This odd observation is due to the same concepts that were discussed about the air and hydro foils. The wind pushing directly on the inside of the sail is the central force. In addition to this is the force of the pressure created by the difference in wind speed on the inner and outer sides of the sail. The part of the boat under the water counters the sideways component of the wind force and the resultant direction of the vessel is mostly forwards. Different sail shapes, mast curvatures, boom heights, batten lengths, and sail taughtnesses all contribute to the net force.
Many sports involve the use of projectiles, vehicles, and boats.
The performance of all of these things depends on certain aerodynamic principles. For example, a Formula 1 racing car has a foil on its front which is shaped like an upside down airfoil. This foil creates a downward force on the car increasing the the force of the car on the track which results in greater friction value between the track and the tires. This increased friction value gives the tires more 'grip' on the pavement enabling the car to move at greater speeds. Projectile distances vary depending on which direction they spin.