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Old 26-01-2023, 11:27   #1
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Preventer -- and an accidental gybe

So, a recent post on the Platino thread reminded me that I've been meaning to ask the forum about this matter.

This past fall, our last sail of the year actually, we were running down the Chesapeake Bay in 20+, DDW Wing on Wing. A great ride, covered about 90 miles with an average speed through the water of over 8.5kts. Seas were rough for the Bay, maybe 2-3 foot.

We were running on Autopilot, with a friend who's a little thin on experience (after seeing 15.9 knots two days before on the Jersey Coast, she's a little more experienced!) "at the helm." Something tickled the balance, the autopilot lost the bubble, we rounded down and gybed the main. Good news, we had a preventer rigged and tight, so nothing happened. Except, the backwinded main drove us hard to weather (the new weather) and we sat there, beam to the wind, main backwinded, zero water speed, and a heel angle well over 45 degrees. And sat there. And sat there.

I got to the helm, took off the autopilot, put the helm hard to leeward, and nothing happened. I started the engine and gave full throttle, nothing happened (on retrospect, I wonder about oil issues, but no apparent damage). Eventually, she came back off the wind and gybed back, but it took a while (my friend says surfing the Jersey Shore in 30-40 at 15.9 in 8-10 foot seas was "unnerving" but this broach was "scary" -- I almost agree).

So, I keep wondering. What is the lesson learned? Put the autopilot aside, and put having a less experienced sailor at the helm aside (she owns and single hands her own Bristol 30, but she's really conservative). How to prevent/minimize it in the future? How to get out of it? Blowing the preventer causes exactly what the preventer is to prevent (an uncontrolled gybe). Rolling up the jib (a 150% on a 43' boat) is a major chore. Shift my helm from trying to go back down, and instead round all the way up and around? Blow the jib sheet and allow her to round up?

We recovered (and my crew and I are still good friends). But this should be a significant learning moment, and so far I haven't figured out what I should have learned.
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Old 26-01-2023, 11:47   #2
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Re: Preventer -- and an accidental gybe

Sounds like you basically came to hove-to what with the back winded main, albeit with excessive sail area causing the steep heel. The boat was placed into stable configuration and non-responsive.

I would have eased the foresail to allow to make way and thus regain steering and then would have reduced sail.

Your preventor did what it was supposed to do, all good.
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Old 26-01-2023, 12:01   #3
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Re: Preventer -- and an accidental gybe

Sounds like you ended up in some sort of hove-to position. Could you/did you complete the gybe once you get to the helm? If you hardened up on the jib, even slightly, that should get you into a reach which would give you forward drive, which would give you steerage. Trying to drive the boat to leeward with the mainsail locked by the preventer would be tough.

I have no great wisdom on lessons learned, except to say we almost never sail DDW on auto helms (electric or vane). Maybe in the most controlled conditions, but otherwise it's just too risky.

I run a broad reach if I want auto to be in charge.
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Old 26-01-2023, 12:20   #4
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Re: Preventer -- and an accidental gybe

If you had the preventer on a cleat/winch, couldn't you ease it slowly to get forward drive? Or would that be too risky with the backwinded main in those conditions?
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Old 26-01-2023, 12:24   #5
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Re: Preventer -- and an accidental gybe

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Originally Posted by LifesBetterWhenYoureBeating View Post
If you had the preventer on a cleat/winch, couldn't you ease it slowly to get forward drive? Or would that be too risky with the backwinded main in those conditions?
The geometry of preventer is really weird. When tight, it does very well. But it takes very little easing before the main can come flying across. I've learned this by setting it hand tight and seeing that it doesn't hold the main out.
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Old 26-01-2023, 12:32   #6
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Re: Preventer -- and an accidental gybe

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Originally Posted by Mike OReilly View Post
Sounds like you ended up in some sort of hove-to position. Could you/did you complete the gybe once you get to the helm? If you hardened up on the jib, even slightly, that should get you into a reach which would give you forward drive, which would give you steerage. Trying to drive the boat to leeward with the mainsail locked by the preventer would be tough.

