Editing Catamaran (section)

=== Tradeoffs ===

[[File:Catamaran at Straits Quay, Georgetown, Pulau Pinang, Malaysia..jpg|thumb|''Vangohh Seafarer'', a catamaran motor yacht berthed at Straits Quay, Georgetown, Pulau Pinang, Malaysia]]

One measure of the trade-off between speed and carrying capacity is the [[Froude number#Ship hydrodynamics|displacement Froude number (Fn<sub>V</sub>)]],<ref>{{Cite book | last=Newman | first=John Nicholas | author-link=John Nicholas Newman | title=Marine hydrodynamics | url=https://archive.org/details/marinehydrodynam00newm | url-access=limited | year=1977 | publisher=[[MIT Press]] | location=Cambridge, Massachusetts  | isbn=0-262-14026-8 |page=[https://archive.org/details/marinehydrodynam00newm/page/n43 28]}}.</ref> compared with ''calm water transportation efficiency''.<ref name = Watson/> Fn<sub>V</sub> applies when the [[waterline length]] is too speed-dependent to be meaningful—as with a planing hull.<ref>{{ cite journal | last1 = Wilson | first1 = F.W. | last2 = Vlars | first2 = P.R. | title = Operational Characteristics Comparisons | journal = AIAA 6th Marine Systems Conference | page = 11 | publisher = American Institute of Aeronautics and Astronautics | date = September 1981 | url = https://books.google.com/books?id=QboKAQAAMAAJ&q=%22displacement+Froude+number%22 | access-date = 2017-03-31 }}</ref> It uses a reference length,  the cubic root of the volumetric displacement of the hull, ''V'', where ''u'' is the relative flow velocity between the sea and ship, and ''g'' is [[Gravitational constant|acceleration due to gravity]]:
 
:<math>\mathrm{Fn_V} = \frac{u}{\sqrt{gV^{1/3}}}</math>

''Calm water transportation efficiency'' of a vessel is proportional to the full-load [[Displacement (ship)|displacement]] and the maximum calm-water speed, divided by the corresponding power required.<ref>{{cite journal | last = Eames | first = Michael C. | title = Advances is Naval Architecture for Surface Naval Ships | journal = Proceedings | pages = 31 | publisher = Royal Institution of Naval Architects | location = London | date = April 15, 1980 | url = http://cradpdf.drdc-rddc.gc.ca/PDFS/zbd89/p36271.pdf | access-date = 2016-01-31 | archive-date = February 1, 2016 | archive-url = https://web.archive.org/web/20160201081051/http://cradpdf.drdc-rddc.gc.ca/PDFS/zbd89/p36271.pdf | url-status = dead }}</ref>

Large merchant vessels have a Fn<sub>V</sub> between one and zero, whereas higher-performance powered catamarans may approach 2.5, denoting a higher speed per unit volume for catamarans. Each type of vessel has a corresponding calm water transportation efficiency, with large transport ships being in the range of 100–1,000, compared with 11-18 for transport catamarans, denoting a higher efficiency per unit of payload for monohulls.<ref name = Watson>{{ cite book | last = Watson | first = D. G. M. | title = Practical Ship Design | publisher = Gulf Professional Publishing | series = Elsevier Ocean Engineering Book Series | volume = 1 | edition = Revised | date = 2002 | pages = 47–48 | quote = See Fig. 2.1 'Slender' and 'Swath' figures. | url = https://books.google.com/books?id=L4W1XZ9Lf8cC&q=wave+piercing+catamaran+design&pg=PA48 | isbn = 0080440541 }}</ref><!--See chart on P. 47 for catamaran numbers. Look for SWATH: You'll be in the right neighborhood. The transport ship value is on P. 48.-->