A sailboat or sailing boat is a boat propelled partly or entirely by sails. The term covers a variety of boats, larger than small vessels such as sailboards and smaller than sailing ships, but distinctions in size are not strictly defined and what constitutes a sailing ship, sailboat, or a smaller vessel (such as a sailboard) varies by region and culture.
Today, the most common sailboat is the sloop which features one mast and two sails, a normal mainsail and a foresail. This simple configuration is very efficient for sailing towards the wind. The mainsail is attached to the mast and the boom, which is a spar capable of swinging across the boat, depending on the direction of the wind. Depending on the size and design of the foresail it can be called a jib, genoa, or spinnaker; it is possible but not common for a sloop to carry two foresails from the one forestay at one time (wing on wing). The forestay is a line or cable running from near the top of the mast to a point near the bow. In Bermuda, where a rig design influenced by the Lateen rig appeared on boats and came to be known as the Bermuda rig, a large spinnaker was carried on a spinnaker boom when running down-wind. An example of a typical sloop can be seen on the Islander 36.
The cutter is similar to a sloop with a single mast and mainsail, but generally carries the mast further aft to allow for the use of two headsails attached to two forestays, the head stay and the inner stay, which carry the jib and staysail respectively. This is rarely considered a racing configuration; however, it gives versatility to cruising boats, especially in high wind conditions, when a small jib can be flown from the inner stay.
Importantly, the traditional and most accurate definition of a true cutter, however, is not in the number of headsails, but rather that the outermost sails are set on stays that are not strictly structural to the rig itself. This in itself is a function of a much more complicated design set, involving mast placement, mast height, rig, boom length and fore-triangle size.
A schooner can have two or more masts, the aftermost mast taller or equal to the height of the forward mast(s), distinguishing this design from a ketch or a yawl. Top sail schooners are rigged to carry a square sail near the top of their foremast, but generally modern schooners are gaff or marconi rigged.
Dhoni or Doni (Dhivehi: ދޯނި pronounced Dōni) is a multi-purpose sail boat with a motor or lateen sails that is used in the Maldives. It is handcrafted and its use within the multi-island nation has been very important. A dhoni resembles a dhow, a traditional Arab sailing vessel.
This absence of ballast also results in some very real performance gains in terms of acceleration, top speed, and maneuverability.
All these hull types may also be manufactured as, or outfitted with, hydrofoils.
Most monohulls larger than a dinghy require ballast, depending on the design ballast will 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 effectivness. 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.
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 keels, designed to move the weight at the bottom of a sailboat to the upwind side, allowing the boat to carry more sails.
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 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 more similar to designing an aircraft.