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Old 16-10-2012, 22:02   #46
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Re: Rounding Up... Other Tactics & Questions

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Originally Posted by bewitched View Post
Well Stu, we all do things differently. I NEVER use a vang upwind. Leech control exclusively on backstay and main sheet.

Vang on powers the main because it closes the leech

Vang off de-powers the main because it opent the top leech and twists off the sail.

But opening and closing the leech when close-hauled can be achieved by using the mainsheet and/or backstay. Much easier surely?
I feel you went to the wrong sailing school. The Vang De-powers the main. Its job isnt to mess with the leach. It Increases prebend and flattens the sail. Whoever told you otherwise is simply wrong!.

The 3 simple basics of flattening a main are as follows.
Vang on
Cunningham on
Out haul on.

Plus Backstay On (for boats that have one)
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Old 16-10-2012, 22:18   #47
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Re: Rounding Up... Other Tactics & Questions

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Originally Posted by Bash View Post
Some of those Garhauer rigid vangs have a 20:1 purchase. That's impressive, and will certainly facilitate hand-over-hand usage for most boats owned by CF members. However, 20:1 is too slow to be useful for vang sheeting. Gotta pull in 10 feet of line to get 6 inches worth of sheeting. Forget about using that to prevent a round-up.

And you're right, a 200 sq ft main is, ahem, smallish. My main runs 500 sq ft, and at that point taking the vang straight to a winch makes a lot of sense.
If I want to prevent a round-up, I just blow the vang sheet completely. All that's necessary to do that is to push the lever fully forward. The line runs to it's stop, and the boat is restored to how Bristol built it. (no vang!)

That's 6" of sheeting at the vang mounting, which equals a couple of feet at the boom end. More than enough to spill off the top of the sail.

I only use this technique when there is someone available to do the vang while I steer (or vice versa). I can always blow the mainsheet too, as that's by the helm.
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Old 16-10-2012, 22:24   #48
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Re: Rounding Up... Other Tactics & Questions

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Originally Posted by ozskipper View Post
I feel you went to the wrong sailing school. The Vang De-powers the main. Its job isnt to mess with the leach. It Increases prebend and flattens the sail. Whoever told you otherwise is simply wrong!.

The 3 simple basics of flattening a main are as follows.
Vang on
Cunningham on
Out haul on.

Plus Backstay On (for boats that have one)
I'm not going off what anyone told me, I'm going off personal experience, which closely agrees with what Bewitched observed. Vang off on a beam reach depowers the top of the sail by loosening the leach and letting the air spill. I can watch it happen, and the boat go from 30 degrees heel with vang on to 15 degrees with vang off. It's like you took your foot off the gas.

I know you could also ease the main sheet. But the vang off approach seems to reduce power without the noisy and destructive flapping of the leach that depowering with the main sheet causes.
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Old 16-10-2012, 22:28   #49
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Re: Rounding Up... Other Tactics & Questions

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Originally Posted by ozskipper View Post
I feel you went to the wrong sailing school. The Vang De-powers the main. Its job isnt to mess with the leach. It Increases prebend and flattens the sail. Whoever told you otherwise is simply wrong!.

The 3 simple basics of flattening a main are as follows.
Vang on
Cunningham on
Out haul on.

Plus Backstay On (for boats that have one)
You don't have to agree with me....

but you might want to have a look at what North Sails (the world leader in racing sails) have to say on the subject of mainsail trim

Not a mention of the vang

North Sails: Mainsail Trim - Introduction
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Old 16-10-2012, 23:23   #50
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Re: Rounding Up... Other Tactics & Questions

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Originally Posted by bewitched View Post

Second Pic (black sail): Reaching (it says A3 on the sail, but it doubles as our Code 0). Note that the boom is still pretty high on the boat and the top leach is primarily controlled by the main sheet and masses of twist off to keep the slot. Dropping the boom here just closes the slot. At this point of sail in any breeze it would be almost physically impossible to control the top leech with the vang. This boom angle will be achievable for most boats with a traveller.

