# vang and preventer



## TSOJOURNER (Dec 16, 1999)

Basic question from a learner.
Is there any reason that I cant use one block and tackle to serve as both a vang and preventer and just move the bottom block from the mast to the rail when needed? (I have mid boom sheeting) 
The preventer would need more line which is messy but I dont lead them back to cockpit.
Similar enough ratios?
Why not?


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## nolatom (Jun 29, 2005)

Theoretically you could, but the two things serve different purposes, though they sometimes share them a little.

A vang by definition is rigged on the same pivot point as the boom/gooseneck, so as to keep a steady tension on the leech no matter whether you trim or ease the mainsheet.

A preventer, rigged to the rail, is there primarily to prevent a jibe if you bear off too far past the lee. When trimmed in close, it also tensions the leech. But to keep the same leech tension, you'd have to readjust it every time you ease or trim the mainsheet.

So if you want consistent leech tension (and boom height) and also something to help prevent an accidental jibe, then you need two separate block and tackle systems. Also, you may want the vang tension during a jibe, which is something you can't do with just a preventer, which has to be let go and shifted to the new lee side during and after the jibe.

Even with mid-boom sheeting (and traveler?), which sort of acts like a vang farther out than boom-end sheeting does, you'd still need a vang *and* a preventer if you really want the advantages of both.


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## billyruffn (Sep 21, 2004)

To add to the good comments in Nolatom's post above, your vang is probably attached to the boom forward of the midpoint. Although some boats will use preventers that are attached at or near the mid point of the boom, doing so increases the risk of breaking the boom. Ideally, a preventer should run from the end of the boom forward to the bow. Booms can break while broad reaching / running downwind with preventers rigged when the boat takes an big roll and the end of the boom drags in the water. When the preventer is attached mid-boom the middle of the boom wants to stay put while force of the water pushes the end of the boom aft. Rigging the preventer to the end of the boom helps balance the force of the water. 

I used a mid-boom preventer for years and took some mean jibes with it, including a really violent jibe one night when the Aries decided it didn't like the course we were on while we were screaming along in a 25 knot trade wind (scared the s--t out of me). Nothing broke, but it caused me to rethink the real purpose of the preventer and to re-rig with a more traditional system. My new end-of-boom-to-bow preventer uses more line and is a bit more work to set up and change over when we do jibe, but I think it works better. The end-of-boom set up allows me to get the preventer much tighter (less movement when we do jibe unintentionally).

The system I use now is rigged as follows: 

A very stetchy braided line runs the full length of the boom. The end at the gooseneck has an eyesplice. When not in use I cleat this line off near the gooseneck and it lies nicely out of the way. I have two braided lines (one each port and starboard) that run from the cockpit to the bow (on deck), then through strong blocks attached to the bow cleats on either side, then under the lifelines and back on the outside of everything to the shrouds. When the preventer is not in use these the working ends of two lines are clipped to the shrouds. To set up the preventer I un-cleat the line attached to the boom and shackle it to the end of the line that runs to the bow. I have to go to the mast to do this, but don't have go to forward of the mast. I then take up any slack in the preventer from the cockpit. When we change tack, I sheet the main in hard, go forward and re-rig the preventer to the other side. I then jibe the main, trim the sail and then set up the new preventer.


The two weak points in this set up are the block at the bow and the snap shackle that connects the two pieces of line. I oversized both for safety. I would not recommend using just any piece of line for a preventer. Ideally, it should not only be strong, but fairly elastic as well so that the stretch in the line can absorb some of the shock transferred to the rig in an accidental jibe.


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## Omatako (Sep 14, 2003)

nolatom said:


> A vang by definition is rigged on the same pivot point as the boom/gooseneck, so as to keep a steady tension on the leech no matter whether you trim or ease the mainsheet.


Not really.

In my experience, the block system that goes from the boom to the base of the mast (a lot of modern boats use a block system in tandem with a sprung telescope or hydraulic rams) to control tension of the leech is called a kicker and is not the same thing as a vang.

A vang *is *a preventer and is connected between the boom and the rail when running off the wind. The kicker stops the boom from lifting when the main sheet is eased but the vang holds the boom to the side to "prevent" crash jibes.

Billyruffn, your system is very rare. I can't recall ever seeing one like that. How would one experience an "accidental jibe" with this system connected?

