Splicing and the Locked Brummel

[nacra533]

Not to get on a soap box, but a word of caution. I and others have stated this many times previously, but there are a lot of new folks to the forum splicing line that were not part of the original discussions regarding whoopies, UCRs, and the like.


-A Locked Brummel is LESS strong than a regular buried splice. It looks more secure and handles better in no or low loading situations, but the breaking strength is less than a regular buried splices. For Hammock usage, most are not getting that close to the BS of the line so there is some margin of safety there. I use locked brummel in the majority of my splices when loading is less of a concern than the no/low load situation. It saves me from stitching the bury. Locked brummels cause a shearing stress in the line instead of tension which line is rated for. If you're doing it the small stuff, I suggest derating the line. You're probably still fine depending on sag angle and your weight. Remember, at a 30 degree sag angle, the tension in EACH line = your weight (not half of it). As sag angle decreases, tension increases significantly, at 15 degrees sag angle, tension in EACH line is almost double your weight. There is a great chart on HF that shows loading as a function of sag angle. I have no idea of how to find it.

-Tapers- I've seen a couple posts regarding being able to splice the line without tapering. The taper is part of the splice. It lessens the stress concentration at the end of the bury. Many tests have shown the failure of an improperly tapered splice is at the location where the bury ends. It also fails at much less than the advertised splice strength. Splicing without a taper is an incorrect splice. If use choose to do it, I would derate the line to what a typical knot has (about 50-60%)

-Manufacturer's splicing guides.
Regardless of what you read on this site, including my own posts, or any other, follow the manufacturer's splicing guide. They make the line and put their name behind it WHEN splices are done by a professional rigger according to their instructions. The test their line and know all sorts of things that we aren't privy to like coefficients of friction of the line, the coating, how much diameter reduction under load (how much a splice squeezes the bury), etc. High tech, Class 2 lines like spectra/dyneema/amsteel, vectran, etc were created for commercial use like tug boats, cranes, winch lines, etc.. They are just recently (last 5 years or so) getting priced where folks can afford to use them recreationally.

I see no harm if the mfr says bury 6" and you decide to bury 10". If the recomended bury is x fids or 2", what does it cost you to bury a few more inches. Weight and cost are neglible and it's not worth the risk in such a small line.

[Poppabear]

Thanks for the wise words of advice / warning. It is much appreciated.

[goodcaver]

wow, I didn't know that at all. Well shoot, does this mean I should redo my whoopies?

Would just tying a fixed loop on the end derate the amsteel less than a locked brummel splice?

[WV]

I've used shorter buries (5 - 6 inches) with locked brummels for dynaglide whoopies. What do you think? Should I just add some stitiching or re-make them with longer buries? Does passing the cord through itself weaken it? Anybody have an idea?

[TiredFeet]

I've used shorter buries (5 - 6 inches) with locked brummels for dynaglide whoopies. What do you think? Should I just add some stitiching or re-make them with longer buries? Does passing the cord through itself weaken it? Anybody have an idea?

If you look again at the Samson splicing guides they recommend a shorter bury in conjunction with the locked brummel than for a plain bury. 3.5 fid lengths for the bury on a plain bury and 2.25 fid lengths for the bury with a locked brummel. They describe the locked brummel in the guide for the whoopie sling and since the weak point there is the adjustable bury, maybe they figure a shorter bury is okay. So maybe an equal length bury might be needed for both the locked brummel and plain bury for a stand-alone fixed eye.

I just checked Brion Toss's book on the locked brummel splice for dyneema. He recommends the bury to be 72 diameters which works out to be 3.27 fid lengths, which is a lot closer to Samson's recommendation of 3.5 fids for the plain bury. So for stand alone fixed eye splices using the locked brummel, maybe it should be the same length as for the plain bury. I notice that Brion also recommends stitching the bury done after the locked brummel. That treats it just like a plain bury.

Of course for hammock suspensions using something like 3 mm amsteel or something stronger, most people will be so far under the rating of the rope that a shorter bury is probably okay. But then the added weight is negligible so why go shorter?

[zoovegroover]

I am one who signed on to the forum late in the discussion. Although I have been backpacking with a hammock since the Hennesey first hit the scene, the hammock forums are new to be by less than a few months!!

