OK.....Let's Get Into The Meat Of SRT !!!!

[TheTreeSpyder]

As Nick has reminded us before, internal rope workings can be like stange Voodoo.........

i think on braided lines working, cranking, moving over an arc for 100% strength efficiency, of a standard flexible line of polyester/nylon braid; that 8x the line diameter for the pulley is the standard recomendation. The pulley should be sized and shaped correctly on the bottom and sides of the 'sheave' to support the 'belly' and sides of the line properly, to screech this high efficiency out.

Conversely, on a fixed hang without being cranked and worked around that curve of the pulley and entering all those dynamics, i think that 3x rope diameter for the mounting, for 100% rope strength efficiency, same rope construction constraints is the standard quote.

Orrrrrrrrrrrrrrrrrrrrrrrr something like that!
Peace,
:alien:

P.S. Because i've been maid to agree with you no who again in the same lifetime, i burden you with my favorite bowline and tying method....

 

[NickfromWI]

From the New England Ropes webpage on Braided Safety Blue 16-strand arborist climbing line...

"Recommended D/d ratio is 8:1 "

http://neropes.com/arborist/default.htm

My concern, guys, is not so much if it's okay to use a carabiner in the aforementioned manner. Nor do I care about sheave size for our lines (Mike, you DO use a 4" thimble on your climbing lines, right?). The big question: When is it okay to stray from the reccomendations of the manufacturers?

Apparently we do it often. Some of you folks are putting up quite a fuss over the side-loaded carabiner. Yet, I get no straight answers.

love
nick

 

[RescueMan]

Rules and Recommendations

Nick asked:

When is it okay to stray from the reccomendations of the manufacturers?

Apparently you missed my post on the bottom of page 18 of this thread, or else you're just being ornery!

There is an enormous difference between a manufacturer saying DON'T side load a carabiner, and a manufacturer saying "for maximum strength, maintain a minimum of a a 4:1 diameter ratio for pulleys."

- Robert

 

[RescueMan]

Capsizing Bowline

Murphy asked:

If set properly what would cause it to capsize???

It's not only the "cowboy bowline" with the outside tail that can cause this, but a properly-tied bowline - even a backed up one - can capsize during a lowering if the half-hitch (the rabbit hole) gets snagged and dragged upwards, moving it above the bight around the standing part.

This actually turns the knot into a slip-apart knot, not a true slipknot, and it will fail instantly under load.

Spyder's pictures illustrate this well.

- Robert

 

[TheTreeSpyder]

Thanx, never heard that before on the loop getting snagged!

The bowline animated .gif i posted is of making a 'DBY' with the slip knot method(fergot to say that); making the same bowline knot with this backwierdz strategy is in itself an explanation of how the knot could invert/capsize IMLHO. That being said, i really don't think that making the finished bowline with this slip knot method makes it more likely to slip out the same way, it is just easier to see and view the mechanics i think. Also i think that the DBY comes close to 8 in symetry (easier on eye to quick check), strength, security; slip knot method darned easy to make. Especially when you want to get just part of the bowline made, then wait for something to be brought, stretched, swung etc. to you, to capture real quick in the 2nd stage with only part of the knot to finish. The slip knot part, can be achieved then laid aside, hung on thumb so you can use your hands, or on a stob, this holds especially well in wait for you to need it with the friction and rigidity of the 2 turns together rather than 1 i think.

i remebered where i got the numbers for the line bend efficiencies (well, some of 'em). Samson's Climbing Line Guide they used to give out on request; then later viewable/downloadable from Samson Rope Ruides . Some interarresting points throughtout the guide- a real must have IMO! It is even better than the previous, expanded 10 or so more pages, just for us!!

Top of Page 26, has a table of maximum rope strengths for bends, different on a pulley or on a 'pin' that i assumed (pin)when i read it before meant, just a hanging point/swinging? Not, turning on a pulley/ working across an arc, all kinds of dynamics going on internally, just hanging/swinging. If that is true, that would be like a knot i think. Taking that rule of thumb presented, the 2 line diameters the arc of the half hitch chokes gives approximately the strenght of the bowline i thought.