Andre


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## sailingdog (Mar 19, 2006)

Andre-

The Boom Vang is usually a block and tackle that goes to the mast base and is used to control the mainsail shape. It is generally called a kicker if it is a solid vang, not just a block and tackle, and can support the boom in place of a topping lift. 

Most boom vangs are not preventers, and are not connected to the rail. Most preventers don't help with sail shape all that much either, since they're mainly pulling forward on the boom, rather than down. 

IMHO, a boom brake makes a lot more sense than does a preventer. In many situations, a preventer can become a serious problem and often can result in the boat being knocked down or pinned down, and then can only be released under a high load, which is fairly dangerous to do. A boom brake allows the boom to move, but at a fairly low speed, where it is not going to be a danger to people in the case of an accidental gybe. 

Most modern boom brakes are also adjustable in tension for the wind conditions and are often controlled by a line lead aft to the cockpit.


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## billyruffn (Sep 21, 2004)

Omatako wrote:

Billyruffn, your system is very rare. I can't recall ever seeing one like that. How would one experience an "accidental jibe" with this system connected?

------

I was using an incorrect term. I was referring to the mainsail going aback -- you're right, technically you don't jibe unless the boom comes across. I've never had a jibe with the preventer rigged, but frequently had the sails unexpectedly go aback. When the wind's up and the swells are big that's no fun either.


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## JohnRPollard (Mar 26, 2007)

scosch said:


> Basic question from a learner.
> Is there any reason that I cant use one block and tackle to serve as both a vang and preventer and just move the bottom block from the mast to the rail when needed? (I have mid boom sheeting) The preventer would need more line which is messy but I dont lead them back to cockpit. Similar enough ratios? Why not?


Scosch, The short answer is "yes you can" use your vang as a preventer. This is not the ideal arrangement -- better to have a separate preventer that you can deploy when necessary -- but it is better than running without a preventer at all. Many many sailors do exactly as you describe.



Omatako said:


> In my experience, the block system that goes from the boom to the base of the mast (a lot of modern boats use a block system in tandem with a sprung telescope or hydraulic rams) to control tension of the leech is called a kicker and is not the same thing as a vang.Andre


Omatako, Not wishing to get into an etymological debate here, but I think this may be a question of regional differences in terminology and usage. In North America, the distinction between a vang and kicker is more-or-less as SailingDog describes in his post above. "Preventer" is a more general term used to describe any device that is deployed to prevent the boom from jibing unintentionally when sailing off the wind. They can resemble the same block and tackle system often employed for the vang or can be rigged in other ways such as Billyruffn described above.



billyruffn said:


> My new end-of-boom-to-bow preventer uses more line and is a bit more work to set up and change over when we do jibe, but I think it works better. The end-of-boom set up allows me to get the preventer much tighter (less movement when we do jibe unintentionally).


Billyruffn, Your end-of-boom preventer is more often seen on boats sailing off-shore or making longer coastal passages. It seems to be a preferred arrangement for many experienced off-shore sailors. Personally, I have never been comfortable with this approach.

One important consideration when rigging a preventer is that while it may succeed at preventing a sudden accidental jibe, it may not be able to prevent a jibe altogether. In certain heavy wind and sea-state conditions, the sail may become backwinded and overpower the vessel's ability to correct its course. With an end-of-boom-to-bow preventer, the crew is then left with two options: (1) allow the boat to continue spinning up into the wind before releasing the preventer line (which would probably entail a very dramatic broach); or (2) if sea-state or limits on navigation do not permit option (1), the preventer must be eased and the boom allowed to jibe across.

The problem with option (2) is that following this course of action will require easing the preventer line until it bears up hard against the shrouds, placing enormous lateral loads on them. And this will occur at about the same moment that the angle of the line from the bow to the boom-end will lose most of its purchase (i.e. mechanical advantage), so the preventer will no longer be able to overcome the tremendous leverage being exerted on the boom via the backwinded sail. At that point the only option will be to release the preventer entirely and let the boom jibe violently. In addition to risking damage to the boom or the leeward rigging with the jibe, there is risk that the windward rigging, probably the spreader, will be damaged if the preventer line is permitted to bear up against the shroud prior to release.

For these reasons, I prefer the mid-boom preventer that is secured to the reinforced portion of the boom where the vang attaches, and led outboard to the point of maximum beam just aft of the shrouds. To prevent shock-loading the boom, the preventer line can be stretchy and can be secured to the boom via a shockles or similar high-strength elastic material.

