I am a big fan of rope and knots. I recently joined this forum and have been running into alternative options. I keep seeing where folks are making and/or using continuous loops. Why not just use an appropriate knot instead? Are there advantages to a continuous loop other than cosmetics and to prevent a knot from getting in the way? It seems that a continuous loop would slip before a proper knot would fail.
Amsteel is much stronger spliced than knotted, and we use Amsteel because it's very strong for its weight.
Having used continuous loops without failure, and being an admitted knot phobe, I'm going to say, just because... in order to let the knowledgable folks who know a lot more about these things chime in. In the meantime, I'm going to use my loop in the channels and clip my suspension of choice to it.
"I wonder if anyone else has an ear so tuned and sharpened as I have, to detect the music, not of the spheres, but of earth, subtleties of major and minor chord that the wind strikes upon the tree branches. Have you ever heard the earth breathe... ?"
- Kate Chopin
Continous loops do look nice, but they are actually stronger than knots. Generally when ropes are put on a load test machine they fail at the knot. Right angle or greater bends in a rope make for a weak spots and knots can de-rate a rope by 50% or more. The bury technique de-rates a rope more in the 12% range. As with anything, not all knots are bad and not all burys are equal either. Also, if your rope is rated at 2000 lb and you de-rate it 50% with a knot, you still have a 1000 lb test rope. So using a knot will work just fine for most suspensions. I use a combination of both myself.
-Mark
-SlowBro
"Do what you can, with what you have, where you are."-Theodore Roosevelt
Don't forget knots slip with Amsteel and the like
Very informative. Guess I'll have to learn how to splice now.
This claim that continuous loops are stranger than knots raises an interesting follow up question. At best, a continuous loop could only out-perform a given knot under certain conditions (e.g. a 1/32" bury would certain fail first). This raises an interesting follow up question. For a given class of cordage, it must be possible to graph the percentage of preserved strength by the length of bury used. Similarly, you could then plot the preserved strength for different types of knots. But until someone takes the time to do this, I will have to grant that a continuous loop may be more reliable under certain conditions. However, it does not seem reasonable to select or reject a continuous loop for reliability reasons without having such a graph to understand what an appropriate bury length would be required to outperform knot alternatives?Originally Posted by SlowBro
This also makes me wonder what conditions a continuous loop may weaken under (similar to how different knots weaken under certain conditions). For example, do they slip easier when subjected to vibrations or volatile dynamic loads.
Are there any compelling field observations from the community on the matter of reliability?
Interesting Knot Strength Info
A straight or un-knotted rope is assumed to have 100% strength.
Strong Knots
Blood Knot 85–90% (Barnes); 80% (Day)
Flemish Bend 81% (Frank and Smith)
Figure Eight Loop 80% (Frank and Smith)
Double Fisherman’s 79% (Frank and Smith)
Moderately Strong Knots
Butterfly 75% (Frank and Smith)
Bowline 60% (Day)
Overhand Knot 60-65% (Luebben )
A Weak Knot
Overhand Bend <50%
Guide for popular splices
Grog Sling
Commonly used in the hammock community to create continuous loops. It is said to maintain 100% rope strength, but is not reliable over time as this splice does not employ stitches to prevent the splice from pulling out.
Long Bury Splice
Commonly used in the hammock community to create fixed loops at the end of cordage. It is said to maintain 90% rope strength. One source recommends using the Long Bury Splice on the ends of a rope to create a continuous loop for long term use in lieu of the Grog Sling technique.
This source suggests a minimum bury length of 36 times the ropes diameter must be used to perform as prescribed. Furthermore, it suggests that slippery rope should use 72 times the ropes diameter. Since most applications in the hammock community are using slippery rope, the later should be used.
1/8" Amsteel should have a bury of at least 10"
7/64" Amsteel should have a bury of at lest 7.9"
I will note that the majority of applications I have seen on the forums for continuous loops (and fixed loops) are using significantly shorter bury lengths. In the case of short continuous loops (e.g. commonly used to lark's head suspension loops onto the end of hammocks), a proper knot is likely to be more reliable. A continuous loop would need to have a circumference longer than 20" (10" across when pulled tight) to fit two 10" buried ends (in theory you could overlap the buried ends for a 10" circumference) to perform as prescribed.
However, I commonly see 10" or longer bury lengths being suggested for whoopie slings, which is sufficient and should give superior performance over a knot.
Your info applies to conventional rope and is not even close for Amsteel Blue and other high modulus materials.
Scroll down to page 17 of this paper for charts showing the percentage of retained strength for both conventional and high modulus ropes...http://www.orosha.org/pdf/grants/osu/runninglines.pdf
Strength derived from the bury depends on proper length and technique of the bury. Generally 3-3.5 fids (a fid is 21 x the rope diameter) are required for Amsteel.
Yes, plain buries can work their way out under no load conditions and is the reason rope manufacturers recommend locking methods such as locked brummels and lock stitching.
The reality of continuous loops 'as we typically use them' is that they rarely (if ever) come undone and never while under load (given proper bury lengths).
And the over expanding of the outer cover would be expected to derate the construction considerably.
FWIW, strength ratings of Amsteel Blue have been derived from break testing with a spliced eye in both ends so a proper eye spice does not derate the strength below Samson's ratings.
Last edited by gmcttr; 09-27-2015 at 06:57.
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