Leach Telltales on the Jib

[thinwater]

Many of us have these on our mainsails. Generally, unless you have a rotating mast, they are more useful than body telltales.

What about on the jib?

• They are common on some classes.
• They don't last too long because of the beating they take tacking, and because they are not protected from UV.
• Hard to see unless you are steering from leeward. Mostly useful for setting the twist, not for steering.
• The rules for reading them are slightly different from body telltales of from mainsail leach tell tales.
• Best (durable) materials?

 

[PaulK]

Jib telltales a bit aft of the luff are prevalent on most classes. If you don't see them, perhaps it is because the boats with them are so far ahead of you they're not visible. If you can't see them on your own boat, change your seating position. Ours seem to last reasonably well over many seasons. (ten or more?) On different boats we've had wool yarn, nylon (from the sailmaker) and cassette tape. Leech telltales on the jib is a different animal. Have never seen them, even on the boats behind us. Might be worth considering, however.

 

[stickinthemud57]

I recently had a veteran sailboat racer come sailing with me on a few outings to help me tune my rigging and school me in the dynamics of sail shape, draft, etc. He recommended that I put some tels at the leach of my jib, but not for the reason I thought. He said they would be useful for when I was running (mostly) downwind, wing on wing, to evaluate wind flow at the leach of the sail. He made no mention of whether they would be useful when sailing upwind. His attention was more on making sure that the jib tels were flying from top to bottom when close-hauled, and that jib twist would be determined by positioning of the fair leads.

Details:
His advice was to never run dead downwind, that sailing slightly off the wind would result in better Velocity Made Good, i.e. get you to the downwind mark sooner than a straight downwind run. For instance, with the wind coming directly from the south, instead of sailing dead north (0 degress), one would sail on a heading of 30 degrees with the jib flying to starboard (with the aid of a whisker pole, of course). This would set up a condition where the wind is flowing from the leach to the luff so the the leach is acting at the luff, making important to evaluate airflow at the leach to ensure proper trim.

As to your specific questions, I don't have the expertise to offer comments.

 

[shemandr]

I've rarely, if ever, see leech tell tails on a jib. I suppose they would be helpful - the more information about how the sail is interacting with the wind the better. Right? I set the twist on a jib by turning upwind and watching which set of tell tails breaks first. If it is the top set I move the cart forward. If it is the bottom I move the cart back.
Leech tell tails on the main tell me if there is flow over the sail and if the main is over trimmed. If the top tell tale curls around the main now and then you know the main is not over trimmed. I guess the jib wouldn't be any different.
I agree they would probably take a beating.
I think the difference boils down to the mast. Tell tails on the luff of the main wouldn't be too useful. I do think a set of tell tails about 30% back from the mast can help set the depth of the sail . If those aren't flying you may have too much depth in the lower mainsail and the flow is detaching prematurely.

 

[Davidasailor26]

I’ve always thought of leech telltales on the main as a product of necessity rather than the optimal location. I thought that the mast creates an area of disturbed air near the luff of the main, making the leech a better indicator than the normal location a few inches behind the luff. The leech tales only really tell half the story though - whether the sail is over trimmed and stalled. The only way to tell if the main is under trimmed is if it’s back winding. A jib doesn’t have the encumbrance of the mast disturbing its airflow, allowing the telltales at the luff that indicate both over and under trimmed.

 

[stickinthemud57]

I’ve always thought of leech telltales on the main as a product of necessity rather than the optimal location. I thought that the mast creates an area of disturbed air near the luff of the main, making the leech a better indicator than the normal location a few inches behind the luff. The leech tales only really tell half the story though - whether the sail is over trimmed and stalled. The only way to tell if the main is under trimmed is if it’s back winding. A jib doesn’t have the encumbrance of the mast disturbing its airflow, allowing the telltales at the luff that indicate both over and under trimmed.

That makes a lot of sense. My dad's boat did not have tels on the main, just the jib. Trimming the main meant letting it out until it luffed and then pulling it in just enough that it didn't.

 

[DArcy]

Luff tell tales on a main are a good idea too. Ever sail a Laser? There is some disruption from the mast but the flow reestablishes fairly quick. Luff tell tales on the main help to set the draft. The leach tell tales are very helpful on the main as stated above to ensure you aren't hooking the leach and setting proper twist.
I've never seen leach tell tales on a jib or genoa, now I'm wondering if that might be a good idea.

 

[thinwater]

I thought this was a know thing. I've used them for some time. (not my boat)

jib leach telltales

 

[danstanford]

My jibs have one leech telltale in the top 25% of the leech and the tuning guide says always keep that one flying. Often as we sheet the jib for beating a look up will see that one either dropping or flowing way to leeward and changing the twist or easing the sheet will bring it back to flying properly. Great tool in my opinion.

