I have been trying to work with the twist on my boat but it seems to me that my main does not twist off at the top like many pics i have seen and from what I have read here??
Twist ??
- Thread starter Cmp1110
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Try letting out the main sheet then setting the boom position with the traveler. If that does not provide any twist then something (vang?) is holding down the boom. The boom must rise to allow the leach to twist
Cmp1110: OK, but a little more detail is needed. Does your mainsail twist off at all - how much? I know it's hard to give a visual picture using words but do your best. Here's how I describe it. Form your right hand vertically as if you were going to present a salute. Now turn your finger only to the right. That's twist. The top of the sail (your fingers) are open. Turn your fingers only to the left and your closing off the twist. If your mainsail does twist off maybe you're at the max. What mainsail sail trim controls are you using to adjust twist?
While we're at it - how does the twist on your jib look? Do you adjust the twist on our jib?
While we're at it - how does the twist on your jib look? Do you adjust the twist on our jib?
I have a hunter 28.5 with a masthead rig a 110 jib and a partial battened main, soft vang, and traveler,and a cunningham.
I have your chart and book and it has been super helpful especially in light air.
When I sight up the leech of my mainsail it looks to me as if it is not twisting off at all. Our sailing characteristics are favorable boat sails well good speed not overpowered.
The twist in the jib is the same as the main very little if any. I have tried to induce twist by easing the main sheet but it seems that the angle of attack changes but twist does not seem to change
I have your chart and book and it has been super helpful especially in light air.
When I sight up the leech of my mainsail it looks to me as if it is not twisting off at all. Our sailing characteristics are favorable boat sails well good speed not overpowered.
The twist in the jib is the same as the main very little if any. I have tried to induce twist by easing the main sheet but it seems that the angle of attack changes but twist does not seem to change
also my boat has a backstay so it kind of seems to me the head of the main is small to accomadate the backstay if that helps
thank you for any and all help
thank you for any and all help
Cmp1110: Let's get the jib out of the way first. A 110 is a very small sail - it's more like a storm jib so you don't have much to work with.
Included with your SAIL TRIM CHART was a QUICK REFERENCE. Note that the twist controls for the mainsail are primarily the boom vang and secondarily the mainsheet. Also note that the mainsheet not only adjusts twist but it also involved with draft position, and as you've found out -- angle of attack. So, when your messing with the mainsheet you're also dealing with other elements of sail trim that you may not have wanted to adjust - like angle of attack.
What is the adjustment you're using for the boom vang when you're trying to induce twist? Is it cranked down all the way or completely loose? Say you're closehauled and you loosen the boom vang all the way - the top 1/3 of the sail should open up. As you crank down on the boom vang the top 1/3 should close up.
At this point I wouldn't mess with the backstay. Leave that sail trim control until last. Actually, on a masthead rig with a "telephone pole" mast, I wouldn't mess with it at all.
One of the reasons you're making good speed is that there is probably no twist in the top 1/3 of your sail. The entire sail is driving. As you induce twist and open up the top 1/3 you're spilling power and slowing down.
Included with your SAIL TRIM CHART was a QUICK REFERENCE. Note that the twist controls for the mainsail are primarily the boom vang and secondarily the mainsheet. Also note that the mainsheet not only adjusts twist but it also involved with draft position, and as you've found out -- angle of attack. So, when your messing with the mainsheet you're also dealing with other elements of sail trim that you may not have wanted to adjust - like angle of attack.
What is the adjustment you're using for the boom vang when you're trying to induce twist? Is it cranked down all the way or completely loose? Say you're closehauled and you loosen the boom vang all the way - the top 1/3 of the sail should open up. As you crank down on the boom vang the top 1/3 should close up.
At this point I wouldn't mess with the backstay. Leave that sail trim control until last. Actually, on a masthead rig with a "telephone pole" mast, I wouldn't mess with it at all.
One of the reasons you're making good speed is that there is probably no twist in the top 1/3 of your sail. The entire sail is driving. As you induce twist and open up the top 1/3 you're spilling power and slowing down.
Just a thought; Perhaps you are not sailing in wind strong enough to twist the sail. Do you have telltales on the leech of your main? These telltales help me a lot in adjusting twist. If the wind is very light I use the topping lift (with the vang slack) to induce twist and make the top tale fly.
cwkemp: Yes sir, that's the way you do it in very light air. I don't know why that works, even though RichH has explained it to me a million times, but I discovered it many years ago by accident. I raised the mainsail in very light conditions and got distracted before disconnecting the topping lift.The boat seemed to like it so I left it attached.
Before I purchased the Garhauer Rigid vang I used the topping lift but with the vang I installed it so the boom was 10 degrees above horizontal so I'm set up for very light conditions before I even leave the dock.
Before I purchased the Garhauer Rigid vang I used the topping lift but with the vang I installed it so the boom was 10 degrees above horizontal so I'm set up for very light conditions before I even leave the dock.
My best guess re: mainsail twist
Twist is controlled by leech tension (more tension = closed leech = less twist, and vice versa). Mainsail leech tension is caused by a downward pull on the sail from the boom - which pivots both horizontally and vertically at the gooseneck. The boom is pulled down deliberately with the vang, and unintentionally by the mainsheet tension when sailing closehauled. Both controls counteract the tendency of the boom to move outward and rise as the sail fabric goes into tension in response to the airflow over it.
Mainsail twist is increased by easing leech tension, i.e., reducing downward pull on the boom by easing the vang (as some mentioned) or easing the mainsheet and adjusting the traveler to maintain the proper angle of attack (as Bill Roosa pointed out).
There's also a "hidden" downward pull... the weight of the sail, boom, mainsheet tackle, vang tackle and anything else hanging on the boom (dutchman flaking system sail cover? lazy lacks? reefing lines? solar water heater?). Under normal conditions, the tensioned sail fabric is more than able to support the boom and everything on it. However, in light air, the entire sail goes limp - except for the leech, which is forced to go into tension because it is farthest away from the gooseneck. That tension holds the leech of the sail "closed" (even with the vang and mainsheet slack) and you can't induce any twist. Tensioning the topping lift to support the boom takes the tension off the leech, allowing it to "open" and add twist to the sail.
Adjusting a rigid vang to support the weight of the boom does the same thing.
Twist is controlled by leech tension (more tension = closed leech = less twist, and vice versa). Mainsail leech tension is caused by a downward pull on the sail from the boom - which pivots both horizontally and vertically at the gooseneck. The boom is pulled down deliberately with the vang, and unintentionally by the mainsheet tension when sailing closehauled. Both controls counteract the tendency of the boom to move outward and rise as the sail fabric goes into tension in response to the airflow over it.
Mainsail twist is increased by easing leech tension, i.e., reducing downward pull on the boom by easing the vang (as some mentioned) or easing the mainsheet and adjusting the traveler to maintain the proper angle of attack (as Bill Roosa pointed out).
There's also a "hidden" downward pull... the weight of the sail, boom, mainsheet tackle, vang tackle and anything else hanging on the boom (dutchman flaking system sail cover? lazy lacks? reefing lines? solar water heater?). Under normal conditions, the tensioned sail fabric is more than able to support the boom and everything on it. However, in light air, the entire sail goes limp - except for the leech, which is forced to go into tension because it is farthest away from the gooseneck. That tension holds the leech of the sail "closed" (even with the vang and mainsheet slack) and you can't induce any twist. Tensioning the topping lift to support the boom takes the tension off the leech, allowing it to "open" and add twist to the sail.
Adjusting a rigid vang to support the weight of the boom does the same thing.
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