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Old 08-08-2014, 01:39   #1
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Some Things I've Learned About Sail Trim Recently

Considering how painful and difficult the lessons were, and how long it took me to learn them, I thought I would share, in the hopes that it might shorten the process for someone else.

I learned to sail first in dinghies, then in long keel, old-fashioned boats. My present boat is my first with a modern hull form (bulb keel, semi-balanced rudder, etc.).

It has taken me years to figure out very basic things about sail trim in this boat, something which is embarrassing. I wonder if there are not others out there who like me have found the transition to modern boats difficult.

The most important lesson I learned was to finally figure out how to deal with weather helm. I at first thought there might even be a problem with my rig. Above a certain wind force, the helm became overwhelming, and I simply couldn't figure out how to trim it out. On previous boats, letting down the traveler and flattening the mainsail would always do it -- it was all about sail balance.

I eventually started reefing the main sail deeply without reefing the headsails, trying to move the center of effort of the sail plan forward. This didn't help. One day I found myself, for some reason, sailing under yankee alone, with no mainsail up at all, and I still had weather helm. Then a light bulb went off in my head -- it's not the sail plan causing this.

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. Unlike on my previous boats, the sail plan balance has very little effect on helm balance -- and I guess the reason is that this rig is much, much higher aspect than on my old-fashioned boats with their long keels, short masts, and long booms. This rig is very tall and the boom is modest in length. It makes it much, much easier to balance (and this is definitely a big plus) than what I grew up with. I would say even -- the sail plan on this boat is inherently balanced, and I was wasting my time trying to correct it.

Man, I wish someone had told me this five years ago. I wasted years of fiddling and struggling before figuring this out.

This whole problem led me to another mistake -- misuse of the traveler. The first thing I would always do on my old boats when getting a little overpowered was to let down the traveler. So all those years struggling with weather helm, I would do what I was taught, let down the traveler, then try to trim the mainsail with outhaul and mainsheet. But I could never get rid of the "speed bubble" behind the mast, and in general, the mainsail just wouldn't draw with the traveler down, when hard on the wind, no matter how much I fiddled with it.

Wow, what a mistake. That's just not what you use the traveler for, on this boat. I've learned that on this boat, the traveler is the main and most important sail control, going upwind. The mainsail is exquisitely sensitive to angle of attack, and when close hauled, on this boat, the mainsheet has little to no effect on that -- all it does is control leech tension (totally different from previous boats). So now sailing close-hauled, the first thing I do with the mainsail is to get the shape right for the wind strength, get the draft in the right place, and only then play with the traveler, working it until the air is flowing smoothly around both sides. No more speed bubbles! And it means that in all conditions, when hard on the wind, the traveler is never just let down. It is usually somewhere near the centerline of the boat, sometimes even above it (especially with the mainsail reefed). If I need to depower the main, I first flatten it as much as I can, but then set right about reefing it. The huge advantage of in-mast furling is that you can reef in infinite increments, effortlessly, and even more important is that the sail gets flatter, the more you reef it. So unlike the case with a headsail, the shape just gets better and better as you reef it.

The third important thing I've learned, and this just these days, is the amazing power of barber haulers for the headsails, but there was a separate thread about that.

I hope this is of some use to someone -- if only someone had told me all of this four or five years ago!
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Old 08-08-2014, 02:28   #2
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Re: Some Things I've Learned About Sail Trim Recently

Boy I sure wish I could spend a couple of hours with you on your boat. While you have had 5 years to experimentally find out what works you still may be overlooking a few things.

While all boats are sensitive to heel angle they don't all react the same way so what is working on your boat may not translate directly to someone else - i.e. hull shape impact on weather helm.

You've got it right about flattening the main to depower initially but I hope you recognize that a flat sail has a very narrow steering angle. So in choppy seas and shifting conditions you may still find yourself frustrated.

While it sounds like you are sorting out how the main works and should work - I really suspect that the big deal for you is understanding the genoa trim and lead angles.

I don't think the North sails trim series goes into sheeting angles much but it is a good place to re-review.

And there's no harm, no foul in taking a class. We had a North Sails class here and "all" the serious and experienced skippers were there. The best part was the instructor was a successful racer and the break and bar conversation was where some real jewels came out.
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Old 08-08-2014, 03:34   #3
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Quote:
Originally Posted by Ex-Calif View Post
Boy I sure wish I could spend a couple of hours with you on your boat. While you have had 5 years to experimentally find out what works you still may be overlooking a few things.

While all boats are sensitive to heel angle they don't all react the same way so what is working on your boat may not translate directly to someone else - i.e. hull shape impact on weather helm.

