Possibly, the most important part of your windsurfing board is the sail that is attached to it. Windsurfing sails are usually made with monofilm which is a very strong material made from different types of polyester and Kevlar. There are two dominant types of sails that are popular on the market today; camber sails and rotational sails. Each has its advantages and disadvantages and each has a specific method of use.
Cambered windsurfing sails have plastic devices (camber inducers) that are attached to the sail and cup around the mast of the board. They help to hold the sail firm and in the proper shape in any force of wind. Cambered sails allow riders to reach maximum speed levels while remaining stable. While these style of sails are extremely light weight they are hard to maneuver and are not recommended for newcomers. These type of sails are meant for professionals, long time windsurfers and even racers.
Rotational windsurfing sails have battens that are attached toward the back of the mast. They are able to move with the wind so that the sail is able to rotate freely about the mast of the board. The rotational sail offers less power, and overall less stability. However, they are heavier and easier to handle and thus recommended to newcomers. Rotational sails are also much easier to attach to the board and can easily be replaced. These types of sails are often recommended for recreational use only. Because of their low stability it is difficult to perform tricks or sail in harsher weather with this style of sails.
Every windsurfing sail is attached at two points to the mast; the tack (the top of the mast) and the clew, (towards the lower quarter of the mast). There is also a set of pulleys that allow you to extend or retract the sail. The sail is tuned by adjusting the downhaul and the outhaul. Generally, the sail has to be tightened more for stronger winds. Adding tension shifts the center of effort up higher on the sail. This also makes the sail flatter and easier to control, but less powerful. Releasing the tension of the sail brings more overall depth to the sail as well as more low-end power. It shifts the center of effort upward and to the front, and may limit speed by increasing aerodynamic resistance.