Sail Area Wind Force Calculator

How is this calculated?

The wind load acting on your sails is calculated using the standard aerodynamic force equation:

$$F = \frac{1}{2} \rho v^2 A C_d$$

• F (Force): The total wind pressure pushing against the sails.
• $\rho$ (Air Density): Standard sea-level density is calculated at 1.225 kg/m³.
• v (Velocity): Wind speed, which is squared. This means doubling the wind speed quadruples the force acting on your rig!
• A (Area): The total exposed area of your sails.
• $C_d$ (Drag Coefficient): A constant representing the aerodynamic efficiency of the sail shape. A standard value of 1.2 is used here for generic cloth sails.

Why does this matter?

Understanding wind force is crucial for reefing decisions. Because wind force increases exponentially with wind speed (due to the squared velocity variable), waiting too long to reef can put excessive, sudden strain on your rig and cause severe heeling. For example, the force at 20 knots is four times greater than the force at 10 knots.