surface areas.<ref>{{Cite web|url=https://www.chicagotribune.com/news/ct-xpm-1986-05-04-8602010405-story.html|title=Ships on Stilts|last=Kaharl|first=Victoria|date=May 4, 1986|website=chicagotribune.com|language=en-US|access-date=2019-03-25|archive-date=2019-03-25|archive-url=https://web.archive.org/web/20190325020707/https://www.chicagotribune.com/news/ct-xpm-1986-05-04-8602010405-story.html|url-status=live}}</ref> Triple-hull configurations of small waterplane area craft had been studied, but not built, as of 2008.<ref>{{Cite journal|last=Dubrovsky|first=V.|date=2008-08-22|title=An example of a triple-hull SWA ship of ultimate longitudinal shift (hull structure mass estimation)|journal=Ships and Offshore Structures|volume=3|issue=3|pages=263–265|doi=10.1080/17445300801989014|s2cid=110921016|issn=1744-5302}}</ref>