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How to use a preventer on the C250?

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TakeFive
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Initially Posted - 10/01/2011 : 19:49:13

Since we've started doing more wing-on-wing sailing when going DDW, I'm considering modifying my vang with snap shackles to use as a preventer by connecting to the baby stay stanchion bails. But first, a few questions, since my sailing texts and Chapmans make only a brief mention of preventers:

What is the best snap shackle design to use?

What is the correct sequence of events for jibing? Do you detach the preventer first, or just loosen the sheet and detach the vang after the boom has moved over? Do you do anything to slow the rate of the boom travel, or just let it go?

If/when an accidental jibe occurs, what is the correct response to the backwinded sail? Do you adjust course to undo the jibe? Or if you want to continue with the jibe, do you just release the sheet and allow the boom to cross? Is it difficult to release the sheet under these conditions due to excessive tension holding the cam cleat closed?

What happens if an accidental jibe happens in a heavy blow? Is there danger of the boat being spun around or knocked down? What is the appropriate response to this? Is there danger of damage to the stanchions or boom?

Sorry to pester with these questions. Normally I'm willing to try things out and tweak them, but when it comes to jibing technique I prefer to do my homework first. I found some threads that mentioned preventers, but none gave details about how to actually use them.

Rick S., Swarthmore, PA
PO of Take Five, 1998 Catalina 250WK #348 (relocated to Baltimore's Inner Harbor)
New owner of 2001 Catalina 34MkII #1535 Breakin' Away (at Rock Hall Landing Marina)

Edited by - TakeFive on 10/01/2011 20:11:28

GaryB
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Response Posted - 10/01/2011 : 20:56:20

I've never used a preventer so I can't help with that question.

When I want to gybe I slowly change course and either pull in the sheet (my preferred method) or grab the whole main sheet setup and pull it across just as the main starts to swing across. The only issue with the second option is my hand has gotten caught between the back-stay and the sheet assembly a couple of times. Sooner or later I'm going to lose a finger or break my hand. For that reason I will only use the second option if the winds are light. Either way it keeps the boom from slamming from one side to the other.

Allowing the boom to swing uncontrolled can cause several problems. First and foremost, if someone isn't paying attention they could be severely injured or killed by the boom swinging across at a high rate of speed. The boom could also swing up and catch the back-stay possibly bringing down the whole rig. If it swings cleanly across uncontrolled and slams to a stop on the other side there's a good possibility of breaking something.

I've only had the boat gybe once in higher wind conditions and the boom slamming across was violent. I was lucky I was by myself and nothing broke. I tried to steer back the other way but it happened so quick the boat was just starting to turn by the time the gybe was over. I don't remember the boat wanting to spin around or feeling like it was going to get knocked down but I could see how that could happen under the right conditions. Since that time I try not to sail DDW if the winds are up.

If you're going to gybe you have to keep the boom under control.

Edited by - on

TakeFive
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Response Posted - 10/01/2011 : 21:37:18

I've jibed many times before, and know how to do so safely. My question was specifically about how to use a preventer, which if properly used could reduce the likelihood of an uncontrolled jibe if, for example, there is a sudden wind shift. But the details of how to properly use a preventer are sketchy in the references that I have, hence my questions.

Edited by - TakeFive on 10/02/2011 06:31:52

dmpilc
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Response Posted - 10/02/2011 : 05:52:29

You would detach the preventer before gybing and reattach it on the new side after getting everything set on the new course. In an accidental gybe, I adjust the main on the new side as quickly as possible while the crew handles the headsail.

Edited by - dmpilc on 10/02/2011 05:57:27

Steve Milby
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Response Posted - 10/02/2011 : 07:04:39

Like you, I haven't seen much good, detailed information about the use of a preventer. I only use a preventer in lighter winds, when sailing downwind and the wind isn't strong enough to hold the boom to leeward reliably. Sometimes the boat will be lifted by a wave or boat wake, and the boom will swing over to windward in light air. I use a preventer to prevent the boom from swinging. I don't use any kind of tackle with mechanical advantage in that situation. I just tie a line to the boom, and then tie it to a lifeline stanchion or other convenient place, using a slip knot. Then I lead the line to the cockpit. When I want to release the preventer, so I can maneuver the boat, I tug on the line, the preventer releases, and I am free to steer in any direction.

