Sail trim in light to moderate air

[Triton106]

Don,

I posted my question on another forum and was redirected to your forum from there. Hope you can help me and others become a better sailor in light to moderate air. Here is my question.

Most people are familiar with the strong wind and wave conditions on San Francisco Bay in the summer months. However, not too many sailors know about the light wind conditions during the winter months. For example, for the last several weeks the wind strength has been in the range of 0-10KT with guts to 15KT. To sail efficiently on the bay with our plastic classics and aging sails requires us to be very skilled at sail trimming which I have not paid much attention to until now. Since many forumites sail on the east coast and maybe southern california I hope to learn from you guys.

I have also been reading sail trimming books and articles such as Annapolis Book of Seamanship and Chapman Piloting but they are not easy to understand and summarize in simple and easy to remember ways. So could someone tell me -

In 0-5 KT wind sailing to windward - how should I sheet the main and jib. Where shold I place the boom and jib car? Where should I place the traveler car? How tightly should I sheet the boom vang, the main downhaul? How do I use telltails?

In 5-10 KT wind sailing to windward - same questions.

In 10-15 KT wind sailing to windward - same questions.

Thanks very much in advance for your time and insights.

Triton106
Alameda, California

 

[Stu Jackson]

Light air - flat mainsail

Medium air - fuller mainsail

Heavy air - flat mainsail

I do what you describe all year round, too.

Move your jib fairlead car to have the jib luff telltales flow smoothly.

Pretty simple.

You should buy Don's book and chart. Answers your questions, good for the economy, too.

 

[Don Guillette]

triton106: Stu's given you most of the settings. Space here really doesn't permit a complete outline. I could write a book and chart answering your questions --- which is what I did!! My SAIL TRIM CHART will provide you with the settings for all the sail trim controls on your main and jib for all points of sail and wind conditions right down to where to place your crew.

The problem with most books on sail trim including Dennis Conner book Sail Like A Champion (which is my bible) is that the info's all over the place. For example the traveler might be on pages 25, 82, 135, 281 and 30, The same goes for all the sail trim controls for the main and jib. I found that very confusing. My book THE SAIL TRIM USERS GUIDE has everything you need to know about the traveler in one section and the same with all the other controls for the main and jib. Even the telltails have their own 6 page section.

 

[dkdoyle]

Ok I don't get the flat mainsail in light air. I am certainly not arguing it. I just have not heard that in anything else I have read.

 

[Terry411]

The flat main in light air is because at low air speed the the air cant stay attached to a full shape.

 

[Don Guillette]

dkdoyle: Terry441 has provided the answer. Look at all the new stuff you can learn on the sail trim forum!!

Next time you're sailing in very light to light conditions, check out the boats around you, and maybe your boat also. You'll see them inducing a large amount of draft depth in their mainsail and jib in the mistaken notion that they're going to capture what little air there is. Notice where their boats are going ---- nowhere. You, on the other hand, if you flatten your sails as much as you can will start to move forward. You won't break the land/sea speed record but you'll move.

 

[Stu Jackson]

Ok I don't get the flat mainsail in light air. I am certainly not arguing it. I just have not heard that in anything else I have read.

Try it, and see what happens. The light air here this winter is a perfect time to do so.

I often go out "The Back Door" from the Alameda Estuary, under the Park Street Bridge and the three others, to the south bay. To do so, one needs a high tide, thus the south bay is ebbing to the north.

The light current is enough to keep the boat moving north as I circumnavigate Alameda (island) and with a flat mainsail and a well trimmed jib (our 110 is our largest, and use it for a winter sail; the 85 blade is our summer jib) can get a few knots simply from the boat moving with the current gaainst little to no wind.

It's a fun trip and I do it often.

 

[Joe]

I agree that big is not better in very light air. I have hoisted a tall staysail to very good result in light air under 3kts. The sail has a wire luff, 3 oz. cloth, and fairly flat shape. It's primary use is to augment the racing spinnaker. Back in the day, they were commonly used on masthead rigs to help reaching and running sails. They were tacked to the windward toe rail or foredeck and sheeted through a snatch block on the boom. Since it required extra, experienced crew to operate one, I have rarely deployed it in this way.