Everything here is perfectly agreeable with me - I would note in Pic 2 that the boat is well powered. Twisting off for a "permanent" power reduction makes sense in this photo if not a headsail change.

North doesn't advise twisting off per se - they would probably advise a headsail change first.

If "gusted" in this condition I doubt you would dump more vang - I presume the main trimmer is trimming the traveler.

If the Traveler is dropping to the end of its stop frequently, and the main getting backwinded a lot, twisting off is a good idea - It's about using as much power as the boat needs to go full speed all the time. If the wind is too powerful you need to spill it with the lowest drag possible and a balanced helm.

Great photos BTW.


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Originally Posted by Stu Jackson View Post
How? A deeper mainsail is more powerful. How you do dat?
We need to make sure that we understand flat and rather than type it again...

Quote:
Originally Posted by bewitched View Post
The vang doesn't control the depth of the sail. Outhaul sets the depth of the draft. Cunningham/halyard sets the position of the draft.

As the wind picks up and you heel too much, first reduce the draft by flattening sail with outhaul. As the wind continues to build, move the draft forward with cunningham. As the wind builds further, twist off the top leech with mainsheet. More wind building and its a reef.

The vang has nothing to contribute to this process - all the vang can do is pull down the boom and close the top leech....and upwind you are using the main sheet to achieve this goal.
Yup - Vang don't do "flat" - In fact I have seen guys who "read the book" have the traveler up, the vang cranked and the leech like 30 degrees closed.

Maybe a descriptive analogy of this is a blazing fire in the fireplace with the flue closed.

Quote:
Originally Posted by MarkSF View Post
I'm not going off what anyone told me, I'm going off personal experience, which closely agrees with what Bewitched observed. Vang off on a beam reach depowers the top of the sail by loosening the leach and letting the air spill. I can watch it happen, and the boat go from 30 degrees heel with vang on to 15 degrees with vang off. It's like you took your foot off the gas.

I know you could also ease the main sheet. But the vang off approach seems to reduce power without the noisy and destructive flapping of the leach that depowering with the main sheet causes.
Be careful - If the boom is over the traveler (BW's photo 2) the main and the vang do the same thing - close the leech.

If the boom is over the traveler and you want a permanent power reduction twisting off is valid - the trade off as BW eluded to is the boom will drop to leward as well - That's why he said most boats will have enough traveler... to pull the boom back up to centerline.

I suspect OPs 22 and for sure my 26 have very short travelers so the options are not as high but race boat travelers often almost span the whole beam of the boat for this purpose.


Quote:
Originally Posted by bewitched View Post
You don't have to agree with me....

but you might want to have a look at what North Sails (the world leader in racing sails) have to say on the subject of mainsail trim

Not a mention of the vang

North Sails: Mainsail Trim - Introduction
Yup - The North Sails weekend course also comes with a CD that is a control emulator. I don't know if it is online at their site - You can manipulate the controls and watch the sail shape change.
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Old 16-10-2012, 23:42   #51
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Re: Rounding Up... Other Tactics & Questions

What is this "traveller" you speak of?
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Old 17-10-2012, 00:11   #52
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Re: Rounding Up... Other Tactics & Questions

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I would note in Pic 2 that the boat is well powered. Twisting off for a "permanent" power reduction makes sense in this photo if not a headsail change.

North doesn't advise twisting off per se - they would probably advise a headsail change first.

If "gusted" in this condition I doubt you would dump more vang - I presume the main trimmer is trimming the traveler.
Trimming the traveller initially to position the boom, but for the puffs, its the mainsheet mostly. This must work in sync with spinnaker ease. Spinnaker ease opens the top, main sheet ease opens the top. This is critical to maintaining the slot. I like your analogy about having the fire raging and blocking the flue - never heard it before, but describes it perfectly. If you down traveller with no spinnaker ease, the flue is closed.

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Great photos BTW.
Thanks, but all credit must go to the sail-maker who comes racing with us, he takes loads of photos each time we are out to keep us honest
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Old 17-10-2012, 00:31   #53
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Re: Rounding Up... Other Tactics & Questions

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Originally Posted by bewitched View Post
I like your analogy about having the fire raging and blocking the flue - never heard it before, but describes it perfectly. If you down traveller with no spinnaker ease, the flue is closed.
Well I was also thinking of the closed leech when close hauled - A great big powerful set up and the trailing edge of the sail pointing the wrong way.

