Headsail Trimming – Using the Fairlead

Understanding the Jib Fairlead Position: How It Affects Sail Twist and Boat Heel

As demonstrated in the video, the position of your jib’s fairlead has a significant impact on both sail shape and boat performance. Let’s break down what you observed.

Wind Flow and Sail Twist

When the fairlead is positioned aft (toward the back), you can see the wind at the top of the sail flowing upward and spilling out. This happens because the sail has more twist—the top of the sail is looser and at a different angle compared to the bottom, which is sheeted in tighter. From the stern view, this difference in wind direction between the top and bottom of the sail becomes clearly visible.

Moving the Fairlead Forward

When you move the fairlead forward, it pulls down on the leech (the trailing edge of the sail), closing off the gap at the top. Watch how the wind direction changes—instead of spilling out, the airflow at the top of the sail turns inward and thus putting more force on the sail area at the top. This tighter leech creates more power in the upper portion of the sail.

The Effect on Heel

As the leech tightens and the wind at the top of the sail becomes more efficient, you’ll notice the boat begins to heel over more. This increased heel is caused by the greater force being generated in the upper part of the sail. The tighter the leech, the more power you’re capturing—and the more the boat will heel.

Controlling Your Headsail

This is the fundamental principle of headsail fine trim: by adjusting the fairlead position, you can change the sail’s shape, control the amount of power it generates, and manage how much your boat heels. Moving the fairlead forward increases power and heel, while moving it aft reduces power and allows the top of the sail to twist off, spilling wind and reducing heel.

Learn More

Want to dive deeper into sail trim techniques? Visit www.nauticed.org for a free comprehensive sail trim course.