Twist
- Thread starter Don Guillette
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Rule of thumb
Assuming you are sailing close hauled, when the wind is up you want the traveler (relatively)lower and the sail sheeted in tighter. When the wind is light, traveler is higher and sheet is eased. It is easy to remember if you just think of what it takes to keep the boom close to the center line of the boat - high traveler means longer distance from the car to the boom; low traveler means tighten the sheet. And say, Rick, do you guys ever get any snow in Calgary?
Assuming you are sailing close hauled, when the wind is up you want the traveler (relatively)lower and the sail sheeted in tighter. When the wind is light, traveler is higher and sheet is eased. It is easy to remember if you just think of what it takes to keep the boom close to the center line of the boat - high traveler means longer distance from the car to the boom; low traveler means tighten the sheet. And say, Rick, do you guys ever get any snow in Calgary?
Bob - the S-word
I guess I've moaned too much about the weather here? Bob asks if it ever snows! (Not sure why...) First, on topic: Sail Trim - I've modified my outhaul and boom vang, fixed the jib luff and jib halyard tension, put a better fairlead/cam cleat on the furling line, and added "George's" preventers. I've replaced all my telltails and put some in the middle of the mainsail. I'm getting a whisker pole to try. Lots of sail trim control changes and I can't wait to try them out! Snow: Sure, we get snow off and on all winter (Oct-May), but we're in a pocket in the lee of the Rocky Mountains and get Chinook winds that are very warm and dry and melt all the snow. So, it doesn't accumulate so much in the Calgary area. It can go from -30F to +40F in a couple of hours. A couple of days later it will be 0F again. We've had a snowfall in every calendar month of the year, but it really is a fluke to get snow in July/August. June snow is a surprise but September isn't. Good weather often extends into October. My lake is full of trees and debris from the flooding so I _still_ haven't been able to launch my boat for the season. My sailing season is mid-June to mid_October, with the first and last two weeks often colder than you'd want. We start as early as we can and don't mind the cold sailing in June because we've waited all winter. Same thing in October: we're desparate because the season is about to end for another eight months. On the plus side, sunrise is at 5am and sunset is at 10pm, so we do get long sailing days. Don't ask how much daylight we get in winter... ...RickM...
I guess I've moaned too much about the weather here? Bob asks if it ever snows! (Not sure why...) First, on topic: Sail Trim - I've modified my outhaul and boom vang, fixed the jib luff and jib halyard tension, put a better fairlead/cam cleat on the furling line, and added "George's" preventers. I've replaced all my telltails and put some in the middle of the mainsail. I'm getting a whisker pole to try. Lots of sail trim control changes and I can't wait to try them out! Snow: Sure, we get snow off and on all winter (Oct-May), but we're in a pocket in the lee of the Rocky Mountains and get Chinook winds that are very warm and dry and melt all the snow. So, it doesn't accumulate so much in the Calgary area. It can go from -30F to +40F in a couple of hours. A couple of days later it will be 0F again. We've had a snowfall in every calendar month of the year, but it really is a fluke to get snow in July/August. June snow is a surprise but September isn't. Good weather often extends into October. My lake is full of trees and debris from the flooding so I _still_ haven't been able to launch my boat for the season. My sailing season is mid-June to mid_October, with the first and last two weeks often colder than you'd want. We start as early as we can and don't mind the cold sailing in June because we've waited all winter. Same thing in October: we're desparate because the season is about to end for another eight months. On the plus side, sunrise is at 5am and sunset is at 10pm, so we do get long sailing days. Don't ask how much daylight we get in winter... ...RickM...
Just kidding...
about the snow. When I passed through Calgary in August of '72 on a bike trip, I was real impressed by a guy who said you could ride snowmobiles in virtually any direction all day long in the winter. When I asked him what he did when he got to a fence, he laughed and told me they were all buried under the snow. That's a little more than we usually get around here. I hope you get some great sailing days to practice those trimming skills.
about the snow. When I passed through Calgary in August of '72 on a bike trip, I was real impressed by a guy who said you could ride snowmobiles in virtually any direction all day long in the winter. When I asked him what he did when he got to a fence, he laughed and told me they were all buried under the snow. That's a little more than we usually get around here. I hope you get some great sailing days to practice those trimming skills.
all day long in the winter
The guy said: "you could ride snowmobiles in virtually any direction all day long in the winter". Well, yeah, I had a snowmobile like that once too. ;-) You'd have to drive 3 hours (in any direction) from Calgary to find that much snow. On a New Year's Eve in the mid-70's we got a huge dump of snow. So much snow that several animals just up and walked out of the zoo because it was higher then the cage fences. That was pretty cool. ...RickM...
The guy said: "you could ride snowmobiles in virtually any direction all day long in the winter". Well, yeah, I had a snowmobile like that once too. ;-) You'd have to drive 3 hours (in any direction) from Calgary to find that much snow. On a New Year's Eve in the mid-70's we got a huge dump of snow. So much snow that several animals just up and walked out of the zoo because it was higher then the cage fences. That was pretty cool. ...RickM...
