Educate me on the use of the sail's telltales
- Thread starter Neil
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LadyInBed
Well-known member
Javelin
Well-known member
Hmm, dunno as I've never tried tell tails further back
However the way I expect things should work is they will stream aft but with little airflow.
The reason the tell tails curl is that the boundary layer has detached from the sail causing a bubble of counter rotating air.
These bubbles tend to form either side of the luff and spread back, or leeward aft leech area and spread forward.
SO in theory at least tell tails in the middle should be unaffected until which time one of the bubbles stretches to their position.
However the way I expect things should work is they will stream aft but with little airflow.
The reason the tell tails curl is that the boundary layer has detached from the sail causing a bubble of counter rotating air.
These bubbles tend to form either side of the luff and spread back, or leeward aft leech area and spread forward.
SO in theory at least tell tails in the middle should be unaffected until which time one of the bubbles stretches to their position.
Plevier
Active member
@Javelin
If I can jump in on this with something a bit different?
I've just got a 2008 Dehler 35 - 35ft LOA, 1.95m fin keel (lead bulb), tall fractional rig (P 14.5, I 15, E 4.7, J 4.1), main 42sq.m., standard genoa 33sq.m., only 107%, about 5500kg.
I'm finding it very difficult to control the genoa head, moving cars all the time, and lots of problems backwinding the main. Very fast when you get it right - but that's not often at the moment!
Any thoughts on this rather different rig please?
flaming
Well-known member
We race with a very similar rig. In the light we have found the Jib's top leach tell tale to be the most important on the boat. This MUST be flying. If you choke this off you just stop.
So you often end up bringing the car back in the light - which is slightly counter intuitive - and then only taking it forward when there is enough wind to open out the leach by force of wind. Then ending up going car back again as the breeze builds and you're starting to spill wind from the main.
Javelin
Well-known member
I'd buy into moving the car forward in really light wind.
You need twist in light winds, the shear is quite pronounced when the wind is light and you need acceleration which twist will give you.
What twist won't give you is speed so the trick is to tighten the leech as you get up to speed.
Hmm, control of the genoa head.
Is it flapping or is it hooked, need a bit more info really ?
How tight are you setting the halyard ? (I presume its on a spar)
Not too bothered about main back winding as long as the jib leech tell tails are ok.
It might not look pretty but its not usually going to stop you, er hmm
Unless;
How tight is your main luff ? you should be able to pinch an inch or more, it certainly should NOT be tight.
If it is, it will pull the camber forwards choking the slot and can lead to back winding.
How much pre-bend is in the mast , er wait, tell me more about what the head is doing and confirm your halyards are JUST pulling the sail up and not tensioning the luff on either sail.
You need twist in light winds, the shear is quite pronounced when the wind is light and you need acceleration which twist will give you.
What twist won't give you is speed so the trick is to tighten the leech as you get up to speed.
Hmm, control of the genoa head.
Is it flapping or is it hooked, need a bit more info really ?
How tight are you setting the halyard ? (I presume its on a spar)
Not too bothered about main back winding as long as the jib leech tell tails are ok.
It might not look pretty but its not usually going to stop you, er hmm
Unless;
How tight is your main luff ? you should be able to pinch an inch or more, it certainly should NOT be tight.
If it is, it will pull the camber forwards choking the slot and can lead to back winding.
How much pre-bend is in the mast , er wait, tell me more about what the head is doing and confirm your halyards are JUST pulling the sail up and not tensioning the luff on either sail.
Plevier
Active member
Thanks Ed.
You have tell tales actually on the leech do you?
Mike
(Formerly Troubadour)
flaming
Well-known member
Plevier
Active member
Wow some questions!
The sails BTW are North NorLam 3 years old, in quite reasonable condition as far as I can judge.
The genoa does tend to flap a little at mid height under a lot of conditions but pulling just an inch or two of leech string stops it at the expense of a very slight hook.
The main problem is stopping it twisting out like mad - whereupon it does flap gently at the head - without having the car so far forward that the foot is really loose and bunching up against the guard wires (it's a very low cut sail almost on the deck at the tack, has a below deck furler.)
Do your remarks about halyard tension relate specifically to very light winds? We have tried slackening them then, didn't feel any better.
