How do you set your sails for maximum power in light winds?

G'day, Bundeenabuoy
In really light breeze flatter sail settings ( but not choked) can work as the breeze dosn't have the energy to adhere to the back of the sail if it's to deep. As the breeze increases say from 2 to 3kn to 5 to 6kn start to deepen the sails to increase power. Generally for all conditions but especially light breezes "when in doubt, let it out" don't over sheet , no Cunningham, no or very little vang, ease headsail halyard until small wrinkles appear down the luff. Experiment with sail settings, I had a Spider 22 that went like a rocket up wind I the light with the headsail jammed on flat as a board...go figure?

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Hort said..
G'day, Bundeenabuoy
In really light breeze flatter sail settings ( but not choked) can work as the breeze dosn't have the energy to adhere to the back of the sail if it's to deep. As the breeze increases say from 2 to 3kn to 5 to 6kn start to deepen the sails to increase power. Generally for all conditions but especially light breezes "when in doubt, let it out" don't over sheet , no Cunningham, no or very little vang, ease headsail halyard until small wrinkles appear down the luff. Experiment with sail settings, I had a Spider 22 that went like a rocket up wind I the light with the headsail jammed on flat as a board...go figure?

My steps to initially set the sails would be;
Loosen backstay
Loosen cunningham
Tension main leaving the slightest horizontal wrinkles
Apply minimum tension to cunningham
Raise headsail with similar tension
Use vang and kicker to get all tell tales flowing evenly

UK sailors talk about "The Fourth Corner" being alive....ie the top leach streamers being active all the time in truly light winds.

Bundeenabuoy, yep those steps seem about right to me. I wouldn't use any Cunningham though. If it's really light the tell tails may not fly so you can use some cassette tape tied to the shrouds to work things out & if you concentrate you can usually feel the slightest breeze on your face or back of your neck ( or the ciggy smoke method, I may have to try that myself). Once the tell tails start to fly set the headsail so they all stream back & the main so they all stream except the top leach tell tail which can just flutter back intermittently. As with everything with sailing there's heaps of different ways of doing things but that's how I set things up.
By the way I live in a small place starting with m which I think is fairly close to you, so if you need a hand setting things up let me know.

One thing I'd say is often people have halyards too tight in light stuff.
I like to see what one design guys (J24, Melges 24, Etchells, Farr 40 etc) guys are doing as they do what works as they always have a benchmark.
Most of them have 'scallops' between Hanks on the jib in sub 5knots.
Most sailors are scared of wrinkles but keeping the entry fine and draft aft is far more important in light stuff.
A few other things I try and do;
- don't try to point until boatspeed over 2 knots (approx)
- keep body movements slow
- keep steering inputs and manoeuvres fo a minimum
- keep weight fwd and to leeward

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rumblefish said..
One thing I'd say is often people have halyards too tight in light stuff.
I like to see what one design guys (J24, Melges 24, Etchells, Farr 40 etc) guys are doing as they do what works as they always have a benchmark.
Most of them have 'scallops' between Hanks on the jib in sub 5knots.
Most sailors are scared of wrinkles but keeping the entry fine and draft aft is far more important in light stuff.
A few other things I try and do;
- don't try to point until boatspeed over 2 knots (approx)
- keep body movements slow
- keep steering inputs and manoeuvres fo a minimum
- keep weight fwd and to leeward

everything he says
only thing extra dont worry to much about the front of the sail even if its luffing a bit as long as the leech is open also we often run topping lift on the boom to assist the leech opening
the bit about not pointing till speed achieved cant be empathized enough
we are also assuming the bottom finish is perfect as skin friction is king in low speed

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rumblefish said..
One thing I'd say is often people have halyards too tight in light stuff.
I like to see what one design guys (J24, Melges 24, Etchells, Farr 40 etc) guys are doing as they do what works as they always have a benchmark.
Most of them have 'scallops' between Hanks on the jib in sub 5knots.
Most sailors are scared of wrinkles but keeping the entry fine and draft aft is far more important in light stuff.
A few other things I try and do;
- don't try to point until boatspeed over 2 knots (approx)
- keep body movements slow
- keep steering inputs and manoeuvres fo a minimum
- keep weight fwd and to leeward

Hi Rumblefish,
Thanks for all that.
Could you expand a little on 'keeping the entry fine''?

G'day Bundeenaboy,
When you ease your halyard, the draft, or deepest part of the sail, moves backwards. It will settle near the center, equidistant between luff and leach. This means the luff is flatter, or "finer".

When you tighten your halyard, the draft moves forrard , to settle at about 30% from the luff. This makes the luff rounder, or less "fine".

In stronger winds a rounder entry is better as it is less powerful, heels less, gives you a wider groove to sail in and is more forgiving in seas.

The stronger the wind, the more the increase in pressure forces the draft back to the center anyway, so you need lots of halyard tension to offset this creeping of the draft back to the center as well.


In lighter winds a fine entry is better as the sail shape is more powerful, it heels more but is a lot narrower groove, so harder to steer well. Light airs means flat water, so this helps to offset the "harder to helm" issue.