As SailingDog mentioned, the best all-around solution may be to rig a sturdy break that simply permits a slow controlled jibe rather than preventing it altogether.


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## Plumper (Nov 21, 2007)

I think that the term "kicker" comes from the British word kicking strap which is the same as a boom vang or "vang". The two do the same job. As for using a vang as a preventer, it is very common and sometimes termed a prevang. 

The job of the preventer is to prevent accidental boom jibes but expecting it to work in high winds or extreme conditions is looking for trouble. I believe that preventers are best when used when the boat is rolling and the boom may flop from one side to the other (especially in light airs). Expecting it to hold the boom in place in strong winds when the full force of the wind hits the back of the sail is unreasonable. Something is going to give. Hopefully the preventer will be the weak point, not the boom. In those high wind or extreme conditions the boom brake becomes the device of choice because it allows the boom to cross the centreline but dissipates the powerful boom breaking, sail ripping, gooseneck snapping forces. When sailing off the wind in extreme conditions, particular care should be taken to avoid jibing and in those conditions I would not use a prevang. In lighter airs where the boom will not stay in place because of rolling a prevang is perfect.

Gaz


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## billyruffn (Sep 21, 2004)

JohnRPollard wrote:

In certain heavy wind and sea-state conditions, the sail may become backwinded and overpower the vessel's ability to correct its course. 
----------------
John,

I think the reason offshore sailors use the end boom preventer is that they are often more at risk of jibing because normally don't have someone at the wheel / tiller at all times (relying instead on autopilots or self-steering wind vanes) and, more to the point, they are frequently dealing with larger seas which can increase the tendency for the boat to roll heavily when sailing down wind, thus increasing the risk of sticking the end of the boom in the water.

Coastal sailors don't have to deal with these circumstances quite so often and mid-boom preventers or boom brakes may be the preferable option. As I indicated in an earlier post, I used a mid-boom preventer for several years and it does make it much easier to release the preventer in a controlled manner when the mainsail goes aback. 

Fortunately, I haven't yet experience the situation you describe -- with the sail aback, preventer holding the boom from jibing and the rudder unable to bring the boat back down wind -- but I can imagine it happening. As you suggest, the recovery would be challenging, but so far I've found that the combination of easing the preventer while recovering the slack in the mainsheet and helm action can usually get things back to where you want them. I think there's also a lot to be said for keeping the sail area appropriate to the conditions at hand and having a human being driving the boat (or at least sitting at the helm prepared to react) when the wind and sea state get up. After all, an attentive helmsman is probably the best "preventer" there is.


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## TSOJOURNER (Dec 16, 1999)

*wow, thanks*

thanks for your replies, kind of a can of worms, like a lot of topics between sailors. I was glad to learn it all but I was particularily glad to hear one reply that suggested that what I wanted to do was reasonable if not perfect.
Im trying to sneak up on all the equipment I need to avoid making mistakes, and moving the vang to the rail when necessary seemed a good start. thanks again.


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## JohnRPollard (Mar 26, 2007)

billyruffn said:


> I think there's also a lot to be said for keeping the sail area appropriate to the conditions at hand and having a human being driving the boat (or at least sitting at the helm prepared to react) when the wind and sea state get up. After all, an attentive helmsman is probably the best "preventer" there is.


Billyruffn,

You are no doubt correct in pointing out that keeping mainsail area commensurate with wind strength will improve the situation regardless which preventer method is employed.

But this is the point where I must sheepishly reply that an attentive helmsman may not always be your best preventer. Perhaps I was not as attentive as I should have been, but having myself been at the helm during an accidental jibe that destroyed a mainsail on an off-shore cruising boat , I generally advocate some method of mechanical prevention as prudent whether the boat is steered manually or by autopilot/windvane.


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## soulesailor (Nov 18, 2007)

scosch said:


> Im trying to sneak up on all the equipment I need to avoid making mistakes, and moving the vang to the rail when necessary seemed a good start.


scosch~ I would recommend not doing this. I used my vang as a preventer for a while and, looking back on it, feel lucky I escaped unscathed. I was fortunate enough to meet someone who broke the same boom I use by doing just what I was doing (what you are planning to do). You can rig a simple line from the end of your boom to your bow or a boom brake, whichever you like, for a lot less than a broken boom, not to mention what else might break if your boom lets go.


