Racing sailor killed due to splice failure

[thinwater]

72:1 is the gold standard. With a brummel or good stitching, about 40:1 has proven 100% strength.


Remember that these preventers are attached end-of-boom; snapping the boom isn't really a risk... but I'm not arguing pro-con on the issue. That said, no engineering number was presented, which should be case if it was a designed fuse (electrical fuses are not selected at random). If you are claiming something was a "fuse," you should be able to show, with calculations, how the value was chosen.



And you must train the crew not to loiter in the path of the traveler. That was another of the MAIB findings. But could there have been anyone on the boat that didn't already know that? If so, the crew screening process is nonexistent. And it's not the kind of thing an experienced sailor forgets either. It is ...basic and obvious.

[Caddy Shack]

Why is the taper necessary? It seems like tapering would make the bury more likely to slip, and so one would need to make the bury longer to compensate.

[Training Wheels]

I’d think there’d be more chance of damaging the boom or gooseneck with the hard slam shortly after the preventer parting. Perhaps if your using the preventer strictly as a preventer, and not to stop the boom from moving around, a line with some stretch would be better.

[Paul L]

Originally Posted by Caddy Shack

Why is the taper necessary? It seems like tapering would make the bury more likely to slip, and so one would need to make the bury longer to compensate.

With no taper the outer strands make a sharp turn. Since they don't stertch the forces are focused on individual strands. The splice will be weak at the sharp transition.

[ggray]

Paul, thanks for the photo of what the "before" would've looked like. That's what I had suspected, but when it was termed a "splice", I ruled it out, because as others have mentioned, that isn't a splice.

Regarding the mechanics of the Dyneema splice, I cut apart a splice I had made years before, and was impressed with what I found. The uniform taper was almost rock hard and completely covered by hard, sharp little bumps made by the pressure from the braided (of course) outer cover. It would even say it was beautiful. Cover and core were virtually locked together.

[Dockhead]

Originally Posted by thinwater

. . . And you must train the crew not to loiter in the path of the traveler. That was another of the MAIB findings. But could there have been anyone on the boat that didn't already know that? If so, the crew screening process is nonexistent. And it's not the kind of thing an experienced sailor forgets either. It is ...basic and obvious.

Another useful habit is to lock the traveler down from both sides -- don't leave the lazy side uncleated or off the winch. I am amazed at how often I see this being done.




As to preventers being "fuses" -- I don't think anyone knows how much force their preventers can take, and I am under no illusions whatsoever about mine.


What people forget about is the GEOMETRY. What angle is your preventer at, to the boom? Do you know what the multiplier factor is, for that angle? I think in many cases, especially for boats with aft swept spreaders, like mine, which keep you from getting the boom that far out, it's going to be 5:1 or more, so just 1 tonne of force will put 5 tonnes on the preventer, say.


I don't have any illusions about my preventers surviving any kind of snatch load, so I am very careful to keep them tight at all times. If the boom end kisses the water, I figure there will be mayhem. Fortunately it's hard to touch the boom to the water on my boat as the aft-swept spreader keep the boom from going out very far, and the boom anyway is more than 2 metres above the water. The boom is 6 meters long and the beam of the boat there is almost 5 meters, so I would need to be nearly knocked down, or caught by some really weird wave. YMMV.

[David B]

Originally Posted by rmlarson1098

Sir Robin? As in Robin Knox-Johnston? Sir Robin had nothing to do with this tragedy, unless perhaps he was the captain of the vessel. Which he was not. It wasn't Knox-Johnston's race, and even if it were the ultimate responsibility rests with the skipper. Ocean sailing is dangerous, ocean racing ridiculously so. Sir Robin is a legend, as he should be. No one had ever done what he did - which MANY people felt was impossible - and no one else ever will. Leave him alone.

HEAR, HEAR !

[seacap]

Originally Posted by funjohnson

I see a tapper on both of the brummel splices with the rings on each end. Plus, there is stitching back-up too...

Maybe it was around fitting with too tight of a bend radius?

Attachment 183677

Matt

I would be interested to know this also. If the line was around a shackle or something similar the bend would be too sharp and very prone to failure. I have been running Dyneema as standing rigging in the tropics for 9 years now with no problems. But I’m also aware that sharp bends or hard compression points substantially weaken the line.

[allene222]

First off, it is not at all clear to me that the failure was the splice. Reading the report I see that this line had two propper splices around metal rings at the ends and a brummel splice in the center. The loop formed by that brummel splice was luggage tagged around a padeye on the foredeck. The load was then applied to one of the metal rings and the luggage tag. Taking this we can consider what the limits are. The proper splices are going to be stronger than the line and the failure was not there. The brummel splice would be 50% of line strength so a significant weakening but not outrageous considering the application. The luggage tag might only be 40% of line strength so it might be weaker than the brummel. Looking at the picture, it looks like the two sections after the failure are the same length which would not be the case if the brummel failed. That failure would be down the line at the brummel on one side or the other. What is also missing from this report is the size of the padeye. This was 14mm line. That means that if the padeye was less than 14mm, there would be strength loss due to the bend radius. If it was 1/4 inch padeye, that bend radius would be as weak as the brummel. My guess would be that the padeye was at least that size. I would put the failure at the luggage tag and not at the brummel but ultimately the failure is that the system was not strong enough, not that it was an inherently poor geometry.

