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Go Back   SailNet Community > General Interest Forums > Seamanship & Navigation
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Seamanship & Navigation Forum devoted to seamanship and navigation topics, including paper and electronic charting tools.


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  #11  
Old 07-28-2010
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Quote:
Originally Posted by lydanynom View Post

Is it just me?
It is not just you, and you have made some very keen
observations in your post. Sailing off the wind with a strong
steady breeze can be as easy as winging out the headsail
and keeping the wind astern. Other times it may feel like it is
impossible to get a feel for. As you noted, your apparent wind
can drop to almost nothing and tell tales quickly become
ineffective below 120deg AWA and mainsail trim is not a obvious when
running in lighter winds, you can pull in or let out several feet of
mainsheet with no discernable effect on performance.
The most helpfull device is a masthead wind indicator, like the
ubiquitous Windex. If you keep your boom close to perpendicular
to your AWA, you will be in the ballpark. If you are not using your
wisker pole on the jib, then you will need reach up to get any
effectiveness from the jib. Moving the lead outboard and forward
will help in this regard.
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  #12  
Old 07-28-2010
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For what my opinion is worth... if you're new enough to be asking these questions, and don't get me wrong, they are good questions ... then for pity's sake put the dang gps in the dry bag and pay attention to the boat!

There are enough fine points to fill fifty forums, but the basics are simple. Any fore-and-aft rig, from a 12-meter to a Sunfish, wants to have the wind flowing over the sails at roughly the same angle no matter what the angle to the true wind and no matter what the point of sail.
This is the angle where the sail is acting like a wing (foil if you prefer).

Sounds like you have the hang of beating. Observe the telltales on a beat, and try to visualize what they are telling you about the angle at which the apparent wind is striking the sail. (Angle of wind to sail, regardless of where the sail is relative to the boat centerline.)
Now bear off to a beam reach. Ease the sails until the telltales and the wind in the sail look about the same as they did on the beat. (Until you figure this out, don't mess with the sail shape controls, they will only confuse the issue.) You may have to fiddle a bit between the mainsail trim and the jib trim until you get both right.
You should notice that the apparent wind is a little forward of the beam even though you are sailing directly across the wind. But you should also notice that the angle at which the wind impinges on the sails is about the same as on a beat.
Once you have that nailed, bear off to a broad reach. Not too close to a run, maybe 135 degrees off the wind. Ease the sails and you will discover they are still at the same angle to the wind (not to the boat!) as they were on a beat.
This is how a fore-and-aft sail wants to work, in "lifting" mode like a wing. As you continue to bear off the wind you will reach a point where the sail won't go far enough out to make the same angle. (Unless you are on a Laser, then good luck!) Then the sail is unavoidably in "drag" mode and you get what you get. This is why sailing dead downwind in a normal sloop is slower than jibing from broad reach to broad reach.
Maybe I'm dumping too much qualifying info. I hope you can tease out the basics from what I'm telling you.
Now that you've sailed way down the lake you can get out the gps and use it to find your way back. ;-p
Fair winds
-Glenn
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  #13  
Old 07-28-2010
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Highlandman's summary is excellent.

To respond to your proposition, the first difficult thing for a beginner to learn is how to sail to windward. Even a leaf on a pond can drift downwind, without any assistance from a sentient being. Often you'll see newbies broad reaching back and forth until they can't go any further downwind, and then they motor to windward. If you're sailing to windward reasonably well, you've made it over the first big hurdle.

Sailing downwind isn't difficult to do, but it is difficult to do well. When you're broad reaching, you can still generate aerodynamic drive, but the closer you sail to dead downwind, the less your sails are acting like a foil, and the more they are simply creating drag. As you have seen, telltales often provide less information to you when sailing downwind, simply because in light air, there often isn't enough force left in the wind's movement to lift them. When you don't have telltales or even a masthead vane to reliably diagnose what the wind is doing, then sometimes the only solution is for you to know what sails should look like in the ambient wind conditions, and then trim your sails so that they match the ones that you see in your mind's eye.

When sailing wing and wing, the angle on which you can steer either to port or starboard of DDW is fairly narrow. If you aren't constantly focused on steering, it's easy for a wind shift or for inaccurate steering to cause the boat to gybe unintentionally.

It's also important to know your boat. Most boats are dreadfully slow in light winds sailing DDW. Some ultra light boats accelerate quickly and plane easily when broad reaching in light air. In strong winds, many boats sail most efficiently DDW.

Calvin is generally correct that maximizing sail area downwind is an important element, but sail controls should generally be eased when sailing downwind in lighter winds, to create deep pockets in the sails, and more power.

We can make a few suggestions, but the truth is that learning the fine points of sailing is a neverending process, that will occupy your mind indefinitely. The best way to learn about it is to think about it, read about it, and do it.

Last edited by Sailormon6; 07-28-2010 at 05:08 PM.
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Old 07-28-2010
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Downwind sailing is just less 'intuitive' than upwind, the feedback is more indirect, and most people don't "feel" the wind very well with the backs of their heads.

