Science of Sport: Sailing Can you adjust the sails to make the boats follow the tracks? Do - Think - Learn Move the sails so that the boats follow the tracks. What did you have to do to make the boats follow the tracks? Were you successful? The Science Bit The physics of sailing involves the interaction of the wind and sails and the interaction of the water and keel. To propel a sailing boat the force of the wind needs to be deflected, resulting in the boat travelling in the desired direction and not capsizing. The sails act as aerofoils which deflect the flow of the wind. The keel of the boat stops the boat moving sideways by pushing on the water. Sails propel the boat in one of two ways: 1. When the boat is going in the direction of the wind (i.e. downwind) the sails may be set merely to trap the air as it flows by. The wind pushes on the sail propelling the boat forwards. 2. When sailing towards the wind (upwind) the sails act as aerofoils to propel the boat by redirecting the wind coming in from the side and pushing it towards the rear. By Newton’s 3rd law (action and reaction are equal and opposite) the boat is pushed forwards. Also as the wind flows over the sail, the pressure difference generated by the shape of the sail results in forces on sails including drag and lift. Curriculum Links Forces Identify the effects of air resistance, water resistance and friction that act between moving surfaces Forces and Motion Forces being needed to cause objects to stop or start moving, or to change their speed or direction of motion .