By strong enough, I mean a maximum load probably less than 10x line strength. I use that number by saying this is a failure that could kill someone so the base safety factor should be 5. Then another 2x for either the brummel or the sharp bend radius around the padeye. As has been pointed out in this thread, the geometry might give a 5x mechanical advantage so whatever load is expected on the boom itself, the line should be 50x that strength. I have no idea what the load might be but I will guess that it might be 1000 pounds so you might want the line to be 50,000 pound breaking strength. The line used was not that strong. Any shock load makes it considerable worse but I won't try and calculate that. Dyneema is terrible in shock loading so that needs to be considered as well.

These numbers might be wong as the line diameter was said to be 14mm but it had the cover stripped so the core diameter would have been less. Regardless the setup was not strong enough either because of the tight bend radius or the line itself was not strong enough to work with the load and the 50% loss due to the splice.

I do not feel that the method used was inherently dumb if the loads had been known and the line properly sized. A 50% reduction at the padeye is not that hard to get. They had to attach whatever they use to that padeye and that might cause a similar reduction in strength. And as I said, I suspect the failure was not at the brummel but I would expect if the luggage tag held, the brummel would not be far behind so it doesn't make a big difference.

I had a recent occasion to use a brummel splice as the main strength element. I did have a bury but it was just a few inches. Knowing that the brummel alone would carry 50% of the line strength I could feel safe as the maximum load was 1000 pounds and the line strength was 18,000 pounds. This was obviously a stretch limited application and not a strength limited and nobody dies if it fails so I felt it would be fine. What I am saying is that even if a construction is weaker than line strength, the problem might be just the lack of analyzing the loads and strength rather than the construction technique per say.

[seacap]

Originally Posted by Snore

This is the first time I saw this photo. I agree it is hard to call it a splice failure.

Look carefully at the top 1/2 it looks like someone ironed it flat. Then look at the bottom 1/2. Carefully count the loose ends. I am counted 8, or the number of “big” threads in a single braid line. If this count is correct, then there was no splice in the failure area. This reinforces the assumption that it was not a splice failure.

IMHO it appears to be a rigging failure, likely as the result of chafe. It would be useful to know how long this line was in service and how long was it used on this trip? Also when was the last time the skipper or crew inspected the line?

I think the take away from this is reinforcement of the knowledge that dyneema does not tolerate chaffing. Adding an outer sleeve, and monitoring it for where may have avoided the failure.

Dyneema tolerates chafing better than most if not all lines. I had some of my standing rigging (Dyneema) saw through a mangrove branch during a tropical storm in the Virgin Islands. Only damage it suffered was some fuzz. Plus it is used for drag lines amongst other high chafe situations. It’s not zero chafe, but it is highly resistant to chafe.

[Dockhead]

Originally Posted by seacap

Dyneema tolerates chafing better than most if not all lines. I had some of my standing rigging (Dyneema) saw through a mangrove branch during a tropical storm in the Virgin Islands. Only damage it suffered was some fuzz. Plus it is used for drag lines amongst other high chafe situations. It’s not zero chafe, but it is highly resistant to chafe.

Its slipperiness, and its lack of stretch, both contribute to Dyneema's resistance to chafing which is indeed superior to that of other types of rope.



However, you can still ruin a piece of Dyneema in the twinkle of the eye -- don't ask me how I know

[allene222]

If you look at the failed piece, I think it clear that the brummel did not fail as the failure is not where the brummel was. It looks like a failure of the luggage tag around the padeye. I do not think the luggage tag would slip because of the brummel but a luggage tag is only 40% line strength so I think that is the failure and not chafe or the splice.

[Snore]

Originally Posted by allene222

If you look at the failed piece, I think it clear that the brummel did not fail as the failure is not where the brummel was. It looks like a failure of the luggage tag around the padeye. I do not think the luggage tag would slip because of the brummel but a luggage tag is only 40% line strength so I think that is the failure and not chafe or the splice.

Allene- the flattened part of the line would appear to reflect the radius of the line when it failed. IMHO that looks more like a boom than a luggage tag.

[allene222]

Originally Posted by Snore

Allene- the flattened part of the line would appear to reflect the radius of the line when it failed. IMHO that looks more like a boom than a luggage tag.

The report describes what I would call a luggage tag attachment. From page 28.

The partial splice loop was then passed through a
pad-eye and the hard eyes hitched through the loop to attach the strop to the yacht.

Note that a luggage tag has two sections of rope pressing against the padeye with the point between them being the center and having the loaded line at that point. I see the flattened part of the rope just above the break in the photo. I believe the break is where the load line passed the center of the luggage tag loop and the second flattened part was shattered when the line exploded so you can't see it. The explosion of the line stopped when it got to that part of the luggage tag that was not under load.

Anyway, that is the way I see it.

[Snore]

Originally Posted by allene222

The report describes what I would call a luggage tag attachment. From page 28.

The partial splice loop was then passed through a
pad-eye and the hard eyes hitched through the loop to attach the strop to the yacht.

Note that a luggage tag has two sections of rope pressing against the padeye with the point between them being the center and having the loaded line at that point. I see the flattened part of the rope just above the break in the photo. I believe the break is where the load line passed the center of the luggage tag loop and the second flattened part was shattered when the line exploded so you can't see it. The explosion of the line stopped when it got to that part of the luggage tag that was not under load.

Anyway, that is the way I see it.

Got it. You are 100% right. I kept seeing a boom and couldn’t get past it.