Accessory Cord Use

Icabod

Icabod

Location
North Carolina
I am considering switching from using blake's to either distel or schwabisch with a micro pulley. I'm planning on getting an eye and eye cord made for this application, but am climbing this weekend, and thought I might tie one up and give it a try.

I noticed on an old post someone using 8mm accessory cord for this application, but it's breaking strenght is less than 5000#, is this kosher? Should I wait for a cord with an acceptible load rating, or am I ok to tie one up with my 8mm cord?

Icabod
 

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Since you tie both ends of the cord to your biner, you can double the MBS (you are using a basket configuration). The smaller diameter cords work wonderfully but wear much quicker than 1/2" rope. I would not waste the time getting spliced cords since they are basically throw-away items. I use 5/16" (8mm) New England Sta-Set that I bought on sale for 22 cents per foot. My cost is less than a dollar a cord and it handles better than any other cord I've tried. The MBS is 3000# which equates to a 6000# rating since I'm using both ends.

Last I checked the 8mm Sta-Set was up to 29 cents per foot. Look it up at www.sailnet.com
 
According to the Tree climbers companion (pg 85) the diameter of the cord used for tying the vt to a 1/2" rope should be between 5/16 (8mm) and 3/8 (9mm). So as to size of the rope, you are fine. As for the strength, check the load on your rope. It may be strong enough. Personnally, Id wait to get some that I KNEW for sure was good. Something like Ultra Tech that also has a great heat rating.

Best of luck w/ the new system.
 
Remember that our doubled rope system is already a basket system. The cord is another basket so you could get away with 1/4 of the 5000 lb breaking strength or 1250 lbs. Not that I am recommending pushing the limits but 1/2 should be plenty safe.

Dave
 
I disagree with you here Dave, I think one should follow industry recommendations and stick with 5000 lb
tensile rating.

A micro pulley is not needed with the schwabisch prusik. I discovered this by accident.

Joe
 
"...I would not waste the time getting spliced cords since they are basically throw-away items...."

I know I am super biased, but anyways: Even though the sling you use to tie your friction hitch is a "throw away" item that will last you anywhere from one day to only a few months, I still say go for the spliced ones. A splice is compact and neat. I find the bulky knots to be too cucumbersome. The attachment points on the front of my saddle is prime real estate that I'd rather not waste on unnecessary knots.

love
nick
 
Do splices allow as short a bridges?
Perhaps host diameter (of cord) varies that answer?

Years back a Samson rep i called to 'interogate' on different rope/knotting questions that kept me awake tooo much......

In one of the conversations he told me that throwing a line over a branch and connecting in a 'basket' formation underneath (swing) with Esmet or 100% strength eye splice(eye strength ruled out); was calculated at 165% line strength and not at 200%; for it was not 2 ropes, that would be an upgrade. The theory being, that there would be strain in the loop over branch, with one line that was diffrent than having 2 seperate lines, therefore basket was weaker than 2 seperate lines.

Of course, i asked then about sling ratings etc. of single leg at 100%, basket at 200%, choke at 80% (:: Choke strength x 250%=Basket Strength); He said that a sling would have 4 legs of material, but then i 'countered' w/eye to eye cable being the same 'math' as far as i know. He seemed to think it was an adopted convention, for conservative SWL's therefore with forgiveness built in etc. Also, more conservative ratings with better reputation companies; including Samson and maybe slightly this example. But that was the number they have generated to use and work with in their calculations of these things.

O'Course, he had a live one, tired of being an insomniac (is that redundant?);....... who just had to know then if the friction in the branch changed that factor any, with less shared tension at the top meeting point in high friction branch that rather than all this through a pulley to calculate these things......And he was honest and said he wasn't sure; so i thanked him for all the knew stuff i had learned in the conversation etc.

i remember the conversation, generocity, example and puzzle well. Perhaps things hve changed, that might have been 7+years ago....

So even more reason for doing the right thing, keeping the numbers high, and the SWL's absoulutely overwhelming to task! Especially this one! Time to tread lightly, and look intently,as this brews?
 
Splicing also affects the flexibility of your cord near the ends and therefore affects the way your hitch handles. I had negative experiences using a piece of Sta-Set I spliced up. The stiffness near the ends held the hitch open and kept the hitch from grabbing. I get 1-5 days out of a hitch cord, but all I do is climb. If you only climb an hour or two per day then you can get at least 2 weeks per cord. And if you prefer longer legs on your hitch cord then spliced cords may work for you. I prefer shorter legs on my cord for less slop so the stiff ends affect my hitch.
 
