Building intuition for sail trim

Posted by dripppydripdrop@reddit | sailing | View on Reddit | 44 comments

I’ve been sailing in San Francisco since August. Catalina 320. I’ve taken ASA 101, 103, and will be taking 104 soon. I’ve chartered boats a few times, and am feeling pretty comfortable and competent generally operating a sailboat and doing so safely.

However, every time I get out under sail, I really have very little intuition for what to do about my sail trim. I’ll trim or ease the main and jib based on my point of sail, but if you were to ask me, for a given point of sail, am I over or under trimmed, I would have no idea.

Was sailing the other day and the telltales on my mainsail weren’t flying at all, and I couldn’t tell you why.

I think I’m generally a fast learner but the complexity of sail trim is pretty overwhelming. Luff tension, leech tension, boom vang, traveler, outhaul, jib cars, don’t even get me started on twist..

How do you begin to tackle the problem of building an intuition for this? Is it just a matter of time on the water and experimentation? I’ve read the theory but it doesn’t really stick very well, at least not in an intuitive way that I can easily apply on the water.

Are there any good resources for this? Has anyone ever taken a dedicated sail trim class?

[-]

texasrigger@reddit

This doesn't directly answer your question but one very common mistake that I see on boats is for the jib leads on the port and starboard side to be in different places. You're probably a ways out yet from understand where they should be and what's accomplished by moving them fore and aft but you're hurting your learning curve by not even having them the same since trimming on one tack is different than on the other.

[-]

dripppydripdrop@reddit (OP)

Good call. They often are in different positions and I don’t notice until I get out there (and I don’t bother to change them because I don’t deeply understand what the implications are).

I’ll make it a habit to correct that. What’s a good default position if I don’t know any better? Directly in the middle?

[-]

texasrigger@reddit

It depends on the sail. If you want to picture what they do, picture a very long track that stretches from directly beneath the clew of the sail all the way to your winch. In this scenario you are beating with the sail trimmed all the way in.

Now imagine pushing the car all of the way forward. As you pull tighter on the sheet you are effectively pulling straight down on the clew. There is almost no aft component to the pull. As you tighten it the leech of the sail will get tighter but the foot will stay fairly loose.

Now imagine pushing the car all of the way aft. Now you are pulling tight along the foot but there is little to no downward component to the pull so the crew can lift, loosening the leech and allowing the sail to twist off as you go up.

Now that you see both extremes, imagine finding that sweet spot in between where your foot and leech tension are nicely balanced and the sail has an effective shape all the way up. Where that sweet spot is varies with the size of the sail, how high cut the clew is, and a hand full of other factors. That's one of the reasons that its adjustable. That geometry also changes if you are reefing a roller furling sail.

Your telltales are the best indication of where your car should be. If they are breaking evenly all the way up then the car is perfect. If the top ones are breaking first, push the car forward. If the top ones are stalling (just hanging), move the car aft.

As you get better, there's actually scenarios where you deliberately want to move them away from ideal. For example, in heavy winds you can move them a little aft to allow the top of the sail to spill off and depower. Walk before you run though.

[-]

NotACmptr@reddit

Great explanation. I had an idea and you solidified it, thanks

[-]

texasrigger@reddit

Thanks. It's a bit long winded but I was trying to make it as clear as possible.

nomadicSailor@reddit

My personal golden rule: "if in doubt, let it out"

Mehfisto666@reddit

Eh this something that sounds cool but it's not really true for my experience. I tend to do the opposite

Single-Willow6475@reddit

Yeah feels like thats allgood for cruising but doesn't suit racing

6l6mike@reddit

Could you explain? I'm no racer, but in my simple terms I would say you lose performance if you have the sails too tight, and it's easier to spot a wrong trim with sails too far out. I want to join some hobby races this season, so I'm eager to learn.

7marlil@reddit

When racing, pulling the sails in or out a few inches can make the difference between a 5 knots speed or a 6 knot speed for example, which is more than enough a difference to wim you a race.

"If in doubt let it out" is a statement that is not fit for racing because you do not really have the time to "trial and error". You need to know exactly and immediately how to trim your sails or else you will loose precious seconds. The statement above is adapted to cruising because depowering a boat is rarely dangerous (unless you need the power to maneuver ) and will at worst slow your cruising down a little bit and increase comfort by heeling less.

overthehillhat@reddit

OldTimeyWisdom --- Yes!

Also ''the time to reef is when you first think about it''

You beat me by 1 minute. That's absolutely the golden rule. Neophytes have a strong tendency to overtrim.