I have no great wisdom on lessons learned, except to say we almost never sail DDW on auto helms (electric or vane). Maybe in the most controlled conditions, but otherwise it's just too risky.

I run a broad reach if I want auto to be in charge.
I think that you are trying to suggest what in hindsight I have concluded. Some variation of jib control and helm to allow me to continue further upwind, rather than my efforts to get back down wind and gybe back. As everyone has suggested, I was indeed hove to, stable and stationary.

The challenge of course is the back winded main prevents or at least fights any forward drive from the jib. As the boat would come closer to head to wind, the back winded main might actually become the driving force, and I could actually begin moving astern.

When the wind gets truly forward of the beam, say a 70į wind angle, it would become safe to blow the preventer, as the main would only flop over to leeward in a luffing configuration.
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Old 26-01-2023, 12:39   #7
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Re: Preventer -- and an accidental gybe

How is your preventer rigged? It should come from the bow, outside your shrouds, to the end of the boom. As you ease, the preventer will wrap around the shrouds to keep an angle on the boom. Rigged this way, and on a winch, you should be able to ease it at least to near centerline, where the mainsheet can take over. So, as you ease it, someone else trims in the mainsheet.

If that doesn't work on your boat(because of the position of the shrouds), start the motor, and don't turn against the backwinded main, but with it, and turn the boat 360 (err 300ish?) degrees the other way to get back on your heading. Depending on conditions and if the jib is working, you likely could even do that without the motor.

You could/should practice both maneuvers in light winds, so you get a feel for the process.
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Old 26-01-2023, 12:41   #8
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Re: Preventer -- and an accidental gybe

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Originally Posted by LifesBetterWhenYoureBeating View Post
If you had the preventer on a cleat/winch, couldn't you ease it slowly to get forward drive? Or would that be too risky with the backwinded main in those conditions?
I had an accidental gybe last summer with the genoa poled out and the main prevented tight ... I put the preventer on a winch and eased it, but it did not generate any forward drive, the boat remained hove-to, but it did allow me to bring the boom far enough aft to release the preventer and complete the gybe in a fairly controlled manner. One thing I did learn was that, although the preventer did its job, the forces on the preventer are huge and got bigger as I eased the boom aft, and it wouldn't hurt for me to beef up the preventer rig a bit.

What I probably should have tried, but didn't, was rolling up the genoa and hoping that would help the boat round up. Although the boat was heeled over quite hard and taking waves on the beam, it was stable so furling the genoa would not have been too much of a challenge ... but my mind was focussed on doing something with the main, which was the sail that was causing problems.

On reflection I'd say that it wasn't a scarey event, because the preventer worked, but it certainly was intimidating because a failure in the preventer at that point would have been a disaster.

As a bonus I learned just how far by-the-lee my boat will sail before gybing, and it is much more than I expected.
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Old 26-01-2023, 12:57   #9
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Re: Preventer -- and an accidental gybe

agree the autopilot is not such a good idea DDW. it just doesn't have enough accuracy IMHO.
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Old 26-01-2023, 13:00   #10
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Re: Preventer -- and an accidental gybe

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agree the autopilot is not such a good idea DDW. it just doesn't have enough accuracy IMHO.

Yes. That was my main thought, and is our practice. We never run DDW on auto in anything other than ideal conditions. Better to take a broad reach and do some extra gybes.
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Old 26-01-2023, 13:11   #11
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Re: Preventer -- and an accidental gybe

I think your ideas of turning off the autopilot and hand steering in those conditions is a good one. I also think it is a good idea to have the main reefed to whatever is appropriate if you were not running. It is easy to be lulled into running with too much sail up imo. Sounds like too much sail was up for the conditions. When you were hove-to you had the main trying to drive the stern around while the headsail was working hard to to push the bow back downwind, you were probably going sideways pretty fast, so the rudder won’t do much in that case. You mention that the boat was heeled over and taking waves over the beam. I assume you had the jib poled out but that would have been a good time to forget the main momentarily and release the jib sheet and bring down the pole or just furl it until the pole approaches the stay. The stern should come around and round you up then so you can luff and take the pressure off the main. Personally I would not be trying to turn downwind and return to running after a bad gybe until I had checked everything for any damage, and reefed the main, or furled it altogether, if it is getting too windy for safety.

