Crash Gybe!

[thinwater]

Originally Posted by wholybee

I agree with this. But further, a brake differs from a preventer in that it goes from one rail, to the boom, and then to the other rail. The entire system is under tension, not just the leeward side.

So, with a preventer, the attachment point on the boom can be outside the attachment point on the rail(or bow) But with a brake, the attachment point on the boom can never be so far aft that it goes outside the attachment point on the rail.

I hope that makes sense without my drawing a picture.

Yes. All of that agrees with the instructions and the engineering. When loaded, one side is under 3-7 times more tension than the other, but both are tensioned. Like a winch, without back tension they don't function.

[ShineOn]

Three thoughts:

1. I don't like boom brakes, don't ask me why - I don't know, just never felt comfortable with them
2. UV damage to the line is a very likely cause of stripping the line here, it is extremely difficult to damage the line like this otherwise
3. The mechanics of a boom brake may work best with a slightly stretchy line to take some shock loading out of the system, the latest modern "zero" stretch lines transfer a lot of shock loading (the reason climbers use dynamic ropes to reduce impact of a fall, while rappelers happily use static ropes).

Safe sailing.

[thinwater]

In fact, it is well know among climbers that cam devices can tear the cover off a rope at about 50% strength in a fall. Climbers NEVER use ascenders to catch a fall of more than a few feet, and they try to avoid that. For top rope soling, using two ascenders in series is recommended.


Of course, if the cover had not torn, the boom may have snapped.

[carstenb]

TW. If you look at the pic I posred showing the brake moved forward yyou will see that there is now little angle from the brake to the fastening point on the deck ( this is the teason the brake was mounted so far aft on the boom. To set up a good angle from it to the cleats where it was attached)

Any thoughts on how much angle is necessary?

I welcome comments from others also

[Boatyarddog]

Originally Posted by carstenb

We are on our way down the west coast of the US. We had a crash gybe in the middle of the night (don't these things always happen in the middle of the night?) Fortunately, no one was hurt and we managed to get control of the boom & mainsail despite the traveler car being destroyed.

I think this might be interesting for others - there are some learning points here - the biggest one is that a boom brake needs to be backed up with the line on a winch and not just through a clutch. Feel free to ask any questions you want - I'll try to answer

Disclaimer - Vinni and I have been at sea for over 6 years now - we've made every mistake you can think of, and probably quite a few that lie outside the boundaries of imagination. Here's the story, pics at the bottom. One pic shows the stripped brakeboom line. The other shows the second juryrig we made to keep the boom centered.

WE managed to limp into SF a day or so later on only a poled out genua.
Just so we have something positive to boast about - sailing under the Golden Gate Bridge meant that we had made landfall in both NYC and SF - on the same boat - not too many cruisers can say that.

