When should sails be flattened?

• A. To sail downwind
• B. To increase sail area
• C. To point closer to the wind
• D. To reduce hull speed

Answer: (C)

Flattening the sail reduces its draft, making the sail less curved. This helps when you’re sailing toward the wind because the airflow can stay attached to the sail at a steeper angle, so you generate lift with less drag. In other words, a flatter sail lets the boat point closer to the wind without the sail stalling or causing too much resistance. On downwind legs, you’d want a fuller sail for more power, so flattening isn’t used there. Changing the sail’s shape doesn’t change its area, and hull speed isn’t governed by how the sail is shaped, so those options don’t describe why you would flatten.