Editing Kayak (section)

=== Beam profile ===
[[File:US Navy 041009-N-1810F-044 Journalist 1st Class Lizandra Murray and Chief Petty Officer Mark Rinschler, both assigned to Naval Media Center, Washington, D.C., maneuver their Duckie whitewater boat down rapids.jpg|thumb|Inflatable kayaks tend to be very wide; this is not a problem for the large, broad-shouldered stern paddler. The smaller bow paddler is leaning sideways and sliding her hands along the paddle to improve her leverage. Her safety equipment is also too large. US Navy.]]
The overall width of a kayak's cross-section is its ''[[Beam (nautical)|beam]]''. A wide hull is more stable and packs more displacement into a shorter length. A narrow hull has less drag and is generally easier to paddle; in waves, it will ride more easily and stay dryer.<ref name=long_narrow/>

A narrower kayak makes a somewhat shorter paddle appropriate and a shorter paddle puts less strain on the shoulder joints. Some paddlers are comfortable with a sit-in kayak so narrow that their legs extend fairly straight out. Others want sufficient width to permit crossing their legs inside the kayak.

==== Types of stability ====
{{main|primary stability|secondary stability|tertiary stability}}
[[File:Chines.svg|thumb|upright=2.5|Hypothetical cross-sections of kayaks. Left to right: High primary stability but low secondary stability, lower primary stability but ~same secondary stability, lower primary but higher secondary stability, two extra chines, four extra chines. More [[chine (boating)|chines]] (angles) give a more rounded profile, decreasing stability, tracking, and the [[wetted area]], and increasing speed.|alt=1) a five-sided polygon which is nearly a wide rectangle, with the lower long side (the boat's bottom) a bit shorter than the upper (the deck) and the fifth point (the keel) slightly bending the nearly-flat bottom downwards. 2) The short sides retain the same angle, but the keel is a bit lower and the chines a bit higher. 3) The chines are substantially closer together and higher than the keel so that the angles of the hull at the chines and at the keel are all three approximately equal. 4) Two additional chines make a seven-sided polygon which approximates a half-circle with the flat side up. 5) A 9-sided polygon approximating a half-circle more closely.]]
''Primary'' (sometimes called ''initial'') stability describes how much a boat tips, or rocks back and forth when displaced from level by paddler weight shifts. ''Secondary'' stability describes how stable a kayak feels when put on edge or when waves are passing under the hull perpendicular to the length of the boat. For [[kayak roll]]ing, ''tertiary'' stability, or the stability of an upside-down kayak, is also important (lower tertiary stability makes rolling up easier).{{citation needed|date=May 2021}}

Primary stability is often a big concern to a beginner, while secondary stability matters both to beginners and experienced travelers. By example, a wide, flat-bottomed kayak will have high primary stability and feel very stable on flat water. However, when a steep wave breaks on such a boat, it can be easily overturned because the flat bottom is no longer level. By contrast, a kayak with a narrower, more rounded hull with more [[flare (ship)|hull flare]] can be edged or leaned into waves and (in the hands of a skilled kayaker) provides a safer, more comfortable response on stormy seas. Kayaks with only moderate primary, but excellent secondary stability are, in general, considered more [[Seakeeping|seaworthy]], especially in challenging conditions.

[[File:West Greenland kayak cross-section after Nansen.svg|thumb|A cross-section through a skin-on-frame kayak. The skin touches only at the two [[gunwales]], the two [[strake|stringers]], and the [[keel]].]]
The shape of the cross section affects stability, maneuverability, and drag. Hull shapes are categorized by roundness, flatness, and by the presence and angle of [[Chine (boating)|chine]]s. This cross-section may vary along the length of the boat.

