Dirty Air Meaning in Sailing

Dirty air describes the turbulent and weak wind found directly behind a moving sailing vessel. This air has already passed over the sails of another boat and lost its power. A boat trapped in this zone will travel much slower than a boat in wind. Racing sailors avoid this area to maintain their speed and their position on the course. One specific example occurs when a small boat sails behind a large yacht in harbor. The small boat loses its momentum because the large sails have disturbed the local airflow. The sailor must turn the boat to find clean air to regain the original speed. This concept influences the tactical decisions of every crew during a crowded and competitive race. Understanding the flow of air helps a navigator plan the best route through the water. Staying out of the dirty air of another boat is a primary goal for speed.