Edit: oops, I see I am responding to two different posts. Well it still applies.
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Old 26-01-2023, 13:33   #12
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Re: Preventer -- and an accidental gybe

Thanks for posting -- this is actually a comforting report. When sailing near home on the Hudson river with narrow channels, heavy shipping, and variable winds, we are often poled out wing on wing DDW, but either forced to turn a bit or hit with changing winds, so we get a little backwind on the main. With preventers rigged permanently on both sides, we don't gybe, and of course are always at the helm, but nevertheless I always wondered what would happen if we got caught by wind at a greater angle.

I debated using a boom brake but didn't like the idea of putting that much pressure on the flat side of the boom only a third of the way out, plus didn't want the lines in the way of going forward.

All that being said, I wonder what would happen if a preventer were rigged with some sort of friction slow release like a boom brake? Of course, as the OP points out, once the preventer line from the bow got close to the mast, roughly as the boom passed the centerline, it would lose any further ability to prevent, so you would still get some slamming from the boom, but you would cut out a lot of it this way. Anyone ever try something like this?
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Old 26-01-2023, 14:24   #13
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Re: Preventer -- and an accidental gybe

I will post some of MY experience, some similarity to yours but not exact. You will have to determine if it makes any sense in your situation. Just offering a different possibility.

44’ cutter, 49’ with bow sprit. Twice I broached the boat when caught in an unexpected and sever wind gust. Both time I was at the helm and immediately dumped the main. Both times she was very slow to come back up. The second time in particular it was quite obvious the genoa was holding her down. In short she was “pinned down” until I furled the head sail. She also had weather-helm issues.

Cutting a very long story very short and getting to the relevant bit, the genoa was mismatched to the boat and conditions. My Center of Lateral Resistance is a bit more forward than normal. The genoa Center of Effort was so far aft it was at or behind the CLR enough that the genoa would not counter the mains weather helm.

Once I dug up the designers original sail plan, and found the proper working jib the problems went away.

Yes there were other factors but this was the predominate influencer.

The am thinking that a fully extended 150% headsail may contribute to her being slow to come up.

Again, just an additional thought.
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Old 26-01-2023, 14:27   #14
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Re: Preventer -- and an accidental gybe

Excellent thread!

There are many threads and many articles on how to rig a strong preventer and how not to do it, but few on ...
  • Risk of cockpit-in-the-water knockdown (tender or water ballasted) mono or capsize/pitchpole (multihulls).
  • Recovery. You can ease the preventer (must be releasable), but it will still slam across rather fast once the line gets to a certain angle). The traveler and boom brake can also be part of the process.
Capsize/Knockdown. One some boats this may be a greater threat than the jibe! On multihulls, the traveler should have been all the way down (no vang and best practice anyway) and locked there, so the jibe will not shift the boom that far. From there, the boom can quickly be eased (traveler). and the boat will be on the opposite tack with loose sails. But this may be too late, so running WAW with multuhulls is not for strong weather. When it gets dicy, jibe the main and reach deep. I'll run WAW in certain conditions to enjoy the smooth ride, but I stop before it gets scary. I also have the luxury of not needing to pole-out the genoa, so it is easy to jibe.

I've seen images of canting keel boats that jibed with a preventer. They tend to get held down with mast nearly level until the boom is let across and the keel is centered. I can image there is a good risk of cockpit flooding on a good many water ballasted or tender boats. That can lead to sinking within minutes.

Recovery. You need a way to ease the boom under some control. A wide traveler. Even with a narrow traveller, if it is work of running a preventer, the traveler should be locked to leeward and the vang snug. A boom brake cannot serve as a preventer (it will either slip or break the line or break the boom), but it could help in the recovery.

Thoughts?


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Old 26-01-2023, 14:46   #15
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Re: Preventer -- and an accidental gybe

One way Iíve handled this is to ease the main halyard (usually only a foot or two).
This takes the power out of the main and allows the headsail to bring the bow around.
Then either raise the halyard again (youíll probably need to ease the sheets and/or traveller) or - more likely - put a reef in.
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