You've got it right about flattening the main to depower initially but I hope you recognize that a flat sail has a very narrow steering angle. So in choppy seas and shifting conditions you may still find yourself frustrated.

While it sounds like you are sorting out how the main works and should work - I really suspect that the big deal for you is understanding the genoa trim and lead angles.

I don't think the North sails trim series goes into sheeting angles much but it is a good place to re-review.

And there's no harm, no foul in taking a class. We had a North Sails class here and "all" the serious and experienced skippers were there. The best part was the instructor was a successful racer and the break and bar conversation was where some real jewels came out.
I also wish I'd had you on my boat for a few hours, a few years ago. It would have saved me a lot of grief, I bet.

I have had a lot of very experienced sailors on my boat, including a multiple circumnavigator, a couple of yachtmaster instructors, and countless yachtmaster. None of them, it seems, knew anything more than what little I know about sail trim :bamghead:. I am convinced that sail trim is a black art really mastered by almost no cruisers - something which is really understood practically only by racers.

Since I love to sail for its own sake, I am deeply unsatisfied with this. I would gladly take some classes if I could find a good one.
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Old 08-08-2014, 04:45   #4
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Re: Some Things I've Learned About Sail Trim Recently

Quote:
Originally Posted by Dockhead View Post
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.
It is even more a truth with newest designs, carrying their breadth far aft.
When heeled more and more, the hull is getting more and more assymetrical, and the shape of immersed part force it tu turn to the wind. At the same time rudder is less and less immersed, moving the centre of the lateral resistancy forward (one of the reasons for double rudder arrangement). Anyway - an angle of heel of about 30 degrees is huge. The subjective reception of such a heel is almost of the boat lying on the side (when speaakin of rather modern, quite beamy designs).
Most hulls are now optimised for heel angle between 15 and 20 degrees, not more. One of the most important things is the turn in the sail. What You really need is to control the turn right. When boat is heeling You need more turn in upper part, to spill the wind of the upper part of the sail and keep the hull as level as possible, without depowering the boat.
The cut of the sail should be also adjusted to this demand.
Some years ago I took a part in the regatta organized by a yard. Brand new boat, brand new sails. We had a very good start, but just after we started to lose a places. The wind was not light and quite gusty. After some playing with controls we finished with traveller high up, main not very flat and the vang became the main control. We find the groove and started to overtaking other boats. Helm was easy, mainsail quite heavily twisted. We had barber haulers in place already, so we could control the genoa easily. As it was longish upwind leg and I could spare some minutes, I made a phone call to my sailmaker:
"Andrzej, it is something strange about this mainsail! We are doing good, but only when the sail is really twisted! Boom is near the center, traveller up, and we control the sail mainly by the vang now!"
He laughed out really loud!
"Are You pointing well?"
"Yes, higher than almost any boat!"
"And the speed is good?"
"Yes, we are overtaking them one by one!"
"So what are You camplaining about, exactly? You have a damn beamy boat, so Your sail is cut to work this way! Just open Your leech in gusts, spill the wind up, don't let the boat to heel and go, go, go!"

We won...

Cheers,

Tomasz
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Old 08-08-2014, 05:13   #5
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Re: Some Things I've Learned About Sail Trim Recently

Hell 30 degrees is a LOT of heel for a modern boat. You must really be trying to be powered up, which why you have so much weather helm. Heck on my boat 20 degrees is a lot and I know for a fact that I can reef down and go just as fast by sitting up.

Different boats sail different and there isn't any reason to fight it.
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Old 08-08-2014, 05:14   #6
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Re: Some Things I've Learned About Sail Trim Recently

My 30 year old CAL handles exactly the same; anything over 20° heel and she will turn upwind regardless of rudder input. But with a twisted sail, she'll point like a German Short Hair!
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Old 08-08-2014, 05:30   #7
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Re: Some Things I've Learned About Sail Trim Recently

Thanks for posting dockhead, very interesting, and honest. I wouldn't be too worried about the time it took you to work it out.

Some of the good trimmers I've raced with start out more with trial and error than theory. Gauging speed against other boats around them as much as using shape alone. I guess what they have that I don't is an intuitive grasp of all the options and how they tie together. They also have a big reserve of options to play with instead of getting to tied into one approach.

I remember asking one ex admirals cup trimmer what he was thinking with the headsail. He told me he wasn't really sure, and thought it was seriously ugly and should have been slow, but it was fast. He couldn't say why but was happy to run with it. We did very well.

