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Discussion Starter #1
Hello,

I am racing my boat in a double handed series. This is simple, casual, non-spinnaker racing (for me). I am sailing with my daughter and we're having lots of fun.

Last night we sailed in just about perfect conditions: Wind 7-10 true, flat seas. On the upwind leg I had the sails trimmed in hard. Halyard and outhaul set properly (IMHO). I had the upwind mark programmed into my plotter (B&G Vulcan), I was displaying SOG and VMG to the mark.

I noticed that VMG was highest when it felt like I was pinching. SOG would decrease but VMG would increase. The inner tell tails on the headsail were fluttering. The heasail was in all the way, the cars were set right too (even break of the tell tails from top to bottom.

I definitely felt like I was pinching and if I headed down a little the SOG would increase and the telltails looked better but the VMG decreased.

So, am I best off trying to maximize VMG or steering to the tell tails?

Thanks,
Barry
 

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Hello,

I am racing my boat in a double handed series. This is simple, casual, non-spinnaker racing (for me). I am sailing with my daughter and we're having lots of fun.

Last night we sailed in just about perfect conditions: Wind 7-10 true, flat seas. On the upwind leg I had the sails trimmed in hard. Halyard and outhaul set properly (IMHO). I had the upwind mark programmed into my plotter (B&G Vulcan), I was displaying SOG and VMG to the mark.

I noticed that VMG was highest when it felt like I was pinching. SOG would decrease but VMG would increase. The inner tell tails on the headsail were fluttering. The heasail was in all the way, the cars were set right too (even break of the tell tails from top to bottom.

I definitely felt like I was pinching and if I headed down a little the SOG would increase and the telltails looked better but the VMG decreased.

So, am I best off trying to maximize VMG or steering to the tell tails?

Thanks,
Barry
If the VMG number is better, then that is what you should do, barring any other factors. You were probably able to get away with pinching because of the flat water. Had there been bigger seas you likely would have been forced to foot off a bit for power through the waves.

When you say you were "pinching" how close to the wind were you sailing?

Sent from my SM-G960W using Tapatalk
 

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You’re racing. The fastest time around the course wins. If your electronic way points give you the fastest way around the course then vmg is the only thing that counts. Of course this assumes your electronics account for current, set and there are no wind shifts.
A possible explanation lies in your sails. You’re right they should be the perfect foils to give the best vmg. In which case it’s possible if their are places where there aren’t telltales that are producing most of your drive. This could be from trim or the shape of the sails themself (stretch, creep (if laminated) or other issues.
 

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You didn't say much about how your mainsail was trimmed, except that generally your sails were "trimmed in hard." That suggests that your mainsail was trimmed in to the boat's centerline.

What's the first thing sail instructors teach about trimming the mainsail? Trim it in close and then ease it out until it just begins to lift at the luff. But most racers trim it in to the centerline, so that the sail lays down smoothly from luff to leech.

Maximum speed and efficiency are achieved when the jib and mainsail are in balance. If the mainsail is over-trimmed, the mainsail drives the transom to leeward, and the helmsman must use rudder to counteract that tendency and keep the boat on it's heading. Using the rudder creates drag and slows the boat. If the boat has a tiller, you can feel the tiller pressure, and adjust the mainsheet or traveler to eliminate the tiller pressure. If the boat has a wheel, there isn't much "feel" to help you, and you just have to know that it's happening and trim the mainsail accordingly.

Why did you "feel like it was pinching?" Was it because the mainsail was lifting slightly at the luff? If so, then that means you were probably well-trimmed and steering in the groove.

If the jib telltails are streaming correctly and the mainsail telltails are streaming correctly and the mainsail is lifting very slightly at the luff, your sails are well balanced and rudder drag should be minimal.
 

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When used to race, I would take some races just as practice sessions. Using other boats as trial horses, I would tweak and test, focusing on what worked, without fretting about out come. In fact, those races often accidentally went pretty well, because I focused on sailing well instead of stressing over position. With beach cats, it's usually more about speed than tactics anyway.

Sailing alongside other well sailed boats is a great way to tune. The best trim is boat and condition specific. That's the fun!
 

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Sailing to your best VMG angle doesn't mean your sail trim is optimal. It merely means you're at the most favorable angle, despite the fact that your sail trim might be poor. If you want to maximize speed and pointing, you first have to fine tune your sail trim, and then find the optimum angle for the best VMG.