670979@reddit

A big help would be for you to crew on a racing sailboat, you will learn alot about trim, pointing, sail performance, running gear, etc

shtuffit@reddit

Crew in for a racer in the Sunday beer cans

2878sailnumber4889@reddit

Go racing.

pdq_sailor@reddit

Garry Jobson has written a few books including The Racing Edge which he autographed for me... He wrote that book with Ted Turner not long after they won the 1977 Americas cup... I have been doing this a long ... time and because I love it.. I have become pretty good at it.. I have sailed with and against some of the finest sailors who have ever lived... We stand on the shoulders of giants...

Sail trim starts with observation of what the wind does to the water, the leaves, the birds, the hair on the back of your neck.. Having a technical understanding of how sails work, high pressure sides, low pressure sides adjusting camber, and of course angle of incidence are important... but even fifty years into this I am still learning the fine points about sail trim and I monitor adjustments watching the digital speedometer.. I use everything to adjust sails.. even use. a cigarette in light air to watch which way the smoke moves.. and I am regularly complimented on my sail trim.. In time it does become an innate skill and its one of the most important sailing skills you acquire.. I have to keep learning because changes in technology and sail materials keep evolving.. I had to retune my mast to fit and work with new sails.. Observation and understanding and analytical thinking are all part of it... and its fun...

caeru1ean@reddit

When in doubt, let it out

alex1033@reddit

There is a good concept of thick and thin lines. Thick lines are halyards and sheets. Thin lines are traveler, Barbers, backstay, runners, Cunningham, etc. Kicker can be seen as thick or thin, but you can start with it as a thin and promote it later. Then, you never use any thin line until you fully used the potential of the relevant thick line.

It will significantly reduce the number of options, let you focus on important trim.

Shortly, the halyard sets the shape of the vertical profile of the sail; the sheet sets its position. Once you reached some trim that looks more or less OK, sail straight (= keep the same AWA) and try to tighten or loosen a thick line a bit and observe the shape of the sail, the speed and the helm feel.

After a while you'll begin understanding it.

stblack@reddit

The North U Race Trim book is among the best resources in book form.

https://store.americansailing.com/north-u-racing-trim/

I also recommend crewing with good sailors. If you explicitly ask everyone to vocalize why they’re doing something when they do it, you’ll learn quickly. Good sailors love to talk about sail trim.

Zealousideal-Ad-7618@reddit

I've not read that one, but the problem I find with a lot of racing stuff is it relies on controls I rarely have on the kinds of boats I sail on.

I'd recommend the book Plain Sailing by Dallas Murphy.

ez_as_31416@reddit

dinghy racing. the best. your trim choices have an immediate effect.

Don_T_Blink@reddit

You should sail a dinghy once in a while. The world's best skippers are recruited from dinghy sailing championships.

Raneynickelfire@reddit

These are what tell-tales are specifically for!

SVAuspicious@reddit

Intuition is not the right word. You look at where the wind is coming from and how fast it is and how fast you're going. You look at tell tales and sail shape. You decide what to do based on knowledge.

The key is understanding. Intuition doesn't tell you that fixing main trim or headsail trims may well come from secondary sail controls like jib car position, backstay tension, halyard tension, cunningham, downhaul, outhaul, ...

You don't get any of that or even sheet trim from intuition. You have to know what you're doing.

Bikerbass@reddit

Jump in a single man dinghy, especially a single class boat like a laser as an example. That will teach you more about sailing than anything else.

Racing in one design class of boat will teach you a lot in regard to sail trim.

Had an active debate regarding main sail trim on the boat I sail with a guy who actually did the same training program I did. He would suggest one thing and I’d listen and follow, then repeatedly ignore as he was slowing us down with his sail trim.

But that’s because I spent 4 years of my life as a mainsail trimmer on a one design boat both fleet racing and match racing almost every single weekend on both a Saturday and Sunday.

V10L3NT@reddit

I had this video on VHS and basically memorized the whole thing:

https://www.youtube.com/watch?v=P1n-7czmc14

I'd suggest skipping the glamor shots and intros and digging into the content, which is all still 100% relevant and very clearly laid out:

Mainsail: 7:50
Genoa: 24:40
Spinnaker: 36:15

Bigfops@reddit

As you start the only things you should worry about are the sheets. Observe them and try to have a map in your head as to where the wind is coming from. If you can do that then you can start to develop an intuition for it. Those are the big guns, the rest of what you mention is fine-tuning.

