Sail Trim

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Sail Trim

Postby Interim » Tue May 26, 2015 11:53 am

I finally got on the water yesterday (only the second outing of the year). Unrelenting wind shifts (as happens on inland lakes in the Spring). Periodically I would get a breeze from one direction for a few minutes, and on those rare occasions I had trouble getting the main trimmed right.

If my telltales were streaming properly, I would be luffing. If I cured the luff, the telltales would curl to leeward.

My hope is that this is because I had the bottom 6" of the boltrope in the mast slot. I have a new sail from Intensity, which gives enough boltrope to feed in above and below the opening where the gooseneck goes into the mast. I didn't think I wanted the sail sticking out at the bottom, so I fed it into the slot. But I think doing so crinkled the first bit of the boltrope along the foot, so I couldn't get the outhaul tensioned. The clew was 6-8" from the end of the boom.

Could this have resulted in a sail that was too baggy, and thus would luff too easily? I didn't measure, but I think I was also having trouble pointing when close-hauled.

Thoughts?

--john
1979 DSII
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Re: Sail Trim

Postby K.C. Walker » Tue May 26, 2015 12:32 pm

You don't need that last bit of bolt rope in the mast sail slot above the boom. For your conditions, it does sound like you needed more outhaul, though.

It's unlikely to have too much outhaul unless you have a very powerful outhaul set up. Generally, it is not a problem to put on a lot of outhaul but it is somewhat of a problem to have not enough. As you get more used to setting up you can ease the outhaul for moderate winds. Otherwise, crank it out so that you have noticeable horizontal wrinkles parallel to the boom. This is especially a good setup for light winds and anything over 10 kn or so. In moderate conditions of approximately 5 kn to 12 kn the camber can be about 10% (or about 10 inches from the boom in the middle of the sail and this is under load) in low wind conditions and in higher wind conditions you want a flatter camber at about 7% which in high wind situations means pretty good tension on the outhaul. Mike Gillum (multitime Daysailer national champion) says that he puts on the maximum allowed outhaul tension at the dock and never changes it. This would be a good keep it simple set up for good performance.

It is possible that you also did not have enough downhaul or not a full hoist on the mainsail. In the conditions you describe I will try to set up my sails for the gusts, so I might even add a little Cunningham tension on the luff. This all depends on your particular sail and set up, though.
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Re: Sail Trim

Postby Interim » Tue May 26, 2015 1:31 pm

Thanks, K.C. My wind was varying from 3kn to 15kn, so your advice about setting up for the gusts is useful.

The sail was hoisted all the way, and while the gooseneck was as low as possible, I did consider adding the Cunningham. But didn't. I probably also should have eased the boom vang. Perhaps I was frozen by the adrenaline :o

My outhaul is 1:1. Are other ratios common? I could make a 2:1, if that has been found useful by others.

Now I'm anxious to get back out and do it better.

--john
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Re: Sail Trim

Postby Interim » Tue May 26, 2015 1:38 pm

Here is a related question:

Let's say I'm moving along in 7knots of breeze, and a gust of 15 hits the sail. The boat lies over. I either ease the main or head up a little, and it rights itself.

Does the boat go over because with the gust I lose laminar flow? That is, the sail isn't moving through the air fast enough to maintain attachment. If I waited for the boat to accelerate (assuming windspeed stayed at the 15knots), would it return to a more even keel?

--jf
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Re: Sail Trim

Postby willyhays » Tue May 26, 2015 1:44 pm

Interim:

1. Sounds as though your main is too full. As K.C. mentioned, tighten the outhaul. My outhaul is 4:1. Also, you can flatten the main by tightening the boom vang, thereby bending the mast. Mast bend can also be affected by spreader adjustment. Where are your telltales located, i.e., how far aft of the mast?
2. No. Laminar flow is not the issue. This heeling effect is a function of increased pressure on the sail caused by increased wind speed.
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Re: Sail Trim

Postby willyhays » Tue May 26, 2015 2:02 pm

Waiting for the boat to accelerate will not lead to reduced heel. Actually, if you are sailing upwind, acceleration will result in increased apparent wind speed. (Downwind, the opposite is true.) Increased wind speed results in increased pressure. Assuming all other factors remain unchanged, increased pressure will result in increased heel (upwind).

