Tue. Apr 16th, 2024
Sail Telltales

Telltales (also known as tell-tails) are pieces of fabric, used in sailing to assist with trimming of the sail. They can be attached to both rigging and sails to identify the wind flow in a particular area.

This guide will cover all you’ll ever need to know about telltales (and more)!

It will cover the basics as well as more advanced tips so whatever your ability you should gain something from it.

Why Use Sail Telltales?

When I started taking racing more seriously I told my coach at the time that I didn’t use telltales. What followed was a barrage of disbelieving sentiment, bordering on ridicule. How could you not use telltales? How have you got so far without using them?

I explained sheepishly that I just sailed to the luff of the jib. If that part of the sail started to flap I knew I needed to bear away until it stopped flapping. After a while, you get used to the feeling just before the flap happens so you can bear away in advance of any flapping. This must have been how people sailed before telltales were invented.

So, after being shamed into using them I decided I’d learn how. Turns out, they really are quite useful.

Telltales can:

  1. Tell you if the wind has shifted
  2. Tell you if you can sail higher or whether you are pinching too much
  3. Tell you whether you are over or under-sheeted, or just right
  4. Tell you whether your sail twist is correct
  5. Tell you how the wind is flowing over the sail
  6. Tell you how much kicker to have on off-the-wind.

The main benefit of telltales over watching for the sail to flap is that they are more sensitive. You don’t need telltales, and one might argue it’s better to learn to sail without them. But if you’re taking your racing seriously it’s worth using them.

Telltales for Sail Trim

Note: Below is a general guide that should work in most cases. But it’s always worth checking your class tuning guide for class-specific advice. A quick Google should bring several tuning guides up from various sail makers in your class. Google: “tuning guide [your class]”.


Upwind telltales are used to indicate whether you are over, under or correctly trimmed and whether the sail twist is correct. To put it simply, it tells you whether the sail should be pulled in or let out. It indicates what your angle of attack should be in each area of the sail(s).

There are two types of telltale we use. Draft telltales and leech telltales.

1. Draft telltales are positioned either side of the sail usually around the deepest part of the sail.

2. Leech telltales, unsurprisingly, are positioned on the leech of the sail.

How Do You Read Telltales?

  • If your sail(s) are under-trimmed or you are pointing too high then the telltales on the windward side will stall whilst the leeward ones stream horizontally.
  • If your sail(s) are over-trimmed or you’re sailing too low then the telltales on the leeward side will lift and stall whilst the inside ones stream horizontally.

Try to keep the leeward telltale(s) streaming horizontally and the windward telltale(s) streaming horizontally with the occasional lift.

How do you read Leech Telltales?

  • If your sail(s) are under-trimmed the leech telltales will wrap around the inside of the sail.
  • If your sail(s) are over-trimmed the leech telltales will wrap around the outside of the sail.
  • If the sail(s) are correctly trimmed the leech telltales will flow out evenly.

The top leech telltale is the one most commonly used. As a rule of thumb you want it flying horizontally 80% of the time and breaking 20% of the time. If it’s always flying horizontally that usually indicates you should be pointing closer to the wind.

However, depending on the class and the conditions this optimum percentage can vary between 50% and 100%. Generally, you’ll want them flying horizontally more of the time in very light conditions or choppy conditions.

Using Telltales For Correct Sail Twist

Telltales can also indicate how much sail twist you should have. Twist is the degree to which the sail’s angle of attack varies in the top of the sail in comparison with the bottom.

To establish the correct twist you use the telltales in the top third of the sail. You can either use the draft telltales or the leech telltales.

Guide for using the draft telltales

  • Windward telltale lifting & stalling = too much twist
  • Leeward telltale lifting & stalling = too little twist

Guide for using the leech telltales

  • If telltales are wrapping around the inside of the sail = too much twist
  • If telltales are wrapping around the outside of the sail = too little twist
  • If telltales flow out horizontally 80% of the time = correct twist

Depending on your class, the backstay or kicker (vang) is usually the primary control for controlling sail twist.


Telltales are mostly used sailing upwind. But they do have uses off-wind too.

  1. They can tell you if you have too much kicker downwind. The telltales won’t fly much if you have too much kicker on.
  2. Shroud telltales are good apparent wind direction indicators. Saves you getting neck ache from looking up at the burgee.
  3. Telltales also come in handy if you want to know the direction of wind flow across the sail (e.g. when you’re sailing by the lee).

Telltales and Wind Shifts

Far in the future are the days when we’ll have ginormous wind machines that produce a steady 12 knot breeze over our fancy indoor ‘sailing pools’. Until then, for better or worse, we are stuck with wind shifts.

Telltales can help here too. As we talked about above, we can use the telltales to perfect our upwind sailing angle and sail position. So, if you’re sailing along with both sets of telltales streaming horizontally and one set starts to misbehave without you doing anything then we know there’s been a wind shift.

The side of the sail on which the telltales are stalling can tell you whether it’s a heading or lifting shift.

  • If the telltales on the windward side are lifting and stalling that indicates you’ve been headed and will need to bear away to your new close-hauled course.
  • If the telltales on the leeward side are lifting and stalling that indicates you’ve been lifted and should head up to your new close-hauled course.

An easy way to remember it is to steer towards whichever side of the sail still has its telltales streaming horizontally.

Which Telltales Should You Focus On?

This depends on the conditions and your class of boat.

As a helmsman you’ll probably find the best set of telltales to look at will be the highest ones that you can comfortably and reliably look at for a prolonged period. Giving yourself neck ache is no fun!

In a single sail class these will be the lower set of telltales, usually positioned a metre of so back from the mast.

As a helmsman on a multiple sail boat you’ll likely be spending the majority of your time staring at the jib telltales. These are positioned roughly half a metre back from the luff in roughly one or two metre intervals going up the sail.

The higher telltales are especially useful in light winds as the wind higher up tends to be stronger and more reliable.

If you’re steering to the waves you’ll want to divide your attention between the waves and the telltales. You may find using the lower telltales better as you can see them and the waves in the same frame of vision. No more head nodding!

Shroud telltales

Some sailors like to use shroud telltales. These give you the real wind direction and don’t rely on proper jib trim to be accurate.

There must be a good system for keeping these in place but I am yet to discover it. Over time mine drift down the shrouds into the telltale graveyard at the bottom.

What Material Is Best For Telltales?

If you take a trip to your local chandlery you’ll find nearly all the telltales available are either wool or nylon ribbon. With wool being the preferred choice for the draft of sails and ribbon for the leeches and shrouds.

If you sail somewhere where the wind is often very light then you may want to look at telltales made from a light thread. These will lift with less wind. Though you may find them harder to see. These can be good to use on your shrouds.

My biggest bugbear with telltales is their tendency to stick to sails when wet. And let’s face it; sails tend to get wet every now and then. That’s why I recommend using Teflon coated telltales. Spraying McLube Sailkote on them also does the job.

If I was to make my own telltales I’d change the traditional red for port and dark green for starboard colours. I just find the colours don’t jump out as much as they could. I’d go for the most garish, fluorescent, razzle-dazzle colours available so you can’t miss them.

Telltales should also stand out in colour from the sky. As should the burgee. So definitely avoid anything close to blue or white!


Telltales can tell us a lot if we use them correctly. Experiment with different telltale types and positions to find what works for you. Feel free to go overboard with telltales. No sailor ever went slower because they had too many.

Cloyd Adams