Some Things I've Learned About Sail Trim Recently

[OldFrog75]

Originally Posted by Ex-Calif

How many people are on your boat?

6-8; everyone who isn't needed in the cockpit is on the rail

What is the heel angle under these conditions?

20-30 degrees

What is the boat speed under these conditions?

6 1/2 knots

Why are the Genoa cars back?

To flatten the sail and point higher

Why do you think you need to flatten the mainsail under these conditions?

Depower the sail and reduce heeling while sailing close hauled

What jib/genoa are you flying under these conditions?

135

What "problem" are you solving for? Weather helm?

Rounding up head to wind in gusts

In general at 14 knots your boat (most boats) are fully powered and you should be readily able to achieve hull speed to windward with no adverse weather helm. You definitely do not need to be reefing.

Agreed

After you have "shaped" the mainsail for the prevaililng conditions of wind and sea state there are a couple of methods of depowering the main on the beat.

I'm listening...

I would submit that you should not be trimming with mainsheet on the beat. I raced with a guy for weeks who could not get this concept and actually told the skipper I wouldn't sail on his boat any longer unless they were interested in taking my advice. They now routinely win races or place on the podium.

Once the sails are shaped we use the traveler to spill the wind but as the OP stated when that doesn't work we are forced to ease the mainsheet as well.

They didn't have to buy new sails...

Maybe so but in this case baggy 10 year old sails on a charter boat sounds like a reasonable explanation to me.

Fire away, Cali, fire away...

[OldFrog75]

Originally Posted by Ex-Calif

In general at 14 knots your boat (most boats) are fully powered and you should be readily able to achieve hull speed to windward with no adverse weather helm. You definitely do not need to be reefing.

They didn't have to buy new sails...

As an aside, 5 of us race a J24 on Thursday nights outfitted with performance sails and everything on hard (including an adjustable backstay and cunningham) at a different marina in typically higher winds and we never round up.

[StuM]

"Why are the Genoa cars back?
To flatten the sail and point higher"

If they are too far back,all the tension will be on the foot of the sail and the leech will be bagging putting more draught in the sail.

[Ex-Calif]

Originally Posted by OldFrog75

"Happy button...?" Boats have a button I can push to make me happy Never saw that in the owners' manuals. Maybe I should read the fine print.

The diesel...

Originally Posted by OldFrog75

Fire away, Cali, fire away...

Maybe so but in this case baggy 10 year old sails on a charter boat sounds like a reasonable explanation to me.

First of all I have never been on your boat and the statement above makes me think this is not your boat and this is a rental boat with blown out sails. Maybe there is nothing you can do then but...

6-8; everyone who isn't needed in the cockpit is on the rail

What is the heel angle under these conditions?

20-30 degrees

You need fatter friends - LOL...

If you are getting 30 degrees of heel in 14 knot winds then someone who should be on the rail is not. On a 32 foot boat the only two people in the cockpit on the beat should be driver and main trimmer.

I know it's club racing but a 31 foot boat should be fully crewed with 5 or 6 people and there should be plenty of weight in this wind to keep the boat at less than 15 degrees.

What is the boat speed under these conditions?

6 1/2 knots

So boat speed is good. Heel angle is too high and the boat rounds up.

Why are the Genoa cars back?

To flatten the sail and point higher

If the genoa cars are back the lead pulls more on the foot and you are introducing twist to the top of genoa. You are not making it flat. You are actually depowering your genoa. You may consider moving the cars forward until an imaginary line drawn from the lead in angle of the sheet bisects the angle created by the foot and the leach.

Why do you think you need to flatten the mainsail under these conditions?

Depower the sail and reduce heeling while sailing close hauled

Flattening the main sail will depower the main. dropping the traveller will depower the main. Reefing will depower the main.

Reefing - as you stated at 14 knots you definitely should not be thinking about reefing.

Traveller down - when the main sail is trimmed on the beat. the boom is over the traveller. I get a lot of push back on this one but in this case the vang and the main sheet are doing the same thing - they are both setting the distance from the masthead to the end of the boom - this distance opens or closes the leach.