Also, when the gust hits, the sail is, in effect, moving through the air faster, even though the boat has not yet accelerated. It's all relative. The sail moves through the air at the same rate whether the wind speed is 15 and the boat speed is zero, or wind speed is zero and boat speed is 15 (say because you have a powerful outboard motor).
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Re: Sail Trim

Postby Interim » Tue May 26, 2015 3:53 pm

My telltales are on the leech by the batten pockets. I used to have another set about 1/3 back from the mast, but was told those are more of a distraction from the real point (which is the leech). I suspect this could be a matter of some debate.

Regarding managing the gusts, I'll continue easing the mainsheet. I thought perhaps that if I gave it a few moments it might "self-correct," but now I see that won't happen.

Thanks, all.

--john
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Re: Sail Trim

Postby willyhays » Tue May 26, 2015 4:58 pm

John,
Yes, easing the main, at the right moment, and hiking hard are the quickest ways to effectively reduce heel in a gust. Flattening the mainsail will help by reducing the amount of power the sail generates.

If I may, I'd like to suggest that you consider removing the leech telltales. They too can be a distraction. They have their place, particularly when racing. But for learning to sail and for honing one's skills early on in the learning process I would consider them to be not only a distraction, but a hindrance to the development of the all important ability to sense changes in wind/sail/boat/wave interactions.

This is only my own opinion, and certainly not the only valid perspective, but it is based on many years as a sailing instructor. I hope this is helpful.
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Re: Sail Trim

Postby K.C. Walker » Tue May 26, 2015 9:29 pm

I use a 4:1 outhaul, as well. I know that some racers use 6:1 but I think 4:1 is popular. The higher ratio allows being able to pull on the outhaul easily while underway. I think that 2:1 is likely sufficient if you crank it on at the dock and leave it alone.

To lower the adrenaline factor (in a good way) I recommend not cleating your mainsheet. Especially in gusty situations that you are describing, being able to ease the mainsheet instantly without having to un-cleat really increases your control. You don't want to let the boat heal up if you can help it. First off, it gets you closer to capsizing (the bad kind of adrenaline) and secondly it is slow. The magic piece of hardware to make this work comfortably, though a little pricey, is a ratchet block. In my opinion, it's a wonderful addition to a Daysailer. I feel that it's more than worth the price for the peace of mind and control that it adds. Sailing gloves are also a nice addition.

Though your conditions were gustier than I consider fun, even more moderate conditions are rarely truly steady. The rhythm that you want to develop is ease-hike-trim. The more gusts the more this really is the way to handle it. Instead of having the gust blow you over and slow you down, you can get a burst of speed by keeping the boat on its feet. First thing you want to do is have your attention outside of the boat. Watch the water for the dark texture that indicates a gust is coming (and from what direction). Prepare for this by having a good arm length of sheet that you are ready to ease. That is, you're holding the sheet up by your chest and able to just straighten your arm to ease. Put your toes in the straps (if you don't have them, it's a great cheap addition) lean back, feather up a little bit, pulling in the main. If it's a really big gust you might have to play the main a couple of times, stay hiked out and continue to feather up.

I like tell-tails, all kinds. Sure you can be distracted by them (if you let yourself) but they can be a great learning tool as well (agreed, probably more advanced). In the conditions you were in, they are much less useful. However, in light and moderate conditions they can tell you so much about what the airflow is doing around your sails. For a beginning sailor I think the best wind indicator to have and pay attention to are the ones on the side stays (yarn works). The tell-tails on the sails are for finer adjustments.
Last edited by K.C. Walker on Wed May 27, 2015 12:10 pm, edited 1 time in total.
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Re: Sail Trim

Postby Interim » Wed May 27, 2015 11:46 am

willyhays wrote:consider removing the leech telltales.


Willy-- do you mean to have no tell-tales? If so, I gather you are saying ease to the luff and trim back a little.

