Content deleted Content added
WikiEditor50 (talk | contribs) clean up, typo(s) fixed: between 13-16 → between 13 and 16 (2) |
WikiEditor50 (talk | contribs) |
||
Line 3:
[[File:Points of sail--close-hauled (right) and down wind (left).jpg|thumb|right|300px|Aerodynamic force components for two points of sail. <br />''Left-hand boat'': Down wind with stalled airflow— predominant ''drag'' component propels the boat with little heeling moment. <br />''Right-hand boat'': Up wind (close-hauled) with attached airflow—predominant ''lift'' component both propels the boat and contributes
to heel.]]
[[File:Points of sail--English.jpg|thumb|right|300px|Points of sail (and ''predominant sail force component'' for a displacement sailboat).<br />A. Luffing (''no propulsive force'')
'''Forces on sails''' result from movement of air that interacts with [[sail]]s and gives them motive power for sailing craft, including [[sailing ship]]s, [[sailboat]]s, [[Windsurfing|windsurfers]], [[ice boat]]s, and [[Land sailing|sail-powered land vehicles]]. Similar principles in a rotating frame of reference apply to [[windmill sail]]s and [[wind turbine]] blades, which are also wind-driven. They are differentiated from [[force]]s on [[wing]]s, and [[propeller]] blades, the actions of which are not adjusted to the wind. [[Kites]] also power [[Kite boarding (disambiguation)|certain sailing craft]], but do not employ a mast to support the airfoil and are beyond the scope of this article.
Line 300:
| last = Committee for the National Tire Efficiency Study
| url = http://onlinepubs.trb.org/onlinepubs/sr/sr286.pdf
| title = Tires and Passenger Vehicle Fuel Economy: Informing Consumers, Improving Performance
| access-date = 2007-08-11}}</ref> whereas kinetic friction is normally a constant,<ref>{{cite book|title=Statics: Analysis and Design of Systems in Equilibrium|publisher=Wiley and Sons|year=2005|isbn=978-0-471-37299-8|page=618|author1=Sheppard, Sheri|author2=Tongue, Benson H.|author3=Anagnos, Thalia|author1-link=Sheri D. Sheppard}}
</ref> but on ice may become reduced with speed as it transitions to [[Friction#Lubricated friction|lubricated friction]] with melting.<ref name = Kimball/>
Line 370:
|archive-date = 2012-07-11
}}</ref>
*[[Sailing hydrofoil]]s achieve boat speeds up to twice the speed of the wind, as did the [[AC72]] catamarans used for the [[2013 America's Cup]].<ref name=2013first2>{{cite web|url=http://www.americascup.com/en/news/3/news/18009/emirates-team-new-zealand-gets-leg-up-on-oracle-team-usa |title=Emirates Team New Zealand gets leg up on ORACLE TEAM USA |publisher=
*Ice boats can sail up to five times the speed of the wind.<ref name=Boat_Speed>{{Citation
| first = Bob
Line 792:
| access-date = 2015-08-01}}</ref>
*For light air (less than 8 knots), the sail is at its fullest with the depth of draft between 13 and 16% of the cord and maximum fullness 50% aft from the luff.
*For medium air (
*For heavy (greater than15 knots), the sail is flattened and allowed to twist in a manner that dumps lift with a depth of draft set between
Plots by Larsson ''et al'' show that draft is a much more significant factor affecting sail propulsive force than the position of maximum draft.<ref name=Principles>
{{Citation
Line 819:
===Drag variables===
Spinnakers have traditionally been optimized to mobilize drag as a more important propulsive component than lift. As sailing craft are able to achieve higher speeds, whether on water, ice or land, the velocity made good (VMG) at a given course off the wind occurs at apparent wind angles that are increasingly further forward with speed. This suggests that the optimum VMG for a given course may be in a regime where a spinnaker may be providing significant lift.<ref>
{{Citation| title = Downwind Sails
| publisher = Australian Sailing & Yachting
| date = January 2012
| |||