I'm not exactly a novice when it comes to sail trim ... but I haven't been able to figure out exactly what the vang is supposed to do. My boat has a traveller mounted at seat level behind the companionway. I've heard it explained that the vang assists the traveller in establishing the angle of attack. Also, I've read that the vang also influences the sail shape (draft?) for the lower third of the mainsail. But I haven't been able to see that it influences anything. To me, it seems that it merely pulls down on the boom, which is rigidly fixed (elevation-wise) to the mast. The sheet is either tensioned or slack, with no degree of subtle difference. I suppose that to some extent it is working against the mainsheet, which increases twist as it is eased, but so what? So far, I have merely tensioned the vang and left it be while sailing during the day. Occasionally I will pull on the sheet to see if there is anything I can affect but it always just seems to simply pull against a fixed boom. I feel like if I try to REALLY pull on it, I will simply be attempting to bend the boom, and what sense does that make? I often use the outhaul to adjust for wind conditions and I know that the Cunningham acts like a downhaul to flatten the luff. I have a great deal of experience with windsurfing rigs and know how to use downhaul, batten tension, outhaul, harness line adjustments, etc to perfectly balance my rigs for any wind condition. Much of this experience I have been able to translate to my boat ... but the purpose of the vang still eludes me! Am I trying to see too much in its purpose? Does it require a different setting for each point of sail? I know there are some explanations out there to enlighten me!
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Ah! a kindred soul!
If the dang vang isn't enough; you got the Cunninham too! While learning I asked experienced sailors about these controls and got vague or no info. I've been on the same learning curve you are, just bought the sail trim chart and users guide by Don Guillette from sailnet.com and I think next year is going to be more fun. with your experience on boards you may get by with the charts but the book is worth the price for the bit on "twist" Yeah,"twist" what the hell is that!?
If the dang vang isn't enough; you got the Cunninham too! While learning I asked experienced sailors about these controls and got vague or no info. I've been on the same learning curve you are, just bought the sail trim chart and users guide by Don Guillette from sailnet.com and I think next year is going to be more fun. with your experience on boards you may get by with the charts but the book is worth the price for the bit on "twist" Yeah,"twist" what the hell is that!?
Boom Vang
Boom Vang - vangs the boom, of course! Really, as the boom swings out, the main sheet has less pull-straight-down effect on the boom, especially when no traveler is present. Think in terms of pulling close to your body compared to pulling something at arm's length. To counter the boom lifting up, and the obvious effect on the shape of the main, you just snug the vang with the boom centered. As it swings out, the vang tension increases a bit and keeps the boom from lifting up. You will not likely see a traveler and boom vang on the same rig. A traveler keeps the anchor point under the boom, and a boom vang keeps the boom from lifting up as it swings from side to side. One problem, two solutions. My Mirage 5.5 uses the vang method.
Boom Vang - vangs the boom, of course! Really, as the boom swings out, the main sheet has less pull-straight-down effect on the boom, especially when no traveler is present. Think in terms of pulling close to your body compared to pulling something at arm's length. To counter the boom lifting up, and the obvious effect on the shape of the main, you just snug the vang with the boom centered. As it swings out, the vang tension increases a bit and keeps the boom from lifting up. You will not likely see a traveler and boom vang on the same rig. A traveler keeps the anchor point under the boom, and a boom vang keeps the boom from lifting up as it swings from side to side. One problem, two solutions. My Mirage 5.5 uses the vang method.
Good lokinh out
Good to see your wanting to trim the sail a bit more. Unlike windsurfing you are trimming a sail with greater size as well as use. Your main is for power, you need to figure out were your wind is coming from and how it can create power for the main. With a Vang, and traveler track you have the best of both worlds. My cal only has the track, no vang and I wish I had one. The best use for you vang is for very tight up wind beats as well as your wing on wing down wind runs. Up wind you want the power/heading, gett the jib tight and low and create the biggest pocket as low as possible on your main. when heading up you want to fine where you sail is as tight as possible.you can find fine tuning takle with Harken where you can tune the loweer leading edge to the wind. Some times a tight out haul is'nt it. Get the right jib/ main combo, and then crank the back stay and play with the outhaul/ cunningham combos up wind. Sail the boat alone it really helps to find her zone. Good luck
Good to see your wanting to trim the sail a bit more. Unlike windsurfing you are trimming a sail with greater size as well as use. Your main is for power, you need to figure out were your wind is coming from and how it can create power for the main. With a Vang, and traveler track you have the best of both worlds. My cal only has the track, no vang and I wish I had one. The best use for you vang is for very tight up wind beats as well as your wing on wing down wind runs. Up wind you want the power/heading, gett the jib tight and low and create the biggest pocket as low as possible on your main. when heading up you want to fine where you sail is as tight as possible.you can find fine tuning takle with Harken where you can tune the loweer leading edge to the wind. Some times a tight out haul is'nt it. Get the right jib/ main combo, and then crank the back stay and play with the outhaul/ cunningham combos up wind. Sail the boat alone it really helps to find her zone. Good luck
Don't forget the topping lift
So far everyone working on this question seems to own a Starwind 27, which I'm not familiar with and which may explain why Mike thinks it would be uncommon to see boom vangs and travelers together (I promise you this is the only configuration you will see outside of dinghy sailing, and it's rare to see any new cruising boats without both!). But since you've posted the question in "ask all sailors" I'll mention a factor which might or might not apply to the Starwind: you've got to release or at least adjust your topping lift after raising the main, or it will prevent your vang from pulling down the boom enough to tighten your leach (or, another way of saying it, to straighten your roach; the leach is the back edge of the sail and the roach is its shape). John has a good description of what all of that tightening is trying to do for upwind sailing: the vang allows you to achieve that tightening on the back of the sail where the Cunningham is tightening the front (luff) and the outhaul is tightening the bottom (foot). An incidental use of the vang is to add stiffness to the system so that tacks are more controlled and comfortable and jibes a little less terrifying...
