Where does it say?

[DRA177]

The use of a double loop knot (figure eight, inline, butterfly...) for "two person" loads. I've looked at 1670 / 1983 and did a forum search with no luck. Any thoughts or facts on the two loop vs. single would be appreciated.

[KB1OEV]

I don't think I am familiar with the terms double loop and single loop as you are using them here.

Generally the three knots you listed produce a single loop. I can tie what I call a figure 8 harness knot which results in two loops that you can put your legs through, but I don't know of a way to do this with a butterfly or inline (which I assume means an inline figure 8).

Please explain further.

[jbrescue]

I don't think I am familiar with the terms double loop and single loop as you are using them here.

Generally the three knots you listed produce a single loop. I can tie what I call a figure 8 harness knot which results in two loops that you can put your legs through, but I don't know of a way to do this with a butterfly or inline (which I assume means an inline figure 8).

Please explain further.

This is a double eight. But, to answer the original question, I have no idea what you are talking about either. We never use any sort of double knots. WE use bowlines and eights all the time. We back them up, but never use double eights or any other double knot.

[jmatthe2]

No standard covers when to use what knot. There is only a list of knots a rescuer should know. Some are double loop.

[TNFF319]

Can you post the list or a link to that list, please?

[KB1OEV]

I'm sure others will be able to add to this, but here goes...


to make a loop at the end of a rope
- Figure 8 on a bight
- Figure 8 retrace
- Bowline

to make a loop in the middle of a rope
- Butterfly
- Directional or Inline 8

Connect two ropes together
- Sheet or Becket Bend
- Figure 8 Bend

Tie a rope to an object
- Figure 8 retrace
- Bowline
- Clove hitch

Make a harness
- Double 8
- Swiss Seat (Not taught in my FFI/II)
- Portuguese Bowline (Not taught in my FFI/II)

All knots except those tied in the middle of the rope are tied with overhand or barrel safetys.

I didn't go into which knots you would use for particular applications as that topic is way too broad.

[DCFDRescue2]

The use of a double loop knot (figure eight, inline, butterfly...) for "two person" loads. I've looked at 1670 / 1983 and did a forum search with no luck. Any thoughts or facts on the two loop vs. single would be appreciated.

I would bet you're seeking answers after a "safety" kind of guy said something about double loops for a two person load...

Knots do not generally break in the loop, they usually break where the rope enters the knot. A double loop use more rope, takes more time to tie, ans is not as easy to inspect during a safety check.

I can try and help you out further, give me an e-mail if you'd like:
rescue-2@comcast.net

[jmatthe2]

Add one more negative to DC's list....Double loop knots are not that much stronger than single loop...1-3%...that's it!

Go to NFPA.org and search for NFPA 1670 and NFPA 1006. You can view them for free. The list of knots that are recommended by NFPA to LEARN are in these standards.

If you are looking for merely opinion, mine is that there is a time and place for every knot that you learn. Lowering and raising systems lifting 600 lb. loads do not require two-loop knots. There is enough safety factor to do the evolution with a one loop knot...assuming you have adequatly evaluated the remaining parts of the system.

[DRA177]

DCFD you hit the nail on the head! Was told by a member from another department to "always" use double loop (bight) any time you expect a "two person" 600lbs load, but he could not tell me why or where the practice came from. I don't like the word "always" in the fire service, especially in tech. rescue. I know all teams have variations in how they set up their systems. Select, construct, and use systems commensurate with the organizations needs - per NFPA 1670. My original question was - is there written documentation to back up his claim? I've looked, but maybe not in the right places.

KB1 when I said double and single loop I was being generic, didnt mean to confuse.

Figure eight on a bight (1 loop) can be made into a Double loop figure eight / Double figure eight loop (2 loops).

Butterfly (bi/non directional) can be configured into 2 loops.

Inline eight / Directional figure eight can be configured into 2 loops.

I've used Double loop figure eights (one long loop / one short) for load sharing or distributing anchor points, but it had nothing to do with "two person" loads.

[jmatthe2]

In short then the answer is "no". There is no documentation, other than personal preference and opinion, that says or suggests using double loops for 2-person loads.

[kferrara2002]

jmatthe2 iscorrect in stating the difference is minimal between single loop and double loop eights. A single loop eight will reduce rope strength by 20% appx. Where as a double loop eight will reduce rope strength by 18% appx. Can that small percentage make a difference, sure. However most agencies have that false sense of security when using the double, especially in high line operations. Not only does the knot have to be factored but the overall operation must be calculated with respect to load weight, angles, exerting forces, etc. in order to determine if a certain set-up is sufficient and safe.

[rescuedawg]

The double figure 8 can be seen at animated knots.com. It takes nothing to tie and while it does only give you 3% more that three percent can be an extra 300 pounds. Its a good anchor knot.

[bkdrft]

If we are talking resuce then common practise is to rig everything for a two man load and a single loop 8 is rated/designed for a two man load

Knot efficency: There is some litirature out there that states a single loop 8 reduces the strength of a rope by about 18% where as a double loop reduces the strength of the rope by about 17%. basicaly nothing in it.

My own thoughts on double v's single is simple wear and tear. If you are putting in a full day of training on top of a high rise you will reduce the wear on the rope in the "bend" of the knot, where it contacts the anchours, if you are using double loops. With dozens of rappels going on in a single day or multiple stokes evolutions this may or may not have in impact on the life of your ropes. However, in a recent emergancy rescue, with a kid hanging on for his life, I used single loop 8's in the absolute confidence that they would do their job.

Dave,
B.F.E.S.

[LeeJunkins]

I think what you are talking about is the two in the picture; the double loop is no harder to tie than the single and takes less than one second longer. If dressed both are very easily inspected.
One of the advantages I find in using it is for quick identification when packaging a patient. I use a double for haul lines and single for safety lines.

[FIRELT03]

All that is mentioned in NFPA 1006 chapter 5 section 5.5 is the following:

5.5 Ropes/Rigging.
5.5.1 Tie knots, bends, and hitches, given ropes and webbing, so that the knots are dressed, recognizable, and backed up as required.
(A) Requisite Knowledge. Knot efficiency, knot utilization, rope construction, and rope terminology.
(B) Requisite Skills. The ability to tie representative knots, bends, or hitches for the following purposes:
(1) End-of-line loop
(2) Midline loop
(3) Securing rope around desired objects
(4) Joining rope or webbing ends together
(5) Gripping rope

hope this helps a little
F Clark

[Eno305]

I'm pretty sure the issue here is in handling two people on a single line, tied into a single knot (of whatever description) with 2 bites / loops.

Fundamentally if you apply your 10:1 SSF to your rescue rope- which likely has an MBS of over 40Kn, you actually have enough strength to put two people on one line- excluding a rescuer.

1.3Kn per person, 2.6 for 2 people... X 10 = 26. We subtract 30% off the rope MBS automatically for knots...

But, with that being said...we'd never do it.

[JMac73]

My understanding is that the single 8 is slightly stronger than a double loop, due to less turns in the rope.