The pre-bend is about half a section width, judging visually against a tight halyard. I'm not very happy about its shape, it's mostly up top (the mast does taper) but a North Sails guy who was around had a quick glance and thought it was reasonable.
I've measured the rake at something near 3 degrees which is a lot isn't it? (There is more weather helm than I would like too.) However that was with the pre-bend already in which I suppose distorts the measurement. It's keel stepped and the heel is near the front end of the adjustment track (Selden). Would moving it back change the bend shape? (It's not an easy adjust to play with - rig has to be slacked off.) The forestay is non adjustable and is the OEM original AFAIK so I guess that fixes the rake.
The leeward capstay stays tight when beating, the single lower goes quite slack.
I hope some of that info is relevant and I'm grateful for your interest.
Plevier
Active member
Yes can see them. Another little job to do then!
That rig does look similar (but posher sails!) Is that the Elan?
Can I see a tweaker on the clew? They come as part of the optional "racing pack" on the Dehler but we don't have that. Ditto Cunningham unfortunately.
KREW2
Well-known member
Much has been mentioned about traveller positions. I have a Westerly Storm, and it has two sets of track on either side. One is out by the toe rail, outside the shrouds. The second set runs the same length inside the shrouds just under the coach roof. I have never used them, should I ?
mrming
Well-known member
If I had a set of those I'd use them with my blade jib in conditions where the water's nice and flat and I want to point high.
flaming
Well-known member
Yes, that's the elan. Actually a non standard headsail - we dropped the big overflappers for rating reasons.
We have inhaulers on the jib, they're (in my opinion) pretty essential to make the non overlappers work in the light. We even had the new number 3 cut so it could use them (old one had the clew too low) which means you can swap modes from flat blade like sail to nicely curved deep powerful sail.
Only real disadvantage to the larger jibs we've found is speed in the very (sub 7 knot) light and acceleration in the 8-12 knot range. Plus they can be tweaky as hell.
flaming
Well-known member
With the massive caveat of (but it depends) this actually isn't necessarily a bad thing. In the photo I just put up, you can see how deep that foot is, and that was actually in the pretty early days with that sail, we now routinely lie it against the guardrails in the light.
Ehecatl
Member
+1
Very good, thank you
Very good, thank you
Javelin
Well-known member
There are three main factors affecting the head of your jib (assuming the sail is cut ok)
1, Forestay sag
2, Halyard tension
2, Sheet car position
You'll have to forgive here if I've got the rig set-up wrong.
I think the spreaders have a fair amount of rake aft so most of your forestay tension is controlled by your cap shroud tension, set against the lowers too control fore and aft bend.
I assume given the spreader rake that the mast is fractional so backstay tension bends the mast rather than tightening the forestay.
If the leeward lower is slack up wind in a f3 ish then I think I'd investigate although I'm not sure this will be the cause of your head issue.
I think I'd be inclined to check the capstay static load anyway if you can find a local with a loos guage. ( got a couple here
)
Halyards are there to pull the sails up and keep them there - IT IS NOT used for tensioning the luff.
To tension the luff you use a Cunningham and you only use the Cunningham to de-power to stave off the decision to reef or reduce sail.
So a tight halyard and a cunningham are one and the same thing.
A tight halyard/cunninham will depower the rig by pulling fullness forward and crucially releasing the leach at the top.
This applies to the main and jib.
Given the above is all ok then the car is moved forward for a given sheet tension, hmmm going to be tricky explaining this.
The angle of the sheet from the clew to the car dictates whether it pulls more on the foot or the leech or it's in the middle and pulls both equally.
Sheet tension dictates how much pull is exerted.
So if your angle favours pulling down on the leech but your foot is too rounded you need to back the car aft a little, still keep it favouring leech tension and apply more sheet tension.
Get some insulating tape and mark the sheet at a known position so you can repeat and tune from a known mark.
As Flaming pointed out a bit of foot round is ok especially as the first 5 or 6' of jib does little upwind as the air is so disturbed but it does act as an end plate on the deck.
Weather helm wont be helped if the jib is not powered properly, maybe bringing the mainsheet car well up to windward and releasing a bit of mainsheet tension to give the main a bit more twist will help but at the penalty of reducing the forestay tension the mainsheet applies.
Try (and I don't like it) adding some Cunningham on the main when you get excessive weather helm and see if this helps.
Need to go right now will take a look a little later.
