BBC Sportsailing

Sailing involves a number of different classes of boat, as well as different courses and a system for scoring points according to your finish.

Find out which classes are involved, how the course works, how points are scored and what changes for the medal race.

There are four types of boat used at an Olympic Games.

Dinghy: Finn, Laser, Laser Radial, 49er and 470.

Sailors steer dinghies using a rudder. The crew use their body weight to counterbalance the forces developed by the sail.

The Finn and Laser have a single sail, while the 470 class has a two-sail rig. Both the 470s and 49ers have an additional sail used for the downwind leg, called a spinnaker.

The Laser Radial is similar to the Laser, but uses a smaller sail and a more flexible lower mast.

Keelboats: Yngling and Star.

These boats have a fin fixed below the hull - otherwise known as the keel - while the Yngling boat also has a spinnaker.

Catamaran: Tornado.

These are twin-hulled boats with a centreboard and a rudder on each hull, a two-sail rig and a mainsail.

Windsurfer: RS:X hybrid.

Introduced for the 2008 Olympics as a replacement for the Mistral, the RS:X has a larger sail than its predecessor but is shorter and wider, as well as heavier to manoeuvre.

For each day's competition, the race committee marks out courses using buoys, depending on wind direction and strength.

Boats must sail both upwind and downwind on any course. The initial aim is to work out the fastest route to the first buoy, always placed upwind.

Boats cannot sail directly into the wind, so each crew must zig-zag to reach the first buoy.

On the downwind legs, the 470s, Ynglings, 49ers and Tornados will fly their spinnakers - additional sails used to boost speed. Most courses must be rounded three or four times before crews can head for the finishing line.

Windsurfers have the shortest races, lasting up to 30 minutes, while keelboats can expect races to last up to 75 minutes.

The aim in Olympic scoring is to finish the series of races with the lowest points tally.

If your boat finishes first, you score one point. For second you receive two, three for third, and so on.

Each score is then added together to produce an overall score for the entire series.

Most classes run 11 races in total, except the 49er class, which runs 16.

Once five races have been completed, each crew discards its worst performance from their overall score.

Each series finishes with a medal race, in which the scoring rules change.

In the medal race, points count double - so finishing first earns two points, second four, third six, and so on.

Usually, only the top 10 boats from the rest of the series are allowed to compete in the medal race.

If overall points are tied between boats following the medal race, the boat which scored the fewest points in the medal race takes priority in the standings.

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