That evening, as we approach the critical point of rounding Cape Mendocino, the wind freshens; blowing 20-25 knots and the swells rise to 2-3 meters. It is still comfortable sailing, our mainsail is in the second reef. Capri blasts along making 7-8 knots.
We got 2/3’s of the way round the Cape before the acceleration winds began to pick up. It is now gale force (30+ knots) and the swells have risen to 3-4 meters (12-14 feet). Worse, we have to gybe. Carsten hates to gybe at night. It is difficult for him to orient himself out on the foredeck in the dark when he has to take the poled out genua in from the one side and pole it out to the other. Adding in that the deck is rolling and pitching in the high waves, the wind is shrieking, and he is, as he says, “not a happy camper”. But there is no way around it, we have to gybe to get closer to shore and out of the swells that are growing larger by the minute.
Despite Carsten cursing up on deck, the gybe is uneventful. Carsten takes over the watch and I go below for some well-deserved sleep and a chance to get warm again.
I wake when I hear a huge crash above my head and the Capri jerks around like a top. We’ve had a crash gybe. A big wave came from the side, throwing Capri around. Carsten could do nothing and the wind got behind the mainsail. Carsten says, “Shit, you need to come up right away”, as he shines a flashlight up on the sail to see how bad things are.
“We have a major problem”, he adds.
We have a boombrake mounted to prevent a crash gybe. Unintentional gybes can easily happen when you are sailing at 150-160 to the wind and the waves are running 4 meters. Our boombrake is supposed to either act as a preventer stopping the gybe or at least act as a brake, slowing the entire process down so everything happens in slow motion and there is no damage. Other boats have lost their entire rig in a crash gybe.
So how did it happen if the boombrake is supposed to prevent it? The line from the boombrake goes through a clutch that keeps the line taut. With the line taut, the boombrake allows no movement of the boom. When we look, we see that the outer covering of the line has been peeled back like a banana peel. Once this happened, the clutch can’t hold on to the inner core, which is not as large in diameter as the line with the outer covering. The line then simply slipped through the clutch and the boom gybed.
So why didn’t we also have a preventer mounted? A preventer is another line that is stretched from the back of the boom to a point far forward on the deck, making it impossible for the boom to move. First, because the boombrake should function as well as a preventer. In fact, the boombrake DID function. The reason the outer covering of the line stripped off was that the boombrake was holding the boom (and sail) against the tremendous forces applied by the wind. Secondly, Carsten feels we have so many lines running up on the deck that he is in danger of tripping (and potentially falling off the boat) if we have many more.
What could we do? Not only had the boombrake line stripped (that was a minor problem to fix), worse, the shackle on our traveler was broken in half. This was a serious problem. Without the traveler, there is no place to hook the boom.
To put it mildly, we were in deep ****.
The boom was slammed tight up against the shrouds and held, plastered there, by the wind. We couldn’t sail with it like that. Our first order of priority was to somehow get it back to the middle so we could drop the sail or figure something else out. Until we did that, we could not control the boat. Worse, if a wave threw Capri in the wrong direction, the wind would get behind the sail and we would have another crash gybe, just in the other direction. This time there would be no brake at all. The first gybe, the line covering stripping and the shackle breaking on the traveler must have lessened the speed and force of the gybe.
Carsten acts quickly, diving into the cockpit locker and coming up with a long line with a carabiner hook in the middle. He dons a lifeline and crawls out on the deck as the waves crash over him. I’m desperately trying to hold Capri on a course so we don’t get another crash gybe in the other direction. If Carsten gets hit by the boom, he’ll die. Carsten manages to get the carabiner hooked into the block on the mainsail sheet and then he runs them back to a winch (through the genua car blocks) on either side. Now he can crank in the sail to the middle and control it.
Carsten then ties the mainsail block to the remnants of the traveler car with a length of Dynema. Dynema is ultra-strong rope. It will hold anything, almost no matter what the load. Meanwhile I’ve tried to lay Capri with her stern directly up in the wind. The reader has to understand here that in these high waves, it is simply not possible to turn Capri into the wind. If we try that, we risk broaching, or worse, a knockdown.
Now I’m unlucky. A freak wave crashes in from the side, throwing Capri around and we have a new crash gybe. The soft shackle of Dynema Carsten has rigged, parts with a pistol shot as the line is cut by a sharp edge. Carsten curses up a storm, some of it aimed at me (fair enough). Not only did the crash scare the hell out of him, he almost lost a finger as the lines tightened. Fortunately, it was only “mashed”. Carsten dons his lifeline once again and crawls out on deck to retrieve the boom that is now plastered up against the rigging. Same procedure as before.
We’ve got the boom centered again. Carsten mounts a new and heavier soft shackle in a different way so there is no way it can be cut. We agree that we need to drop the mainsail and continue on the poled out genua. The mainsail, of course, doesn’t drop by itself in this heavy of a wind. Someone has to go on deck and haul it down by hand. Once more Carsten grabs his lifeline and crawls up through the waves running over the deck. This time he ties himself to the mast so he can use both hands to haul the sail down. We’ve agreed that we can run only a reefed genua. We roll the genua halfway out and we’re making 6-7 knots. The waves are still enormous.

Not sure which B Brake your using, but I wouldn't rely on it totally to "catch" a unintentional Gybe.
Back it up with a static line.

Better yet incorporate a snubber into it to cushion it, should your B.B. Or line break.
Extra insurance.

It's hard to tell when a shackle may part, change them out, if they're older or not that robust.
Inspect your gooseneck often as these get forgotten as well.