What about inducing twist?
A Boom Kicker or a rigid vang can be set up to lift the boom say about ten degrees off vertical with the main sail attached and no boom vang or mainsheet applied. Is this a wise decision? Or should the Boom Kicker and or rigid vang be set up to have the boom level without any boom vang of mainsheet tension. I have a Catalina 22 and I have set up my Boom Kicker to lift the boom (with the main bent on) about 10 degrees off vertical. This allows me to loosen the boom vang and mainsheet to spill wind from the main and therefore keep it flying longer before needing to reef. At this time, I feel the effect is beneficial, but I still have some doubts.
A Boom Kicker or a rigid vang can be set up to lift the boom say about ten degrees off vertical with the main sail attached and no boom vang or mainsheet applied. Is this a wise decision? Or should the Boom Kicker and or rigid vang be set up to have the boom level without any boom vang of mainsheet tension. I have a Catalina 22 and I have set up my Boom Kicker to lift the boom (with the main bent on) about 10 degrees off vertical. This allows me to loosen the boom vang and mainsheet to spill wind from the main and therefore keep it flying longer before needing to reef. At this time, I feel the effect is beneficial, but I still have some doubts.
What about inducing twist?
Bayard: When a rigid vang is installed the boom, with no weight on it, should be at about 10 degrees above horizontal. So when you raise the main that is your initial setting and you go from there. As you crank down on the vang you reduce twist. There are some expensive hydraulic system that can be mounted level and then pumped up to 10 degrees or more above horizontal. Both vangs accomplish the same thing. I prefer the rigid vang over the soft vang. There are 2 mainsail controls for twist and they are the boom vang and mainsheet and you are using both of them so your right on the mark.
Bayard: When a rigid vang is installed the boom, with no weight on it, should be at about 10 degrees above horizontal. So when you raise the main that is your initial setting and you go from there. As you crank down on the vang you reduce twist. There are some expensive hydraulic system that can be mounted level and then pumped up to 10 degrees or more above horizontal. Both vangs accomplish the same thing. I prefer the rigid vang over the soft vang. There are 2 mainsail controls for twist and they are the boom vang and mainsheet and you are using both of them so your right on the mark.
A twist question revisted
Don - I was playing with twist a bit and want to re-ask a point that has been discussed somewhat already. First, let me say that when I change trim controls I can see the effect on the telltails, but often I can't reliably measure any speed change because the winds literally change every few seconds. However, more than once I had the bottom mainsail telltails streaming but the top one was wrapped around the lee side. I assumed at this point that inducing twist should _increase_ power and speed? I eased the boom vang to induce some twist and sure enough the top telltail started streaming too, but then the boat slowed down. I was on a close reach at the time. Is this just my variable wind making the test impossible to measure? I think this is the same case where Scott was wondering if one should then raise the traveller a bit to get the power back. Otherwise I have to ask, why do I care to make the top telltail stream if it's going to slow me down? Note that I'm not talking about dumping wind to depower the main -- I'm trying to maximize power and speed in this case. ...RickM...
Don - I was playing with twist a bit and want to re-ask a point that has been discussed somewhat already. First, let me say that when I change trim controls I can see the effect on the telltails, but often I can't reliably measure any speed change because the winds literally change every few seconds. However, more than once I had the bottom mainsail telltails streaming but the top one was wrapped around the lee side. I assumed at this point that inducing twist should _increase_ power and speed? I eased the boom vang to induce some twist and sure enough the top telltail started streaming too, but then the boat slowed down. I was on a close reach at the time. Is this just my variable wind making the test impossible to measure? I think this is the same case where Scott was wondering if one should then raise the traveller a bit to get the power back. Otherwise I have to ask, why do I care to make the top telltail stream if it's going to slow me down? Note that I'm not talking about dumping wind to depower the main -- I'm trying to maximize power and speed in this case. ...RickM...
Twist is dumping
As far as I know, the wind doesn't change direction 20' up so if the wind is moving the same direction at 20' off the water as it is 50' off the water, then anytime you induce twist, you are spill air somewhere in the main and that is why you slowed down. Correct me if I'm wrong fellas.
As far as I know, the wind doesn't change direction 20' up so if the wind is moving the same direction at 20' off the water as it is 50' off the water, then anytime you induce twist, you are spill air somewhere in the main and that is why you slowed down. Correct me if I'm wrong fellas.
Twist is dumping
Franklin: I presume the wind normally comes from the same direction at all mast heights, but the true wind speed will often be greater as you go up the sail. As I understand it, the boat sails on apparent wind. Therefore shouldn't the apparent wind be able to come from a different angle as you go up, owing to the greater component of true wind speed at the higher sail portion in question?
