Physics of Sailing

www.recsports.ufl.edu/wauburg_sailing_chap4.aspx

A sailing boat is powered forward due to the reaction of moving winds against the sails. The energy is then helped by manipulating the wind action and the water speed. If there is very little difference with movement, such as on a calm day with the ocean and weather, the boat will do nothing but drift along. But if it suddenly changes, there is energy created and you can see this when the air beats against the sails and the boat goes against the water. Sails are airfoils and that work by harnessing the wind together to combine much energy and a type of wind called apparent wind, which is the velocity of the sail's wind. The sail then produces a lift using the air around it. This works in nearly all directions but if the boat is faced head to wind it will not move as the wind is too strong to let the boat travel against it. Other Strong built sail boats e.g. iceboats can benefit from these winds as they are designed in a special way. To get out of the head of wind, a sailor needs to tack around an angle bigger than 35°or greater than 80°, just outside of the wind sector. Tacking will give the sails an aerodynamic lift when sailing up wind but down wind, it is soon released.