During the North seminar I attended the instructor talked about two ways to think about the slot these days...

One is the slot is a venturi and the air accelerates through it providing thrust.

The other theory is that the genny and main acting in concert form "one airfoil" shape (imagine it viewed from the top) and all the theory about accelerating the air "through" the slot via venturi effects is being challenged.

In the airplane analogy this is like leading edge slats. The slot is there to keep the flow laminar on the wing and when the slat is extended you are increasing the chord of the wing.

Your jib and main "acting in concert" is in no way inconsistent with this and I don't know what you believe.

This theory says the slot is more important for maintaining laminar flow across the main.

The single airfoil theory says the slot shape is not as critical as all get out. I am not smart enough to argue one way or another but it is compelling.
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Old 17-10-2012, 02:06   #54
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Re: Rounding Up... Other Tactics & Questions

aaaaghh!!....not the slot discussion!!!! Give me an anchor thread any day
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Old 17-10-2012, 06:15   #55
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Re: Rounding Up... Other Tactics & Questions

Yah... In hindsight I wish I hadn't posted that...

With the technology today and the wind tunnels available forum discussions on aerodynamics are somewhat futile...
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Old 17-10-2012, 07:25   #56
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Re: Rounding Up... Other Tactics & Questions

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Fantastic stuff

A vivid lesson of what racing does for your sailing skills. Very few pure cruisers have this level of understanding of how the sails work. Certainly not me.

The only thing I would add is something so obvious to a racer that Dan would probably not consider it worth mentioning, but something which took me a long time to figure out - of crucial importance in handling gusting conditions is having the main in the right shape to start with. If you're near the edge of the wind speed envelope for the amount of sail you have up, it becomes crucial to have the main in its least full shape, so you want full halyard tension to move the draft forward, and you want plenty of vang and outhaul tension to keep the sail relatively flat. This makes an amazing difference (and I really regret how many years it took me to figure that out) - less drag and so less heeling, more lift (proportionately) so you get more usable power out of a strong wind, less weather helm. I now reef quite a bit later than I used to, having figured this out, and gusts don't bother me nearly so much. A floppy, baggy mainsail, on the contrary, in a strong wind, will turn all the wind force in a gust into heeling and rounding up.

Yep, all that is true. I did some sailing in Sweden before I moved to the US and there I mainly raced 16' Hobies first and later a 20' Supercat - that one was a screamer..=*^)

And of course, remembering how the small Swedish wooden day sailers reacted to a strong gust of wind, the first time that happened to me on the Hobie on a lake in Minnesota I rounded up instead of bearing off - resulting in a spectacular part pitch pole and part flip..=*^)

I came up spitting water and wondering "what the h*ll happened?" But I learned pretty quick.

As for the science of sail trim - my older brother bought a sailboat after he had a day on mine while I was back in Sweden in the 80's. Bought a FB 25' sloop very suited to his inland sailing in mid Sweden. He asked me to come help him move it to his home marina and I remember vividly how he refused to accept what I told him about how to power and de-power the main sail.

Same thing happened when we went racing the first time. He could not understand why I didn't move out of the way for other racers..=*^)

Despite his stubborn refusals to do what I asked him we did win the race and because of that his club won the trophy permanently. Got him a lot of brownie points...=*^)

Took him about a year before he sheepishly admitted I had been right all along.

=*^)

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Old 17-10-2012, 08:54   #57
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Re: Rounding Up... Other Tactics & Questions

Great stuff, here. Two things.

1) In the circles I grew up in, "vang sheeting" doesn't mean playing the vang. It means setting vang tension to fix the upwind sail shape (esp. twist) and trimming the sail in and out with the main sheet. Most dinghies are sailed this way in moderate breeze because they don't have a traveller, or the main sheet is simply easier to play than the traveller. On most boats with a traveller you leave the vang loose upwind, because the traveller sets the twist, and vang tension isn't needed until you bear off, the traveller's down, and you start to ease the main sheet. Note that at some point in the transition to a strong breeze it becomes wise to switch from vang sheeting or playing the traveller to playing the main sheet - vang off - so the boom can rise, allowing twist and depowering the sail. This leads us to the next point.

