How To Trim A Sail Properly


Ideally, once you rig your sailboat and sail off, the air is supposed to flow across all sides of the sails smoothly. The sails should feature a rigid appearance, with no flopping or puffiness.

To keep the sailboat sailing efficiently and in balance, adjusting the sail shape is usually necessary. If you are just getting started with sailing, you may not know how to adjust the sail shape. By showing you how to trim a sail, we hope to help you have a smooth sailing experience once you put on your sailing shoes.

Trimming the Jibs

When discussing sail trimming, starting with the headsail makes sense for 2 major reasons:

  • The jib is responsible for directing the airflow to the mainsail.
  • The jib creates lift and also offers a portion of the sailboat’s forward momentum.

Position the Jib

The jib’s luff/leading edge is supposed to face directly into the wind. This allows the air to stream evenly on both sides. When trimming the jib, you should be focusing on ensuring that the entire sail, from the head to foot, is presented to the wind evenly, at an ideal angle.

You should ensure that the sail does not feature any horizontal or vertical wrinkles. Horizontal wrinkles indicate that the halyard does not have enough tension. By increasing the tension of the halyard, you should be able to flatten the sail. As the speed of the wind increases, increasing the halyard tension is generally necessary.

Vertical wrinkles along the jib’s luff indicate that the halyard features too much tension. You should be able to get rid of the wrinkles by easing the tension a little bit.

Jib Sail Trimming

After positioning your halyard properly, you should shift your attention to trying to trim a sail. To judge the correct trim, you should use the telltales.

There should be 3 sets of two telltales, one on each side of your sail. These should be set along with the sail, near its luff, evenly.

When you are sailing upwind, your goal should be to have all the telltales streaming back, on the 2 sides of the sail, uniformly, from the bottom to top. You will need to trim a sail whenever the telltales stream forward or flutter, indicating airflow turbulence. The turbulence generally results from the incorrect presentation of the sail to the wind.

Once you wear your sailing hat and board the sailboat, you should focus on comparing the telltales from bottom to top. Any issues can be adjusted pretty easily by adjusting the jib’s fairlead position.

If you trim a sail by making use of forwarding lead placement, this will cause a more direct and downward leech pull. This will straighten the leech and bring the upper sail inward. Once you bring the upper sail inward, it aligns more with the flow of the wind. The telltale matches those on the lower part of the sail.

You can figure out the ideal position of the jib leads by using the boat steering wheel to turn the sailboat into the wind. When doing this, watch the telltales.

As the sail starts to luff, all the telltales should also start fluttering at the same time. If the top telltales end up lifting first, too much tension exists on the sail foot and the lead has to be moved forward. If the bottom telltales lift first, you should move the lead aft.

This tactic should be ideal when sailing in winds featuring a speed of approximately 15 knots. As the strength increases, you will need to move the lead blocks aft. This should help reduce pressure in the overpowered sail, opening the leech of the sail up, to spill out the excess air. This should increase sailing safety.

Trimming the Mainsail


Hoist the mainsail and eliminate both vertical and horizontal wrinkles by adjusting the halyard tension. Again, you will need to think about the presentation of the sail to the wind from top to bottom first, and then laterally.

The mainsheet’s traveler generally controls the sail’s bottom half directly and the top to a lesser degree. If you figure that you will be sailing upwind after wearing your sailing shorts and pants, you should move the traveler so that the middle and lower telltales stream back. While this is an ideal setting for the lower sail, the upper part may need tweaking with the sheet.

When sail trimming the mainsail, you need to note that the sheet tension controls the upper leading edge directly, with a lesser effect on the lower section. If you decide to trim a sail by tensioning, you will be pulling the upper portion in. This will alleviate the inward telltale fluttering. Easing the sheet will allow the upper mainsail to billow more, exposing its outer side to more wind, and hence controlling the telltale fluttering.

If you are not new to sailing, you probably already know that the wind higher aloft is generally stronger and more aft compared to the wind available at the surface. This is referred to as the wind shear.

Due to the wind shear, it is generally necessary to trim a sail differently up higher than at the deck level. The outer telltale fluttering generally calls for sheet easing until the outer portions gain access to enough air.

If the mainsail sail trimming is ideal in light to moderate breezes, the boom is generally parallel to the upper batten. With greater wind aloft, the top batten is supposed to be eased more.

Adjusting the Draft Depth and Position

Both the position and depth of the draft in a sail are crucial trim considerations when sail trimming. This is because they influence the sail power, degree of weather or lee helm, and pointing ability.

You should move the draft depth forward or decrease it as the wind strength increases. Alternatively, you can change the course to a point higher.

In very light winds, you should restrict the depth. An overly deep draft will allow the light air to lose contact with the mainsail. The draft depth is moved aft and increased when falling off the wind and in moderate or light breezes.

Globo Surf Overview

Irrespective of whether you will be wearing your sailing sunglasses for the first time or you have sailed in the past, learning how to trim a sail is important. Sail trimming, when done properly, can help you and your crew sail faster. If you follow the tips in this article, sail trimming should be much easier for you.

More Sail Reviews:


  1. Basic Sail Trim,
Globo Surf
My name is David Hamburg. I am an avid water sports fan who enjoys paddle boarding, surfing, scuba diving, and kite surfing. Anything with a board or chance I can get in the water I love! I am such a big fan I decided to start this website to review all my favorite products and some others. Hope you enjoy!