Editing Catamaran (section)

== SWATH and wave-piercing designs ==
[[File:Small waterplane area twin hull swath1 large.jpg|thumb|A SWATH ship has twin hulls (blue) that remain completely submerged.]]

Two advances over the traditional catamaran are the ''[[small-waterplane-area twin hull]]'' (SWATH) and the ''wave-piercing'' configuration—the latter having become a widely favored design.

SWATH reduces wave-generating resistance by moving displacement volume below the waterline, using a pair of tubular, submarine-like hulls, connected by pylons to the bridge deck with a narrow waterline cross-section. The submerged hulls are minimally affected by waves.<ref name = Misra/> The SWATH form was invented by Canadian [[Frederick G. Creed]], who presented his idea in 1938 and was later awarded a British patent for it in 1946. It was first used in the 1960s and 1970s as an evolution of catamaran design for use as oceanographic research vessels or [[submarine]] rescue ships.<ref>{{ cite book | last = Helfers | first = John | title = The Unauthorized Dan Brown Companion | publisher = Kensington Publishing Corp. | date = 2006 | pages = 271 | url = https://books.google.com/books?id=_v1QMucvtUYC&q=SWATH+Frederick+G.+Creed&pg=PA271 | access-date = 2016-01-27 | isbn = 0806535806 }}</ref> In 1990, the US Navy commissioned the construction of a SWATH ship to test the configuration.<ref>{{ cite book | title = Jane's high-speed marine craft | publisher = Jane's Information Group | edition = 24 | date = 1991 | url = https://books.google.com/books?id=5XQZAQAAIAAJ&q=SWATH+Thomas+G.+Lang | access-date = 2016-01-27 | isbn = 0710612664 }}</ref>

SWATH vessels compare with conventional powered catamarans of equivalent size, as follows:<ref name = Misra>{{ cite book | last = Misra | first = Suresh Chandra | title = Design Principles of Ships and Marine Structures | publisher = CRC Press | date = 2015 | url = https://books.google.com/books?id=8o_wCgAAQBAJ&q=SWATH+ship | access-date = 2016-01-27 | isbn = 978-1482254471 }}</ref>

* Larger wetted surface, which causes higher skin friction drag
* Significant reduction in wave-induced drag, with the configuration of struts and submerged hull structures
* Lower water plane area significantly reduces pitching and heaving in a seaway
* No possibility of planing
* Higher sensitivity to loading, which may bring the bridge structure closer to the water

[[File:US Navy 031104-N-0000S-001 High Speed Vessel Two (HSV 2) Swift is participating in the West African Training Cruise.jpg|thumb|[[HSV-2 Swift]], a wave-piercing catamaran, built by [[Incat]] in [[Tasmania]], Australia]]

[[Wave-piercing hull|Wave-piercing]] catamarans (strictly speaking they are [[trimaran]]s, with a central hull and two outriggers) employ a low-buoyancy bow on each hull that is pointed at the water line and rises aft, up to a level, to allow each hull to pierce waves, rather than ride over them. This allows higher speeds through waves than for a conventional catamaran. They are distinguished from SWATH catamarans, in that the buoyant part of the hull is not tubular. The spanning bridge deck may be configured with some of the characteristics of a normal V-hull, which allows it to penetrate the crests of waves.<ref>{{ cite book | last = Husick | first = Charles B. | title = Chapman Piloting, Seamanship and Small Boat Handling | publisher = Sterling Publishing Company, Inc. | page = 16 | date = 2009 | url = https://books.google.com/books?id=S4FwbS8StvEC&q=wave-piercing+catamaran&pg=PA16 | access-date = 2016-01-26 | isbn = 9781588167446 }}</ref>

Wave-piercing catamaran designs have been employed for yachts,<ref>{{ cite magazine | last = Caprio | first = Dennis | title = Loomes 83 | magazine = Yachting | volume = 190 | number = 1 | pages = 81–84 | issn = 0043-9940 | date = July 2001 | url = https://books.google.com/books?id=2ERAe-BngWsC&q=wave-piercing+catamaran&pg=PA81 | access-date = 2016-01-26}}
</ref> passenger ferries,<ref>{{ cite book | last1 = Yun | first1 = Liang | last2 = Bliault | first2 = Alan | title = High Performance Marine Vessels | publisher = Springer Science & Business Media | date = July 8, 2014 | page = 206 | url = https://books.google.com/books?id=3wcDzNJpXf0C&q=passenger+ferries&pg=PA206 | access-date = 2016-01-26 | isbn = 978-1-4614-0868-0 }}
</ref> and military vessels.<ref>{{ cite news | last = Brumley | first = Jeff | title = Unusual ship visits Mayport after 6-month deployment to African waters | newspaper = Florida Times-Union | location = Jacksonville | date = October 5, 2011 | url = http://jacksonville.com/news/florida/2011-10-05/story/unusual-ship-visits-mayport-after-6-month-deployment-african-waters | access-date = 2016-01-26}}
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