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Kenomac · 25-07-2019, 22:52

I’m going to re-enter this discussion just to make two important points:

1. After reading the complete report, its obvious to me that 90% of those responding on this thread haven’t taken the time to do the same.

2. This occurance can happen to anyone, its not about the preventor failing, its about a cascade of events.

We presently own two boats, one is an Oyster 53 which had the exact same event occur just three weeks ago due to the same cause... an autopilot compass malfunction. Thankfully, nobody was hurt, possibly because I was the only one on deck when it happened. The sea state at the time was different, 20-25 knots from the stern, boat traveling at 8 knots so the wind being experienced was around 15-18 knots with a 1 meter chop on a bright sunny day perfect for sailing. Our other boat is almost identically sized to the doomed vessel at 36 ton and just unter 20 meters in length, so yes I can play out the possibility of this happening in my head.

The two people who perished were clearly the result of a cascade of events, first the one fellow moving across the main sheet to get to the steering wheel and being struck by the main sheet. These things happen extremely fast, people forget to think and sometimes just react... stuff happens. The swinging boom and main traveler then took out the steering and hydraulics... yes I can see the possibility of this happening on our 62 which is hydraulically controlled.

This was NOT about a preventer failure.... it was about an autopilot malfunction which lead to a preventer failure which resulted in some quick reactions leading to two deaths.

It can happen to any of us even if one has what appears to be a stout preventer rigged properly. It happened to me... it happened to them... it can happen to you.

I had a fellow onboard at the time of the gybe who’s a good friend and sailing companion, but not a sailor. After reading the full report, I’m just glad he was down below using the head when this happened, because he’s also the kind of person who just reacts without thinking through the consequences of his actions. This could just as easily have been me, through no fault of my own that you’re discussing.

Please review post #3 for a description of what happened to us.

Kenomac · 25-07-2019, 23:24

Futhermore... to believe this same event can’t happen to you because you have “X” for a preventer or have “Y” as a boom brake is simply foolish IMO. A cascade of events can happen to anyone.

**Dockhead** · 25-07-2019, 23:26

Quote:

Originally Posted by Kenomac

You’re sadly mistaken....something WILL break. Ours was tight.

The physics don't lie.

I've never seen your setup, and don't know the angles involved or the strength of the cordage and anchor points. It was obviously not up to the job if it broke from simple backwinding of the main, but mine is.

Nikki S · 25-07-2019, 23:38

I am always debating how best to rig the preventer on our 49ft. There is nothing that points to a preventer ever being rigged before we bought her, third-hand. But someone must have rigged something to get from Sydney to Whitsundays multiple times as per the log book....The options are limited without adding some hardware.... I was taught one way on RYA courses, but my husband prefers advice from experienced friends’ , which differs from what I was taught. It’s such a standard necessity that I can’t understand why it wasn’t an obvious part of the rigging seeing as everything else was left onboard by the previous owner, from harnesses to soft drinks ....

**Dockhead** · 25-07-2019, 23:52

Quote:

Originally Posted by Kenomac

Futhermore, and to believe this same event can’t happen to you because you have “X” for a preventer or have “Y” as a boom brake is simply foolish IMO. A cascade of events can happen to anyone.

I agree with this.

You can design and operate your system to deal with various sets of conditions, but when you encounter some unplanned-for combination of conditions, then all bets are off.

How to deal with that, and minimize the risks is called seamanship.

For example, my preventer will hold the backwinded main with a safety factor of more than 200%. But it will not hold the boom if the boom gets dipped, and it will not hold the boom if there are dynamic loads.

Therefore, I don't use the mainsail in really strong conditions, above F8 or when the sea is seriously up. I put away the mainsail and secure the boom amidships. And I don't rely on the topping lift and mainsheet to hold the boom; I rig a pennant to a midship cleat. That

I would not want a boat with an 8 meter, 700kg boom, not ever. I don't know what kind of crew and what kind of gear you would need to have proper control of such a beast. I don't even like my own boom, which is 6 meters long and I guess weighs 80kg or something.

I think this story settles it for me -- for a boat the size of Platino, I would want a ketch rig.

**Dockhead** · 26-07-2019, 00:04

Quote:

Originally Posted by Nikki S

I am always debating how best to rig the preventer on our 49ft. There is nothing that points to a preventer ever being rigged before we bought her, third-hand. But someone must have rigged something to get from Sydney to Whitsundays multiple times as per the log book....The options are limited without adding some hardware.... I was taught one way on RYA courses, but my husband prefers advice from experienced friends’ , which differs from what I was taught. It’s such a standard necessity that I can’t understand why it wasn’t an obvious part of the rigging seeing as everything else was left onboard by the previous owner, from harnesses to soft drinks ....

My advice would be to sort out, with the help of a professional rigger if necessary, a bulletproof preventer setup. It's a life or death item of gear, as you can tell from this case.

The engineering is pretty straightforward -- you will get the best angles running the preventer to the bow, and most boats can use a bow cleat for this. But you don't have a fair lead to a bow cleat, or if these are not strong enough, you will need strong pad eyes in the rail, through bolted through the hull-deck joint and with strong backing plates. See the broken pad eye in the accident report

.