Franklin: I presume the wind normally comes from the same direction at all mast heights, but the true wind speed will often be greater as you go up the sail. As I understand it, the boat sails on apparent wind. Therefore shouldn't the apparent wind be able to come from a different angle as you go up, owing to the greater component of true wind speed at the higher sail portion in question?
Yes to wjssr
I think it is well known and accepted that the true wind velocity is greater at the top of the mast. I've seen claims ranging from 40% to double compared to deck (or boom?) level. As "wjssr" points out, add this to the boat's "wind" from forward movement and the apparent wind direction changes as you go up (comes from further aft as you go up). I drew some vector diagrams recently that showed the difference can be from 5 degrees close-hauled to 15 degrees on a beam reach for some simple cases. This is why the top telltail curls around to the leeward side of the mainsail without twist. Induce some twist and then all the telltails stream just like Don teaches. However, when I try to test this my boat slows down instead speeding up. I would think that I would at least see the heel increase since the top of the main has better airflow and more lift. Hopefully the speed would increase as well. My squirrelly winds make it hard to detect the differences. Maybe it's the wind, or maybe I induced too much twist during my tests. I'm asking what I should be able to expect in practice and keep trying until I can see it on the water. ...RickM...
I think it is well known and accepted that the true wind velocity is greater at the top of the mast. I've seen claims ranging from 40% to double compared to deck (or boom?) level. As "wjssr" points out, add this to the boat's "wind" from forward movement and the apparent wind direction changes as you go up (comes from further aft as you go up). I drew some vector diagrams recently that showed the difference can be from 5 degrees close-hauled to 15 degrees on a beam reach for some simple cases. This is why the top telltail curls around to the leeward side of the mainsail without twist. Induce some twist and then all the telltails stream just like Don teaches. However, when I try to test this my boat slows down instead speeding up. I would think that I would at least see the heel increase since the top of the main has better airflow and more lift. Hopefully the speed would increase as well. My squirrelly winds make it hard to detect the differences. Maybe it's the wind, or maybe I induced too much twist during my tests. I'm asking what I should be able to expect in practice and keep trying until I can see it on the water. ...RickM...
Main telltails as twist indicator? - answer to old question
On 06/15, I asked this question: "I was wondering if the top mainsail telltail will sometimes curl to windward and sometimes to leeward, indicating you need less or more twist respectively". I tried this last week and found that as others stated, the top telltail curls to leeward when you need more twist. However, I couldn't get it to curl to windward. Before that happens, the sail itself starts to luff. Seems obvious now! ...RickM...
On 06/15, I asked this question: "I was wondering if the top mainsail telltail will sometimes curl to windward and sometimes to leeward, indicating you need less or more twist respectively". I tried this last week and found that as others stated, the top telltail curls to leeward when you need more twist. However, I couldn't get it to curl to windward. Before that happens, the sail itself starts to luff. Seems obvious now! ...RickM...
Rick: Jib telltales react to attached flow. To visualize what is happening to your jib and mainsail you should picture them in a wind tunnel with smoke blowing over the sail. The problem with the mainsail leech telltale is that they are indicating "exhaust flow". The wind has already left the sail. You will never see this on a mainsail but a mate would probably be better off with a set of doubles (just like on the jib)on the top about 3" back from the leech. The proceedure as to how to set twist (along with a bunch of other things) is contained in my Sail Trim Chart but for those who don't have the chart, here's how you set the proper twist in the main: 1) Sail Closehauled. 2) Position traveler so boom is near center. 3) Trim mainsheet until top batten is parallel to the boom. The top batten can point slightly to weather and the top telltale should be streaming - if it curls, ease the mainsheet. 4)Ease the traveler down and OBSERVE THE LEECH FROM TOP TO BOTTOM. If the TOP breaks first - trim the sheet as you have too much twist. If the bottom breaks first - ease the sheet as you do not have enough twist. 5) Twist should now be set. To check it start with step 2 again. This time the sail should break evenly from top to bottom. If not then re adjust. 6) Once you get it set, bring the traveler up until you get to about 3 to 5 degrees of weather helm.
yes to wjssr
Rick: Here's the bottom line. With all things being equal - in other words, assume you have your main and jib perfectly set for the wind conditions and closehauled point of sail. If you open up or twist off the top of the main or jib, the boat will slow down as you are spilling air thus reducing the power of the sail. If you go back the other way and close off the top of the sail the boat will pick up speed because you are using all the power from the top to the bottom that both sails can give you. It is not possable for the opposite effect to happen (boat slows down as you close off the top or eleminate twist - unless you did something to effect the situation.
Rick: Here's the bottom line. With all things being equal - in other words, assume you have your main and jib perfectly set for the wind conditions and closehauled point of sail. If you open up or twist off the top of the main or jib, the boat will slow down as you are spilling air thus reducing the power of the sail. If you go back the other way and close off the top of the sail the boat will pick up speed because you are using all the power from the top to the bottom that both sails can give you. It is not possable for the opposite effect to happen (boat slows down as you close off the top or eleminate twist - unless you did something to effect the situation.
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