Optimizing performance to windward is primarily about optimizing sail trim, not about optimizing your VMG angle.
 

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Sailing to your best VMG angle doesn't mean your sail trim is optimal. It merely means you're at the most favorable angle, despite the fact that your sail trim might be poor. If you want to maximize speed and pointing, you first have to fine tune your sail trim, and then find the optimum angle for the best VMG.

Optimizing performance to windward is primarily about optimizing sail trim, not about optimizing your VMG angle.
VMG angle is a bit contradictory, My understanding of VMG is velocity made good toward a fixed point. The actual angle will vary as you approach that point.
 

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Some of this depends upon the program used to calculate vmg but the ideal is to have the best vmg with the sails perfectly trimmed and the tell tales horizontal.
Image you on a reach but need to be on a beat. While on the reach your boat speed is higher than on a beat (true for every sailing polar) and the telltales are perfect. You don’t touch the sheets and go to a beat. Now your boat speed falls but your vmg rises. This is an extreme example as in this scenario your sails will luff to to the point where drive will be lost. But there are multiple points before this occurs where your telltales will go squirrelly but vmg improve.
Suggest go on a day sail. Find a situation that reproduces your experience. Put the boat on AP course setting. Then fool with the trim watching vmg. Vmg will improve further when ideally trimmed.
The OP notes light air 7-10kts. Here you have two choices. Go for a very flat sail to prevent back eddies and maintain laminar flow across the sails. Or increase draft and cord to get the most drive from the sails. One will be faster. The sails will look very different although angle of attack is the same.
Examine your sailing polar. In general the point at which boat speed falls as you continue to head up is the point at which you are “pinching”. This is true cruising or racing. It’s built into the basics of your boat. You may not do as well as your polar as your sails age. I pinch to get around a headland or some such situation when cruising but try to avoid pinching while racing. While racing will try to stay right at the edge of pinching which requires a very alert helm. Someone reading the water (if light air) not just the wind indicators. Some one reading the natural oscillations of wind direction in moderate to light air. In heavier air although you need to consider that you also need to consider the seas trying to stall the boat so angle of attack may vary. This requires very alert trimmers keeping up with the changes the helmsman is making as necessary.
 

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Color me stupid but.. if your GPS plotter program is accurately computing VMG as max... it hardly matters how your sails are trimmed.... your are moving a fast as you can toward your destination. It may be counter intuitive... that your sails APPEAR to be less than properly trimmed... but the VMG tells a different story.

The curious thing is WHY are the tell tales telling you a different story than your computer?

Could it be that your keel will is not trimmable provides lift related to current and heel?
 

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Discussion Starter #13
Hi Guys,

Thanks for all of the comments.

On the boat I normally race on I usually trim main. On that boat the owner drives. He's good at it and we are successful. However, he's not a fan of electronics. The trimmers trim and the driver drives. He steers to the tell tails but since no one is looking at VMG I don't know if the VMG would increase if he headed up a little more or down a little. Next time I will use my hand held GPS and try to pay attention to that.

On my boat for upwind work I will set halyard tension, outhaul, headsail cars, backstay, etc for the wind conditions. Then we trim the sails and I steer. On Monday the headsail was in as much as possible. The top third of the leach was against the shrouds so I can't trim in any harder. The mainsheet was on hard and the traveler was used to pull the boom to center line. Normally I would sail to keep the tell tails streaming. Monday was first time I really paid attention to VMG and that's when I noticed VMG increasing when i was 'pinching'. There was minimal weather helm and the boat sails very nicely.

The sails are in good condition. The main is dacon, bought in 2015. The headsail is a 135 laminate, bought in 2016. Bottom is clean, foils clean.

Next time I'm out for a day sail I will do some more testing and tweaking.

Barry
 

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There have many times when I am sailing back to my then mooring out in Shelter Island when the wind was very light and I decided to motor sail because I didn't want to tack. I would roll in the head sail and try to keep the main up without "losing its sailing shape" . I was motor sailing too hard on the wind I got no help from the main and worse it was more drag. I found that the main could add a bit of speed as long as it was drawing. Now way could I sail that close to the wind with two sails or even one.

Don't forget to consider the impact of current on your VMG and CMG.
 

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Do you get the same phenomenon in stronger wind?. How far do you need to let sails out to get them looking good? Do you trim front to back? Is the jib over trimmed closing the slot and making the main luff? Do the shapes of jib and main match?
I like you don’t understand this. Have gone faster with part of the sail out of trim and the rest good at times but not the whole thing.
 

