SRT

S

Sawdust

Location
Bucks Co. P.A.
Ok, we understand that 50lbs. on one side needs 50 on ther other and makes the top 100.
But I'm still convinced that tying off to the trunk doesnt have same effect as pulling or lowering that set weight.
All that rope resting on and distributing weight along 80 foot of tree seems to have SIMILAR effect as "fishing pole set up"for rigging. It's obviously not the same.
Also the rope is anchored, and there is no down force on the anchored side. This is just Me thinking. I always try to lay my line over as much as possible with SRT.

One more thing, Anybody heard of an USHBA ascender/descender. I used it before but dont truly understand how to use it to its potential. It seems nice. Though it does not hold Arbo ropes well. Nice piece though.
 
Think of the rope and your set point as an old fashioned scale, where you put the object to be weighed on one side and add weight on the other side until it balances.
If you weigh 175 lbs and hang on one side of a rope over a limb, it will pull out unless there is the equivalent of 175 lbs on the other side. Where this balancing weight comes from doesn't matter, but if it isn't there you will pull the rope out and land on your butt.

If you are using both sides of the rope, each side is holding half your weight. So the total weight on the holding point of the rope is only 175 (plus the weight of the rope). As soon as you release one side of the rope, it will pull out without a balancing weight (or force) equal to your weight.

Hope this helps.
 
Yes this is true. Your 200 pounds puts 400 pounds of force on that sucker you call nothing but a chicken wing. I wound think that maybe the amount of force may be less do to some friction involved but minimal.
 
One way of reducing the 2:1 load on the access limb would be to let the access line run through a number of other limbs. Not having to isolate the main limb is one of the major advantages of SRT. If you want to belly over a limb or two that's fine. I generally try to get a straight shot on the access leg of the rope. Mark wrote an article in the April 2000 TCI about rigging. He shows how the load is reduced by multi crotching.

Today I had a limb that was a little bit small for a 2:1 load but was in the perfect place for access. After I got the end of my static line on the ground I tied a butterfly knot in the long leg of the access line. Then I slipped the end of the rope through the loop and choked the butterfly onto the limb. Now I only had a 1:1 load and I could retrieve the access line when I got back to the ground. This didn't leave me the back door that I like to have with the Gri Gri but that's a comprimise I was comfortable making.

Tom
 
I think the safety factor (for personal security) of one to ten that we (should) respect for our hardware, should also be applied to the access limb. Even more so, since we are not dealing with tested numbers but just with the climber's eye and experience. I NEVER footlock up to a limb that I consider to be unsafe for SRT. The opposite situation is much more likely to happen: If I can't find a single limb good enough for double rope ascent, I might (as Tom said) turn to multi-crotching SRT.
If a single limb is not considered safe enough for SRT, it should not be used for double rope either! That would mean using a safety factor of less than 2 to 1!

Sergio
 
I think it may be important to piont out that the line needs to actually be in a crotch or crotches not just hanging out over some limb .srt is great I use it just about every day and the only trouble I have ever had was the rope not resting in the crotch.I always prefer sending up a bowline when ever possible.I sometimes will send my friction hitch up slammed into the crotch ,srt up lanyard in clip on and go to it anybody see any problems with that?
 
Roachy,

I sometimes will send my friction hitch
up slammed into the crotch ,

What do you mean "slammed into crotch"?

srt up lanyard in clip on

Could you elaborate? What system do you use for SRT? Do you use your climbing rope as the access line?

and go to it anybody see any
problems with that?
 
Yea Tom in this case my climbing line would double as my acsses line ,I just tie my version of the VT and let my micro pulley take it up as I pull the tail of my rope ,this rides up to the crotch then on with the ascenders and footlock up then lanyard in lossen the vt ,tie in and go.
 
That is a good tip to keep in mind Roachy, thanks for sharing it. Another useful application of the technique you describe is using the v.t. as an adjustable mid-line knot. I have used it as an adjustable false crotch. It would seem appropriate to use it to choke the climbing line on a spar, adjust the length of the non-load bearing end of the rope to retrieve the rope, and descend on a descender.

Question: would it be appropriate to descend with a Grigri using 1/2 inch/12.7 mm climbing line for this application? It would be used when chunking down a spar.

BTW Mark Chisholm, I've already heard at least 1 retired climber wish he had the srt type descending setup for chunking wood you wrote for TCI(?) magazine. I read that article and didn't need it till a year later and remembered it when I did need it. It has saved me many headaches. It's an exceptional descending technique. I'm glad I get to use it.

Joe

[ September 28, 2002: Message edited by: joe ]
 
Thank you Joe. It was always a problem in my mind to think about chunking down or lowering wood without a really "secure" system. My father liked it the first time I showed him (back who knows when) and I've used it , or a newer version, ever since. It is good to hear possitive feedback on it.