It takes experience to suss out what works. mostly, on a broad reach or a run, you're trying to ease the forces on the rudder so you steer, and hence "brake", less. So you heel the boat to leeward to induce weather helm, and to windward to induce lee helm. In between these two is the ideal of neutral helm, where the boat's center of lateral resistance is directly below the sails' center of effort. It's why dinghies are heeled to windward on a run.

Be patient, and it will come. Or it may never come. My wife is downright deadly upwind, can get in any boat and make it point and foot better than anyone else. But she hates steering downwind and isn't that fast at it. So don't feel bad if it never gets 'natural' for you, though it probably will.
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Old 07-28-2010
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Quote:
Originally Posted by bobmcgov View Post
Bag out the main (ease outhaul and downhaul), and then vang the boom. Maybe give a tug on your leech line, if you have one. The combination will curl the leech in while keeping max draft on the sail. Our SJ21s have no roach at all on the mainsail, so you don't need to vang too hard to prevent the top from twisting off. By vanging, you can ease the boom out farther without the sail hitting the spreaders -- and as Sailordave says, you want that boom out as far as you can get it, to milk lift as long as possible.
I have leech lines on all my sails, main, jib and genoa, but I have no idea what to do with them. It's the one sail control I have not even touched yet. None of the leeches chatter so I've taken a don't fix what isn't broken approach. ;-)


I assume your spreaders are raked like mine -- what are your thoughts about the sail flattening against them and the shrouds?
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Old 07-28-2010
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Originally Posted by smackdaddy View Post
Better yet, set up a Global Regatta course for your area (unless there already is one). Racing on our short course in Lake Travis has really helped me learn quite a bit in a short time.

Global Big Freakin' Regatta. Possible?

Lots of fun. But I need to sail faster if I'm going to catch those Chessie dudes.
Hey! Cool!
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  #17  
Old 07-28-2010
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Quote:
Originally Posted by lydanynom View Post
I have leech lines on all my sails, main, jib and genoa, but I have no idea what to do with them. It's the one sail control I have not even touched yet. None of the leeches chatter so I've taken a don't fix what isn't broken approach. ;-)


I assume your spreaders are raked like mine -- what are your thoughts about the sail flattening against them and the shrouds?
My spreaders are only raked an inch or so; since the shroud chainplates nearly align with the center of the mast, there's no point sweeping them much more. Our normal mast prebend is only an inch, ~4" bend with the backstay on hard.

If your main is touching the spreaders on a reach, vang more. Srsly -- we can get the boom out 80 degrees to the centerline without contacting those wee tubular spreaders. DDW is harder. You could add chafe patches if you want; we added rubber booties instead. Besides, we generally sail deep reaches rather than DDW, unless we have the kite up. It's faster.

ETA: We sail a Mk1, so the shrouds & spreaders may differ.
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Last edited by bobmcgov; 07-28-2010 at 05:32 PM.
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  #18  
Old 07-28-2010
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I only have two things to say here-

1. What a GREAT post! I love a good conversation I can learn from, this is a perfect example. Thanks to all.

2. 15-20 hours per week? I'M JEALOUS!!!

Mike
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You should, I agree, present more perpendicular surface area to the wind while sailing downwind. You want to do this by easing out the boom to get the boom perpendicular to wind direction.

However, don't go one step futher and start creating even more surface area by hauling in hard on the outhaul and vang and therefore flattening the sail.

You want to keep the belly in the sail because it can still generate some amount of lift with the curvature. Also, if you imagine that most of the force on the main (sailing downwind) is because the wind hitting the sail has to change directions from perpendicular to the boom to parallel to the sail (energy then transferred by a change in momentum) then you'll get more energy from this with added belly. With an entirely flat sail, the wind would change direction by only 90 degrees. With belly in the sail, the wind would change direction by >90 degrees and therefore would transfer more momentum (it would go from hit the sail squarely to leaving the edges of the sail slightly "backwards").

Just remember ... parachutes sail downwind very effectively ... and they are both perpendicular to the wind with a lot of belly. Also, the same goes for spinnakers.
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  #20  
Old 07-28-2010
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Sailing Up, Across, and Down Wind

I find sailing up wind fun until a point. When the waves are big and the winds strong (30 kts or very gusty), I find it not enjoyable. Strong constant winds with relatively flat seas are ok. But once we starting fighting the helm, with a reduce headsail and a reef in the main, it's time to rethnk the plan. I don't mind tacking as long as it isn't every few minutes.

Beam reaches are fun, again unless the winds are shifty or the waves large. I actually find it sometimes difficult to trim the sails, especially if the boat wallows in the waves or if the wind is not steady.

Downwind, I pretty much dislike most times as my boat is a deep fin keel and has a relatively flat transom, so any waves really push the boat and make her rolley poley all over the place in any type seas. That being said, one of the sweetest things I have done this year was sail wing-n-wing without a pole in about 7 kts of wind. Wind direction was steady (+ 5 deg), which the only way we could have done this. I really hate gybing when the wind pipes up. Too much going on for two people on our boat sometimes.

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