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...The curious thing is WHY are the tell tales telling you a different story than your computer?...
They aren't. Telltales describe the flow around certain parts of the sail. But what is the best flow pattern? That varies with the boat, the condition of the sails, and the boat. Some lifting and some stalling can be correct, depending on the course.

You are seeking best VMG. Telltales are only a part of the picture, like oil pressure or engine rpm to a race car driver. Lap time is what matters. This is why trial horses were so vital before VMG computers (they still are), because not everything is visually obvious.
 

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Barry, I'm a firm believer in steering with a very light touch. A sailboat with a well tuned rig will tell you how to steer it. If you're sailing closehauled and a little puff comes along, and the boat heels a little more, and you have to tug a bit more on the tiller to hold it's heading, that's the boat's way of telling you that it will be happier if you'll let it head up to windward 2-3 degrees. A happy boat sails faster and points higher. If you can let the boat come to windward 2-3 degrees while maintaining the same boat speed, your VMG will improve. If you don't let the boat head up 2-3 degrees in that situation, you'll have to hold it off the wind with the rudder, and that will cause drag and a loss of boat speed. When the puff subsides, you'll have to bear off the wind to keep your speed and VMG optimized.

I think your mainsail is slightly overtrimmed when it's trimmed to the centerline. When you let the boat come up to windward slightly, it takes a little pressure off the mainsail, reducing rudder drag slightly, so your boat pointed 2-3 degrees higher without losing boat speed, and that's why it produced an improved VMG.

My suggestion is, when you're closehauled, ease the mainsail off from the centerline until the luff just begins to lift, and then trim it in just a skosh. Then steer with a very light hand on the helm, and, when the boat tells you it wants to head to windward a bit in a puff, let it. That will maximize your boat speed, pointing and VMG, and reduce drag 100% of the time.
 

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How does your instrument system derive VMG? Is it VMG relative to true wind? Or to a waypoint? How sophisticated is your wind instrument?

IMO, you should be, first, picking your angles based on strategy and lay lines to the mark or destination, and then subsequently maximizing boat speed at that chosen angle.

In other words, “sail to target speeds”.
Figure out how to tell the difference between direction headers and velocity headers. How you drive and trim is different between the two.

Google “velocity header target speed” and “sailboat target speeds”
 

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How does your instrument system derive VMG? Is it VMG relative to true wind? Or to a waypoint? How sophisticated is your wind instrument?

IMO, you should be, first, picking your angles based on strategy and lay lines to the mark or destination, and then subsequently maximizing boat speed at that chosen angle.

In other words, “sail to target speeds”.
Figure out how to tell the difference between direction headers and velocity headers. How you drive and trim is different between the two.

Google “velocity header target speed” and “sailboat target speeds”
Great point. My instruments use a waypoint for VMG wind has nothing to do with it. Whatever factor improves the VMG it will show... upwind or downwind or no wind.
 

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Discussion Starter #20
Hi Judy,

Thanks for your note.

My electronics are a B&G Vulcan plotter, Raymarine ST50 wind, speed, depth. They are integrated so the plotter can calculate true wind.

The courses we use are windward leeward. I have the marks programmed into the plotter and the plotter is displaying SOG, VMG, COG, DTW, TTW, BTW, and a bunch of other things. The Vulcan is designed for sailing and will display laylines, polars, etc.

I also have a garmin GPSMAP 78SC. It is not integrated to any instruments but does have waypoints in memory.

The Garmin and Vulcan both display VMG and it was very very close on both.

Since the course is windward leeward for the upwind leg I usually just trim the sails in as far as possible - headsail sheeted in until the leetch hits the shrouds, main in as far as possible, then traveler up to get boom on centerline, and then I steer to the tell tails.

I will do some research on velocity header target speeds.

Barry



How does your instrument system derive VMG? Is it VMG relative to true wind? Or to a waypoint? How sophisticated is your wind instrument?

IMO, you should be, first, picking your angles based on strategy and lay lines to the mark or destination, and then subsequently maximizing boat speed at that chosen angle.

In other words, “sail to target speeds”.
Figure out how to tell the difference between direction headers and velocity headers. How you drive and trim is different between the two.

Google “velocity header target speed” and “sailboat target speeds”
 
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