Ever get those days where both your leeward and windward telltales on your jib collapse if you steer up/off a degree? That's too fine an entry, to remedy simply increase halyard tension.



Edit: when you increase halyard tension, ease your sheet first, or do it in the middle of a tack. Don't do it fully powered up, its not the best thing for your sail to be stretching the luff when under load..

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shaggybaxter said..
G'day Bundeenaboy,
When you ease your halyard, the draft, or deepest part of the sail, moves backwards. It will settle near the center, equidistant between luff and leach. This means the luff is flatter, or "finer".

When you tighten your halyard, the draft moves forrard , to settle at about 30% from the luff. This makes the luff rounder, or less "fine".

In stronger winds a rounder entry is better as it is less powerful, heels less, gives you a wider groove to sail in and is more forgiving in seas.

The stronger the wind, the more the increase in pressure forces the draft back to the center anyway, so you need lots of halyard tension to offset this creeping of the draft back to the center as well.


In lighter winds a fine entry is better as the sail shape is more powerful, it heels more but is a lot narrower groove, so harder to steer well. Light airs means flat water, so this helps to offset the "harder to helm" issue.

Ever get those days where both your leeward and windward telltales on your jib collapse if you steer up/off a degree? That's too fine an entry, to remedy simply increase halyard tension.



Edit: when you increase halyard tension, ease your sheet first, or do it in the middle of a tack. Don't do it fully powered up, its not the best thing for your sail to be stretching the luff when under load..

I have really appreciated all the knowledgeable advice given me on this topic.
What a clear explanation you have given.
Thank you.
Were you a teacher or did you miss your calling?

SB would this be an example of the halyard too tight in a 12 knot wind.
I am still getting used to setting the light rig on a small boat in relation to my previous boats but in this case it was caused by the reef line getting jammed on the mast block when hoisting and not realising.
edit : actually more like 5 knot wind.

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Bananabender said..
SB would this be an example of the halyard too tight in a 12 knot wind.
I am still getting used to setting the light rig on a small boat in relation to my previous boats but in this case it was caused by the reef line getting jammed on the mast block when hoisting and not realising.
edit : actually more like 5 knot wind.

Perfect, thanks BB! Nice red line for trimming btw.
-You can see draft is pulled forward due to the luff tension.
- That's a medium/heavy air mode for halyard tension. (Or a jammed reef line .)
- Sail is depowered as the draft is forward.
- Probably had a nice wide groove.
- Compared to the rest of the sail, the entry is round enough where it's decreased the angle of attack to a point where it's luffing. (dependent upon if BB wasn't luffing for a bazillion other reasons of course)

Another bonus for a finer entry, this means the wind angle over the leading edge of the sail (luff) can be a lower angle of attack. More "on the nose". Halyard tension brings the angle of attack backward, or a higher angle as the shape of the leading edge changes. This forces you off the wind in the same conditions.

The mainsail is a bit different to me on the headsail on setting halyard tension. The tension will be generally near the same of course, but my main is set by matching the AoA of the slot, which is more to the beam of the boat due to the wind slowing down for the entry to leeward of the mainsail.
I look for clean air sticking to the back two thirds of the main to leeward, so I set my main halyard tension to where the leeward and rearmost telltales on the main are all streaming nicely. So a bit of luffing is fine on a main but not a headsail!

Bundeenaboy,
in case you've never done it, when next sailing, get someone to steer for you, go to windward and get forward of the forestay. Look back and up along the forestay to the head of the jib. You'll see it straight away.
If you have too much jib halyard tension, the sail will be noticeably flattened right on the entry, or the luff.
If it's too loose on the tension, the sail is noticeably bagged away on the entry, or luff.
Firm leading edge, nicely curved on the entry, even if the sail is wrinkly? Nice halyard tension.

Note: Ensure the correct backstay tension is set first, as this obviously has a big impact. Too little backstay sags the whole forestay in a big curve. That can't be fixed with halyard tension, that's backstay.

Thanks for the feedback and hints SB.
Was sailing from Horizon S to JW and could not work out why main was slack near boom even when hauling on halyard so took photo. I do need a couple more tell tails on main. Never thought to slacken halyard to move draft. Sometimes the grey matter between the ears does not compute what I'm looking at. Not much wiggle room to leave cockpit to unjam the reef line where I was when I realised.

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Bundeenabuoy said..

Hort said..
G'day, Bundeenabuoy
In really light breeze flatter sail settings ( but not choked) can work as the breeze dosn't have the energy to adhere to the back of the sail if it's to deep. As the breeze increases say from 2 to 3kn to 5 to 6kn start to deepen the sails to increase power. Generally for all conditions but especially light breezes "when in doubt, let it out" don't over sheet , no Cunningham, no or very little vang, ease headsail halyard until small wrinkles appear down the luff. Experiment with sail settings, I had a Spider 22 that went like a rocket up wind I the light with the headsail jammed on flat as a board...go figure?