In that time, I have sewn a few hammock bodies and experimented with 7/64" Amsteel. The latest work was to create a pair of locked Brummels at both sides of a length of 7/64" AB using the McDonald method recently discussed. I tapered the splice and rounded up to 3" for the FID factor. I have one side whipped to the gathered ends of my DIY Hennesey clone and the other end larks head to a couple of descending rings. At the other side of that are long 1" poly straps for adjustment. I spend an hour hanging in it the other night and all seemed well. I weigh 175. Should I be concerned about the long term prospects for this application? I was going to incorporate it in a WBBB clone I have planned...

I also made a set of whoopies with the locked McDonald/Brummel splice on the fixed side...

I guess I need to wade deeper into the discussion. Intuitively, I would have thought the locked Brummel would be stronger than the simple stitched bury to create a fixed eye.

Didn't that McDonald splice come off of a sailing forum? Is it not loaded the same way we load the hammock suspensions?

This is my first post. Sorry I did not introduce myself. I have been lurking for a while astounded by how far all things hammock has come over the past few years!! In the past month, I have ordered a WBBB, OES Spinn tarp, Tenkara fly kit, DIY wood stove, Four Dogs wood stove, Amsteel, Lash-It, etc., etc. This forum has been a real drain on the wallet!!

Much thanks for the free distribution of information and knowledge!

[Knotty]

wow, I didn't know that at all. Well shoot, does this mean I should redo my whoopies?

Would just tying a fixed loop on the end derate the amsteel less than a locked brummel splice?

On a whoopie, the locked brummel is not the weak link. So for that application at least it doesn't help to use a standard spliced eye.

From Samson:

Using Amsteel Blue whoopie slings for suspending hammocks is a very interesting application. Thanks for the link to the thread on the hammock forum, it's a good discussion.

Recently the reduction to 60% of average break strength for Amsteel Blue whoopie slings was suspected to be a low value. Testing showed that it is actually around 80% depending on the size of the rope. On every test done the break location was at the point of the adjustable whoopie tail exit.

In collusion, the locking brummel has less impact on break strength reduction than the "sudden transition in size where the adjustable section exits the bury". If a traditional buried eye replaced the brummel, the same strength reduction would be expected because the adjustable bury exit is the weakest link.


Best regards,

Mark Pederson
R&D Engineer

http://www.hammockforums.net/forum/s...ad.php?t=12319

[TiredFeet]

-A Locked Brummel is LESS strong than a regular buried splice. It looks more secure and handles better in no or low loading situations, but the breaking strength is less than a regular buried splices. For Hammock usage, most are not getting that close to the BS of the line so there is some margin of safety there. I use locked brummel in the majority of my splices when loading is less of a concern than the no/low load situation. It saves me from stitching the bury. Locked brummels cause a shearing stress in the line instead of tension which line is rated for. If you're doing it the small stuff, I suggest derating the line. You're probably still fine depending on sag angle and your weight. Remember, at a 30 degree sag angle, the tension in EACH line = your weight (not half of it). As sag angle decreases, tension increases significantly, at 15 degrees sag angle, tension in EACH line is almost double your weight. There is a great chart on HF that shows loading as a function of sag angle. I have no idea of how to find it.

Knotty - do you have a reference for this?? Brion Toss rates the Locked Brummel with bury at as close to 100% of virgin rope as you care to get. This is for Dyneema/Spectra ropes. Samson rates the plain bury at 90% to 100%, so I have always taken the two claims to mean that the Locked Brummel does not de-rate the splice at all. He has done a lot of testing of ropes and splices and so I assume that his claim is based on his personal testing. I have been relying on his claim in this regard and would appreciate it if you have a counter reference.

-Tapers- I've seen a couple posts regarding being able to splice the line without tapering. The taper is part of the splice. It lessens the stress concentration at the end of the bury. Many tests have shown the failure of an improperly tapered splice is at the location where the bury ends. It also fails at much less than the advertised splice strength. Splicing without a taper is an incorrect splice. If use choose to do it, I would derate the line to what a typical knot has (about 50-60%)

This is excellent advice and a good reminder for even the old hands at splicing. I always use the tapering method recommended by Samson rope in their splicing guides.

I've also found that doing the taper as per their guide before the splice makes doing the splice a LOT easier.

