Racing sailor killed due to splice failure

[Paul L]

Allene222
Where are you getting tbe 50% for the brummel without a bury and 40% for the luggage hitch. The brummel sounds high and the luggage hitch sounds low. Just interested, not challenging.

[Pete7]

Originally Posted by Dockhead

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 found a calculator on the Harken website a while back for calculating sheet loads. For my 31ft yacht I think the main sheet is 350kgs in 30 knots and 500kgs in 42 knots.

If the geometry increases the load by 5:1, then a 10mm piece of double braid would break. Even 20mm of braid on braid only offers a 3:1 safety margin.

Worrying.

Pete

[allene222]

Originally Posted by Paul L

Allene222
Where are you getting the 50% for the brummel without a bury and 40% for the luggage hitch. The brummel sounds high and the luggage hitch sounds low. Just interested, not challenging.

There was a long thread on Sailing Anarchy that was started by someone with a screen name Estar. He had a test setup and did a ton of testing. Interestingly, the back and forth between the two of us led so some significant developments particurally in the area of knots and such in Dyneema. Anyway, the single brummel without a bury was right at 50% +-. The luggage tag slipped at 40% so there wasn't really a break number. In this application the luggage tag cannot slip because of the brummel. My main point is that the data presented does not show that the Brummel itself was the point of failure. The report actually does not say the Brummel was the point of failure, just that the failure was in that are of the strop.

The test report concluded that the primary failure mode was consistent with overload
failure at the strop’s partial splice, which might have been exacerbated by uneven
loading of the splice, resulting in fewer fibres bearing the load, thereby creating a
high stress point and pinch points.

My observation is that the overload happened at the apex of the luggage tag.

Clearly this strop was not strong enough. I think the fault lies in the idea that you need 72 diameters for the bury. That led to needing the luggage tag trick because he didn't have enough length to do two 72 diameter buys. A 36 diameter bury is enough, 27 has been shown not to slip. That would have allowed single sections with eye splices on each end and the luggage tag of the eye would have been full line strength.

[Paul L]

Estar is Evans Starzinger of Beth and Evans.
His numbers are probably pretty right on. But I don't see that they apply on the luggage tag in this case. I would expect that the luggage tag would have approached 100%, although one side would have jammed up on the brummel when it slipped and may have caused the failure at the brummel.

[allene222]

Originally Posted by Paul L

Estar is Evans Starzinger of Beth and Evans.
His numbers are probably pretty right on. But I don't see that they apply on the luggage tag in this case. I would expect that the luggage tag would have approached 100%, although one side would have jammed up on the brummel when it slipped and may have caused the failure at the brummel.

I seriously doubt it is 100% but it is hard to really say what the strength of this arrangement is. You would have to test it to know and that has not been done. I still think the line under load broke the apex of the luggage tag. I see that as a stress concentrator as the report says might happen and I think that caused the failure. Maybe it was 50%, maybe 99%. What we know for sure is that the system wasn't strong enough and what I am saying is that the fault is not the partial splice.

I just got a free flying jib and put a 7mm heat set STS luff line in to carry a halyard load of 1000 pounds. I used a brummel and a very short bury. I didn't count on the bury but rather on the 50% line strength of the bare brummel. The line is rated at 18,000 pounds and works just fine under the 1000 pound halyard load. Evan's work was essential to this design and I am very grateful he did it. Unfortunately he had issues with people misusing it and took down his website but you can still find it and I have a link on my own website if you need it. Not sure if I gave my site but it is L-36.com

[Paul L]

Originally Posted by allene222

I seriously doubt it is 100% but it is hard to really say what the strength of this arrangement is. You would have to test it to know and that has not been done. I still think the line under load broke the apex of the luggage tag. I see that as a stress concentrator as the report says might happen and I think that caused the failure. Maybe it was 50%, maybe 99%. What we know for sure is that the system wasn't strong enough and what I am saying is that the fault is not the partial splice.

I just got a free flying jib and put a 7mm heat set STS luff line in to carry a halyard load of 1000 pounds. I used a brummel and a very short bury. I didn't count on the bury but rather on the 50% line strength of the bare brummel. The line is rated at 18,000 pounds and works just fine under the 1000 pound halyard load. Evan's work was essential to this design and I am very grateful he did it. Unfortunately he had issues with people misusing it and took down his website but you can still find it and I have a link on my own website if you need it. Not sure if I gave my site but it is L-36.com

Your site is great and I have used it often.