--john
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Re: Sail Trim

Postby Interim » Wed May 27, 2015 11:55 am

K.C.--

I was single-handing last weekend (the trip that prompted my questions). Specifically, it was memorial day, and "confused seas" would understate the pattern of wakes on the lake. I was cruising with the tiller extension in one hand and the mainsheet in the other. One way to look at it would be that I was fine-tuning my reaction time (responding to boat movement rather than anticipating wind shift). I need to get better at having my head out of the boat when single handing. Usually my partner is watching for other craft and puffs.

I don't have a ratchet block on the main. Just a cam cleat, but in those conditions it is always in my hand. I also don't have hiking straps, so the hiking portion of my response is more of a slight lean. On your advice, I think I'll invest in some.

I'm starting to think I'm the only one with a 1:1 outhaul. For the price of a small block, I bet I can at least get to 2:1.

Thanks for all the thoughts. I really like the debriefings I get in this forum after my outings.

--john
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Re: Sail Trim

Postby GreenLake » Wed May 27, 2015 4:51 pm

Useful discussion.

Three or four observations:

Outhaul

For the price of a small double block you can get a workable 3:1. This involves using the clew grommet like a block. You tie the outhaul to the clew, route it through #1 sheave of the double block, through the clew grommet, through the #2 sheave of the double block, and from there on forward along the boom to a cleat.

I find this powerful enough to adjust on the water. I used to have dedicated small single block, instead of routing the outhaul through the grommet, but I found that this reduced how far I could pull on the clew -- the two blocks would touch before the sail was fully stretched. Using the grommet gives me an extra 1.5".

Ratchet blocks

For the main, get a ratchet block; you won't go back. I replaced the block at the center of the boom where the main makes a 90 degree bend with a Ronstan Orbit 55 Ratchet block; it really cuts down on how hard I have to hold the main. Mine is set to "auto", which engages the ratchet action once you put a minimum load on the sheet. There is a difference among brands when it comes to ratchet blocks (I have both, on different boats).

The Harken (at least some models) have a very easy to use knob/lever to engage/disengage the ratchet action. The Ronstan is very fiddly (hence I leave it on auto, but that setting works well for me).

The Ronstan, in a test by a sailing magazine, was found to have double the holding strength of any of the competitors tested. It is harder on the sheet, so you may need to buy a new sheet a few seasons earlier. However, because it holds so well, it works well in the location I described. (I even fit these ratchets for the jib sheets; the effect is not as dramatic, as I would cleat the jib in more conditions than the main, but I've been out in situations where I appreciated that upgrade).

Ease hike trim
Thanks, K.C., very nicely explained.

Nature of the wind
If the wind is gusty, it is because faster wind, from higher up, gets transported down to the surface by turbulence, where it hits the surface, initially coming a bit from above, but spreading out in a fan (as shown by the telltale ruffles). Because the fan spreads out, depending on which side of the midline you are, you will get different wind angle. That's on top of the wind direction as a whole oscillating or changing.

Other times you can have wind shear. Where the wind direction changes from near the water to near your masthead. On a bad day, you can see the jib being blown one way, while main (and wind indicator) behave as if the wind comes from another direction. Some days it can seem impossible to find a sail trim that works.

Tell tales
I'm with K.C., you are better off with them. But add them over time, as you learn to read and react to each set. The basic ones are the jib tell tales 1/3 up and a foot behind the luff. With a relatively flat jib, if both are streaming (and you've explored how far you can nudge the boat upwind before the inside one flutters up) you are pointing. A second set 2/3 up will tell you whether your jib fairleads need to be moved for-and-aft. You want both sets to stream at the same time.

Leech telltales on the main, at each batten, trim the main until the top one flicks backwards every so often. From there, you can add further ones as needed. They really make the airflow over the sails visible.

Main halyard and Cunningham
I suspected that the shackle I used to connect the main to the halyard was stealing 1-2" of hoist. I replaced it by a knot (and not a sloppy bowline with a big loop). I hoist the main all the way, then pull the boom down to its stop and tie it off with a boom strop. That sets basic tension for the main. Luff tension I can further add via Cunninghmam.
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Re: Sail Trim

Postby willyhays » Thu May 28, 2015 9:34 am

Lots of good info in these posts. It seems that we are all in agreement that telltales are very helpful, particularly as one advances in skill (more on that later), and that learning to feather the boat into the wind while playing the main, that is, easing and trimming, in and out, over and over, is an effective practice.