As an upwind, light air sail, however, it's been a revelation. I let the luff sag off a bit, without letting it become too full. I have attached a few addktional tell tails to the leech to help me monitor the air flow. I sheet it normally through the genoa track.....the angle being around 10-12 percent, because the short foot puts the lead at the widest point on the boat. The result is a fairly open slot that allows just a small amount of re direction, but not too much to stall the main.

Wire luff, lighter cloth, flatter shape........... that's the difference between this sail and a big ass genoa... and it works pretty well.

 

[dkdoyle]

K guys I will give it shot. We have lots of light air days in fla. the next time I have a 5 to 10 knot breeze I'll try it and let you know. We went out in a 31 Irwin today and were moving along at 6+. Practicing for the Gasparilla regatta. Now I just need the pirate outfit.

 

[Don Guillette]

dkdoyle: 5 to 10 knots of wind is not very light to light winds - at least not in my neck of the woods.

 

[RichH]

Triton 106 - hopefully this will give a better explanation (and wind-up with Stu's recommendations):

The true answer is gained by the use a tell-tales and how they 'behave' and by watching the speedo for its 'maximum speed' ... the goal is get 'all' the tell tales flying straight back AND the speedo so show its maximum possible reading.

The amplitude and period of the oncoming waves is also important .... waves require more 'draft' (more power from the sails); 'flat water' requires less draft and results in the faster sailing, etc.

How much draft? ... what Stu stated as an 'initial setting' .. and then you make minor adjustment in sail 'shape' and 'trim' .... with the ultimate goal - to get the tell tales flying correctly AND to see and get to the maximum possible speed reading on the speedo (or maximum VMG on a so equipped GPS).
The tell tales will show you precisely which way to make the shaping and trimming adjustments - just watch the tell tales and speedo ...... simple !!!!!!

 

[Steve Connell]

After tell-tails there is "VSpar."

 

[Triton106]

Thanks Don and everyone! All great stuff... a lot to learn here.

Of course as soon as I brought up this subject and looked forward to put some of your recommendations to practice last weekend we were greeted with 20 knots wind with guts in mid 20's in the Oakland estruary! So, instead of practicing light wind techniques my crew and I were busy practicing reefing and depowering with traveler and main sheet control. The estruary never felt so narrow. It seemed that we tacked about every 15 seconds. Luckly on the way back it was a nice broad reach run all the way. Which brought up another question, is the jib telltale suppose to stream back during a beam to broach reach? Because no matter what I tried they refuse to stream back and just flopped around to my utter dismay.

 

[Don Guillette]

Triton106: It's easy to make the telltales stream when closehauled or on a close reach. It gets more difficult when you're on a beam reach and almost impossible from a broad reach to a run because instead of the wind coming across the sail from front to back, the wind is is pushing the sails like a kite. You're sailing downhill. Do a google search of a diagram of "points of sail" and you'll see what I'm talking about. If the telltales on a broad reach to a run are going to go anywhere they'll stream downwind or forward. When sailing downwind I use the masthead fly instead of the telltales. I personally don't even look at the telltales on that point of sail. In fact, since I never look at them I don't know where they stream.

That's a very simplistic explanation. I'm just a "hillbilly sail trimmer". In other words, I don't know why a lot of things happen. I just know how to make whatever situation I'm in work for me and trim accordingly. I can't provide the explanations that RichH, Joe from San Diego, Stu J or Alan and a few others give - those guys are more scientific than I am and they know scientifically WHY things work. Hopefully, they'll chime in here and provide a better explanation.

Here's an interesting point that you'll see when you google "points of sail". Assume the wind doesn't change direction, which doesn't happen, but assume it remains constant. Notice the position of the sails relative to the wind don't change -- the boats position to the wind changes. It's as if the boat has a dowel coming up through the keel and the boat is pivoting on its axis.

Tune in for a better explantion from the scientific guys!!

 

[Clark]

You might be able to get your tells to stream some on a beam reach but even that might require a more outboard sheeted jib. Deeper than that you can pretty much forget about the tells; you're operating in an almost 100% drag (no lift) conditions.

 

[mulldog47]

Have you tried moving your main traveler to windward when sailing upwind in light air?