Tell Tales on Fully Battened Main
- Thread starter DinoKanuck
- Start date
Tell Tales on the leech at each of the battens is pretty standard. I've never used luff tell tales on the main and never used leech tell tales on the jib.
Unless it is a rotating mast, leach only on the main. You will have flow on the windward side and the leeward telltales are too affected by mast turbulence and genoa wash to mean much. Leach only tells you what you need to know.
I suppose leach tell tales on a genoa would function, but they would not last long. On a roller-furler they would be exposed and fluttering 24/7, and folding a hank-on sail would rip them off.
I suppose leach tell tales on a genoa would function, but they would not last long. On a roller-furler they would be exposed and fluttering 24/7, and folding a hank-on sail would rip them off.
It makes sense to have additional telltales on a roller furling jib. As the jib is furled the luff moves and buries the first row of tell tales, another reef and the next set is buried. I suppose the same would hold true on a in mast mainsail furling system. However, on a full-batten it isn't necessary.
Trim on the main is pretty simple (getting there may not be). The tell tales showed be streaming aft, except the top one which should kick forward every now and then.
Trim on the main is pretty simple (getting there may not be). The tell tales showed be streaming aft, except the top one which should kick forward every now and then.
Only plan is to make the leap from a partially battened main which tells me lots about the air flows on the sail to a fully battened main that provide not such information.
One of the drawbacks of the full battened main is indeed that it can look like it is trimmed well, but isn't.
The key to mainsail trimming, on either a FB or partial batten sail, is to get the tell tales flowing aft up and down the leech. If the air flow is good at the leech, then the sail is trimmed correctly. Most of the power from the main comes from the aft end of the sail. The airflow should be attached and turbulence free. When he telltales suck forward, there is turbulence and the sail is stalling, when they are streaming, the airflow is attached and has little turbulence. The exception being the uppermost tell tale. Occasionally flipping forward is good trim. The flipping forward is caused by sail twist and altitude. Winds aloft are often a few degrees different from deck level winds.
My previous fully battened main had only telltales near the luff. My new FB main has four leach tell tales. What a difference in being able to trim correctly. Read the above post from dlochner.
This simple book can help a whole lot with learning how to read telltales and trim your sails. You'll be considerably further ahead of the vast majority of other sailors if you use this guide. https://shop.sailboatowners.com/prod.php?51998/Sail+Trim+Users+Guide
I actually like it, with 6,7,8 likely a bit crowded. You may be able to reduce to a total of 3 rows on luff/body. A draft stripe is also helpful. My mainsail had just one on each side in the main body of the mainsail, of directly above location #11 which is useful.
As drawn, you would have 22 telltales.
As drawn, you would have 22 telltales.
Do a search for Arvel Gentry. You'll get some good information about tell tale placement on headsails and mains and how to read them. You can start by reading about his many works here.
http://gentrysailing.com/theory.html
This article is probably most germane to your question.
http://gentrysailing.com/pdf-theory/Checking-Trim-on-the-Wind.pdf
http://gentrysailing.com/theory.html
This article is probably most germane to your question.
http://gentrysailing.com/pdf-theory/Checking-Trim-on-the-Wind.pdf
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Three single tells sewn to batten pockets on the leech, .... if they aren't flowing, the air has become detached.... that's what you need to know to set your twist. The luff tells won't tell you anything, because of the turbulence behind the mast. On a mainsail, the power is in the back half of the sail.... while the front half of the headsail will provide it's power. If you think of the headsail and mainsail as one continuous foil with a vent.... the flowing telltales at the entry and exit are indicating continuous attachment.
Once I attached a pair of tells to the approximate center of the lower chord in the main.... thinking I could get outhaul data.... guess what... it flowed no matter what. Changing draft depth or position, or even adjusting the slot..... none of that did anything to that indicator. I found simply watching the speedo and the leech tells helped with the slot... as did draft placement and depth.... it all reverts to maintaining attachment.
Once I attached a pair of tells to the approximate center of the lower chord in the main.... thinking I could get outhaul data.... guess what... it flowed no matter what. Changing draft depth or position, or even adjusting the slot..... none of that did anything to that indicator. I found simply watching the speedo and the leech tells helped with the slot... as did draft placement and depth.... it all reverts to maintaining attachment.
Back to the OP, you've been given lots of advice, some I would bank on, some well is a bit dated. The one big question that has not be asked is what is the reason you want or need 22 tell tales on the mainsail? There might be good reasons, curiosity about laminar flow might be at the top, but without knowing the whys and wherefores of all that yarn fluttering on the sail, it is difficult to suggest that more than 4 leech tell tales would be sufficient.
Is there a reason to add all that yarn?
If you want to delve into the nuances of sail trim, read (or perhaps try to read) Stuart Walker's book on Sail Trim. Remember that some of these books and articles were written years ago and apply to the sails and rigs of years ago. Some information may no longer be relevant, especially the trend towards larger mains and smaller headsails.
Is there a reason to add all that yarn?
If you want to delve into the nuances of sail trim, read (or perhaps try to read) Stuart Walker's book on Sail Trim. Remember that some of these books and articles were written years ago and apply to the sails and rigs of years ago. Some information may no longer be relevant, especially the trend towards larger mains and smaller headsails.