I don't like to use a preventer in strong winds, because I don't like the sails strapped down in a way so that I can't release them quickly and easily. In strong winds I prefer to simply steer the boat accurately, so that the mainsail doesn't get backwinded. It means that you have to focus your attention on steering. If I sailed in a lot of long, all-night races downwind, I might see it differently, but in the all-night races that I have sailed, such as the Governor's Cup, we have never used a preventer, and never felt a need for one.

In strong winds, I balance the alternatives. What would I rather have happen? Would I rather break the gooseneck on the boom, or rip a fitting out of the deck? My best answer is "Neither." Both alternatives are unacceptable. The best way to avoid them both is to steer the boat accurately downwind, and focus.

Some say that a preventer adds safety. It seems to me that there's nothing safe about a boat that broaches in high winds because of a preventer. Crew can go overboard and be lost. With regard to safety, it seems to me to be six of one and a half dozen of the other.

Racers do many things that, for anyone else, would constitute poor seamanship, such as carrying too much sail area, when they should have reefed. I think, if the conditions are so violent that you need a preventer to hold the boom down, good seamanship dictates that you should have reduced sail area or perhaps changed your course to one other than downwind, so that you don't need to even consider a preventer.

Edited by - Steve Milby on 10/02/2011 07:38:05

britinusa
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Response Posted - 10/02/2011 : 07:27:56

We have a stainless steel carabiner on the lower end of the vang where it attaches to the mast.
[url="http://www.marinepartdepot.com/new316ststca2.html"]

here's one on Marine part depot[/url]

Often running 'gull wing' (it's a Brit thing

) we don't use a preventer simply because we're probably not going to be there for long (frequent wind changes in the Bay)
However, if we were planning on running on a long track, then I would just ease the vang, attach the carabiner to the lee babystay shackle and then tighten up on the vang before heading DDW.

Edited by - britinusa on 10/02/2011 07:31:45

John Russell
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Response Posted - 10/02/2011 : 08:43:18

I don't use a preventer for precisely the reasons Steve explained above. If the wind should suddenly shift at the same time my attention wanders, trouble will ensue.

I think sailing DDW is the most difficult and unforgiving point of sail. So, when I'm downwind, I'll usually set a course so that the winds is slightly to port or starboard depending on tack. Sometimes it's a little harder to keep the headsail full but, with tweaking, it works for me.

I also rarely jibe -- only do it in pretty light winds. I typically do what has been called a "chicken jibe". I simply tack the boat through 270 degrees. This is the same method I use to heave-to (sorta). It slows the boat to a managable speed and everything happens nice and easy without damage to the boat or my head. In the event of an accidental jibe, you have essentially hove-to --although with lousy sail trim so the boat won't really stop. Trim the sails and get the boat stopped and use that time to collect your thoughts and decide the best course of action. Oh, yeah, and to find out if anything broke. I would probably then tack the jib to regain speed and then tack to my desired course.

<blockquote id="quote">quote:<hr height="1" noshade id="quote"> What happens if an accidental jibe happens in a heavy blow? Is there danger of the boat being spun around or knocked down? What is the appropriate response to this? Is there danger of damage to the stanchions or boom?<hr height="1" noshade id="quote"></blockquote id="quote">Yes, and it could be severe but not nearly as much damage as the risk to your head. I think DDW in a big blow is precisely the wrong point of sail. Broad reaching is probably much safer.

Edited by - John Russell on 10/02/2011 08:43:53

vholmstrom
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Response Posted - 10/02/2011 : 09:22:11

It seems that when sailing DDW in a strong blow, the Jib alone would get you close to hull speed. Then you and the crew could relax without having to duck in a hurry.

