Enter the lift force, drag force, and the apparent wind angle into the calculator to determine the total sail force.

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## Sail Force Formula

The following equation is used to calculate the sail force.

SF = [L*sin(a) – D *cos(a)] + [L*cos(a) + D*sin(a)]

- Where SF is the total sail force (N)
- L if the lift force (N)
- D is the drag force (N)
- a is the apparent wind angle (degrees)

## What is a Sail Force?

Definition:

**A sail force is the total force on a sail.**

There are two types of sail forces that you need to understand: lift and drag. The first is the force that propels the sailboat forward, while the second is a force that resists movement.

## How to Calculate Sail Force?

Example Problem:

The following example outlines the steps and information needed to calculate Sail Force.

First, determine the lift force. In this example, the lift force is calculated as 50N.

Next, determine the drag force. The drag force in this case is 20N.

Next, determine the apparent wind angle. This is measured to be 47 degrees.

Finally, calculate the sail force using the formula above:

SF = [L*sin(a) – D *cos(a)] + [L*cos(a) + D*sin(a)]

SF = [50*sin(47deg) – 20*cos(47deg)] + [50*cos(47deg) + 20*sin(47)]

SF = 59.499 N