How to attach to the boom depends on the boom. I guess the boom end is the best place on most boats, but note the question above about the angles. In any case, you must be sure that the attachment is strong enough.

Then obviously the cordage needs to be strong enough, considering anything in the preventer which can weaken it, like a knot or a splice. Note the discussion about this in the accident report. Unlike the Platino crew, I trust quality snap shackles, and use Wichard forged snap shackles on the ends of my preventers. So there are no knots involved. I am using dyneema cordage which does not lose strength to minor chafe, as the cover is non-structural. Normal poly double braid may lose quite a lot of strength due to quite minor scuffs, and UV degradation.

**Don C L** · 26-07-2019, 00:29

While I agree a preventer should be as strong as possible, and though the geometry of what you describe makes sense, I am still not sure how practical it will be to run from the boom end to the bow, (and remember that the preventer will have to be run back to the cockpit so it can be released quickly if needed too) compared to the more typical set-up. Also, personally, I'd prefer to rely on a chainplate bolted through the hull rather than a pad eye through the hull/deck joint. But beyond all that, yes I think things should be overbuilt, but then never rely on them too much. That may seem illogical but it makes sense to not get lulled into a false sense of security by overbuilding any particular thing. Focusing on the preventer solely here risks not seeing the hardware failure was only one of a collection, and cascade, of failures as some have noted. Certainly, if they had had a more robust preventer, and it's pretty clear they should have, things may not have been as tragic. But as many here have pointed out, there were ways to have avoided being in that situation in the first place.

Kenomac · 26-07-2019, 00:36

I would never trust a snap shackle to handle any kind of shock load, and I think nearly all professional riggers would agree. We had one oversized snap shackle sized for a spinnaker halyard for a 60ft yacht break five weeks ago under just a 280 pound shock load. Fortunately, a tied on safety rope was in place at the time and my mate only dropped one foot from a height of four feet.

I would never trust one of those things, we always use double bowline or figure eight knot when heading up the mast olong with a safety line. Snap shackles are NOT made to take on a shock load. I wish I still had the broken one lying around to show, but I must have thrown it out.

**Jim Cate** · 26-07-2019, 00:50

Quote:

The sea state at the time was different, 20-25 knots from the stern, boat traveling at 8 knots so the wind being experienced was around 15-18 knots with a 1 meter chop on a bright sunny day perfect for sailing.

Ken, I submit that if your preventer failed under such conditions it was woefully under engineered. Even with a full backwind, with only 15-18 AWS it should not be anywhere near failure point.

This does not represent a cascade of events leading to a failure, it is simple undersizing of the gear. I'm surprised that you can't see that. The failure occurred under modest conditions without extenuating circumstances, at least as you have twice described it, so whether it was due to inadequate size of line, a knot or splice weakening it, chafe or sun damage weakening it... it WAS TOO WEAK, or it would not have failed under these conditions.

I agree that no matter how strong it might be, an event that overcomes it can be imagined. This was no such event.

Jim

RaymondR · 26-07-2019, 01:03

Let us review what may have occurred had the preventer not failed.

The boat is careening down wind with a following wind and sea running against a considerable swell. The autopilot is unable to respond to a combination of sea, swell and wind loads and this causes a jibe. The boat swings beam on to the sea and, because of the adequately rigged preventer, suffers a knockdown. Crew members at the wheel and in the cockpit are thrown into the sea. Crew members below are injured by being thrown across the extensive cabin spaces. etc. etc.

I would call the report comprehensive but not amazing or incredible as like most of these after-the-fact reports it starts from the viewpoint of a perfect world. These things are going to happen. If Boeing, probably the worlds most experienced aircraft designer and builder, and fully professional airline pilots, overall probably the most highly trained group of equipment operators, still manage to let aircraft fall out of the sky, what hope is there for the amatuer sailor.

We are going to pit ourselves against the sea, and we are going to pit ourselves against the sea in a vast variety of vessels, we, and the vessels will encompass a vast spectrum of capacities and capabilities and occasionally we are going to lose the gamble and suffer the consequences.

Kenomac · 26-07-2019, 01:11

I think its time once again to exit this discussion... leaving it to the CF team of experts to critique and Monday morning quarterback.

My warnings and opinions based on personal experience rather than theory, have been clearly stated.

Goodbye

DumnMad · 26-07-2019, 01:23

Quote:

Originally Posted by Dockhead

For example, my preventer will hold the backwinded main with a safety factor of more than 200%. But it will not hold the boom if the boom gets dipped, and it will not hold the boom if there are dynamic loads.

200% doesn't seem so much when proper shackles have 500% FOS on WWL

B23iL23 · 26-07-2019, 01:38

I can't determine whether the boat had a traveler but It did have an arch just forward of the helm. It looks like this failed in the gybe, allowing the boom to get free.

The thought that truck me was they carried out a big upgrade to the boat, including I assume , a new boom (the boat is an old design and that boom looks far more recent) - did they also upgrade the mainsheet, blocks, securing points etc.