Why Continuous Loops?

[SpitballJedi]

Initially, I used a continuous loop because it seemed easier to move my whoopies from one hammock to another because I can just remove it from the loop instead of threading and un-threading it through the sewn channel. I find I don't do much switching so it's kind of pointless. Maybe it would make more sense on a whipped end.

Also, I thought if I had an ascending ring or beaner in between the whoopie and loop, it would create a drip block when it rains and protect my hammock from getting wet.

Currently, I don't use a continuous loop. Instead, I just run my whoopie right through the sewn channel. I've been in the rain a few times, nothing serious or heavy for an extended period, but have not had my hammock get wet.

If I'm expecting heavy rains or going on multi-day trips, I might put my loops and rings back on. But so far, I have not felt the need.

[SlowBro]

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?

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?

Yes, of course you are right, a short bury would be inadequate just like a single overhand knot is inadequate. Early on, at least a couple years ago the hammocking community here became aware of continuous loops and burys. We had a problem that the very light and very high strength but very slippery dyneema and spectra ropes we wanted to use would not hold a knot very well. We were helped in our quest by the arborists who have been using whoopie slings and buried end loops for their work climbing trees.

The name for the length of a safe bury is call a "fid length" and is 21 times the diameter of the rope. So for a 1/4" rope it would be roughly 21 x 1/4 = 5.25 inches.

Why is it called a fid and why 21 times the diameter? A fid is actually a tool used to splice ropes and apparently a fid length takes its name from that.
The 21 times the diameter seems to be a reasonable distance to get nearly 100% strength. That is- a fid length is a join that has the integrity of the original rope. No knot that I know of can do that. I think it was the rope companies that came up with this number and nomenclature so search on New England Rope or Samson for information on splicing.

However, I would check out this website (Click Here) for some of the experiments you were looking for. Hopefully that will help you in your quest.

-Mark

[troyji]

The name for the length of a safe bury is call a "fid length" and is 21 times the diameter of the rope. So for a 1/4" rope it would be roughly 21 x 1/4 = 5.25 inches.

Mark, if you look a few posts back, we discussed that a safe bury length is actually 3 to 3.5 fids. You will typically find 72 x diameter as the recommended bury length. So minimally you should use 72 x 1/4 = 18 inches. I have found that folks on the forum routinely use inadequate bury lengths - degrading the strength of the cordage by an unknown factor.

For example, I have found where folks build 8" loops (16" circumference) from 1/8" amsteel using a 4" bury. A safe bury would be 72 x 1/8 = 9 inches. Because there are 2 buries, the minimum safe loop size for 1/8" amsteel is 9" (18" circumference). For 1/4" amsteel, the minimum would be an 18" loop (32" circumference).

[TominMN]

Mark, if you look a few posts back, we discussed that a safe bury length is actually 3 to 3.5 fids. You will typically find 72 x diameter as the recommended bury length. So minimally you should use 72 x 1/4 = 18 inches. I have found that folks on the forum routinely use inadequate bury lengths - degrading the strength of the cordage by an unknown factor.

For example, I have found where folks build 8" loops (16" circumference) from 1/8" amsteel using a 4" bury. A safe bury would be 72 x 1/8 = 9 inches. Because there are 2 buries, the minimum safe loop size for 1/8" amsteel is 9" (18" circumference). For 1/4" amsteel, the minimum would be an 18" loop (32" circumference).

Technically, for a CRL, only one of the buries needs to be of the length necessary to maintain cord strength. Most folks are using 2.8mm (7/64") amsteel and there is sufficient margin in the cord strength to use a bury that does not maintain 100%. Most folks use equal length buries on an 8" CL, often substantially less than 8", and you'd be hard-pressed to find failures on these CLs if they are properly spliced. Chances are that, when and if they fail, it will be from wear associated with long use or damage to the fibers from hardware or bends and the failure will not be related to the bury at all. One could argue that, when 1/8" (3.2mm) amsteel is used, there is so much margin involved that the bury can be relatively short.

[SlowBro]

Mark, if you look a few posts back, we discussed that a safe bury length is actually 3 to 3.5 fids. You will typically find 72 x diameter as the recommended bury length. So minimally you should use 72 x 1/4 = 18 inches. I have found that folks on the forum routinely use inadequate bury lengths - degrading the strength of the cordage by an unknown factor.

For example, I have found where folks build 8" loops (16" circumference) from 1/8" amsteel using a 4" bury. A safe bury would be 72 x 1/8 = 9 inches. Because there are 2 buries, the minimum safe loop size for 1/8" amsteel is 9" (18" circumference). For 1/4" amsteel, the minimum would be an 18" loop (32" circumference).

troyji, Ooops! You are right that the recommended bury length should be 3 to 3.5 fids. There is no doubt that a longer bury does add to the strength of the splice. Anyway, one can "get away" with much shorter buries especially with comparatively static loads like hammock suspension. If you look at THIS rather detailed analysis by "Beth and Evans website" of breaking strength of knots, burys, stitching, and other joins you will find the following statement.

"Regarding bury length . . . quite short bury's will carry full strength. Under a slow 'static load' 18:1 will slip, but 27:1 will hold. I tested 27:1, 37:1 and 46:1 bury's under a significant drop load (50lbs falling on a 4' 1/2" dia Dyneema line as the 'fall line'). All three samples slipped about 3 diameters, which I take to be the "constructional take up" of the splice (without any stitching), but then all three held. Extra bury length is of course always a nice thing and double 27:1 = 54:1 (which is near the typical bury recommendation) would seem to be conservative, but these results do suggest you can 'get away' with a shorter bury if it is necessary to make the piece."

Ok, not a ringing endorsement of shorter buries, but the rest of the article clearly demonstrates that proper knots weaken the rope more than proper buried splices fail due to slipping, which I believe was your original question above.

Anyway, thanks for correcting my error- 3 to 3.5 fids it is.
-Mark

[troyji]

I don't know about you all, by my 275 pounds of manliness enjoys a visit from the wife in my hammock from time to time. Ain't no way I am letting a short bury catch me off guard at the wrong moment! I'll take the long bury, thank you very much!