I had a guy that I had trained from scratch use it when he needed it. He got rattled off of his gaffs during a log lowering job and his lanyard slipped right down. The only thing that kept him on the spar was his climbing line that was cinched off with a running bowline and his friction hitch. He thanked me that day!
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Since then I have modified it some, but I still feel that it was one of the most altering techniques that I had come up with to this day. Solving a safety issue is always a nice thing to do.

Joe, thanks for all of the math and science links. They are really useful and interesting to read as well
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Roachy, interesting idea. I first was exposed to that technique at the ISA show this year. Robert Phillips had shared that concept with me over a beer. He had other uses for it, but it was neat nonetheless. I showed it at the MSA conference last month and people were taking pictures of it there. I guess that I am not the only one who liked the thought.
 
Here's another SRT system to look at: http://www.rescueresponse.com/html/news02-02/highlight.html


From what I can gather, the Gri Gri can be used for short rappels. I think the limitation is 50m. The limitation is that the Gri Gri doesn't have a good way of dissipating heat. If a Gri Gri, actually any rap device, is used, the descent should be slow. If you touch the device with bare skin and its too hot, slow down.

The single rope spar descent system would be a good application for the Gri Gri instead of the climbing hitch. Since all of the climber;s weight would be on the hitch, it gets hot and locks up hard.

Good idea Roachy!

Tom
 
I always used to use a figure eight when chunking down wood. It has always been something I have tried to do with less and less moves. There is alot that happens from your last cut to your next. I used my 8 so much I actually wore it out. Has anyone seen an 8 with deep groves worn in it from after only 15 descents tops?

I have also found the tying and untieing blocks took up alot of time. When I first started using blocks instead of cutting notches in the wood I would just tie it off with a bowlin. Now I really like using the cow hitch. The only problem with that is when you get down to really big wood you need a really long sling. So if you don't have a sling that large you have go back to a timber or bowlin. Are there any better, quicker ways of attaching blocks on large diameter wood?
 
Are you using the 8 for lowering wood or as a descender? Don't you find that the ropes get hockled?

You could get a loopie to use as an adjustable anchor. A loopie has an adjuster like in a whoopie sling but in a loop configuration. I find that loopies are much more usable.

A buddy of mine worked as a rock blaster on the Crazy Horse monument in South Dakota. They worked off of 8's. Brad showed me how they would wear out the 8's because of all the grit in their ropes. The wear patterns made a really pretty wrap around the device.

Tom
 
I would tie a tag line to top of the log that was going to be lowered and then descend down on that line with an 8 and then strap in and set up a block.
 
Roachy, One thing that Robert used it for was for hauling up a dbl. sheaved pulley to enable him to utilize a 4-1 mech. adv. system. He also used a 3-1 and a 5-1 with a friction hitch or a gri-gri. He likes these types of systems for ascending. It has a lot of possiblities.
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On Tom's subject of the loopie sling, some don't realise that this configuration should also figure a 70% increase in rated strength over a whoopie sling of the same diameter.

I have used SRT on poles for a long time. I remove the pulley from the VT, tie a Distel and back it up with a Muenter hitch below. When testing this set up in the lab, the hitch would hold a factor 1 fall, with around 650Kg of force measured. This means it will stop your fall without serious injury, but the hitch may have to be cut to descend or be rescued. I'm currently testing a new prusik cord that should prevent the melting to the line (Could be the answer to our dreams!).

With the Muenter hitch under the Distel hitch, a ground worker can control the desc ent whilst the climber/rescuer only needs to work the hitch. It is much quicker to take the muenter off than other devices when descending and retying.

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Jump up here on top of the spar and I'll talk you down to the next level using SRT. We're standing here with our lanyards around the spar.

The top of the tree is gone now so there aren't any tie ins left. I could just continue down using one or two lanyards. That's fine but awkward and doesn't allow me to get to the ground incase of emergency. What we'll do is set up a retrievable SRT system before we drop down. Take your climbing line and let enough of a tail down to reach where we expect to make our next cut. Now tie a mid-line loop knot, your choice: bowline on a bight, figure eight on a bight, butterfly and there are more. Clip a locking biner into the bight and the running end of the climbing line. We're going to descend on the running end of the line via SRT. When I'm using this system I use one of several descenders that I own. IF you use a figure eight or other rap device be sure to have an autoblock tied as a backup. A Gri Gri could be used for short descents. A bobbin is a good choice. The Kong Indy is a good choice since it has a "sweet spot".

OK...time to drop down and get into position for the next cut. Rap down and get your lanyard on the spar. Sometimes you will be able to make the face cut while in the SRT rig. Getting into a comfortable position is much easier than working off of spikes and a lanyard. Now it's time to retrieve the rope from the choker up above. Slack off the tension or remove the rap device all together. Pull down the tail of the rope. Since the running end goes through a biner, you'll be able to slide the in line bight down to your nes position. Now all you have to do is reset the choker in the same fasion and continue down the spar.

Tom
 
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