There is another way to close the leach and I get push back on this one too. On a masthead rig many people believe that the backstay doesn't impact the main as it opposes the forestay. Not true - the backstay bends the mast in the middle - more backstay pushes the middle of the mast forward and increases the distance from the leach to the luff - flattening the sail. But it also introduces twist in the main (shorter distance from masthead to boom tip) which means you have to vang or mainsheet harder (on the beat) to shorten the leach again.

Tightening backstay also moves the draft aft and may require cunningham to move the draft forward again. And yes I know you stated you don't have a cunningham but you should be aware what backstay does if you use it.

So once you have set the leach length leave the vang and the mainsheet alone - by changing the vang or mainsheet there are several other controls impacted.

Outhaul - make sure the out haul is on pretty tight. A loose outhaul moves the lower foot closer to the mast - this closes the lower leach - a closed lower leach steers to weather. With a bagged out sail however this is a compromise/crapshoot.

So the final piece of background is that with bagged out mainsail you may never be able to flatten the main. You can only pull on the 3 corners. The middle may never flatten - As you try to flatten the main you are moving the draft back and this reduces pointing.

I have sailed briefly in your waters, my experience is you get ocean chop. You actually would do better with a fuller main as a fuller main accelerates better. Give up a little pointing and accelerate out of the troughs and you may end up getting around the course faster. With a bagged out main you really don't have much choice.

The boom should be at the centerline and above in this wind. The top batten should be parallel to the boom or even slightly closed. It took me a long time to really understand this.

You should try to think about other things - this boat cannot be overpowered in 14 knots and you should not be looking at ways to depower the main in 14 knots.

I've been on a lot of boats where after the tack the genoa trimmer is done but the sail is way out of trim. I've taken up to 5-6 inches of sheet in after a trimmer thinks the genoa is trimmed. It's an unnatural act for many people to pull that hard on a boat.

What "problem" are you solving for? Weather helm?

Rounding up head to wind in gusts

So here is my remote diagnosis and I am not being critical so take it with a grain of salt.

- Your crew "cannot" be in the right place on the beat - 6 X 150# = 900# on the rail of a 32 foot boat must make the boat flat in 14 knots.
- You may be inadvertently twisting off the genoa with car position
- The genoa is "set and forget" on a tack (on the beat) especially in these winds - the genoa trimmer should be #1 on the rail and the first person to come down in prep for a tack.
- You should consider giving up a little flatness in the main sail especially a bagged out main sail. Vang hard, mainsheet hard makes a "round" belly too far aft, pulling "sideways" not forward because the draft is too far aft.
- The main trimmer needs to be active and the crew needs to be calling the gusts. I know you said that you don't have or want a full blown race crew but that's what race crews do. The traveler is dropped - sometimes way dropped - in heavy gusting conditions. You should be able to slowly drop the traveler and see the "bubble" at the luff as the genoa starts to backwind the main. With traveler well dropped you could have a big bubble in the luff but the middle and back of the sail is still pulling. On my boat dropping the traveler along (and it's only a meter long) drops heel angle (when powered up) but at least 5 degrees.
- Finally the skipper needs to be actively steering. Up into the gusts and down into the lulls.

All in all I think your weather helm and rounding up are twisted off genoa and not sheeting the genoa hard enough. Oh and the crew needs to hike out if you really are getting 20-30 degrees of heel in 14 knots.

Ok - how'd I do?

[Snowpetrel]

I remember my grandfather telling me as a ten year old on one cook strait crossing about the genoa vs yankee and staysail. He had found on his boat that the genoa caused much more weather helm than the yankee/staysail combo. I found this surprising as a kid as it went against what I had read about weather helm, ie bigger headsails reduce it... I have since found that often weird things happen with boats. Maybe it was the added heel, maybe the sail was flogged out, I don't know. But I have often found reducing headsail also reduces the weather helm on some boats.

It's interesting that in a real blow you can often sail to windward under a storm jib alone. In 60 knots it's pretty effective. In 30 knots headsail alone is often crap to windward.

And many a ketch can sail downwind fine with just a mizzen set in stronger winds. Weird but true!