[nacra533]

wow, I didn't know that at all. Well shoot, does this mean I should redo my whoopies??

No need. Just be aware there is a reduction and the safety factor is not as high. As I mentioned, I use them primarily on hammocks and sailing rigging.

...

Didn't that McDonald splice come off of a sailing forum? Is it not loaded the same way we load the hammock suspensions?

Sailors (which I am) use it frequently. There are several reasons. Spectra is primarily used on contol lines and running rigging (the stuff that gets adjusted alot) Often on control lines, the line is PLENTY strong and it becomes a function of block/pulley /sheave size and strength vs. handling ability/how easy is it to pull it. Also, control lines tend to flog, which can shake a plain buried splice loose. That's the reason for stitching at the beginnning of the bury., but stitching stiffens the line and whipping the bury fattens it. Both impede the smooth flow of the line around a block. Another reason is they are frequently loaded, then unloaded.

On a whoopie, the locked brummel is not the weak link. So for that application at least it doesn't help to use a standard spliced eye.

I totally agree with Knotty. It is not the weak link in a whoopie. He has done a lot of research in to whoopies.

Knotty - do you have a reference for this?? Brion Toss rates the Locked Brummel with bury at as close to 100% of virgin rope as you care to get.

Toss is a rigging guru and he should be believed as long as you know terminology he is referring to. See below on terminology differences. My reference, which may be outdated, is OSHA, arborist, and rigging standards prohibit or discourage a locked brummel in 8 or 12 strand class II line for life support or load support overhead. The also prohit or discourage the "weaveing" the line before the bury. I've seen data that prohibits it (by demonstrating the allowed splices with dimensions) and I've seen data that discourages it by causing the line to be derated to the point it does not make sense to do it.

Terminology differences
There is a difference between a locked brummell and a brummell /weave/lock stitch. Different manufacturers use different terminology.

This is what I call a Locked Brummell. Samson calls it a locked brummell. NE Ropes calls it a Brummell. Notice how one tail goes through the standing part and the other tail does as well. Look closely at the last picture. Samson's current whoopie sling shows this technique as well. I believe it to be weaker than a straight bury or a Brummell splice.

http://www.jamestowndistributors.com...+Eye+Splice%29

This is what I call a Brummell in Figure 2. Samson calls it a Brummell or weave, NE Ropes call it a lock stitch. I believe it to be as strong as a straight bury.
http://www.jamestowndistributors.com...Lock+Stitch%29

One point as to why you should follow manufacturers instructions. Samson eye splice 12 strand class II 2006 shows a straight bury, with no locked brummel nor weaving/lockstitch (which Samson and I call a brummel). In Samson's Eye and Tail splice, they use the brummel/weave splice/lock stich, but the instructions clearly state (in small print) which lines it is appropriate for. Amsteel is not one of them. The locked brummel requires you to use both ends of the line in forming the eye OR turning the line inside out. I suspect that it is easier to obtain an exact total length using this splice. It is very difficult with a straight bury. Marlow and NE Ropes both recommend a brummel/weaving/lockstitch splice for their 12 strand class II dyneema. Although, NE Ropes calls a "locked brummell" a "brummell" and a brummel/weave a lock stitch, again.

The point of my original post was not to discourage the use of the locked brummel. Like I mentioned, I use it primarily in several different arenas. My primary point was to encourage folks to pay attention to line breaking strengths and derating factors. Derating factors can be significant.

One example for knots: in double braid class 1 line, like dock lines on a boat, a bowline knot retains 55% of original breaking strength. In double braid with a specta core (Amsteel is spectra), it retains 40% of it's original strength. More than 1/2 of it's strength is gone.

Knotting small specrta/amsteel significantly reduces the breaking strength. It also does not hold knots well.

Some add

Long post to say, hang from it if your sag angle and body weight give you a margin of safety you are comfortable with. I do.

[TiredFeet]

nacra - I'm taking my guidance from Brion's "Book 5 Basic Braided Splices". On pages 65 through 78 he gives instruction on making the Locked Brummel splice with illustrations. His Locked Brummel is exactly the same as Samson's Locked Brummel, just a different method of getting there - Brion's method only needs one end of the rope. Also, he specifies that the splice is specifically for "High Modulus" ropes, i.e., dyneema and spectra are what he mentions specifically, or what Samson calls Class II ropes and that "Properly done, this splice will approach 100% efficiency in strength and security."