Bottom of Page 12, brings out a point about the type of knot termination choice to prevent sideloading the carabiner as much as possible.

Excellent, Excellent Guide IMLHO; so i won't say anymore now, unless someone can't get to it! Loads of points and discussions eminent i think.

i think a lot of rigging is about being the inspector and placing everything in maximum strength/minimal loading (umm unless you can inverse those properties, to your advantage ) ; that is equitable as a habitual style, art, mental puzzle and exercise to be better at each.

Orrrrrr Something like that...
:alien:

 

[Kneejerk Bombas]

I've been playing around with something new, to me anyway.
One time the SRT really shines is for limb walks. I came up with a way to cross back and forth from DdRT to SRT. Simply tie a midline loop in the running end, just above your hitch, and clip the standing end to it. Now your SRT. Do your limbwalk and when you get back switch back to DdRT.

 

[Tree Machine]

Clarification

Diagram ?

 

[Tree Machine]

I understand clearly what you mean. It's an excellent method for the DbRT devotees to 'give SRT a try', if only for a few moments, without having to set up a classic SRT rig. Give everyone a diagram, though, so everyone is real clear what you mean. G'job Mike. -TM-

 

[murphy4trees]

Simple enough.... sweet idea Mike... reducing the amount of line a climber needs to move by half, while loosing very little of the benefit of the 2:1 MA, because there isn't much weight on the line...
That'll have to be included in the book!!!!
TM,
Its pretty much just the way MM said..
tie an alpine butterfly or other midline knot such as a doubled fig 8 or fig 9 just above your climbing hitch....
unclip your biner and spliced eye from saddle and clip to midline loop.... continue moving out the limb on the single line with same friction hitch... I like that one a lot...

 

[Kneejerk Bombas]

Originally posted by TreeCo
The only problem I see is that the carabiner may get side loaded pushing up against a limb as the climber limb walks. Or even a tangle with brush in the carabiner.

Dan

That would never happen.

If you start out where you don't have to decsend, and plan to return, no footlocking or pantin needed.

 

[RescueMan]

Just a question

I'm always thinking ahead to a possible self-rescue scenario.

Not that tree climbers ever fall on a limb-walk, but IF you did would your fine-tuned climbing VT (or whatever hitch you use) catch you in a shock-loading fall on single rope?

And, if it did, how hard would it be to climb back up with footlock and hitch on single rope?

- Robert

 

[Kneejerk Bombas]

Personally, I'd footlock back up, or footbrake down to the next limb and re-acsend. Another option for me, is to use my lanyard to pull myself back up DdRT.
When ever I climb, if the swing potential gets high enough that I might injure myself in a fall, I safety in.

 

[Kneejerk Bombas]

What's the best mid line knot for this?

 

[Lumberjack]

I would say buterfly or the directional 8.

 

[NickfromWI]

How 'bout a slip knot!

 

[NickfromWI]

Here's a pic to show.....

If you don't like the slip knot, I'd say go with a Butterfly.

love
nick

 

[RescueMan]

I'll often use a similar techique in rock-climbing when I get to a belay station and have to "limb walk" a ways from the anchor to get a better line of sight to my second whom I'll be belaying up.

I'll use a clove hitch to attach to the anchor 'biner. The fact that it cinches down on the 'biner makes it less likely that the 'biner will turn and get side-loaded.

- Robert

 

[Kneejerk Bombas]

The clove sounds smart. Once you are done, you pull out the biner and the knot falls apart, no untying.

 

[Kneejerk Bombas]

Originally posted by NickfromWI
Here's a pic to show.....

If you don't like the slip knot, I'd say go with a Butterfly.

love
nick

What the heck is in that pan on the top shelf in the background??
I hope that's not your dinner!

 

[NickfromWI]

Funny! I don't even notice that thing anymore! That's all the sawdust that I swept up after I got building my splicing table!

That's edible, ain't it?

love
nick