Glad your okay.
Boatyarddog

[thinwater]

Originally Posted by Boatyarddog

Not sure which B Brake your using, but I wouldn't rely on it totally to "catch" a unintentional Gybe.
Back it up with a static line.

Better yet incorporate a snubber into it to cushion it, should your B.B. Or line break.
Extra insurance.

It's hard to tell when a shackle may part, change them out, if they're older or not that robust.
Inspect your gooseneck often as these get forgotten as well.

Glad your okay.
Boatyarddog

Let's discuss snubbers.


1. I've tested the Gybe Tamer on several boats. I'm not sure if it is still produced. It's hard to balance enough stiffness for hard windward sheeting with enough softness to cushion a jibe.




2. Dynamic traveler line (climbing rope). Quite a few sailors have tested this over long periods. It works with few down sides. I've used it for years. The only downside is that the traveler cannot be on an end stop. Yes, it stretches a bit in the puffs, but all this does is momentarily lower the traveler an inch, which is not a bad thing.

3. Dynamic pendant. You could insert a short length of dynamic rope above the tackle. I'm thinking about doing this on my F-24. I have tested it on other boats. Or I might try the Gybe Tamer again (I did have it on this boat for a time).
4. Nylon mainsheet. Stretches too much, doesn't absorb enough. No dice.



Other suggestions?

[thinwater]

Originally Posted by carstenb

TW. If you look at the pic I posred showing the brake moved forward yyou will see that there is now little angle from the brake to the fastening point on the deck ( this is the teason the brake was mounted so far aft on the boom. To set up a good angle from it to the cleats where it was attached)

Any thoughts on how much angle is necessary?

I welcome comments from others also

as far as I know, all of the makers have the same basic instruction in their manuals. The anchor points should be as far outboard as practical, and the distance from the anchor to the mast, and from the gooseneck to the the saddle, should be the same. The saddle must must scribe an ellipse through the air, with the rope connecting the foci and the co-vertex, except the foci are on a different plane from the elipse. https://en.wikipedia.org/wiki/Ellipse


If the height of the boom, the spacing of the anchors, and the distance down the boom are equal, The length of the line at 90 degrees is 3.23X. When the boom is centered the length of the line is 3.46x, requiring some (7%) stretch and slowing the jibe somewhat at peak force. (Note that this stretch is spread over the full run of the line to the cockpit, so probably only a few %.) If the saddle is farther aft, it will swing outside the anchors and you will have no control. If the line is twice as far out the boom, the line length becomes 4.57X at 90 degrees and 4.89x in the center, again about 7% stretch. But there was no control through much of the swing, and the forces increase because the angles are much worse when the swing starts.


The 7% (3% overall) stretch pretty much means it needs to be polyester. Nylon is too much, Dyneema not enough.

(please check my math).

[nmccubbin]

Deciding where to attach the preventer to the boat is complex.
When sailing normally, a line to the bow gives the best angle. A line down to the toe-rail amidships has a horrible angle that will multiply the load when gybing by up to ten times.
As you said, a preventer line from the bow has a bad angle AFTER the gybe.
So far, our accidental gybes have been unspectacular with a line to the bow, since the sail came across slowly to not far past amidships and we were able to control it.
If stuck, we could have then attached a line to the opposite toe-rail

[Brian Renwick]

Originally Posted by wingssail

The strongest force occurs when the boom has already started to swing. The momentum is immense. And the leverage is much greater against the mainsheet and traveler (and boom brake) if they are positioned at the mid boom.

I think it is critical that two things are done to be able to stop the boom from coming across if the wind gets behind the mainsail:

1. A preventer from the end of the boom to a strong point forward (AT THE WIDE PART OF THE BOAT) then back to a winch.
2. Putting plenty of pressure on the preventer so that the boom has no slack to get started moving or get any velocity going.

If the boom is secured in its position and the preventer has a good angle and is attached to strong points then even if the wind gets behind the sail the leech of the main sail may only fold over and while the wind will fill the back of the sail the boom hopefully not build any momentum and will hold in its position.

Of course this can still lay you over, but things can be managed. (You slowly release the preventer and let the boom come across, the recovery the steering and get things going properly.