As for the jib, if you are close-hauled, you can trim the jib, cleat it, then steer to the jib. In other words, head the boat up toward the wind, just until the jib barely begins to luff (it's more like a "bubble" develops on the luff of the jib), then head down slightly until the bubble disappears. Then repeat this over and over. If you are using telltales on the jib instead of looking for the slight luff of the jib (the bubble) you watch the telltale on the windward side of the sail. As Greenlake said, as soon as the telltale starts to lift you know that you are "on the wind," that is, pointing approximately as close to the wind as you (usually) want. Whereas watching for the bubble works well in a gross sort of way, watching the telltales works in a far more nuanced way.

A few more thoughts on telltales: I agree completely that telltales are great. I always use them. I don’t know anyone who races without them. The reason I like teaching people to sail without using them is because it helps them to develop their ability to feel/sense the wind, its direction, speed, and moods and changes, as well as their ability to sense the interaction of the boat itself with the wind and waves. I like to have students steer with their eyes closed (for brief periods of time) to enhance this experience. (I keep my hand very close to the tiller and mainsheet while doing this exercise.) Later, as what I would call their "whole sensory" skills develop, I teach them to use telltales.

As an analogy I like to think of tuning a guitar. A beginner player could learn to tune with an electronic tuner, but that is not the same as learning to tune without it. A more apt example is learning to navigate on the water. One could learn to navigate using a GPS, but that is different from learning to navigate without it. I believe that one who learns to navigate without a GPS can develop a comprehensive and nuanced ability that is unlikely to be matched by one who starts out using a GPS. The same could be said for outboard motors. You can learn to dock the Day Sailer using an outboard. And by doing so you would learn valuable maneuvering skills. But you are unlikely to develop the level of sailing skill that you would develop by docking under sail.

Both GPS and outboard motors are wonderful, useful tools, and I use those and others, including telltales, depth sounder, compass, and knot meter. But the first seven years of sailing I did not use any of those.

The ears, skin, nose, eyes, body, and brain are also wonderful, useful tools. I believe that using them to learn in an intuitive, sensory (somatic) way can lay a foundation of comprehensive and nuanced ability, which can then be built upon, honed, and expanded throughout one's entire sailing life.
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Re: Sail Trim

Postby GreenLake » Thu May 28, 2015 11:29 am

People are very different in how they sense the wind. Down to what body parts people use. I was surprised to learn that someone I sailed with used his ears to feel where the wind came from.

The main technique is to hunt for the best pointing trim. Both telltales and sail shape (bubble/flutter) require essentially the same approach, because you can get a false reading if sailing too far off the wind. I think both methods are more alike than different; I would contrast them with sailing based on the Windex at the mast top. There you look at something that has no relation to the sail, and will in fact sometimes show a wind that's not experience by the sail lower down (whenever you have strong wind shear, for example).

I agree with you 100% on the dangers of sailing by chartplotter.

Looking at an unrelated signal is what I see happening with GPS. In coastal / lake navigation we normally look for land marks. That keeps the eyes out of the boat, where we can then also look for changes in the wind, wave state, tide lines, traffic and all sorts of things that GPS knows nothing about (floating, partially submerged stuff that's big enough to damage a boat comes to mind).

Having GPS makes it tempting to sail on the screen, or as I call it "sailing the video game". I think you tend to loose all feel for the boat.

I'm not a sailing instructor, but I've had several dozen people new to sailing on my boat over the years. And my tentative conclusion is that it's really hard to predict what will "click" for them, and in what sequence. Whether it's learning styles, or preconceptions or what. Always a different story.
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Re: Sail Trim

Postby K.C. Walker » Thu May 28, 2015 1:28 pm

Sailing with eyes closed definitely would add a new dimension to learning to "sail by the seat of your pants". I like it! I think I will introduce this as a teaching technique. Thanks.
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