Anyway, good tips from you, and a reminder not to get to set in our lazy cruising ways...
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Old 08-08-2014, 06:29   #8
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Re: Some Things I've Learned About Sail Trim Recently

Dockhead,

I couldn't agree with you more. Sail trim is a black art. Damn few cruisers really understand it (unfortunately, although i'm reasonable at trimming - I'm not one of the blessed few who truly understand)

In my day job, I actually have the time and resources to study this and I'm still not great at it.

After years of trying, I'm just this and last season beginning to be satisfied with my sail trim when close hauled or on a reach.

sailing downhill - well the goal is still in front of me as they say.
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Old 08-08-2014, 07:16   #9
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Re: Some Things I've Learned About Sail Trim Recently

Hmm.... Full sail in a blow, sails trimmed and rail down. I think i'll leave the helm apply the wheel brake and make a pot of coffee.

I guess there's still some merit to sailing long keeled double enders.

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Old 08-08-2014, 07:32   #10
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Re: Some Things I've Learned About Sail Trim Recently

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Originally Posted by Dockhead View Post
I also wish I'd had you on my boat for a few hours, a few years ago. It would have saved me a lot of grief, I bet.

I have had a lot of very experienced sailors on my boat, including a multiple circumnavigator, a couple of yachtmaster instructors, and countless yachtmaster. None of them, it seems, knew anything more than what little I know about sail trim :bamghead:. I am convinced that sail trim is a black art really mastered by almost no cruisers - something which is really understood practically only by racers.

Since I love to sail for its own sake, I am deeply unsatisfied with this. I would gladly take some classes if I could find a good one.
Maybe in my hubris I am overstating my "abilities" - LOL...

Snowpetrel has it right - sometimes it is about experimentation. At King's cup in 2012 we were on a Jeneneau 36 "charter boat" class. We had to race the charter sails. Tiny jib, tiny main and a ridiculously small asym.

In one race we were behind with not much to lose and a fairly tight angle. We partially unfurled the jib while flying the asym and picked up 1/2 knot. We messed with foot length and picked up over a knot in light airs. We attributed it to improving the flow in the slot.

One thing we couldn't do was sail deeper than about 165. There were 4 36s in the fleet and at one point we separated from the guys ahead and went DDW flying everything we had - asym & jib goose-winged and main. We separated for about 30 minutes (they sailed the angles) and when we came to the gate we were about exactly the 6 -8 boat lengths behind we were at the beginning - LOL...

So you have to be curious and you have to experiment - the books aren't always right... The inciteful guys may not have the answer but they often know "somethings not right"
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Old 08-08-2014, 09:02   #11
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Re: Some Things I've Learned About Sail Trim Recently

I have had the same experience regarding heel angle. If I trim or configure the rig to let the boat stand up the hull shape is more efficient, the ride is better and the deck is drier. In the area that I cruise we get steep short period waves. As the wave height increases and the period remains the same the hull cannot ride over it and must thrust it aside. This takes more power at the very time when it makes sense to shorten sail. I usually loose about a knot when going to windward. The point being that there is a performance loss unless the wind continues to increase. The boat performs the same, full rig at 15 knots or Yankee and mizzen at 25 knots. With winds over 25 knots the waves begin breaking and flatten somewhat. The speed picks up again until the wave period increases and the height starts to build again. This leads me to want a low aspect ratio jib that can be flown on the inner forestay to make more power in the fore triangle without becoming lee happy or generating excessive heel once the main is down. All in all it makes me appreciate gaff rigs. How to make power without putting the rail down so far that hull drag increases.
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Old 08-08-2014, 09:32   #12
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Re: Some Things I've Learned About Sail Trim Recently

Hey Dockhead , great post , and a great help to many.

I learned to sail in dinghy's when I was 12 and still sail them today, also spent time teaching. The last dinghy, which almost killed me was an International 14 . Now we are talking about sensitive to sail trim LOL. Even so one of my best reads on sail trim in a larger boat was this book .
Sail Power: THE COMPLETE GUIDE TO SAILS AND SAIL HANDLING by Wallace Ross — Reviews, Discussion, Bookclubs, Lists

A light read

Regards
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Old 08-08-2014, 10:04   #13
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Re: Some Things I've Learned About Sail Trim Recently

Yep, hull shape is oft overlooked when it comes to weather helm. As I've noted in another post recently regarding a specific boat, some designs are truly defective in regard to that. To me the mark of a good designer is one who can balance the hull well heeled as well as flat.
The wetted area needs to be balanced fore and aft or the drag changes things.
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Old 08-08-2014, 10:05   #14
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Re: Some Things I've Learned About Sail Trim Recently

Sail Trim Users Guide
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Old 08-08-2014, 13:37   #15
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Re: Some Things I've Learned About Sail Trim Recently

Have you explored backstay tension?
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