So far everyone working on this question seems to own a Starwind 27, which I'm not familiar with and which may explain why Mike thinks it would be uncommon to see boom vangs and travelers together (I promise you this is the only configuration you will see outside of dinghy sailing, and it's rare to see any new cruising boats without both!). But since you've posted the question in "ask all sailors" I'll mention a factor which might or might not apply to the Starwind: you've got to release or at least adjust your topping lift after raising the main, or it will prevent your vang from pulling down the boom enough to tighten your leach (or, another way of saying it, to straighten your roach; the leach is the back edge of the sail and the roach is its shape). John has a good description of what all of that tightening is trying to do for upwind sailing: the vang allows you to achieve that tightening on the back of the sail where the Cunningham is tightening the front (luff) and the outhaul is tightening the bottom (foot). An incidental use of the vang is to add stiffness to the system so that tacks are more controlled and comfortable and jibes a little less terrifying...
It's a Vang Thang
The need for a vang primarily occurs when sailing off the wind or dead down wind. Then the filled main wants to lift the boom up and because the mainsheet is eased out farther than on any other point of sail, it is not very effective at holding the boom down. The vang, however, doesn't really care how far out the boom has swung, because it is still the hypotenuse of the same right triangle and thus holds the boom in the same location, vertical-wise. Additionally, a rigid vang can take the boom's weight off the sail to let it shape out better in very light air when running or reaching. It is also good for supporting the boom when the main has been dropped.
The need for a vang primarily occurs when sailing off the wind or dead down wind. Then the filled main wants to lift the boom up and because the mainsheet is eased out farther than on any other point of sail, it is not very effective at holding the boom down. The vang, however, doesn't really care how far out the boom has swung, because it is still the hypotenuse of the same right triangle and thus holds the boom in the same location, vertical-wise. Additionally, a rigid vang can take the boom's weight off the sail to let it shape out better in very light air when running or reaching. It is also good for supporting the boom when the main has been dropped.
Scott: I'm not sure where to start so I'll try the beginning. The boom vang and the mainsheet are the main controls to adjust TWIST in the mainsail. Increasing tension on both REDUCES twist and easing tension INCREASES twist. The boom vang is also used to adjust draft position along with the cunningham (or halyard), mainsheet, mast bend and outhaul. Increasing tension on those controls moves the DP forward and decreasing tension moves it aft. All of the controls for the mainsail must be used together or they end up working against each other. In other words, just cranking on the cunningham (or halyard will not change the draft position vewry much - you need to use all of them to get 100% efficiency. The boom vang has nothing to do with the angle of attack. The boom vang applies an up and down control and angle of attack is horizontal. Additionally, the amount of tension applied depends on the point of sail and the wind condition. You asked if you were trying to see too much in its purpose. Yup, but that is common because some of these controls are confusing but simple to understand when explained in a logical and plain English manner.
Good explanations!
Thanks, I get a better picture with this thang now. I have to admit, most the time we get underway, I realize that I forgot the topping lift! Why is it that after 4 or 5 times telling my 13-year old crewmate to give me some slack on the topping lift, I still get a blank look? Also, I've been criticized for being too mean when I use my authoritative captain's voice!
Thanks, I get a better picture with this thang now. I have to admit, most the time we get underway, I realize that I forgot the topping lift! Why is it that after 4 or 5 times telling my 13-year old crewmate to give me some slack on the topping lift, I still get a blank look? Also, I've been criticized for being too mean when I use my authoritative captain's voice!
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