On most of the race boats I've played with we played the traveler much more than the main sheet. Pretty much easing it down as we heel to keep her on her feet. I try to dump it just as the gust hits before the boat starts heeling any, and get it back up just before the gust dies. But I am no expert at this stuff...

[Snowpetrel]

^^ The new boats an old two tonner, controls for everything. Inner and outer genoa tracks, hydraulics everywhere, and gigantic winches growing like toadstools everywhere. The mast is prebent with checkstays and runners. I'm gonna need to get a handle around all this stuff pretty quick... But it will be fun to play with all the fancy stuff, and I am sure to learn a thing or two.

[OldFrog75]

Originally Posted by Ex-Calif

Ok - how'd I do?

Thanks for the comments. I'll have to get back to you later - on my way out the door to double-hand a Dufour 375 in a 25 mile race - similar conditions but newer boat with much newer sails.

Could be other issues with the 2004 Beneteau: baggy sails, shallow shoal keel, narrow rudder arc stop-to-stop, no cunningham, etc, etc.

OT but did I hijack this thread? I hope not. That would have been rude of me.

[poiu]

Originally Posted by Dockhead

...
As it turns out, the new boat is exquisitely sensitive to heel angle. Unlike my previous boats, which all liked to sail with the rail in the water, this one won't tolerate a heel angle over 30 degrees. Weather helm on this boat, as it turns out, is almost a linear function of heel angle. Optimum heel angle is 20 degrees or less -- over 20 degrees, helm is getting strong no matter how the sail plan is balanced. Over 30, and the boat is unsailable, with the rudder out at 20 degrees or more dragging the boat down...

I've got the designer's detailed polar calculations for my boat, which is a very similar design to yours. Cutter rig, bulb keel, same furling, similar proportions, hull shape etc. Just maybe a bit heavier pro-rata and a less powerful skeg rudder. The designer's figures show maximum designed heel is 25 deg. When on the wind between 10kt and 20kt the optimum heel is 15 to 25 deg, with corresponding reefing to achieve this. Above 20kt the heel is at 25 deg for most on the wind angles. When sailing I end up maybe a bit below the designed numbers - low 20s. It makes for a nicer sail, slower maybe as I also have a lot of weather helm. So my experience and the designer's figures confirm something similar to what you have found. About 35 deg heel is the warning sign that I have messed up and am at risk of losing control. At that heel angle I will have full rudder.

[Auspicious]

Originally Posted by Dockhead

I have played with backstay tension, but it doesn't do much on my boat, as I have a masthead rig, triple aft-swept spreaders and a very hefty mast section. Backstay tension is magic on fractionals, but not on rigs like mine.

Originally Posted by Dockhead

We do set the running backs with the staysail, mostly to get the sag out of the inner forestay.

Right - I too have three sets of spreaders swept aft, albeit not terribly far.

What I have found on my boat is that backstay tension directly adjusts forestay sag which in turn greatly affects pointing, especially as wind speed increases. I get the best pointing with least heel when I don't let sag get above about 6" / 15 cm. Off the wind and in light air easing off the backstay powers up the headsail.

My boat isn't set up to fly the jib and staysail together so I don't get interactions between the backstay and runners.

I don't have a furling main - conventional sail with full battens. That shouldn't make any difference since the mast doesn't bend regardless.

[OldFrog75]

Originally Posted by Ex-Calif

So boat speed is good. Heel angle is too high and the boat rounds up.

If the genoa cars are back the lead pulls more on the foot and you are introducing twist to the top of genoa. You are not making it flat. You are actually depowering your genoa. You may consider moving the cars forward until an imaginary line drawn from the lead in angle of the sheet bisects the angle created by the foot and the leach.

Perhaps rather than "flatten the sail" I should have said "narrow the angle of attack" and "decrease the depth of the draft".

We have experimented with the genoa cars and found that moving them forward adversly affects our pointing ability relative to other boats in the fleet and increases our tacking angles by as much as 20 degrees. So it becomes the lessor of two evils in 14 kts - rounding up or not pointing as high

Tightening backstay also moves the draft aft and may require cunningham to move the draft forward again. And yes I know you stated you don't have a cunningham but you should be aware what backstay does if you use it.