A chine typically increases secondary stability by effectively widening the beam of the boat when it heels (tips). A V-shaped hull tends to travel straight (track) well but makes turning harder. V-shaped hulls also have the greatest secondary stability. Conversely, flat-bottomed hulls are easy to turn, but harder to direct in a constant direction. A round-bottomed boat has minimal area in contact with the water, and thus minimizes drag; however, it may be so unstable that it will not remain upright when floating empty, and needs continual effort to keep it upright. In a skin-on-frame kayak, chine placement may be constrained by the need to avoid the bones of the pelvis.<ref name=antropometric_measurements>{{cite web|url=http://www.kayakways.net/kayaksandpaddles/kayakfitting/|title=kayakways.net – Kayak Fitting|website=Kayakways.net|access-date=November 29, 2017|archive-date=February 24, 2020|archive-url=https://web.archive.org/web/20200224060810/http://www.kayakways.net/kayaksandpaddles/kayakfitting|url-status=dead}}</ref>

[[Sea kayak]]s, designed for open water and rough conditions, are generally narrower at {{cvt|22|-|25|in|cm|order=flip|round=5}} and have more secondary stability than recreational kayaks, which are wider {{cvt|26|-|30|in|cm|order=flip|round=5}}, and have a flatter hull shape and more primary stability.<ref>{{Cite web |date=June 10, 2021 |title=Touring vs Recreational Kayaks - Brooklyn Kayak Company |url=https://brooklynkayakcompany.com/blogs/our-blog-2/recreational-vs-touring-kayaks |access-date=October 10, 2023 |website=brooklynkayakcompany.com}}</ref><ref>{{Cite web |title=Types of kayaks |url=https://www.mec.ca/en/explore/about-kayaks |access-date=October 10, 2023 |website=MEC |language=en}}</ref>

==== Stability from body shape and skill level ====
<gallery mode="packed" heights="200">
File:Weight distribution kayak.svg|The position of the center of gravity is affected by body shape. The lower the CoG, the higher the primary stability.
File:Stability for beginners.svg|Two different approaches to giving beginners more stability; left, a wider kayak, right, outriggers lashed across the stern deck
</gallery>

The body of the paddler must also be taken into account. A paddler with a low [[center of gravity]] (COG) will find all boats more stable; for a paddler with a high center of gravity, all boats will feel tippier. On average, women have a lower COG than men.<ref name=seakayak/><ref name=kayarchy_women/><ref name=kayarchy_kids/> Women generally may fit a kayak about 10% narrower than the kayak that would fit a similarly sized man. Commercial kayaks made for women are rare.<ref name=kayarchy_women/> Unisex kayaks are built for men.<ref name="long_narrow"/> Younger children have proportionately smaller and lighter bodies, but near-adult-size heads, and thus a higher center of gravity.<ref name=kayarchy_kids/> A paddler with narrow shoulders will also want a narrower kayak.

Newcomers will often want a craft with high primary stability (see above). The southern method is a wider kayak. The West Greenland method is a removable pair of outriggers, lashed across the stern deck.<ref name=kayarchy_kids>{{cite web|url=http://kayarchy.com/html/02technique/007seakayakingforkids/000.htm#childsizekayaks|title=Kayarchy – sea kayaking for kids|website=Kayarchy.com}}</ref><ref>{{cite web|url=http://www.traditionalkayaks.com/travelsandadventures/championships.html|title=Championships|website=Traditionalkayaks.com|access-date=November 29, 2017|archive-date=April 22, 2021|archive-url=https://web.archive.org/web/20210422145612/http://www.traditionalkayaks.com/travelsandadventures/championships.html|url-status=dead}}</ref> Such an outrigger pair is often homemade of a small plank and found floats such as empty bottles or plastic ducks.<ref>{{Cite web|url=http://freyahoffmeister.com/expeditions/greenland-national-championships-in-sisimiut-2006/|title=Greenland National Championships in Sisimiut 2006|website=Freyahoffmeister.com|access-date=February 23, 2022}}</ref> Outriggers are also made commercially, especially for fishing kayaks and sailing. If the floats are set so that they are both in the water, they give primary stability, but produce more [[Drag (physics)|drag]]. If they are set so that they are both out of the water when the kayak is balanced, they give secondary stability.<ref name=hobie>{{cite web|url=https://www.kayakshed.com/product/hobie-sidekick-ama-kit/|title=Hobie Gear SideKick AMA Kit Hobie Kayak Outrigger|website=Kayakshed.com}}</ref><ref>{{Cite web|url=http://wavewalk.com/blog/2016/03/04/outriggers/|title=Outriggers – Wavewalk® Stable Fishing Kayaks, Portable Boats and Skiffs|website=Wavewalk.com|access-date=February 23, 2022|archive-date=August 12, 2020|archive-url=https://web.archive.org/web/20200812202447/http://wavewalk.com/blog/2016/03/04/outriggers/|url-status=dead}}</ref>