Note that New England Ropes has another method for making a Locked Brummel using only one end of the rope, but I have never been able to really execute their method. Their method also ends up with exactly the same splice.

So we have so far 3 methods of obtaining a locked brummel:

1. Samson Ropes method, which is probably the easiest, but requires both ends of the rope
2. Brion Toss's method which requires only one end of the rope and, for me, is only slightly harder to execute than Samson's method
3. New England Rope's method which requires only one end of the rope and which I have not been able to successfully execute.

All 3 methods will give you exactly the same splice. I find it interesting also that Brion is the only one that recommends also stitching the bury after a locked brummel. I think this is because of his background in sailing, which as you pointed out so well, loads and unloads the splice a lot and so requires securing the bury more than a hammock suspension does.

Also, I think you have to understand that Brion's guidance on the Locked Brummel splice and the strength includes the bury after the locked brummel. Without his actually stating it, I get the sense that the locked brummel isn't there to provide strength to the splice, the bury provides that, but to help manage the load/unload cycle problem. So yes, if you are going to do a locked brummel alone, no bury afterwards, then the brummel should probably not be used for life support situations. However, following the locked brummel with a bury I think changes the splice considerably.

I think that most (all??) people on the forums are following Samson's guidance in the locked brummel in the whoopie sling pdf and following it with a bury. In fact, I think if you look back over the threads, it is pretty much taken for granted that the the locked brummel splice on the forums actually refers to the combination of a locked brummel splice followed by a bury splice.

So in the end, I think after writing the above that we probably mean the same thing and that the only thing that separates us is the terminology.

Toss is a rigging guru and he should be believed as long as you know terminology he is referring to. See below on terminology differences. My reference, which may be outdated, is OSHA, arborist, and rigging standards prohibit or discourage a locked brummel in 8 or 12 strand class II line for life support or load support overhead. The also prohit or discourage the "weaveing" the line before the bury. I've seen data that prohibits it (by demonstrating the allowed splices with dimensions) and I've seen data that discourages it by causing the line to be derated to the point it does not make sense to do it.

Terminology differences
There is a difference between a locked brummell and a brummell /weave/lock stitch. Different manufacturers use different terminology.

This is what I call a Locked Brummell. Samson calls it a locked brummell. NE Ropes calls it a Brummell. Notice how one tail goes through the standing part and the other tail does as well. Look closely at the last picture. Samson's current whoopie sling shows this technique as well. I believe it to be weaker than a straight bury or a Brummell splice.

http://www.jamestowndistributors.com...+Eye+Splice%29

This is what I call a Brummell in Figure 2. Samson calls it a Brummell or weave, NE Ropes call it a lock stitch. I believe it to be as strong as a straight bury.
http://www.jamestowndistributors.com...Lock+Stitch%29

One point as to why you should follow manufacturers instructions. Samson eye splice 12 strand class II 2006 shows a straight bury, with no locked brummel nor weaving/lockstitch (which Samson and I call a brummel). In Samson's Eye and Tail splice, they use the brummel/weave splice/lock stich, but the instructions clearly state (in small print) which lines it is appropriate for. Amsteel is not one of them. The locked brummel requires you to use both ends of the line in forming the eye OR turning the line inside out. I suspect that it is easier to obtain an exact total length using this splice. It is very difficult with a straight bury. Marlow and NE Ropes both recommend a brummel/weaving/lockstitch splice for their 12 strand class II dyneema. Although, NE Ropes calls a "locked brummell" a "brummell" and a brummel/weave a lock stitch, again.

The point of my original post was not to discourage the use of the locked brummel. Like I mentioned, I use it primarily in several different arenas. My primary point was to encourage folks to pay attention to line breaking strengths and derating factors. Derating factors can be significant.

One example for knots: in double braid class 1 line, like dock lines on a boat, a bowline knot retains 55% of original breaking strength. In double braid with a specta core (Amsteel is spectra), it retains 40% of it's original strength. More than 1/2 of it's strength is gone.

Knotting small specrta/amsteel significantly reduces the breaking strength. It also does not hold knots well.

Some add

Long post to say, hang from it if your sag angle and body weight give you a margin of safety you are comfortable with. I do.