Editing Sailboat (section)

==Keel==
All vessels have a [[keel]], it is the backbone of the hull. In traditional construction, it is the structure upon which all else depends. Modern monocoque designs include a virtual keel. Even multihulls have keels. On a sailboat, the word "keel" is also used to refer to the area that is added to the hull to improve its lateral plane. The lateral plane is what prevents leeway and allows sailing towards the wind. This can be an external piece or a part of the hull.

Most monohulls larger than a dinghy require built-in [[ballast]]. Depending on the design of the boat, ballast may be 20 to 50 percent of the displacement. The ballast is often integrated into their keels as large masses of lead or cast iron. This secures the ballast and gets it as low as possible to improve its effectiveness. External keels are cast in the shape of the keel. A monohull's  keel is made effective by a combination of weight, depth, and length.

[[Image:MariahQuarterView.jpg|thumb|upright|Sailing [[yacht]] with a fin keel]]
Most modern monohull boats have fin keels, which are heavy and deep, but short in relation to the hull length. More traditional yachts carried a full keel which is generally half or more of the length of the boat. A recent feature is a [[winged keel]], which is short and shallow, but carries a lot of weight in two "wings" which run sideways from the main part of the keel. Even more recent is the concept of [[canting keel]]s, designed to move the weight at the bottom of a sailboat to the upwind side, allowing the boat to carry more sails. A [[twin keel]] has the benefit of a shallower draft and can allow the boat to stand on dry land.

Multihulls, on the other hand, have minimal need for such ballast, as they depend on the geometry of their design, the wide base of their multiple hulls, for their stability. Designers of performance multihulls, such as the [[Open Ocean Performance Sixties|Open 60's]], go to great lengths to reduce overall boat weight as much as possible. This leads some to comment that designing a multihull is similar to designing an aircraft.

A [[Centerboard|centreboard]] or [[daggerboard]] is retractable lightweight keel which can be pulled up in shallow water.