Hold up,

Joe, explain a little better... you dont need a micro pulley with the schwabisch? Are you advancing the hitch manualy, or do you have another trick up your sleeve? I thought I would try a keychain biner first, does that work?

By the way, I'm probably going to stick with my blakes on this climb, until I can get an ii cord or at least some new cord that I remember the mbl, and that is designed for arbo use. The more I think about it the more I worry, the biggest factor on a friction hitch is not dead load, but heat and friction so I'm sure that the cord would burn through from ascent-descent activity before snapping under my <180# weight. Between a faster ascent, and what is probably going to be a long climb I'm afraid that cord is going to get trashed while I'm on-rope, I'll never know until the hitch is off the line and I can inspect. Sounds like my local friendly arbo supplier is going to be getting some of my buisness soon.
 
Ive done some testing lowering heavy loads fast via an accessory cord hitch. I really doubt a single climber could melt 8mm cord to failure on a single drop. Any one else have any experience with this?

Dave

PS Joe, do you disagree with the theory of 1/4 load or do you just not feel comfortable on anything less than 5000lb?
 
I've tried, burned my hand before I could melt through any strands of the cord. Then when the hitch gets too hot to hold, you let go and it grabs/ stops rather than letting you fall. I think I might be able to burn through a couple strands if I had a 50' descent and welder's gloves. But the cord would probably get too soft and grab the host rope before melting through.
 
Making double braid '2 ropes in 1' a good choice strength, flexability, and 'backup' line inside with this heat factor? Better material would be better, but in a given material the best choice of construction to this purpose?

Down here in this heat (just starting, but must psyche through whole summer and not acknowledge it......)i don't wear gloves either; but from rescue/mountain/spelunking books gather that due to heat, especially in emergegencies and reaction to let go, gloves would be the requirement. Prolly give the last small buffer from saw vibration too.

And kinda from gymnastics we were taught to let callusses build(sanded down w/emery cloth) build, rip off leaving holes! And Pain! To develop toughened hands to task, rather than wearing the leather 'grips' and babying them (hands) all the time. Almost developing 'soft' callusses. Though against these heat factors, that wouldn't 'hold' all that well; but i guarantee there is something to that line of thought.....
 
Cam: tie a schwabisch then advance it as if you were using a micro pulley without the micro pulley. It worked for me.

Dave: There's good cord on the market sold by arborist suppliers which makes me perfectly happy and fulfills industry standards.

Joe
 
": tie a schwabisch then advance it as if you were using a micro pulley without the micro pulley. It worked for me."

errr...you guys still arent very clear as to whats actually doing the pushing...the carabiner maybe? Do you have the flexibility to advance the hitch by pulling the rope in many different directions?
 
Yoav,

I'm not sure what you are asking, but my understanding of the rig, and what I have observed while setting it up in my kitchen, is that the schwabisch hitch is advanced by the pully, or, hopefully (for the sake of my gear budget and backcountry toting weight), by a mini 'biner attached to the saddle. The weight of the falling end of the rope should be enough to self tend the hitch, am I right? If not where is the benifit of the advanced hitches.
 
"I'm not sure what you are asking, but my understanding of the rig, and what I have observed while setting it up in my kitchen, is that the schwabisch hitch is advanced by the pully, or, hopefully (for the sake of my gear budget and backcountry toting weight), by a mini 'biner attached to the saddle. The weight of the falling end of the rope should be enough to self tend the hitch, am I right? If not where is the benifit of the advanced hitches. "


Err...As I understand it and use it regularly, its mostly so you can tighten the hitch with one hand, as opposed to the one hand grab one hand slide you use without a pulley/clip. The weight of the falling rope is not enough to pull it down by itself, it can be handy but the same setup works fine for very short lanyards as well.
Even without the pulley, the advanced hitches just behave better than the 3up3down prussik. Are we on the same page? sorry if im being confusing.
 
Gear like pulleys or carabiners are not needed for one handed operation of the schwabisch hitch. This characteristic may depend on cord length.

Joe
 
I gave it a shot

I tried a schwabish on Yale XTC out of some 3/8 nylon double-braid. It just wouldn't advance without a pulley. What's the secret here?

love
nick
 
Re: I gave it a shot

Nick: I don't know what to tell you. I use a tenex cord spliced by Sherrill. They use the schwabisch hitch to sell the cord. It really does advance without a pulley or carabiner for me. Try using a 30"(about 76.2 cm) length of cord excluding the eyes.

Joe
 
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