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## Omatako (Sep 14, 2003)

JohnRPollard said:


> The problem with option (2) is that following this course of action will require easing the preventer line until it bears up hard against the shrouds, placing enormous lateral loads on them. And this will occur at about the same moment that the angle of the line from the bow to the boom-end will lose most of its purchase (i.e. mechanical advantage), so the preventer will no longer be able to overcome the tremendous leverage being exerted on the boom via the backwinded sail. At that point the only option will be to release the preventer entirely and let the boom jibe violently. In addition to risking damage to the boom or the leeward rigging with the jibe, there is risk that the windward rigging, probably the spreader, will be damaged if the preventer line is permitted to bear up against the shroud prior to release.


That was going to be my next question. While the sail is backed and the boat is busy rounding up, how do you release the line that runs to the bow? Especially in the middle of the night in a heaving sea and a good strong blow? I would guess with real sharp knife and a character-building jibe. Definitely not for me

Also, John (and SD) - yep I reckon you're right on the regional interpretation issue and will accept that as is.

Andre


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## billyruffn (Sep 21, 2004)

Omatako wrote: While the sail is backed and the boat is busy rounding up, how do you release the line that runs to the bow? Especially in the middle of the night in a heaving sea and a good strong blow? I would guess with real sharp knife and a character-building jibe. Definitely not for me

----
O, the line runs from the end of the boom forward to the bow, through a block (mine is attached to the bow cleat with a spectra strap) and back along the deck to the cockpit. 

------------

JohnRPollard wrote: Perhaps I was not as attentive as I should have been, but having myself been at the helm during an accidental jibe that destroyed a mainsail on an off-shore cruising boat , I generally advocate some method of mechanical prevention as prudent whether the boat is steered manually or by autopilot/windvane.
----
Yup, "attentive" is the operable word, but I agree entirely -- mechanical prevention is key. Because it doesn't take much "inattention" (maybe reaching for a cup of coffee as the boat slides off a wave) for a jibe to ruin your evening.

Preventers are a pain in the ass to rig and operate, but I find them very useful, especially when you have new/young/inexperienced crew at the helm. Preventers let you say to your young nephew, "See, that's what I was saying about not getting the wind get too far 'by the lee'," without it costing you a couple grand.


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## TSOJOURNER (Dec 16, 1999)

*brake?*

Ok, seems moving the vang from the mast base over to the rail to act as a preventer is generally discouraged but possible. 
So instead of a seperate preventer, I think some of you like the idea of a boom brake. Is this an entirely seperate device from the vang? Is a a stretchy line that one attaches to the end of the boom, runs forward to a block and then back to a cockpit cleat? And the brake is somekind of friction device somewhere on this line? Where do I find one? Sounds like it would be cheaper than the block and tackle set up of a preventer.


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## soulesailor (Nov 18, 2007)

scosch, check out this other thread Gyb'easy, lots of talk there about preventers, two types of brake and a link to some pictures.


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## PeterPentz (Jun 9, 2007)

*How do I set up a preventer?*

This is my first go at blogging on this website. I am an older dog and have taken up full-time cruising of late. Although I have been sailing most of my life, there is so much to learn about cruising. Judging by the quality of input on Sailnet, there are obviously some very experienced and skilled sailors out there, so I am my questions will be simple fodder.
I have purchased a Bavaria 44 at she is currently in Croatia, waiting my return from Australia at end April when I wil sail her down to Greece and spend the European summer there. I need a boom preventer and wondered if you could advise what gear I should aquire - specs of the block and tackle etc. The more you can tell me the better!! Never set one up before.

I wouold also appreciate some advice on ground tackle, but think maybe I should set up a new thread for this?

Many thanks

Peter


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## JohnRPollard (Mar 26, 2007)

PeterPentz,

Welcome to SailNet and congratulations on your new Bavaria. That should be a nice cruise in and around the Greek Islands. Also, we have a SailNet member that lives in Croatia (I think), screen name Tomas. He may be a good local resource for you. (Haven't seen him around lately but I seem to recall he was going off for a charter in the Caribbean about this time).

We often point new members to this thread to help them understand how SailNet is set-up and to get more out of it:

http://www.sailnet.com/forums/showthread.php?t=39379

To answer some of your above questions.

Regarding the anchor, yes, that should be the subject of another thread. But before you post your question, I would suggest you use the "Search" function to review some of the many threads that have already been posted on that subject. Then ask away.