Edited by - vholmstrom on 10/02/2011 09:23:42

TakeFive
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Response Posted - 10/02/2011 : 11:19:34

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by vholmstrom
 It seems that when sailing DDW in a strong blow, the Jib alone would get you close to hull speed. Then you and the crew could relax without having to duck in a hurry.
<hr height="1" noshade id="quote"></blockquote id="quote">
That is a good point, and I would not knowingly use the main for DDW sailing in a heavy blow, for the reasons you mentioned.

There was one time in October last year when I did have a sudden shift and acceleration of the wind with no warning. In retrospect, I discovered a cloudless front had come through, with winds going from about 10 kt to 31 kt (as recorded on nearby sensors), and shifting from W to N, with absolutely no warning. I was not going DDW at the time, but it was scary enough to make we worry about accidental jibing under even the best of conditions.

At the time, we had the wind over the port stern quarter, intentionally avoiding DDW. When it gusted and shifted simultaneously, we heeled over about 30 degrees, and I had to make a snap decision whether to turn downwind or upwind (which would momentarily heel the boat even more). I opted to turn upwind because I was afraid that if I turned downwind, the wind might shift back and cause an uncontrolled jibe. It was harrowing, but I made the right choice because the wind DID shift back, and we probably would have had an accidental jibe if we tried to go downwind on the puff. This whole process repeated itself once more (ripping our genoa in the process) before we dropped the sails and motored home. Even after dropping the sails, the puffs were strong enough to heel us over 15 degrees on bare poles.

Even though we avoided an accidental jibe, the experience was enough to alert me to the ever present possibility of a sudden shift causing a jibe. If a preventer could buy me a few extra seconds to pull in the mainsheet to get control of a jibe, it could be a helpful safety feature. But, as some have pointed out, the preventer itself could cause other problems of its own.

Edited by - on

GaryB
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Response Posted - 10/02/2011 : 16:34:56

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by RhythmDoctor
 <blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by vholmstrom
 It seems that when sailing DDW in a strong blow, the Jib alone would get you close to hull speed. Then you and the crew could relax without having to duck in a hurry.
<hr height="1" noshade id="quote"></blockquote id="quote">
[quote]...with absolutely no warning.<hr height="1" noshade id="quote"></blockquote id="quote">

Could the change in the wind pattern on the water be seen before the wind arrived (IE: white caps coming towards you where you may not have had any around you or larger waves moving in your direction or from a different angle vs the waves near your boat)?

Edited by - on

TakeFive
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Response Posted - 10/02/2011 : 19:34:57

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by GaryB
 Could the change in the wind pattern on the water be seen before the wind arrived (IE: white caps coming towards you where you may not have had any around you or larger waves moving in your direction or from a different angle vs the waves near your boat)? <hr height="1" noshade id="quote"></blockquote id="quote">
It was a year ago and happened fast enough that I don't remember everything exactly. But I pulled up the track to confirm that I was only 0.1 nm from the windward shore (remember, it's a river), so I suspect there wasn't enough fetch for any significant waves to develop.

In fact, there are times when we're close enough to shore that wind shadows from large buildings and docked freighters (and the wind tunnels that develop between them) can cause interesting eddies in the air.

Edited by - TakeFive on 10/02/2011 19:37:08

JohnP
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Response Posted - 10/03/2011 : 10:05:50

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by Steve Milby
 <ul><li>I only use a preventer in lighter winds, when sailing downwind and the wind isn't strong enough to hold the boom to leeward reliably.</li><li>I don't like to use a preventer in strong winds, because I don't like the sails strapped down in a way so that I can't release them quickly and easily.</li><li>In strong winds I prefer to simply steer the boat accurately... </li></ul>
<hr height="1" noshade id="quote"></blockquote id="quote">I agree with what Steve said, which I edited here for brevity.

While sailing one time with Paul Zell in SF Bay, I learned that a preventer is very nice in light or moderate winds when on a dead run. Paul rigs it to one side or the other based on the best position of the boom for the winds. He had a whisker pole for the jib under these conditions, and the boat is very stable to wind shifts.