Not my boat and no adjustable backstay so we sail it like it is.

So once you have set the leach length leave the vang and the mainsheet alone - by changing the vang or mainsheet there are several other controls impacted.

Outhaul - make sure the out haul is on pretty tight. A loose outhaul moves the lower foot closer to the mast - this closes the lower leach - a closed lower leach steers to weather. With a bagged out sail however this is a compromise/crapshoot.

Agreed

So the final piece of background is that with bagged out mainsail you may never be able to flatten the main. You can only pull on the 3 corners. The middle may never flatten - As you try to flatten the main you are moving the draft back and this reduces pointing.

Agreed and increases heeling force as the CE moves aft as well.

I have sailed briefly in your waters, my experience is you get ocean chop. You actually would do better with a fuller main as a fuller main accelerates better. Give up a little pointing and accelerate out of the troughs and you may end up getting around the course faster. With a bagged out main you really don't have much choice.

Agreed

The boom should be at the centerline and above in this wind. The top batten should be parallel to the boom or even slightly closed. It took me a long time to really understand this.

Maybe, maybe not. Top batten parallel to the boom might not provide the twist necessary to minimize rounding up. On this boat, with the boom to windward of the centerline I'm not even sure we could tighten the mainsheet enough to get the top batten parallel and if we did it would move the draft so far aft it would exacerbate the problem we are trying to correct for.

You should try to think about other things - this boat cannot be overpowered in 14 knots and you should not be looking at ways to depower the main in 14 knots.

You wouldn't think so...the easy solution is to ease the mainsheet and travel down enough to keep the boat flat but it puts the boom so far to leeward it offends my aesthetic sensibilities when close hauled. And maybe that's the crux of the problem, I'm trying to keep the boom centered (or just slightly to leeward) with the top batten parallel when close hauled and it just doesn't work on this boat in those conditions.

I've been on a lot of boats where after the tack the genoa trimmer is done but the sail is way out of trim. I've taken up to 5-6 inches of sheet in after a trimmer thinks the genoa is trimmed. It's an unnatural act for many people to pull that hard on a boat.

Generally sheeted to within an inch of the shrouds while close hauled. Maybe that's too much in this case.

So here is my remote diagnosis and I am not being critical so take it with a grain of salt.

- Your crew "cannot" be in the right place on the beat - 6 X 150# = 900# on the rail of a 32 foot boat must make the boat flat in 14 knots.

Don't know where else to put them

- You may be inadvertently twisting off the genoa with car position

Understood but the narrower attack angle enabled us to point higher which we thought was the priority given the competition

- The genoa is "set and forget" on a tack (on the beat) especially in these winds - the genoa trimmer should be #1 on the rail and the first person to come down in prep for a tack.

Agreed

- You should consider giving up a little flatness in the main sail especially a bagged out main sail. Vang hard, mainsheet hard makes a "round" belly too far aft, pulling "sideways" not forward because the draft is too far aft.

Understood. Without a cunningham, the outhaul and main halyard might be our only effective tools

- The main trimmer needs to be active and the crew needs to be calling the gusts. I know you said that you don't have or want a full blown race crew but that's what race crews do. The traveler is dropped - sometimes way dropped - in heavy gusting conditions. You should be able to slowly drop the traveler and see the "bubble" at the luff as the genoa starts to backwind the main. With traveler well dropped you could have a big bubble in the luff but the middle and back of the sail is still pulling. On my boat dropping the traveler along (and it's only a meter long) drops heel angle (when powered up) but at least 5 degrees.


Although we like to do well, part of the objective is to give everyone a chance to do and learn so everyone gets a turn at whatever they want to do and the main trimmer for the day is not always the most qualified or experienced.

- Finally the skipper needs to be actively steering. Up into the gusts and down into the lulls.

Agreed and this is on me. First to admit I'm not as skilled here as I would like to be

-All in all I think your weather helm and rounding up are twisted off genoa and not sheeting the genoa hard enough.
Genoa is always sheeted hard. Might have to move the cars more forward (again) and sacrifice 5-10 degrees in pointing ability when the winds are up a little.