2) It's understandable if you're still confused about whether you use the vang to "power" or "depower" the main on a reach, because it depends on the conditions. Forget the "depower" concept for a moment and think about how you use the vang as the windspeed changes and you "change gears." (A) In light breeze the vang is off. The weight of the boom determines mainsail twist. The other sail controls are also loose,and the mast is straight and the draft full and forward. (B) As the breeze builds from light to moderate you increase vang tension - in concert with other sail controls - to flatten the main, bend the mast forward, move the draft aft, etc. You may think of this as "depowering." However, the vang also increases leech tension, prevents excessive twist from developing, and maintains optimum trim all the way up the mast. This actually maintains power through the whole of the sail. So at this point it's not really about "powering" or "depowering;" the vang is just one sail control that helps you switch gears for the conditions, maintaining optimum sail shape. (C) Now the breeze builds from moderate to strong (ie, the situation in the OP) At this point you change gears by easing the vang (or at least you don't tension it further), allowing a healthy amount of twist in the leech, thereby "depowering" the upper part of the mainsail. Note you maintain some power in the lower part of the mainsail, which is where you want it to avoid excessive heel.

Conclusion - shifting gears from moderate to strong breeze: Upwind - as you become overpowered you can switch from vang sheeting or playing the traveller, and instead you can ease the main sheet, creating twist and depowering the top of the sail. Reaching - the mainsheet is already eased, and the traveller is already down. So the only way to create twist is to ease the vang, allowing twist and depowering the top of the sail.

To those who point out that you can luff up before the puff hits (or head off if you're sailing deep enough), or reef in advance... point taken. Smart use of the vang just gives you one more tool in your toolbox.
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Old 17-10-2012, 10:55   #58
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Re: Rounding Up... Other Tactics & Questions

On the vang the o sh*t control on big race boats is a button on the floor by the wheel. Stomp on it to dump the vang. For the OP your boat probably has the standard Hunter blown out 150% gen in a gust you can dump all the main and still be overpowered. If the day looks close to the top of your wind range change down head sail size. If you don't have a smaller sail move the blocks back and twist the head way off. My wife worried also take her out and tell her your going the put the rail down. Sheet it in tight and head down until you get her beam to the wind. Wind isn't going to dump a keel boat waves do. No amount of me telling her worked this did.
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Old 17-10-2012, 12:02   #59
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Re: Rounding Up... Other Tactics & Questions

"So here is the question for the forum. If overpowered in a gust while sailing on a beam reach what would be your preferred reaction at the helm. "

This was the original question for this thread, What you would do with the helm. On a lot of boats the helmsman can easily dump the traveller and that should happen but what can you do with the helm?

First of all, if you are in traffic (racing), You can't head up or fall off much but let's assume you have plenty room. If you were closehauled you could easily luff a little (head up) in the puffs to keep the boat sailing flatter but on a beam reach I think you are better falling off a little but if your wife is at the helm and panicking and you tell her to fall off she might well send you into a gybe.

On a catamaran, in this situation, you have to be extremely careful because if you decide to head up, the momentary centrifugal force from the turn increases the healing force and can cause a capsize.

In your particular situation, Your wife (at the helm) should head up to a closehaul, you should then sheet in the genoa. Now the boat is powered up up with the headsail and the main is luffing. Now you are in a perfect position to easily reef the main.
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Old 17-10-2012, 12:11   #60
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Re: Rounding Up... Other Tactics & Questions

Dump the main sheet. If you are not setup to do so in seconds, then get setup that way. Rounding up will just make you heel further. How is it your traveler is easier to dump than the main sheet...? I've been on racing boats where one person runs the mainsheet, he never cleats it off on a reach and adjusts according to the wind puffs.... working constantly to keep it full but keep the boat flat-ish.
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