I went home and rigged 2 preventers. I use a large carabiner like BritinUSA on each side of the boom vang bail with lines leading to blocks held with snap shackles attached to stanchion bases port and starboard, and then back to the cockpit. No need to go forward to use one of them on a run.

The port and starboard preventers remain rigged all the time and I can use one whenever I see the wind is light enough and I decide it is safe enough to run straight downwind. Under these conditions I can relax. If the main becomes backwinded I can either correct course or the boat can even do a 360 with no movement of the boom. Since the wind shifts often in my sailing area, preventing an accidental jibe adds to my pleasure.

In strong or gusty winds (12-15 kt+) I avoid running downwind and instead choose to sail on broad reaches to keep the boat under control and keep the main hauled in most of the way. I can jibe safely and do not risk broaching.

I've never seen other C25/250s with 2 permanent preventers, but I really like them. They are easy to set up and use.

Edited by - on

Sloop Smitten
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Response Posted - 10/04/2011 : 09:14:58

I use a snap shackle to connect my preventer to the boom vang bail. The other end is tied to the base of the rear shroud. The snap shackle can be released under load making it a much safer connection.

Edited by - on

TakeFive
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Response Posted - 05/26/2012 : 11:19:36

So it's time to reawaken this thread. I still have not rigged a preventer, and increasing confidence and conservatism over the conditions that I'm willing to do DDW sailing may make it unnecessary. While I try to avoid DDW, my narrow river and narrower area outside the channel (if there's shipping traffic present) causes me to run DDW occasionally.

But still I wonder what I might do to have a preventer handy in case I ever want it. (I'm all about having extra contingencies that I may never use, such as my second reef.)

What I would really like is something that will give me early warning of an impending jibe (by making noise), or something that might slow down the jibe without preventing it completely. Here's what I'm thinking of doing:

Instead of shackling my boom vang's lower block directly to the eye near the mast base, add a bail shackle (which can be released under load):

<center>

</center>

If I want to use a preventer, remove the shackle from the mast and attach it to the baby shroud bail on the appropriate side. Leave the vang like that without engaging the vang sheet in the cam cleats. In the case of an accidental jibe, the 4:1 purchase of the vang will make some noise to alert me, slow down the jibe through friction (but not stop it, because the cam cleats are not engaged), and give me some time to adjust the direction of the boat to stop the jibe and restore the boom's position. By using a bail that can be released under load, I have the ability to completely let the thing go should all other attempts to release the preventer fail.

Have any of you tried this? What are the pitfalls that I may not be recognizing? What size/working load of bail shackle should I buy?

<center>

</center>

Edited by - on

Stinkpotter
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Response Posted - 05/26/2012 : 14:18:54

I also wouldn't use a preventer in heavy air. I always felt the risk would be that the backwinded main would stop the boat, taking away my steerage, and then try to broach it. At that point, I might have no control, and releasing the preventer could be a dangerous proposition. I'm imagining an ugly scene... and I don't think it's entirely imaginary. (I've used a backwinded main to make a boat back up, so I've seen how some of this might work.)

As John suggested, I tend to aim toward a broad reach rather than DDW in heavy air, and I also did a lot of genny-alone sailing in those conditions. I'm not too afraid of jibing from broad-to-broad, by doing an "S" turn while hardening the mainsheet to center the boom. But I've also resorted to the 270 when things were really kicking. When NOAA reports an approaching squall line and the western horizon has disappeared, my first move is to get the main down and wrapped.

Then there's the dreaded downburst--I was hit by one in our little Daysailer. It seemed like the wind was blowing from all directions at once--hard! Jibe-jibe-jibe! I just hardened the mainsheet and hung on!

Edited by - Stinkpotter on 05/26/2012 14:24:11

JohnP
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Response Posted - 05/27/2012 : 20:15:17

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by JohnP
I went home and rigged 2 preventers. I use a large carabiner like BritinUSA on each side of the boom vang bail with lines leading to blocks held with snap shackles attached to the genoa track port and starboard, and then back to the cockpit. No need to go forward to use one of them on a run.

