Editing Propeller (section)

==Types of propellers==

===Variable-pitch propeller===
[[Image:Controllable pitch propeller schematic.svg|thumb|right|A controllable-pitch propeller]]
[[File:Rudder and propeller Beached fishing vessel Nørre Vorupør Denmark 2017-04-14.jpg|thumb|right|A variable-pitch propeller on a fishing vessel]]
Variable-pitch propellers may be either controllable ([[Variable-pitch propeller (marine)|controllable-pitch propeller]]s) or automatically feathering ([[folding propeller]]s). Variable-pitch propellers have significant advantages over the fixed-pitch variety, namely:
* the ability to select the most effective blade angle for any given speed;
* when [[motorsailer|motorsailing]], the ability to coarsen the blade angle to attain the optimum drive from wind and engines;
* the ability to move astern (in reverse) much more efficiently (fixed props perform very poorly in astern);
* the ability to "feather" the blades to give the least resistance when not in use (for example,  when sailing). For large airplanes, if the engine is uncontrollable, the ability to feather the propeller is necessary to prevent the propeller from spinning so fast it breaks apart.

===Skewback propeller===
An advanced type of propeller used on the American [[Los Angeles-class submarine]] as well as the German [[Type 212 submarine]] is called a '''skewback propeller'''. As in the [[scimitar propeller|scimitar blades]] used on some aircraft, the blade tips of a skewback propeller are swept back against the direction of rotation. In addition, the blades are tilted rearward along the longitudinal axis, giving the propeller an overall cup-shaped appearance. This design preserves thrust efficiency while reducing cavitation, and thus makes for a quiet, [[Stealth technology|stealthy]] design.<ref name="JMCWebCreation and Co, 2009">{{cite web |title=Silent propellers|url= http://www.francehelices.fr/silent-propellers.htm|website=France helices |publisher=JMC Web Creation & Co|access-date=July 21, 2017 |date=2009|archive-url=https://web.archive.org/web/20070926223647/http://www.francehelices.fr/silent-propellers.htm|archive-date=September 26, 2007|url-status=dead}}</ref><ref>{{Citation | title = About Propellers | publisher = GSI Tek props | place = UK | url = http://www.gsitek-props.co.uk/about_propellers.htm}}</ref>

A small number of ships use propellers with [[winglet]]s similar to those on some airplane wings, reducing tip vortices and improving efficiency.<ref>Godske, Bjørn. "[http://ing.dk/artikel/dansk-udviklet-energibesparende-propeller-solgt-til-man-dieselturbo-128613 Energy saving propeller]" (in [[Danish language|Danish]]) ''[[Ingeniøren]]'', 23 April 2012. Accessed: 15 March 2014. [https://translate.google.com/translate?hl=da&sl=da&tl=en&u=http%3A%2F%2Fing.dk%2Fartikel%2Fdansk-udviklet-energibesparende-propeller-solgt-til-man-dieselturbo-128613 English translation]</ref><ref>Godske, Bjørn. "[http://ing.dk/artikel/kappel-propellere-baner-vej-succes-hos-man-167005 Kappel-propellers pave the way for success at MAN]" (in [[Danish language|Danish]]) ''[[Ingeniøren]]'', 15 March 2014. Accessed: 15 March 2014. [https://translate.google.com/translate?hl=da&sl=da&tl=en&u=ing.dk%2Fartikel%2Fkappel-propellere-baner-vej-succes-hos-man-167005 English translation]</ref><ref>"[http://www.mandieselturbo.com/1019133/Press/Press-Releases/Trade-Press-Releases/Marine-Power/Propeller-Equipment/Kappel-Agreement-Secures-Access-to-Major-Market.html Kappel agreement secures access to major market]", Man diesel turbo, 30 August 2013.</ref><ref>"[http://www.support-project.eu/supportknowledge/defaultinfo.aspx?topicid=145&index=6 Kapriccio Project] {{Webarchive |url= https://web.archive.org/web/20140315174525/http://www.support-project.eu/supportknowledge/defaultinfo.aspx?topicid=145&index=6 |date=2014-03-15}}" [[European Union]]. Accessed: 15 March 2014.</ref><ref>"[http://www.marinelink.com/news/article/industry-pays-tribute-to-innovation-awards/307142.aspx Industry Pays Tribute to Innovation Awards Winners]" ''Marine link'', 3 October 2002. Accessed: 15 March 2014. Quote: "Winner: the energy-saving Kappel propeller concept from the European Commission-funded Kapriccio propulsion research project. Blades curved towards the tips on the suction side reduce energy losses, fuel consumption, noise and vibration"</ref><!--may not be skewback-->

{{See also|astern propulsion}}

===Modular propeller===
A [[modular propeller]] provides more control over the boat's performance. There is no need to change an entire propeller when there is an opportunity to only change the pitch or the damaged blades. Being able to adjust pitch will allow for boaters to have better performance while in different altitudes, water sports, or cruising.<ref name="Smrcka, 2017">{{cite web|last1=Smrcka|first1= Karel|title=A new start for marine propellers|url= http://www.engineeringnews.co.za/article/a-new-start-for-marine-propellers-2005-03-18/rep_id:4136|website=Engineering News|access-date=July 21, 2017|date=March 18, 2005}}</ref>

===Voith Schneider propeller===
{{excerpt|Voith Schneider Propeller}}

=== Shaftless ===
{{Main|Rim-driven thruster}}
A rim-driven thruster integrates an electric motor into a ducted propeller. The cylindrical duct acts as the stator, while the tips of the blades act as the rotor. They typically provide high torque and operate at low RPMs, producing less noise. The system does not require a shaft, reducing weight. Units can be placed at various locations around the hull and operated independently, e.g., to aid in maneuvering. The absence of a shaft allows alternative rear hull designs.<ref>{{Cite web |date=July 2017 |title=Are rim-driven propulsors the future? |url=https://www.rina.org.uk/Are_rim-driven_propulsors_the_future.html |access-date=2023-01-29 |website=www.rina.org.uk |archive-date=2022-05-24 |archive-url=https://web.archive.org/web/20220524153614/https://www.rina.org.uk/Are_rim-driven_propulsors_the_future.html |url-status=dead }}</ref>

=== Toroidal ===
{{main|Toroidal propeller}}
Twisted-[[toroid]] (ring-shaped) propellers, first invented over 120 years ago,{{cn|date=April 2023}} replace the blades with a-circular rings. They are significantly quieter (particularly at audible frequencies) and more efficient than traditional propellers for both air and water applications. The design distributes vortices generated by the propeller across the entire shape, causing them to dissipate faster in the atmosphere.<ref>{{Cite web |last=Blain |first=Loz |date=2023-01-27 |title=Toroidal propellers: A noise-killing game changer in air and water |url=https://newatlas.com/aircraft/toroidal-quiet-propellers/ |access-date=2023-01-29 |website=New Atlas |language=en-US}}</ref><ref> {{cite patent
| country       =US
| number        =US10,836,466B2
| title         =TOROIDALPROPELLER
| pubdate       =2020
|inventor1-last=Sebastian
|inventor1-first=Thomas
| url =https://patentimages.storage.googleapis.com/d6/fe/53/bea4417ed89176/US10836466.pdf
}} </ref>