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Kayak

It is a type of small human-powered boat and is a covered variant of a canoe, and is often called a canoe in Great Britain and Ireland, typically used with a double-bladed paddle instead of a canoe's single bladed paddle.

The user or paddler sits down in the kayak with feet facing forward. The top of the kayak is covered with a deck. The paddler sits in a hole in the cockpit which may be sealed off with a spray skirt (or spraydeck). This stops water splashing over the boat from entering it, and makes it possible that, should the kayak (capsize), the kayak will not fill with water, and the paddler, with skill, can right the kayak again without taking on water. This manoeuvre is known as an Eskimo Roll.

In modern times kayaks have been further developed into several types including: whitewater, playboats, surfing, sea kayaks, flat-water racing, downriver racing, slalom, canoe polo and recreational. These types may also be subdivided. Modern kayaks are made of plastic, fiberglass, kevlar, carbon fiber, canvas, other fabrics, or wood. They come in one, two, and occasionally three person models. Some sit-on-top boats are also called kayaks, as the paddler propels the boat with a double-ended paddle.

The design of different types of kayak is largely a matter of two types of trade-offs. The first trade-off important to all kayaks is between directional stability ("tracking") and maneuverability. As a general rule, a longer boat is faster while a shorter boat may be turned more quickly. A longer hull creates a smoother transition from the narrow bow to the widest part of the boat and so "cuts" through the water with less resistance much like a sharp knife cuts more easily than a dull one. Longer boats also have a higher maximum non-planing hull speed, but the effect is largely offset by increased friction, and only becomes a significant factor at racing speeds. Kayaks that are built to cover longer distances such as touring and sea kayaks are themselves longer, generally between 15 and 18 feet. Flat water racing kayaks, which are built for maximum speed and efficiency, may be over 20 feet in length. Whitewater kayaks, which generally depend upon river current for their forward motion, are built quite short, to maximize maneuverability. These kayaks rarely exceed eight feet in length, and some specialized boats such as playboats may be only six feet long. The design of recreational kayaks is an attempt to compromise between tracking and maneuverability, while keeping costs reasonable; their length generally ranges from nine to fourteen feet.

Although length is an important feature of directional stability, length alone is a poor basis for guessing at the maneuverability of a kayak. A second design element that should be considered is rocker, or the curvature of the kayak from bow to stern. A heavily "rockered" boat curves more than a boat with little or no rocker, meaning that the effective waterline of the rockered boat is less than for a kayak with no rocker. For example, imagine a hoop 30 inches in diameter. When set on its edge on a table, only a small portion of that hoop touches the table. Although kayak hulls are not so extremely curved as a hoop, it is analogous to what happens when a kayak with rocker is sitting in the water: although the overall length of the boat may be 18 feet, the length at waterline may only be 16 feet. Similarly, although a whitewater boat may only be a few feet shorter than many recreational kayaks, because the whitewater boat is heavily rockered its waterline is far shorter and its maneuverability far greater.

After directional stabilty, the next most important design difference among kayaks is the tradeoff between primary and secondary stability. Primary stability refers to the feeling of "tippiness" one has when seated in the kayak on flat water. Although every kayak will have some amount of side-to-side rocking, a wide kayak normally feels less likely to capsize than a narrow one, and a flat-bottomed boat will feel more stable than one with a rounded or V-shaped hull. However, if one plans to take his or her kayak into rough water, secondary stability may be more important. Secondary stability refers to the ease of righting a kayak once it has been put off balance. The same boats that have lower primary stability will generally be easier to right once they are tipped too far in one direction. Thus, sea kayaks, which are meant to be taken into open water and rough conditions, are generally narrower (22-25 inches) and less stable feeling than recreational kayaks, which are wider (26-30+ inches) and have a flatter hull shape. Until recently, whitewater kayaks had very rounded hulls. Radical changes in design philosophy, however, have lead to whitewater kayaks with very flat hulls that allow them to sit on top of the water (planing hull) rather than in the water (displacement hull) like most other boats.

There are, of course, many more elements of kayak design— see the external links for more information. Most kayaks are rigid hulled, although folding kayaks that can be transported easily, and inflatable kayaks are not uncommon.
A special type of kayak using pedals allows the kayaker to propel the vessel with underwater "flippers" .

See also:

Canoe
Royak
Canyoning
Playboating
Squirt Boating

See:
• Boat
• Boat Manufacturers
• Boat Types
• Skipjack Boat
• Mainsail
• Bermuda rig
• Watercraft
• Kayak
• Kayak Origins
• Folding Kayaks
• Recreational Kayaks
• Sea Kayak
• Whitewater Kayaking

• Adirondack Guideboat
• Vermont Fishing Dory

This article is licensed under the GNU Free Documentation License.
It uses material from the Wikipedia article "Kayak".