1, Forestay sag
2, Halyard tension
2, Sheet car position
You'll have to forgive here if I've got the rig set-up wrong.
I think the spreaders have a fair amount of rake aft so most of your forestay tension is controlled by your cap shroud tension, set against the lowers too control fore and aft bend.
I assume given the spreader rake that the mast is fractional so backstay tension bends the mast rather than tightening the forestay.
If the leeward lower is slack up wind in a f3 ish then I think I'd investigate although I'm not sure this will be the cause of your head issue.
I think I'd be inclined to check the capstay static load anyway if you can find a local with a loos guage. ( got a couple here
)Halyards are there to pull the sails up and keep them there - IT IS NOT used for tensioning the luff.
To tension the luff you use a Cunningham and you only use the Cunningham to de-power to stave off the decision to reef or reduce sail.
So a tight halyard and a cunningham are one and the same thing.
A tight halyard/cunninham will depower the rig by pulling fullness forward and crucially releasing the leach at the top.
This applies to the main and jib.
Given the above is all ok then the car is moved forward for a given sheet tension, hmmm going to be tricky explaining this.
The angle of the sheet from the clew to the car dictates whether it pulls more on the foot or the leech or it's in the middle and pulls both equally.
Sheet tension dictates how much pull is exerted.
So if your angle favours pulling down on the leech but your foot is too rounded you need to back the car aft a little, still keep it favouring leech tension and apply more sheet tension.
Get some insulating tape and mark the sheet at a known position so you can repeat and tune from a known mark.
As Flaming pointed out a bit of foot round is ok especially as the first 5 or 6' of jib does little upwind as the air is so disturbed but it does act as an end plate on the deck.
Weather helm wont be helped if the jib is not powered properly, maybe bringing the mainsheet car well up to windward and releasing a bit of mainsheet tension to give the main a bit more twist will help but at the penalty of reducing the forestay tension the mainsheet applies.
Try (and I don't like it) adding some Cunningham on the main when you get excessive weather helm and see if this helps.
Need to go right now will take a look a little later.
Plevier
Active member
Thanks, lots to think about, some quick responses below.
There are three main factors affecting the head of your jib (assuming the sail is cut ok)
1, Forestay sag
2, Halyard tension
2, Sheet car position
You'll have to forgive here if I've got the rig set-up wrong.
I think the spreaders have a fair amount of rake aft so most of your forestay tension is controlled by your cap shroud tension, set against the lowers too control fore and aft bend.
I assume given the spreader rake that the mast is fractional so backstay tension bends the mast rather than tightening the forestay.
### Yes 90% fractional, 2 sets swept spreaders, discontinuous Dyform rigging, backstay has 32:1 adjuster on it.
If the leeward lower is slack up wind in a f3 ish then I think I'd investigate although I'm not sure this will be the cause of your head issue.
### It doesn't seem right, but not fiddled with it as since it's only 1/3 of the height I couldn't see it affecting the headsail and I didn't want to push the bend higher than it is.
I think I'd be inclined to check the capstay static load anyway if you can find a local with a loos guage. ( got a couple here
### 8mm Dyform - is that in the range of a Loos gauge? They are very tight. No slackening of downwind one when beating. Edit - yes it is in the range of a big expensive Los gauge!
Halyards are there to pull the sails up and keep them there - IT IS NOT used for tensioning the luff.
### Thinking about that!
To tension the luff you use a Cunningham and you only use the Cunningham to de-power to stave off the decision to reef or reduce sail.
So a tight halyard and a cunningham are one and the same thing.
A tight halyard/cunninham will depower the rig by pulling fullness forward and crucially releasing the leach at the top.
This applies to the main and jib.
### I've never seen a jib with a cunningham - is it common?
Given the above is all ok then the car is moved forward for a given sheet tension, hmmm going to be tricky explaining this.
The angle of the sheet from the clew to the car dictates whether it pulls more on the foot or the leech or it's in the middle and pulls both equally.
Sheet tension dictates how much pull is exerted.
So if your angle favours pulling down on the leech but your foot is too rounded you need to back the car aft a little, still keep it favouring leech tension and apply more sheet tension.
### Understood.
Get some insulating tape and mark the sheet at a known position so you can repeat and tune from a known mark.
As Flaming pointed out a bit of foot round is ok especially as the first 5 or 6' of jib does little upwind as the air is so disturbed but it does act as an end plate on the deck.