Regarding the preventer, reviewing this thread is a good place to start. Also, the subject has been addressed previously, so using the "Search" function should turn something up. Here's another recent thread that discussed boom brakes:

http://www.sailnet.com/forums/showthread.php?t=40129

And here are some external links to articles that discuss preventers:

http://www.sail-world.com/index.cfm?SEID=2&Nid=40976&SRCID=0&ntid=0&tickeruid=0&tickerCID=0

http://www.bermudarace.com/Portals/0/Uploads/Documents/surgeon_preventer_2007_2.pdf

Finally, if you have additional questions, please do not hesitate to post them.


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## sailingdog (Mar 19, 2006)

I'd recommend a Dutchman boom brake rather than a preventer. I believe a boom brake makes for a safer installation overall.

The Dutchman boom brakes are sized according to the area of the sail.


PeterPentz said:


> This is my first go at blogging on this website. I am an older dog and have taken up full-time cruising of late. Although I have been sailing most of my life, there is so much to learn about cruising. Judging by the quality of input on Sailnet, there are obviously some very experienced and skilled sailors out there, so I am my questions will be simple fodder.
> I have purchased a Bavaria 44 at she is currently in Croatia, waiting my return from Australia at end April when I wil sail her down to Greece and spend the European summer there. I need a boom preventer and wondered if you could advise what gear I should aquire - specs of the block and tackle etc. The more you can tell me the better!! Never set one up before.
> 
> I wouold also appreciate some advice on ground tackle, but think maybe I should set up a new thread for this?
> ...


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## TSOJOURNER (Dec 16, 1999)

*vang, preventer, Boom stay*

Try this Boom Stay
http://www.mv.com/ipusers/whale/tillerstay/boominfo.html
This system works as vang preventer & boom brake. designed for smaller vessels.
I have used blocks to create a stronger system for my 34 ft vessel. It allows great sail shaping control, And when you jibe allows the sail to slide across at a controlled rate. Single line control no going forward.


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## Rockter (Sep 11, 2006)

It is shown de-activated here...










...but it has worked fine for me.

It never lets the boom get away from you, and yes, when you alter the mainsail sheet, you have to adjust it again, and when you throw a tack or a gybe you have to walk it over to the other side. I could run two of them I suppose, but they might get a bit clumsy.

I would not be without it for a moment, it did not cost much, and it got me home to Scotland from Houston.

Rockter.


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## Vincent Sorrentino (Apr 12, 2006)

I have a cape dory typhoon.I would like to install a vang.I feel that there is only 1 foot from the cabin top to the boom.How far back on the boom and how much lower can i go from the boom.


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## christyleigh (Dec 17, 2001)

sailingdog said:


> I'd recommend a Dutchman boom brake rather than a preventer. I believe a boom brake makes for a safer installation overall.
> The Dutchman boom brakes are sized according to the area of the sail.


..... and Defender has a Sale on them right now. I ordered one yesterday.


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## sailingdog (Mar 19, 2006)

Christyleigh-

Congrats... if you need a hand with it...give me a shout. 

BTW, there's a good article in this month's Blue Water Sailing about installing and setting up a preventer...but I still recommend a boom brake instead.


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## christyleigh (Dec 17, 2001)

sailingdog said:


> Christyleigh-Congrats... if you need a hand with it...give me a shout.
> BTW, there's a good article in this month's Blue Water Sailing about installing and setting up a preventer...but I still recommend a boom brake instead.


Actually this is my second one. A few boats ago I installed one on my Nimble Arctic 25 Pilothouse. It didn't come with a Vang so the Boom Brake served a dual purpose. Not quite as effectual as a dedicated Vang but it did help a lot to keep the boom down on runs.


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## Plumper (Nov 21, 2007)

scosch said:


> Basic question from a learner.
> Is there any reason that I cant use one block and tackle to serve as both a vang and preventer and just move the bottom block from the mast to the rail when needed? (I have mid boom sheeting)
> The preventer would need more line which is messy but I dont lead them back to cockpit.
> Similar enough ratios?
> Why not?


Anybody see the latest "Good Old Boat" magazine article that argues that this kind of setup (actuall a double prevang) is safer and easier to use. It is a good article that makes some interesting points.


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## PJFORD (Aug 11, 2011)

Using the vang attached to the toe rail on my boat allowed for a much more stable downwind wing-on-wing arrangement. Of course conditions always dictate sailset (rolling heavily can be perilous), and I used it generally in lighter winds with the "150" set opposite.


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