Where should telltales and leach ribbons be placed on a lug sail? There are some places that are better than others.
We provide leach ribbons on our standard sails and we are providing telltales on most sails now. These are quite easy to use as in a previous article.
No … you don’t need as many as the photo below – I was doing sail development work. But it did help me understand which telltales work best on a lugsail.
General Explanation of telltales and leach ribbons
Conventional sail body telltales should be at the maximum depth of the sail. That makes the windward telltale more accurate for judging the depth of the sail. If you can’t get the windward tuft so placed to fly then the sail is too full and the air is finding a short cut across the windward side leaving the windward tuft hanging or flipping around.
Bruce Taylor’s Goat Island Skiff showing the telltales flying nicely. The location is pretty accurate too. Top telltale is above the masthead. Lower telltales are at the maximum depth of the sail or maybe slightly forward of that point.
Specific location of telltales and leach ribbons on a Lug Sail
The “problem” with lug sails is that you have a wake from the mast down one side of the sail. We know it has very little affect on the amount of actual power available, but it is going to mess up the telltales on that side.
A telltale in the head of the sail near to or above the mast top will work.
And you might be able to get some others to work some of the time and make some decisions about settings on one tack knowing that they are more or less duplicated on the other, where the telltale might not be working so well
The way the leach ribbons work is that when a sail is oversheeted there is a wedge of separation that starts at the back of the sail. The wind can’t quite make it to the edge of sail without losing contact on the leeward side. Separation.
And the leach ribbons pick that up nicely.
Telltale positions and special considerations
I’ve got telltales everywhere on my racing lugsail. Because I have to diagnose the sailshape for further development. So I can see which ones are working and which ones provide the best guide. As suggested above the photo below shows telltales above the first reef. I would suggest just using the third telltale back.
The best place to put telltales on a lug is in the head of the sail just above the top of the mast to avoid interference.
With the other telltales further down the sail we generally just put them at the maximum draft of the sail. Too close to the mast and they are not reliable. And as the distance from mast to maximum sail draft is not a large distance this is the best place for the lower telltale and the mid telltale.
Additionally, if the sail has reefs we put the lower telltale about a foot (300mm) above the lowest reef so it is still functional with that reef tied in.
Racing setup for a balance lug Mainsail
I go out about 10 minutes early for the race and sail some of the first upwind leg.
If the boat has a jib the jib lead angle and sheet tension need to be set up first.
To set up a lug mainsail I work out what mainsheet tension I’m likely to need in the lulls.. If the wind is strong I want to reduce the sail by reefing and/or flatten the sail out with lots of downhaul tension. See article “What is this crease in my lugsail?“.
So sailing upwind the aim is to have the correct mainsheet tension for best boatspeed and pointing. Steer so the upper telltales and happy and both streaming aft.
While the upper sail is happy have a look at the lowest telltale. We don’t have a lot of options to trim the lower mainsail separately from the upper main on a lug. But it is an opportunity to get the lower sail to the correct sail depth.
With the upper sail working nicely look at the lower telltales. If the windward telltale is waving around randomly or pointing forward and the leeward telltale is pointing aft then the lower mainsail is too full/deep and the outhaul needs some tension to flatten out the bottom part of the sail. Once adjusted get the boat moving again and the upper telltales streaming and double check the lower telltales are OK now.
If the opposite it true and the windward telltale is flying and the leeward one is not (spinning or pointing forward) then the bottom of the sail is too flat, so ease the outhaul. Again head off upwind and doublecheck that in the lulls and with the upper main trimmed that both telltales in the lower sail are OK.
If BOTH lower telltales are unhappy … it is more important to get the leeward one working as that is about 70% of the power of the sail. Sometimes this can be caused by the telltales being a bit behind the maximum depth of the sail. This can make them excessively fussy!
Other Functions of Telltales on a Lug Sail
All our articles on Lug Rigs, use, tuning and tweaking are here.
Another function apart from sail setting is using the telltales/tufts for steering and sail trip. To find the low acceleration part of the groove or the higher pointing. “A separation bubble also forms at the luff. “A separation bubble also forms at the luff. A regular tuft system won’t detect this until the sail is fully stalled, but the Gentry tuft system will. This is why jib tufts are positioned slightly further forward than those on the main… in the hope of detecting the separation. Once the separation reaches the maximum sail depth, the flow on the leeward side will completely separate and never reattach to the sail.”
But EXPERIENTIALLY it is possible to sense all of this and you don’t have to have any tufts at all.
We know the feeling of power and speed drops when the boat starts luffing even a little. Drop down a little and the power available becomes exponentially larger through a very narrow angle. Drop away from the wind a bit more and it suddenly disappears.
you can see our learn to sail article about finding the groove by feeling the boat even without telltales
How to trim sails by feeling the boat – LINK
That’s how we are teaching people on Lake Ta’al. To really note the feeling of being in the groove directly and to sense the radically different feeling of the boat. The power really comes on with a lug and it is clean and precise because of the unimpeded luff.
A few hours steering like this and sensing the power band is time well spent. Our students pick it up in an hour or so, any extra time is refinement.
I’ve realised in my own sailing the reason I don’t need to luff the sail to keep the right angle like a learner is because I feel the powerband directly. I think most people comfortable with steering do, but I’ve never really analysed it before.
The familiarity with the narrower power band means the steerer doesn’t need to do little trial luffs to find out where the wind is so often.
A mast or spar on the front of the sail allows for a wider range of angles of attack. This is because its rounded shape helps direct airflow onto the sail without causing such a distinct separation bubble. On a jib luff, this effect is more pronounced as the curve is tighter around the sharper edge allowing the Gentry system to detect the size of the separation bubble.
Here is a link to the Arvel Gentry article. One of the great thinkers and explainers.