### I've clearly been too bothered about that.
Weather helm wont be helped if the jib is not powered properly, maybe bringing the mainsheet car well up to windward and releasing a bit of mainsheet tension to give the main a bit more twist will help but at the penalty of reducing the forestay tension the mainsheet applies.
### Yes we do that.
Try (and I don't like it) adding some Cunningham on the main when you get excessive weather helm and see if this helps.
### Rigging a cunningham is on the job list (the sail has the cringle)
Need to go right now will take a look a little later.
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Javelin
Well-known member
I wonder if that leeward lower would tighten when you apply backstay tension or at least it should.
In which case it tends to suggest that either the spreaders are not angled back enough or indeed there is not enough capshroud tension - Max 25% of swl but I try and keep it around 20%.
Yup big loos and yup buying the full range plus rod rigging guage was not cheap.
On non roller foresails for racing I'd say cunninghams were reasonably common.
However most jibs these days are on a roller foil, so the trick is, as long as you are using a sk75 or better dyneema halyard (i.e. one that doesn't stretch) is to pull the sail up to a point where at the bottom you can twist an inch or so luff by 90 degrees with your fingers, or pull the luff down with your fingers and it should move an inch-ish.
Then get your insulating tape out and mark the halyard just as it enters the clutch.
When it starts to blow and you're thinking "hmm we might have a bit too much sail up", grind in the halyard 3 or 4 inches (might need more depending on the size of your luff) and that'll open the leech and flatten the sail.
Don't fall into the trap of thinking that halyard tension has anything to do with forestay sag. It did 20 years ago when you sailed that old Enterprise but sag is all down, in your case, to your capshroud tension amd to some extent, mainsheet tension.
Your backstay is the primary control of leech tension on your mainsail, so I'd use that before using the cunninham on the main.
You said, I think, you had backwinding on the main, this could be because your main halyard was too tight and pulling the fullness forward but also if the foot round on the jib really was as big as you suggest then that could be pushing air via the slot at too much of an angle.
We covered this solution earlier which was to bring the car back a little and use more sheet tension.
Its a shame you're not up this way as a couple of hours on the water would sort it.
Edit: Just noticed the comment on pre-bend - Possibly a bit much so tightening your lowers a bit might help.
Again remember to mark your starting positions - tuning is all about marking, trying something, moving the mark if its better or going back if its worse.
In which case it tends to suggest that either the spreaders are not angled back enough or indeed there is not enough capshroud tension - Max 25% of swl but I try and keep it around 20%.
Yup big loos and yup buying the full range plus rod rigging guage was not cheap.
On non roller foresails for racing I'd say cunninghams were reasonably common.
However most jibs these days are on a roller foil, so the trick is, as long as you are using a sk75 or better dyneema halyard (i.e. one that doesn't stretch) is to pull the sail up to a point where at the bottom you can twist an inch or so luff by 90 degrees with your fingers, or pull the luff down with your fingers and it should move an inch-ish.
Then get your insulating tape out and mark the halyard just as it enters the clutch.
When it starts to blow and you're thinking "hmm we might have a bit too much sail up", grind in the halyard 3 or 4 inches (might need more depending on the size of your luff) and that'll open the leech and flatten the sail.
Don't fall into the trap of thinking that halyard tension has anything to do with forestay sag. It did 20 years ago when you sailed that old Enterprise but sag is all down, in your case, to your capshroud tension amd to some extent, mainsheet tension.
Your backstay is the primary control of leech tension on your mainsail, so I'd use that before using the cunninham on the main.
You said, I think, you had backwinding on the main, this could be because your main halyard was too tight and pulling the fullness forward but also if the foot round on the jib really was as big as you suggest then that could be pushing air via the slot at too much of an angle.
We covered this solution earlier which was to bring the car back a little and use more sheet tension.
Its a shame you're not up this way as a couple of hours on the water would sort it.
Edit: Just noticed the comment on pre-bend - Possibly a bit much so tightening your lowers a bit might help.
Again remember to mark your starting positions - tuning is all about marking, trying something, moving the mark if its better or going back if its worse.
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Plevier
Active member
Many thanks - I will experiment!
bluemoongaffer
New member
Followed this thread with a lot of interest - it has all been really helpful - thanks