eye and eye slings

[treeclimber165]

Hey guys,
I just made myself a couple 5/8" slings for various rigging duties. Since learning how to splice, I'm seeing all kinds of ways to save money and make my own stuff. I wanted to check out some N.E. nylon double braid that I saw on sale so I bought 20'. After cutting it in half and splicing each end I ended up with 2 slings that are 6' long. Rating on the rope is 13,600 so it's more than enough for practically any rigging aloft. The rope is very soft, but I don't think it will snag as badly as the (very expensive) Tenex slings on the market. The slings cost me $8.60 each versus $42 for a Tenex sling.
I have a 16' Tenex sling but many times I need something shorter. I think these will work nicely.

 

[hillbilly]

Tenex...how about some swedish Dynex ?
12 mm has a breaking strength just above 36 000 lbs
http://www.poly.se/shared/produkter/170.htm

 

[MasonGrey]

This may be a little off subject...(Brian, I know you're a stickler for about that). I am going to ask anyway. Can someone explain to me what is tensile strength, Safe Working Load(SWL), and breaking strength? If I have a rope with 13,500lb tensile strength, how is SWL determined?

 

[hillbilly]

Determined by the appllication in which it is to be used.
A safety factor of 5-12 is typically used in rigging applications.
A safety factor of 15 or more is typical for life critical applications.
Divide the tensile or breaking strength by the desired safety
factor and you get SWL.

 

[heartland]

Originally posted by MasonGrey
If I have a rope with 13,500lb tensile strength, how is SWL determined?

A design factor of 10 is recommended by "The Tree Climbers Companion", the ISA Certification Study Guide and professionals from ArborMaster. Use same calcs as hillbilly suggested to get the working load limit (WLL), that is:

tensile strength / design factor = wll

So, your 13,500 rated rope has a wll of 1,350. Somebody can correct me if I'm wrong, but I think SWL and WLL are the same thing......

 

[MasonGrey]

Thanks Hillbilly and Heartland.

T/C, sounds like you are getting pretty good with your splicing. If I remember correctly it hasn't been that long ago that you tried your first splice. I think I will do some reading up and give it a whirl.

 

[treeclimber165]

New England Ropes recommends a WLL of 4-1 to 12-1 depending on risk. Tensile/ breaking strength is the average maximum before a new rope will break. My main concern is at what point do you start damaging the rope. With 13,600# tensile, I know I'm good for 1,360# every day with occassional shock loading up to 3,400 without damaging rope fibers. Virtually all of my rigging comes in below those numbers and I have heavier slings for big rigging. I was going for lighter weight and smaller slings for every day use rather than the big 3/4" Tenex.

I also have a couple loops I tied out of short pieces of 1/2" Safety Blue arbo rope. I use them with a steel rigging biner and a screw link for most light rigging. I drape the loop over the fork, attach the 'biner to one side and the screw link to the other side. Then I run my lowering line through the 'biner and screw link. Damage free rigging with almost no friction and the sling is removable from the ground just like a friction saver. Tie an overhand knot on the carabiner side of your lowering line and pull it through. The knot will pass through the 'biner and grab the screw link to pull the sling out of the tree.

 

[geofore]

splice

I'm going to make a hard copy of your first post on how hard it is to splice. With a few more years of splicing you are going to wonder what it was that gave you fits when you first started to splice. If I were you I'd learn to splice three or four different types of rope and practice on those days when you have time to doddle around. Turns out it is a fun hobbie aside from the money it will save you and then they will say, "I know some old timer that does his own splicing." that will be you they're talking about.
Have fun

 

[John Paul Sanborn]

For light rigging I use I&I splices with 3/8 tenex. it is so easy to use and has a SWL of 550#. Get the 9/16 and the SWL is 900#. My 3/8 costs under under .35/ft. so a balnancer I made for a buddy cost around 10.50 in material.

Tensil is Minimum Breaking Strength (MBS)and SWL per ANSI Z133 is 10:1. For manrated equipment ANSI specificly states MBS minimums.

IMO the ABS is a marketing tool for the cordage companies, i would not want to have a below average run when I'm pushig the limits.

 

[Tom Dunlap]

Look in the new catalog for a good description of this dish of alphabet soup.

Another place to read about how these ratings apply, read Arborist Equipment.

Unless all ropes and gear are tested in the same method we'll have a variable that we can't control or understand. Some ropes are pre-stretched to a percentage of their rated breaking strength then a allowed to relax for a time. then they are brought up to a higher percentage and relaxed. then they get pulled to breaking. If a brand new rope is taken right to breakage there will be a different number. This is one very good reason to have higher safety factors. Who ever wished that they worked in an environment that was MORE risky?

Tom