The port and starboard preventers remain rigged all the time and I can use one whenever I see the wind is light enough and I decide it is safe enough to run straight downwind. Under these conditions I can relax. If the main becomes backwinded I can either correct course or the boat can even do a 360 with no movement of the boom. Since the wind shifts often in my sailing area, preventing an accidental jibe adds to my pleasure.

In strong or gusty winds (12-15 kt+) I avoid running downwind and instead choose to sail on broad reaches to keep the boat under control and keep the main hauled in most of the way. I can jibe safely and do not risk broaching.

I've never seen other C25/250s with 2 permanent preventers, but I really like them. They are easy to set up and use.
<hr height="1" noshade id="quote"></blockquote id="quote">

I revised my previous description from last year, that is, these lines are rigged to sturdy blocks along the genoa track.

To reiterate, these lines stay ready for use next to the jib sheets in the cockpit at all times. I don't like running DDW, but sometimes it's important for one reason or another. I sail singlehanded but without an autopilot, and I need to get refreshments or equipment once in a while while running downwind. The preventers reassure me that a catastrophic, accidental jibe will not occur with my good old boat and its standing rigging of various ages up to 34 years.

I think that having two preventers is safer and much more convenient than using only one. I don't have to go forward to re-rig anything if I turn from a broad reach to a dead run, or from a dead run to broad reach on the other side. I just attach or detach the opposite side's preventer to its cleat.

The preventers are used with gentle or moderate winds. In strong winds there is no question that the boom must be free for trimming in an instant and a preventer must not be employed.

They are just more specialized running rigging that makes sailing more fun.

Try two preventers - You'll like them!

Edited by - JohnP on 05/27/2012 20:18:35

JohnP
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Response Posted - 05/27/2012 : 20:29:24

So to add two preventers to your C-250 you would need two additional genoa track cars, two blocks attached with snap shackles or carabiners or D-shackles or whatever to the cars, two attachments of your choice to the boom vang bail, two lines led from the boom vang through the blocks back to the cockpit, and two cam cleats, clam cleats, or horn cleats on the coaming or on the cabin top next to your jib sheet winches.

Sounds like a lot of stuff! I got those parts from Bacon's in Annapolis and from Minnie's in Costa Mesa, and they were at a big discount, of course. For the preventer lines I am using some inexpensive, braided, 3/8" line that I picked up at Harbor Freight.

Edited by - JohnP on 05/27/2012 20:32:53

TakeFive
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Response Posted - 04/06/2013 : 19:34:24

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by vholmstrom
 It seems that when sailing DDW in a strong blow, the Jib alone would get you close to hull speed. Then you and the crew could relax without having to duck in a hurry.
<hr height="1" noshade id="quote"></blockquote id="quote">
It's time to reawaken this thread once again. I just got home from the "Safety at Sea" training in Annapolis, and the instructors reiterated over and over that preventers should always be rigged.

Now we have no plans to go offshore, and the main scenario that they painted was large following seas pushing the stern around and causing an unintentional jibe. So it might not be as critical for us.

Last January we did quite a bit of running in 20-30kt breezes on a charter boat in BVI, and we got pretty close to hull speed on jib alone, so that's definitely the safest way to run DDW in a strong breeze. We also have a whisker pole on our own boat that can make the jib even more effective in that circumstance.

But this year I think I am going to rig preventers. I have a couple of extra blocks that I'll shackle to the baby-stay bails that are welded to the base of the stanchions, and will run 1/4" line to the attachment bail used by the boom vang, and back to a couple of cam cleats that I have on my port and starboard coamings. This configuration was suggested to me by one of the Safety at Sea instrutors. I may never actually use them because I avoid DDW with the mainsail up, but they'll be rigged just in case.

Edited by - TakeFive on 04/06/2013 19:35:31

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