How to Use Jib Telltales

The little yarns on your headsail are the fundamental clues to your sailboat’s sail trim and different conditions require a different look.
What your telltales are telling you: “Telltales flowing” is good when underpowered. “Telltales dancing” (windward) can be good when overpowered. “­Telltales stalled” (leeward) is bad and means not fast. Illustration: Tim Barker

Telltales are the most ­ubiquitous and simplest piece of equipment found on any sailboat, and even in this age of powerful race electronics, nothing is more reliable or true than these trusty yarns—or fabric strips—that serve as our guide to good sail trim. They’re an effective teaching tool for beginning racers, especially those on the headsails, so let’s focus on the basics of our jib telltales.

There are two fundamental uses of telltales: We can use them as guides to steer by, as the lower luff telltales indicate how the oncoming wind is interacting with the front of the jib, or we can use them to help us trim the jib more effectively, using the telltales at the upper luff of the sail, and especially the leech telltales.

It’s true that sailboat races can be won through fast sail trim and precision steering, and using the telltales effectively can help you do both. They let us see how the wind is interacting with the jib, which is the info we need to trim the sail right and to steer the boat to windward most efficiently.


Let’s start with some advice on placement. New sails come with telltales, and these are usually well-placed and an appropriate material. But I will often adjust the location slightly and sometimes add a few more to help fill in the picture of how the wind is flowing across both sides of the sail. Wool telltales that might come with a new sail tend to get snagged on the sail stitching, so applying a light coat of McLube on the sail can help prevent that from happening.

Luff telltales need to be a contrasting color, and it is good to have a different color on both sides of the sail. For most jib materials, using green for the starboard side and red for the port side works well. On black or darker-colored headsails, white telltales work best.

I like to have the port and starboard telltales offset slightly, with the starboard side about 1 inch higher than the port. I also like to use a row of three to five short telltales for the steering telltales because they provide a little more information about where the flow is attached to the front of the jib. For the other luff telltales, a single set per location is adequate. They should be placed 10 to 20 percent back from the luff.


For luff telltales, I prefer to use light-gauge wool for more sensitivity.

Leech telltales tell us how the wind is exiting the jib. In particular, they are key indicators of leech stall, when the jib is trimmed too tightly for the wind to travel around it. The leech telltales might need to be a heavier material because they take a beating when tacking. Put them 15 to 30 percent down from the head. Bright red is a good color that contrasts with the sky.

Now for the fun part—using your telltales to go faster. First, let’s discuss using them to set up the jib for the conditions. Essentially, the luff telltales show us the sail’s twist, and the leech telltales show us how tightly it is trimmed.


In underpowered ­conditions, we are usually trying to have the upper and lower luff telltales break evenly, indicating that the wind is hitting the whole luff at an even angle for max efficiency. Use jib-lead adjustments and jib-sheet changes to achieve this.

In overpowered conditions, we need to twist the jib to reduce heeling moment, so the inside upper telltales will not be flowing. This is OK. However, the leech telltales should never be stalled for more than a short time. Keep them flowing at least 80 percent of the time, even when underpowered. If they stall, you need to ease the jib sheet or move the lead aft to open the upper leech and ­re-create flow.

Once the jib is set up ­correctly, we use the steering telltales to keep the jib (boat) at the right angle to the wind. As a basic guide, we want both windward and leeward telltales flowing straight aft in lighter wind, or when there are waves. In stronger wind, and especially flat water, we can sometimes be inside the windward telltale, but never stall the leeward side for more than a second or two.


There are some subtleties in reading the telltales. “Full flow” is when both windward and leeward yarns are flowing straight back. This will provide maximum efficiency when underpowered. “Telltales dancing” means the yarn is flickering or streaming up slightly. Having the windward steering telltales dancing can be good, especially when overpowered. “Telltales stalled” is when the telltale is streaming the wrong way, a definite no-no for the ­leeward telltales.