Why is the advice given to have all the mainsail telltales flowing except the top one, which should be flicking around back about 50% of the time?
Telltale reading
- Thread starter Quoddy
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Who told you that? I would accept the top one flicking around about 50% of the time but I'd not try and trim it that way. You can get it to flow in most conditions but if you have to have one end (head or foot) not flowing the head has less sail area and contributes less to the over all effort so cut corners there and not down low where all the power comes from.
Qouddy: The top telltale is your TWIST indicator and the most important telltale on the mainsail (the middle telltales on the jib are the most important ones to watch). To put it simply, if the top is curling back that means you've applied too much twist. If applying twist was what the sailor wanted to do then he's accomplished his mission but normally you want ALL telltales on the main and jib streaming.
There's one exception -- if you have a masthead rig and really want to be trick you should trim the middle jib telltale so it FLIPS up about every 2 to 5 seconds. What that means is your now at the highest and most efficient point on the lift/drag curve. I really don't know what the lift/drag curve is but I'll bet RichH, Joe from San Diego and Stu J can explain it. It's like a lot of technical things associated with sail trim -- I can't scientifically explain them but I know how to make them work for me. I can't explain how boost works on an engine or gears on a bike but I know what happens when I change gears or punch the accelerator. Since I'm a hillbilly country boy with most things, I just care that they work for me.
There's one exception -- if you have a masthead rig and really want to be trick you should trim the middle jib telltale so it FLIPS up about every 2 to 5 seconds. What that means is your now at the highest and most efficient point on the lift/drag curve. I really don't know what the lift/drag curve is but I'll bet RichH, Joe from San Diego and Stu J can explain it. It's like a lot of technical things associated with sail trim -- I can't scientifically explain them but I know how to make them work for me. I can't explain how boost works on an engine or gears on a bike but I know what happens when I change gears or punch the accelerator. Since I'm a hillbilly country boy with most things, I just care that they work for me.
Occasional 'flicking' of the leeward tell tales tells one that the set/trim/shape is ON the exact hairy edge of a separation stall. Just 'this side' of a separation stall (leeside tales 'flicking' or drooping) is where the air stream velocity is at its highest.
With cruising sails - cut with large 'forgiveness' there can be a very large difference between luffing and separating ... if youre not constantly 'testing' to be towards the 'separating' side of the range, you can easily get caught & held close to the 'luffing side' of the angle ... and wind up with poor relative sail output in comparison to getting the 'max' out of the sail when at close to a separation stall.
When in 'pitching' conditions, with the boat 'bounding' through and into waves, the top of the mast will not have a constant speed but a speed-up / slow-down period of oscilation in time with the amount and timing of the 'pitching'. In those conditions when the mast top is going aft relative to the boat, the leeward tale at the top will 'flick' and when the mast top is going forward the windward tale will flick ... and a good helmsman will steer within that range to keep ALL the tales streaming straight back ... but occasionally 'testing the tales' to establish the best 'average' ... Im talking 'grand prix' type match racing where absolutely EVERYTHING is done to absolute maximum limits to continually gain 'a few inches' of advantage over your competitor.
With cruising sails - cut with large 'forgiveness' there can be a very large difference between luffing and separating ... if youre not constantly 'testing' to be towards the 'separating' side of the range, you can easily get caught & held close to the 'luffing side' of the angle ... and wind up with poor relative sail output in comparison to getting the 'max' out of the sail when at close to a separation stall.
When in 'pitching' conditions, with the boat 'bounding' through and into waves, the top of the mast will not have a constant speed but a speed-up / slow-down period of oscilation in time with the amount and timing of the 'pitching'. In those conditions when the mast top is going aft relative to the boat, the leeward tale at the top will 'flick' and when the mast top is going forward the windward tale will flick ... and a good helmsman will steer within that range to keep ALL the tales streaming straight back ... but occasionally 'testing the tales' to establish the best 'average' ... Im talking 'grand prix' type match racing where absolutely EVERYTHING is done to absolute maximum limits to continually gain 'a few inches' of advantage over your competitor.
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Or - if the top is flowing all the time the sail is undertrimmed relative to the point mode you are trying to sail. The top telltale fluttering tells you that you are on the edge of over trim which is a superior mode to being undertrimmed. It's not really that you want that tell tale to flutter. But you want to know the main can't be trimmed further in for that wind and sailing angle. Its analagous to the spinnaker luff folding by 12 inches. By the time I post this Rich will have said it better...
Shemandr: You weren't quick enough -- RichH beat you to the punch!! I beat him by barely under 1 hour but that's because I was just lucky and happened to turn on the computer before he did. Once RichH, Joe from San Diego or Stu J, plus a few others, answer a question what is there to say except DITTO on that subject.
I totally agree with Bill Roosa. Whose advice are you taking? If it were possible to keep the mainsail's top leech telltale flowing 100% of the time. then you'd be a god.... but if you're able to get it flowing 50% of the time.... that's normal and good enough.
Why? because the top telltale is very close to the mast and is hard to keep flying straight. The problem is that the mast causes turbulent flow across the sail, which keeps the telltale in disturbed air flow.
On my masthead rig I just have single telltales on the leech of the main tied to the the top three batten pockets. The only windward/leeward telltales I have are the mid-chord set, and I pay very little attention to them.
Some of the posts I've read so far mention headsail telltales.... but that wasn't the question.... so I'll make no comment.
Rich's and Shemandr's comments are interesting.... but, uhmmm... I don't know what you would do with that information though. I mean if you were able to get the top tale flowing 100% of the time, would you be unhappy? Would you constantly play the sheet as the boat bobs over a few waves to adjust the twist? NO.... You're more likely to use the tiller or traveller for those temporary changes and leave the twist set in a more compromised position.
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