My steps to initially set the sails would be;
Loosen backstay
Loosen cunningham
Tension main leaving the slightest horizontal wrinkles
Apply minimum tension to cunningham
Raise headsail with similar tension
Use vang and kicker to get all tell tales flowing evenly

Sounds good. You may have to be careful loosening the backstay. If the mast goes too straight, the mainsail draft can be pulled too far forward. It varies from boat to boat. Normally, there's no cunno at all in light winds. Horizontal wrinkles off the luff can be fast!

There's some good advice here from Hort, Rumblefish and others.

There's a lot of potential work involved in getting the right balance of forestay tension and mast bend in a rig like yours and mine. Often, if you want to get really keen, this can mean easing off the forestay in light winds to allow the jib luff to develop sag for a more powerful shape. On Farr 40s etc they used to send guys up the rig pre-race to adjust the diagonals and caps, as well. There's a fair bit of trial and error unless you're a pro or used to the class - I'm still working on the tune for my 36'er.

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shaggybaxter said..
G'day Bundeenaboy,
When you ease your halyard, the draft, or deepest part of the sail, moves backwards. It will settle near the center, equidistant between luff and leach. This means the luff is flatter, or "finer".

When you tighten your halyard, the draft moves forrard , to settle at about 30% from the luff. This makes the luff rounder, or less "fine".

In stronger winds a rounder entry is better as it is less powerful, heels less, gives you a wider groove to sail in and is more forgiving in seas.

The stronger the wind, the more the increase in pressure forces the draft back to the center anyway, so you need lots of halyard tension to offset this creeping of the draft back to the center as well.


In lighter winds a fine entry is better as the sail shape is more powerful, it heels more but is a lot narrower groove, so harder to steer well. Light airs means flat water, so this helps to offset the "harder to helm" issue.

Ever get those days where both your leeward and windward telltales on your jib collapse if you steer up/off a degree? That's too fine an entry, to remedy simply increase halyard tension.



Edit: when you increase halyard tension, ease your sheet first, or do it in the middle of a tack. Don't do it fully powered up, its not the best thing for your sail to be stretching the luff when under load..

Good stuff but just one point, Shaggy - in Sydney light winds often don't mean flat water, so we tend to sail with headsails that are deeper forward in light winds to allow us to get through the slop.

Years ago, boats coming from England sometimes use to have their luffs modified for Sydney to make their headsails deeper to suit the slop - there's pics of them around with a vertical luff panel inserted.

G'day Chris,
That makes perfect sense, thanks!

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shaggybaxter said..
G'day Chris,
That makes perfect sense, thanks!

There has been a lot of mention of sail shape here which is all important. In ultra light airs the trick is to keep the boat moving, even if it is not directly to where you want to go, as long as you are making VMG to the mark ( if going away from the mark, throw the anchor out). Keep a good eye out to where the true wind is as it is easy to ghost through a lull where the apparent wind can look a long way forward and come out totally over sheeted. It is very easy to over sheet in ultra light air. The heavier the boat the more this comes in to play. With my boat at 57' and 20t , I can glide for a long way through a lull, but if I stop it takes a lot to get the boat moving again, so I try to keep the boat moving even if not directly at the mark.
In light airs be very aware of the tide and plan ahead, it is very easy to be swept sideways and miss a mark. Watch your speed over ground and make sure you are going forward, don't be afraid to drop the anchor.
sail shape is one thing in light airs but tactics are just as important, if not more important as you can make big ground on the opposition if you get it rite.

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Chris 249 said..

Bundeenabuoy said..

Hort said..
G'day, Bundeenabuoy
In really light breeze flatter sail settings ( but not choked) can work as the breeze dosn't have the energy to adhere to the back of the sail if it's to deep. As the breeze increases say from 2 to 3kn to 5 to 6kn start to deepen the sails to increase power. Generally for all conditions but especially light breezes "when in doubt, let it out" don't over sheet , no Cunningham, no or very little vang, ease headsail halyard until small wrinkles appear down the luff. Experiment with sail settings, I had a Spider 22 that went like a rocket up wind I the light with the headsail jammed on flat as a board...go figure?

My steps to initially set the sails would be;
Loosen backstay
Loosen cunningham
Tension main leaving the slightest horizontal wrinkles
Apply minimum tension to cunningham
Raise headsail with similar tension
Use vang and kicker to get all tell tales flowing evenly

Sounds good. You may have to be careful loosening the backstay. If the mast goes too straight, the mainsail draft can be pulled too far forward. It varies from boat to boat. Normally, there's no cunno at all in light winds. Horizontal wrinkles off the luff can be fast!

There's some good advice here from Hort, Rumblefish and others.

There's a lot of potential work involved in getting the right balance of forestay tension and mast bend in a rig like yours and mine. Often, if you want to get really keen, this can mean easing off the forestay in light winds to allow the jib luff to develop sag for a more powerful shape. On Farr 40s etc they used to send guys up the rig pre-race to adjust the diagonals and caps, as well. There's a fair bit of trial and error unless you're a pro or used to the class - I'm still working on the tune for my 36'er.

Thats great Chris

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Bundeenabuoy said..
How do you set your sails for maximum power in light winds?

Where possible is it always preferable to tighten the Main rather than the Cunningham?
My concern is the wrinkles that appear below the Cunningham attachment point which I presume would disturb the optimum airflow.