 

[Davidasailor26]

I thought this was a know thing. I've used them for some time. (not my boat)

jib leach telltales

Interesting. Do you find that they stall sooner than the leeward luff tales?

 

[Marmalade]

From Quantum
"Telltales can be used on the leech to indicate flow on a non-overlapping jib. As usual, it is the top telltale that counts. Usually there is only a single telltale in the upper 25% of the leech. Trim too hard or pull the lead too far down (or too far forward) for conditions and that telltale will stall. Twist is essential in a non-overlapping sail so you always want the telltale flying.

Additional telltales are also used sometimes in the upper sections of the mainsail across the middle of the sail. They help refine the twist picture and give a more subtle indication of how hard you are trimming the mainsail. They may indicate stalled flow before the leech telltale disappears. Again, they are in the top sections of the sail because that is where the sail will stall first if over trimmed. If they are too close to the mast the disturbed flow behind the spar will make them useless."

 

[thinwater]

Interesting. Do you find that they stall sooner than the leeward luff tales?

Slightly after. The body telltale can lift when there is only a very slight separation close behind the forestay, sometimes caused by the thickness of the foil itself. Another cause (?) is placing the body telltales too far forward.

I think as a general rule, body telltales work better for steering, and leach telltales work better for setting twist. Leach tell tales also seem to read more reliably in lighter winds (it does not take as much to get them working).

 

[FastOlson]

Unusual discussion, at least to me. The jib tell tails have always been vital to trimming when on the wind. Most boats nowadays have furling jibs, so only the leach ones get much UV exposure, and those do have be replaced occasionally. Some jibs even have little clear windows to make it easy to read the 'tales' on both sides.
Usually, we watch them to remind us not to over-trim that sail....!

 

[thinwater]

Unusual discussion, at least to me....

That is why I started it! I don't pretend to know the answers.

My most resent jib is the first one I have used these on. They seem helpfull, but I also like a lot of tweaks.

 

[FastOlson]

My most resent jib is the first one I have used these on. They seem helpfull, but I also like a lot of tweaks.

On your multihull, you must have to change sheeting angles pretty quickly as the apparent wind keeps moving forward!

I betcha it's a lot of fun!

 

[jssailem]

It is an interesting query.
I have not had or raced boats with tell tails on the leach of the Jib. That I am sure structures my opinions.

When I purchased my new genoa in 2020, North sail put tell tails on the luff, none on the leach.

Here is a video and racing footage on the Etchells class boats and how they are tuned.

https://www.northsails.com/sailing/en/2022/01/lets-talk-rig-tuning-with-andy-rice-charlie-cumbley

Watching the video, I notice a couple of boats in the class had leach tell tails. Most did not.

I have gone, on the racing boats, to marking the sheets for different wind speeds and tack positions. My boat is not racing, so I do not have optimum adjustment of the sheet blocks. I have pin slides and they are positioned based on the conditions as I cruise.

Arvel Gentry, during his initial exploration of how sails function had over 70 tuffs of yarn taped to his jib. He refined that to having 3 sets of 3 on the luff. That is the way my North Sail was constructed, no windows.

Then as the video suggests, you need to go out and sail your boat a lot to begin to understand, decipher, which trim conditions makes you and your boat go fast.

I can see how a tell tail on the luff might help a sailor new to going fast with his/her boat. The challenge is understanding what you are seeing and how that makes a boat fast or slow in the given conditions. Gentry and Frank Braithwaite are my go to instructors.

 

[shemandr]

I once saw a video (Probably linked from this forum), that showed airplane wing or tail wing with regard to a tail stall (I'm not a flyer so my terms may be off). My point was that there were tails all over the foil (Wing). I think this ties in with Gentry's 70 tuffs. He was an aeronautical engineer, I think. Mo' tails, mo' better.

 

[thinwater]

... I have gone, on the racing boats, to marking the sheets for different wind speeds and tack positions. My boat is not racing, so I do not have optimum adjustment of the sheet blocks. I have pin slides and they are positioned based on the conditions as I cruise....

Gentry and Frank Braithwaite are my go to instructors.

Yup, those are smart guys.

If you have pin-leads, investigate 3D leads, using a rap ring or low friction ring to direct the leads. By combining down-haul and out-haul you can get a lot of adjustability with very few $$. The convertion cost me peanuts, just a little rope (Amsteel with covers in the parts that cleat), some rings ($8 rap rings), and some cam cleats. The result is complete control over the clew position in seconds. It's a continuous line, so not much spaghetti in the cockpit.

3D Leads