This has happened on our boat, in about 26kts true (that's the last I remember seeing, the wind was building) and I was careless when I took over the helm from the autopilot and I turned down too far and got the wind behind the main.

The main filled from the back and rounded the boat up (rounded down, technically speaking), then pinned us on our side. But the preventer held, everything was calm, except we were on our side, completely.

My other mistake (other than carelessly turning the boat and jibing) was having the preventer on a cleat instead of a winch. It was hard to release, like impossible, with one hand while I still held the tiller with the other. Judy came up and we got things handled but not before the mainsail ripped in half.

The key point I want to reiterate: The preventer goes from the end of the boom to the widest part of the boat, not to the bow. Some people run the preventer to the bow but then, when the boom is being released, you lose the angle and you lose all leverage.

I'm not going to comment on the boom brake because I have little experience with them but having it in the middle of the boom adds greatly to the pressure on it.

I guess a third point is, be careful when sailing on autopilot. The wind can change and put you close to a gybe.

One point to be aware of if leading the preventer to a midships point: extra leverage if the angle down to the deck is high. Perhaps a compromise will be appropriate, if a point further forward is still quite beamy. There’s a good accident investigation report which I recommend:

https://www.maritimenz.govt.nz/conte...eport-2016.pdf

This accident resulted in the deaths of two of the five crew, and the loss of the rig.

[thinwater]

Originally Posted by wingssail

The strongest force occurs when the boom has already started to swing. The momentum is immense....

Interesting. I've jibed boats with boomless mains and there is still a good slam, but less and different.


There is still momentum. Consider that the air on both side of the sail must suddenly go from 10-20 knots to nearly zero, and that this bound layer may be about as heavy as the boom. Of course, the stop is a little more cushioned, but it drives the gooseneck forward and contributes to the rigging loads. How abrupt it is depends on the sail materials and battens; it can be a real bang on a laminate sail with full battens.


Interesting.

[JMaav]

Very interesting discussion. I think you have all covered the boom brake issues well.
My question relates more to, essentially, single handling at night on a downwind tack.
First, I remove whisker poles and similar bow necessities when by myself at the helm. (Too many opportunities for tacking issues), and often reduce jib size when running both sails. Sacrificing speed for safety at night.
Alternatively, Being on third reef, may have warranted dropping the main, as you’ve already indicated.
Curious if you might have lost more than 2-4 knots of speed in conditions described with main down.

As you already know, sailing downwind at night requires constant feel for what is coming from behind. Preparing for that broaching gust of wind that can often occur in wind conditions you describe might be worth more forethought in future.
I have been knocked down many times, even when I prepare.
Sometimes taking it slow is the safest approach.
Smooth travels from here-on.

[carstenb]

Originally Posted by JMaav

Very interesting discussion. I think you have all covered the boom brake issues well.
My question relates more to, essentially, single handling at night on a downwind tack.
First, I remove whisker poles and similar bow necessities when by myself at the helm. (Too many opportunities for tacking issues), and often reduce jib size when running both sails. Sacrificing speed for safety at night.
Alternatively, Being on third reef, may have warranted dropping the main, as you’ve already indicated.
Curious if you might have lost more than 2-4 knots of speed in conditions described with main down.

As you already know, sailing downwind at night requires constant feel for what is coming from behind. Preparing for that broaching gust of wind that can often occur in wind conditions you describe might be worth more forethought in future.
I have been knocked down many times, even when I prepare.
Sometimes taking it slow is the safest approach.
Smooth travels from here-on.

We always reef down when the winds grow
We are always at least in the 2nd reef at night. We should have dropped the main well begore the gybe especially when the swells grew to 12-14 feet
Our bad
With those swells there is too much of a chance of a broach resulting in the gybe

We have many times run on just the poled out jib

[barryglewis]

[QUOTE=JPA Cate;3678382]First, let me say, sorry the Cape Mendocino gale got you. It is a well known "bad spot" to norther Calif. ocean sailors. I am so glad no one was seriously injured, and sorry about the mashed finger.

