Editing Sailing (section)

====Effect on apparent wind====
{{Further|Forces on sails#Effect of points of sail on forces}}
True wind velocity ('''V<sub>T</sub>''') [[Euclidean vector#Addition and subtraction|combines]] with the sailing craft's velocity ('''V<sub>B</sub>''') to give the ''apparent wind velocity'' ('''V<sub>A</sub>'''), the air velocity experienced by instrumentation or crew on a moving sailing craft. Apparent wind velocity provides the motive power for the sails on any given point of sail. It varies from being the true wind velocity of a stopped craft in irons in the no-go zone, to being faster than the true wind speed as the sailing craft's velocity adds to the true windspeed on a reach. It diminishes towards zero for a craft sailing dead downwind.<ref name=Jobson/>
{{center|
;Effect of apparent wind on sailing craft at three points of sail
Sailing craft '''A''' is close-hauled. Sailing craft '''B''' is on a beam reach. Sailing craft '''C''' is on a broad reach.<br />Boat velocity (in black) generates an equal and opposite apparent wind component (not shown), which combines with the true wind to become apparent wind.
}}
<gallery mode="packed" heights="300px">
File:Forces on sails for three points of sail.jpg|'''Apparent wind and forces on a ''sailboat''.'''<br />As the boat sails further from the wind, the apparent wind becomes smaller and the lateral component becomes less; boat speed is highest on the beam reach.
File:Ice boat apparent wind on different points of sail.jpg|'''Apparent wind on an ''iceboat''.'''<br />As the iceboat sails further from the wind, the apparent wind increases slightly and the boat speed is highest on the broad reach. The sail is sheeted in for all three points of sail.<ref name = Kimball/>
</gallery>

The speed of sailboats through the water is limited by the resistance that results from hull drag in the water. Ice boats typically have the least resistance to forward motion of any sailing craft.<ref name = Kimball/> Consequently, a sailboat experiences a wider range of apparent wind angles than does an ice boat, whose speed is typically great enough to have the apparent wind coming from a few degrees to one side of its course, necessitating sailing with the sail sheeted in for most points of sail. On conventional sailboats, the sails are set to create lift for those points of sail where it's possible to align the leading edge of the sail with the apparent wind.<ref name=Jobson/>

For a sailboat, point of sail affects lateral force significantly. The higher the boat points to the wind under sail, the stronger the lateral force, which requires resistance from a keel or other underwater foils, including daggerboard, centerboard, skeg and rudder. Lateral force also induces heeling in a sailboat, which requires resistance by weight of ballast from the crew or the boat itself and by the shape of the boat, especially with a catamaran. As the boat points off the wind, lateral force and the forces required to resist it become less important.<ref name=Marchaj1>
{{Citation
 | last = Marchaj
 | first = C. A. 
 | title = Sail Performance: Techniques to Maximize Sail Power
 | publisher = International Marine/Ragged Mountain Press
 | year = 2002
 | edition = 2
 | pages = 416
 | isbn = 978-0071413107 }}</ref>
On ice boats, lateral forces are countered by the lateral resistance of the blades on ice and their distance apart, which generally prevents heeling.<ref>
{{cite book
 |last = Bethwaite
 |first = Frank
 |title = High Performance Sailing
 |publisher = Adlard Coles Nautical
 |year = 2007
 |isbn = 978-0-7136-6704-2}}</ref>