Brummeling

[arigger]

I've read a couple of things on this forum that confuse and concern me.
Afaik a brummel is a brummel and a "stitched" brummel is made up by the lazy. ["Stitched" being the kind that simply passes the tail through the standing part twice before burying.] This seems like it misses the whole point of a brummel, that is, low-load security. In a high-load situation I would rather have no brummel as the hard bends in the splice would inevitably weaken the rope.
Can anyone shed light on this? I'm hoping for an expert opinion here but I'll be happy to respond to questions anyone has.opcorn:

BTW: I like this site... I think a lot of you guys are pretty good at what you know. Thanks.

 

[moray]

Welcome to the site, arigger. It'll be nice to have another rope person here.

I haven't seen anyone talking about the stitched Brummel. All the commercial slings use the Moebius Brummel which obviously gives bullet-proof low-load security.

The question I have is how much does the Brummel weaken the rope? Does the Moebius Brummel with only a very short bury still preserve most of the rope's strength? If so, I could make some very short slings by eliminating most of the bury.

 

[arigger]

By it's very nature a brummel must weaken the rope somewhat... There is, I'm sure, some room to debate that claim, however.
The only loft rigger I've spoken to about it claims that it weakens the rope too much for his purposes, but he's a sailor and sailors use much riskier working load ratios than those of us in industry. [like 2:1]

So depending on your use I'd say a short tail is fine in a splice for, say, your tool lanyard [made some stretchy ones myself that way] but for your ass... S'pose that's up to you.

 

[NickfromWI]

Just to make sure we have our terms right...

The locked brummell is where the tail goes through the standing end, then the standing end goes through the tail. A Mobius Brummell looks the same at the end, but it is accomplished through a more complicated and almost magical route.

The stitched brummell, what I call the through-through brummel (the tail goes through the standing part, then it goes through AGAIN, then is buried).

And then compare this to the straight bury. No crossing or anything...just bury it.

It is easy to obtain 100% breaking strength in the through-through brummell or straight bury. The cost is possible low load slipping...which is avoided by the super necessary lock stitching or whip-lock.

With the locked brummell, you can only get about...90-95% of breaking strength!!! Still pretty damn good, if you ask me.

I've heard differing reports as to if a locked brummell should be done with a long tail or a short. I've seen good and bad breaks with both.

With the straight bury or the through-through, the tail length is crucial.

love
nick

 

[Sassafras]

I have read and have seen demonstrations with the locked brummel. as far as i can see the brummel's function is for low load security. the stitched brummel i have only seen in applications where the traditional brummel can't be constructed. the only thoughts i have is the stitched type is creating some friction ahead of the bury.
I would not sacrifice the depth of the bury after the brummel because that is the strength in the splice.
most of the rope manufacturers have splicing instructions but don't show reasons for their methods. but that is the way they will stand behind with the products they sell.

 

[Sassafras]

Nick
you and i must have been typing at the same time and if feel pretty dumb after reading your precision post.

 

[M.D. Vaden]

Nick
you and i must have been typing at the same time and if feel pretty dumb after reading your precision post.

Nick is our Technical expert: knots, facts, software, editing, name it.

 

[NickfromWI]

No probs!!!

And just to leave you with something to chew on

The locked brumell is ALWAYS possible.

:rockn:

love
nick

 

[moray]

With the locked brummell, you can only get about...90-95% of breaking strength!!! Still pretty damn good, if you ask me.

This is what I wanted to hear! Can you point me to some reference that describes where these numbers come from? I can find next to nothing from cruising the web. Thanks.

 

[arigger]

The locked brumell is ALWAYS possible.

:rockn:

So why make a false brummel?

 

[NickfromWI]

So why make a false brummel?

It is faster and easier.

Moray, I can't point you to anything that says that specifically. I have a few break tests that I've done that lead me to this, combined with input from riggers and splicers around the country. To know for sure, you should break a few yourself just to see.

Sorry I can't be more helpful. One day I will have my own testing bed and I'll be able to publish studies about it!

love
nick

 

[moray]

Moray, I can't point you to anything that says that specifically.
Sorry I can't be more helpful. One day I will have my own testing bed and I'll be able to publish studies about it!

Thanks for the reply, Nick. I found this a couple of days ago: http://www.sailinganarchy.com/forums/index.php?showtopic=54230&hl=

Check Post #30, by Brion Toss. The closest he gets to answering my question is near the beginning, where he talks about multiple Brummels without a buried tail giving a strength of 70+ percent of maximum. Everywhere else the Brummel is used with a full-length tail.

A number of posters worry about one of the things I don't like about Brummels: the tail, without stitching, can easily work its way out. In fact, I think the Brummel tends to pull the tail out! You can rectify this by carefully stitching the throat.

But there is a related engineering problem I dislike even more. You have essentially two completely independent systems working to provide strength to the splice, the bury and the Brummel, yet you want to make sure the bury ends up fully loaded. This gives rise to the symmetrical situation in which, just as in an eye with no Brummel, both legs of the eye have exactly the same load. If a Brummel is in place, it would mean that through the full length of the Brummel, each leg of the rope sees half the load. If there is any slack at all at the throat of the bury--and it is perfectly possible to lock in the slack with stitching--who's to say how much load has to be borne by the Brummel before the bury sees any load at all? In the case where the bury is always slack, the worst possible case, we have maximum asymmetry. At the eye itself, both legs are equally loaded, as they have to be. But at the bottom of the Brummel, where one leg enters the rope to become the bury, that leg carries no load at all. This is exactly the same situation as a Brummel without a bury.

If I knew that a single locked Brummel without a burried tail would break at 70% of rope strength, at least I would know where I stood. Like you, I would love to have a test bed where I could do some real experiments. Until then, or until I read something definitive about it, I will continue to consider the Brummel an engineering mistake and will avoid it whenever I can. The only safe assumption, it seems to me, is that the Brummel is doing all the work, and the tail is doing nothing. So we are back to the question: how strong is a single locked Brummel without a buried tail?