One tip for trim is to ease the sheet until the sail luffs and then haul until it just stops luffing. Keep an eye on the wind vane and if you see it shift, ease the sail again and start over. Always trim from the front to back. Jib first, then main. But I'd say my greatest tip is to see if you can find a smaller boat to sail. Sailing a dinghy or small keelboat will give you a much better sense of the wind than a large boat.

chrisxls@reddit

Sailing on a dinghy -- or even something under 20' -- will make a big difference. You can feel the boat react in your fingertips before you can see it and the changes when you change something are instantaneous and tactile, when they are subtle and happen 10-40 seconds later on the bigger boat.

You can rent El Toro's on Lake Merritt in Oakland.

The rest of this comment is excellent. Big lever first. Trim in til it luffs, ease til it stops. Keep your eye on the windex. Repeat.

dwkfym@reddit

It hasn't really been intuitive for me despite having sailed for a longish time now. I still use draft stripes, tell tales, and constantly look at twist. The only thing that's been sort of 'feel' based for me is boat heel vs boat speed.

tenuki_@reddit

Sail trim starts at the tiller.

knowledgewhore@reddit

I’d say crewing on a race boat would help understand sail trim. Often on charter/rental boats the sails are blown out and difficult to read without experience. Sail a small dingy or a race boat with some crispy sails and you’ll see what’s happening with trim as it’s more obvious in the luff and on the tell tales.

Fred_Derf_Jnr@reddit

Totally agree, especially when it comes to trimming the jib to get the slot right along with the traveller.

The difference in sail setting between a seasoned racer and a cruising sailor is so much different, with the ability to power up/depower being the key difference.

Race trim was so hard to believe at first

All those little tweaks?

But it really was the ''Fastest'' way to learn

nickelchrome@reddit

If you can find an opportunity to sail in a dinghy or a performance keelboat then that’s the easiest way to get a feel for this stuff. The response is so immediate, you can really notice and build the intuition around it. I can always tell when I sail with someone who has small boat experience.

LameBMX@reddit

all good stuff.. but ill add. practice. sail sail sail. learn learn learn.

madworld@reddit

Is there a certain point of sail that is giving you problems? For me it was easier to try to learn trimming one point of sail at a time. Don’t get hooked up on learning everything at once. If there is enough apparent wind, and you are above about 120 degrees, your telltales should be flying.

Twist should be used first if you are a bit overpowered. It’s a first good step when you are heeling too much, but you aren’t ready to reef.

It’s one of those skills that you learn over a long period of time. Easy to get the basics, but long to become an expert (and I’m no expert). If I were you, I’d read up on trimming one point of sail before you go out. Then go out and play with those techniques.

Thankfully you are in the perfect location for this. Sometimes a lot of wind, sometimes little wind (shaded by Treasure Island as an example).

If you want to get really good, then you should try to crew some races. Maybe sail some dinghies (Berkeley has some great options). Those two would go a long way to teaching you trimming.

vballbeachbum1@reddit

As many have said. Ease the sail until it luffs then trim the luff out. Move the jib sheet turn block forward or aft to get the tell tales flying evenly . Sailing close to the wind i like a little luff in the main. Too much weather helm means the main is overtrimmed. I sail an old Catalina 27 and can lock my tiller and adjust the sails to maintain course. I call it " being in the slot" Granted I raced alot in my younger days so it has become second nature to me. Also just as a cruiser I don't do alot of fine trimming. Downhill, outhaul, he'll I don't even have a vang. It broke and I didn't fix it. I am considering a preventer though. Try to get on a race boat that will build your trim expertise.

Lots of sources here to answer your question

Always will be plenty

I Sailed solo in a sailing dinghy when I was 8

Now I'm almost 80

And I still study it --whenever

Personally I started to understand sail trim better in high winds when I needed to depower. Instead of reefing, starting by taking the sheet cart back and ease the traveler. Pull the gennaker tighter instead of letting it out in a panic.

I would say that in general, it's easier to get a feel for sail trim in high winds. When you sail upwind in 18kn of true wind with full canvas every little adjustment you make that gives more power/heel you will feel

supereh@reddit

Ease till it’s luffing. Trim in. Repeat. Make smaller movements as you notice the intricacies of your sail. Repeat.

Drive the boat blindfolded/brim down, see if you can hold the course you think you are by feel.

the-montser@reddit

If both telltales aren’t flying at all, their is either no wind or you are extremely overtrimmed.

Forget about luff tension, leech tension, etc. Learn how to sheet the sail correctly first. The rest is useless if you don’t understand that.

In general you want the sail eased as far as it can be without luffing.

flyingron@reddit

There are a bunch of youtube videos out there on sail trim

iamtheperiphery@reddit

Following