Assuming you have both primary and secondary winches, instead of the "Boom Brake", you can rig double preventers. One of the great things about them is that for only one more line on deck, you can control all gybes. And when the shackle on the traveler breaks, or the boom breaks, you can control what is left of it with the preventers, and center it so that it will not flail from side to side.

We've done this when the shackle broke, when the traveler blocks broke, and even just for centering the boom so as to lower boom loads by avoiding overtightening the main sheet at anchor.* Ours are attached about 1/3 of the way aft on our boom, [just aft of the vang attachment] to a block forward, right by the capshroud, then led aft to the secondaries. The one on the same side as the boom is used like a single preventer tackle, with the benefit that in a seaway, it is easy to ease it across fast as we gybe, and then set the one on the new side.

We keep them led and ready to use, and we usually use the autopilot to gybe, so that one of us eases the 17 ft. boom across, and the other is already beginning to set the preventer on the new side, all done from the safety of the cockpit. We roll up the headsail before gybing, then set it on the new gybe. Yes, there are lines to avoid on deck, but the advantages with a big mainsail of having the dual preventers are enough to make us put up with the extra line per side.
.......
.

Ann

*]

This is almost exactly what we use on Risky, with a similar size boom, and 500sq ft mainsail

[jipcho]

Carstenb,


Everyone who has sailed the oceans for long enough will have experienced an accidental jibe, and a resulting failure somewhere (I've broken my traveller shackle, as well as a brand new heavy steel padeye to which I attached the sheave forward of the boom through which a preventer was led back to a cockpit winch. I have often single handed for days at a time, and was prepared for a controlled jibe by always having 2 preventers ready to go at all times. I'm not familiar with boom brakes, so I can't comment on their usefulness.
From your narrative and answers to some of the very good responses, I think you hit the nail on the head when you wrote:


-" we were already in the third reef on the main. I cheerfully admit that we should have dropped the main and just run on the jib ( as we did after the incident"


This is absolutely correct. In 25 plus knots of wind, I would have put away my mainsail, especially before nightfall, and when approaching the notoriously dangerous Point Mendocino. You could have made the same speed under jib alone, and I would have reefed the jib as well. I always slow my vessel down at night. Especially when alone, I don't want to deal with a crisis, and don't mind taking an extra hour to reach my destination.



You also wrote:



"We frequently do set preventers. From end boom through a cleat. But our foredeck has a poled out genny set in bridle. A dinghy laud upside diwn and tied down. 6 jerry cans a side. On the way up front I aLready have to step over the mainsail sheets sometimes a genua sheet

That said, s..t happens"


I had an inflatable dinghy which I took apart, rolled up, and stored below deck during any long passages. I can understand that if you had a rigid dinghy that might not have been possible, but I am not a fan of lining my deck with jerrycans of fuel. My fuel tanks were small, only 50 gallons, but I carried my my extra 50 gallons of fuel along my stern rail, where they were easy to access, and out of the way.



Anyway, we learn by making mistakes, and thankfully you didn't suffer any serious consequences.



Enjoy your sailing. I'm stuck on land (5 years now, after 15 years of live aboard ocean cruising).

[wingssail]

Originally Posted by carstenb

We frequently do set preventers. From end boom through a cleat. But our foredeck has a poled out genny set in bridle. A dingy laud upside diwn and tied down. 6 jerry cans a side. On the way up front I aLready have to step over the mainsail sometimes a genua sheet

Originally Posted by jipcho

I had an inflatable dinghy which I took apart, rolled up, and stored below deck during any long passages. I can understand that if you had a rigid dinghy that might not have been possible, but I am not a fan of lining my deck with jerrycans of fuel. My fuel tanks were small, only 50 gallons, but I carried my my extra 50 gallons of fuel along my stern rail, where they were easy to access, and out of the way.

I agree with jipco about keeping the decks clear. We think that there should be nothing carried on decks which might get entangled with lines or impede your progress if you need to go forward to say nothing about blocking your vision and, in heavy weather, risk getting knocked adrift by seas. The same for stuff lashed outside of the lifelines.

I recall a woman who arrived in port after a very difficult crossing who reported in a shaky voice, "Bill almost got killed trying to get the kayak back on board."