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  1. #1
    Senior Member nacra533's Avatar
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    Splicing and the Locked Brummel

    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.

  2. #2
    Senior Member Poppabear's Avatar
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    Thanks for the wise words of advice / warning. It is much appreciated.
    Terry

  3. #3
    Senior Member goodcaver's Avatar
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    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?
    A good caver never loses her pack.

  4. #4
    Senior Member WV's Avatar
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    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?

  5. #5
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    Splicing and the Locked Brummel

    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!

  6. #6
    Knotty's Avatar
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    Quote Originally Posted by goodcaver View Post
    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
    Knotty
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  7. #7
    Senior Member TiredFeet's Avatar
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    Quote Originally Posted by nacra533 View Post
    -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.

    Quote Originally Posted by nacra533 View Post
    -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.

  8. #8
    Knotty's Avatar
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    TiredFeet - Not sure what you want me to reference? The quote I posted came from a Samson email that I shared here on the forum. At the time a lot of people were speculating that we could make whoopies stronger by getting rid of the locked brummel so I had asked Samson if that really was the weak link (which it wasn't).

    Logic tells me a plain bury should produce a stronger splice than a locked brummel but I also tend to treat Brion's opinion as gospel. In the end I guess it's academic since either should server well for most hammock applications.
    Knotty
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  9. #9
    Senior Member TiredFeet's Avatar
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    I'm not questioning your quote of the email from Samson.

    In the first post you stated that the Locked Brummel is weaker than a plain bury splice.

    Do you have a reference for this statement. Preferably a reference to someone who has done testing of both splices since without testing it is simply opinion. Of course, whose opinion matters a lot, but testing is essential.

    Quote Originally Posted by Knotty View Post
    TiredFeet - Not sure what you want me to reference? The quote I posted came from a Samson email that I shared here on the forum. At the time a lot of people were speculating that we could make whoopies stronger by getting rid of the locked brummel so I had asked Samson if that really was the weak link (which it wasn't).

    Logic tells me a plain bury should produce a stronger splice than a locked brummel but I also tend to treat Brion's opinion as gospel. In the end I guess it's academic since either should server well for most hammock applications.

  10. #10
    Senior Member TiredFeet's Avatar
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    Quote Originally Posted by WV View Post
    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?

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