Oh and the crew needs to hike out if you really are getting 20-30 degrees of heel in 14 knots.

They do.

Ok - how'd I do?

Very well. Thanks for the commets...

[OldFrog75]

Originally Posted by StuM

"Why are the Genoa cars back?
To flatten the sail and point higher"

If they are too far back,all the tension will be on the foot of the sail and the leech will be bagging putting more draught in the sail.

Not sure I understand this comment. In an extreme case with the car all the way forward, the foot would be loose, the leech tight, a wide angle of attack, and the draft rounding way out to leeward.

[carstenb]

At the risk of being flamed by those who know a lot more than I do about sail trim. I was taught (a long time ago) that you set the genua car so that the leech and foot exhibit the same arc, meaning that the arc the foot describes (no matter how loose or tight it is) should be mirrored in the leech.

Now you have the car set correctly and you can get on with tightening/loosening the sheet.

[cwyckham]

Originally Posted by carstenb

At the risk of being flamed by those who know a lot more than I do about sail trim. I was taught (a long time ago) that you set the genua car so that the leech and foot exhibit the same arc, meaning that the arc the foot describes (no matter how loose or tight it is) should be mirrored in the leech.

Now you have the car set correctly and you can get on with tightening/loosening the sheet.

That's a good start by eyeball. You can also estimate the angle of the sheet bisecting the angle of the clew of the sail.

Once you've got it close, though, you should be tweaking by the lift of the telltales. As you luff up a bit, all three leeward telltales should lift at about the same time. If the top one lifts first, move the car forward and vice-versa.

[Dockhead]

Originally Posted by poiu

I've got the designer's detailed polar calculations for my boat, which is a very similar design to yours. Cutter rig, bulb keel, same furling, similar proportions, hull shape etc. Just maybe a bit heavier pro-rata and a less powerful skeg rudder. The designer's figures show maximum designed heel is 25 deg. When on the wind between 10kt and 20kt the optimum heel is 15 to 25 deg, with corresponding reefing to achieve this. Above 20kt the heel is at 25 deg for most on the wind angles. When sailing I end up maybe a bit below the designed numbers - low 20s. It makes for a nicer sail, slower maybe as I also have a lot of weather helm. So my experience and the designer's figures confirm something similar to what you have found. About 35 deg heel is the warning sign that I have messed up and am at risk of losing control. At that heel angle I will have full rudder.

Interesting. I wish I had polars for my boat.

My boat definitely doesn't like anything over 20 degrees, and I have never experienced (that I can remember) 35 degrees of heel, except maybe momentarily in a gust. I carefully watch rudder angle when I'm sailing hard, and get nervous any time it gets over 10 degrees. I figure at 20 degrees of rudder angle, the boat is already completely out of kilter -- time to urgently reef. I have never had to keep the rudder hard over (45 degrees) -- yikes! Even in 25 -- 30 knots of wind, I keep the heel under 20 degrees. My boat has modest SA/D numbers (16.5 -- made for hard conditions like the English Channel), so on most points of sail I can carry the full press of canvas up to something over 20 knots of true wind. If the heel exceeds 20 degrees, I have to reef, starting with the mainsail.

Today I was trying to make progress directly upwind in 25+ knots, under staysail and reefed main. Separate thread on that. At one point, I had the main completely out, with no yankee at all, just the staysail -- as an experiment. Mainsheet traveler was amidships. As long as heel angle was less than 20 degrees, there was no untoward weather helm -- rudder angle in single digits. So my hunch was right -- on my boat, weather helm is a linear function of heel angle -- almost nothing else matters.

[Dockhead]

Originally Posted by carstenb

At the risk of being flamed by those who know a lot more than I do about sail trim. I was taught (a long time ago) that you set the genua car so that the leech and foot exhibit the same arc, meaning that the arc the foot describes (no matter how loose or tight it is) should be mirrored in the leech.

Now you have the car set correctly and you can get on with tightening/loosening the sheet.

I'll stand by and get flamed right with you. But that's the whole point of the jib car -- to balance the tension of leech and foot. Certainly that's how I use it. If the foot is tight but the leech is loose, for example, then the car needs to go forward. That's pretty basic, isn't it?