The luggage tag has 4 legs to take the load, so it should be very near the strength of the line assuming both legs are being equally pulled on (not the single jib sheet case), in my untested opinion.

[Dockhead]

Originally Posted by allene222

. . . Not sure if I gave my site but it is L-36.com

Ah, you're L-36.com? Welcome; that's a great site which many of us use a lot. I think I got a lot of good material for my sheet lead system from there

[allene222]

Originally Posted by Paul L

Your site is great and I have used it often.

The luggage tag has 4 legs to take the load, so it should be very near the strength of the line assuming both legs are being equally pulled on (not the single jib sheet case), in my untested opinion.

Thank you both for the kind words.

The more I ponder this the more I tend to agree. I would not be at all surprised if the design was very close to line strength and the issue was the load exceeded line strength but this is also an untested opinion.

[Paul L]

Originally Posted by allene222

Thank you both for the kind words.

The more I ponder this the more I tend to agree. I would not be at all surprised if the design was very close to line strength and the issue was the load exceeded line strength but this is also an untested opinion.

Why not 50% of line strength due to the brummel?
14mm is something like 37,000lbs breaking strength.

I'm not convinced that published breaking strength is directly applicable to snatch loads.

[allene222]

Originally Posted by Paul L

Why not 50% of line strength due to the brummel?
14mm is something like 37,000lbs breaking strength.

I'm not convinced that published breaking strength is directly applicable to snatch loads.

1) The way I read it was that it started as 14mm but was just the core so perhaps 10mm?
2) The brummel was not carrying the full load because of the luggage tag. Hard to say what load it would get. I am unclear of the slip load of a dyneema luggage tag but I know from my own testing that if you keep dyneema knots from slipping, they get stronger as you tighten them. That was the basis of the Estar knot and the stronger soft whackle btw. Some will slip at high rates of applying the load and the same knot may not slip if pulled very slowly. I actually saw flames on an Amsteel knot pulled fast.
3) Shock loads are terrible because the dyneema doesn't stretch much so it really multiplies the load to stop whatever mass is has to stop over a short distance so I agree completely with your statement. I mean, if stretch was zero, the force from a shock load would be infinite. But it is not zero and there was probably a lot of it so there might have been significant stretch over the length. Net is I can't tell. I know from my own Dyneema preventer that there is stretch and if you don't use Dyneema, the preventer won't even work, it will just stretch and allow the boom to come all the way across.

[Paul L]

Originally Posted by allene222

1) The way I read it was that it started as 14mm but was just the core so perhaps 10mm?
2) The brummel was not carrying the full load because of the luggage tag. Hard to say what load it would get. I am unclear of the slip load of a dyneema luggage tag but I know from my own testing that if you keep dyneema knots from slipping, they get stronger as you tighten them. That was the basis of the Estar knot and the stronger soft whackle btw. Some will slip at high rates of applying the load and the same knot may not slip if pulled very slowly. I actually saw flames on an Amsteel knot pulled fast.
3) Shock loads are terrible because the dyneema doesn't stretch much so it really multiplies the load to stop whatever mass is has to stop over a short distance so I agree completely with your statement. I mean, if stretch was zero, the force from a shock load would be infinite. But it is not zero and there was probably a lot of it so there might have been significant stretch over the length. Net is I can't tell. I know from my own Dyneema preventer that there is stretch and if you don't use Dyneema, the preventer won't even work, it will just stretch and allow the boom to come all the way across.

Not sure how big a machine yours is, but having some stretch in the preventer makes sense to me. I use dyneema along tne boom and then standard double braid to the bow and back. At somepoint something is going to break, there is always a weak point. My setup is working well so far.

[allene222]

I don't use a preventer any more as I mostly race and just make crew hold the boom out. I race in SF Bay so no waves. It has been many years and my memory is failing so I might have it wrong but what I remember is some Dyneema along the boom from boom end to around the gooseneck so I could get at the end. Then stayset to the bow cleat and back to the cockpit. Too much stretch. Switched to Amsteel all the way. Boom is 17.5 feet and boat is 36 feet.

The other issue is that my mast is more than 6 feet above the cockpit sole so even when we do an accidental gybe nobody gets hit. I do one every few years. When the boom was wood it would put a split in it that I would have to glue back together. Now I use dynamic climbing line for my traveler and we do hard gybes without fear. And the rig is new and aluminum so much stronger. I was dismasted in the Master Mariners Regatta a few years ago.

I agree that some stretch is a good idea. The stretch from my traveler has been great. Some people make fun of me for using stretchy line but as I got the idea from Stan Honey I think I am on safe ground.