Rap Slings

[catbirdseat]

Climbing Ride the Lightning the other day, I noticed bail slings hanging off single bolts. No doubt this was because someone had only a single rope.

 

What was remarkable was that even where there was a belay anchor with two or more bolts, the bailing party used only one of the bolts. The slings were girth hitched when they could have been doubled. Doubling would not only have been stronger, but would have made it easier for the next party to clean from the bolt.

 

I think that an American Triangle would have been preferable to use of only one bolt. Is this not so? Assume that the bolts are 10 inches apart. You'd have redundancy, if not proper equalization.

 

A friend of mine suggested a variant of the American Triangle that uses clove hitches at each bolt. Would this not allow better equalization when all you have is a single shoulder length sling? The girth hitches would use up an additional 5" or so. It would only work if the bolts were pretty close together.

 

Down side would be that it'd be PITA to set up.

[G-spotter]

Using one bolt is actually stronger than using an American triangle. Do the math.

[letsroll]

Another rap sling question. What do people like to use??? I have and still using 1 inch tubular webbing. Yes it is bomber but it is heavy and takes up space. Other options??? 5 mm cord? or less??

[blueserac]

Rap sling material really depends on the whats and wheres. What is the anchor intented to perform like after you use it; what sort of connection interface is employed from anchor sling to rope; what is the traffic going to be like; what, what, what? Where are you placing and using the sling? Are you engaging the anchor in a rarely visited area or are you dropping it in a high use area? Does that help?

 

I remember cleaning a sling from Liberty Bell 3 years ago, it was one that I had placed 3 yrs earlier. It was supertape, and it still had the rap rings I put on it. It had numerous friction burns from rope crossing over it as someone pulled their rope down. On that anchor there was a another sling of 7mm prusik cord, and that route never gets any traffic nor is it subject to UV. Wow.

 

In this case and position I think chains would be best to carry.

 

I have read that rappelling can place between 3-4kn of force onto the anchor, so if you want a margin of safety it isn't much more to pack that. Your anchor should be redundant, at very least, and I am uncertain why that wasn't carried out initially to spawn this thread. How and what do you pack? What is your life worth to you? What is the life of your buddy that you are climbing worth to you? What are the lives of those less aware that will reuse your anchor worth to you?

 

I use 7mm prusik cord after all the reserves of either inch or supertape are gone. In high use areas I have even placed mallions on the bolts, and rap rings to encourage repeated use vs. the pull through.

 

There is an excellent book published by the Alpine Club of Canada, edited by Murray Toft, "Playing It Safe"; it is a great and informative resource.

 

Have your buddy duplicate the amount of additional slings you carry. Consider employing a few tied double-length shoulder slings vs. the sewn dyneema expensive sort.

Edited May 2, 2007 by blueserac

[mattp]

Using one bolt is actually stronger than using an American triangle. Do the math.

 

... then throw away your calculator. People prefer to rely upon two bolts not because they are "stronger" according to your calculations, but because they are thus relying on two bolts rather than one.

 

All the hand wringing over the "American death triangle" has always seemed a little misplaced to me when we are talking about forces of maybe 500 pounds (body weight plus a rope plus a bounce and your vector analysis), and the slings and bolts in question are expected to hold several times that amount. For a failure, a sling or bolt must fail at vastly lower than its expected strength, and the odds of both slings (those who rely on two bolts rarely rely on just one sling) and both bolts failing vastly below expected strength are way small. Even assuming no friction where the sling passes through the hangers, or between the sling and the rock (did your calculator correct for these?) the additional "force" imparted by the use of the "death triangle" is not that significant.

[high_on_rock]

I find it odd that we are all willing to take a whipper fall on a bolt, but want two bolts for a Rappel? If there are two there I will use them, but I personally have no issue rapping off of a single bolt.

[mattp]

I don't know about you, but I for one do not willingly take "a whipper" onto a single bolt with no other back up. Unless there are other bolts or gear anchors below that one, and a decent belay anchor as well, I'm generally not willing to take the chance.

 

I will rap on a single bolt some times, but I am always keenly aware of the fact that when performing bolt replacement I have found bolt strengths to vary a lot more than appearance would suggest and even a shiny 3/8" bolt could be worthless.

[dan_forester]

Another rap sling question. What do people like to use??? I have and still using 1 inch tubular webbing. Yes it is bomber but it is heavy and takes up space. Other options??? 5 mm cord? or less??

 

I switched to carrying 1/2" webbing - plenty strong and takes up a lot less space.

[Alex]

In the winter I carry 6-7mm perlon for rapping off v-threads like everyone else; that works for summer-time too. But I *do* like the old 1" tubular stuff, perhaps only for nostalgic reasons.

 

I tend to cut down a lot of worn-out or useless rap slings/stations in the mountains. Most of the anchors I see these days are 5/8" webbing. In the Rockies you might be on a well-travelled ice route and find 3-4 slings and/or cord on 3-4 different trees at the top of a route, all within arm's reach. As a rule I'll clean trees, but leave existing v-threads in-situ if they look good. On something alpine or rock thats commonly-climbed like Das Toof, the nests get so large: there is really no point in leaving the faded crusty slings in there when beefing up the anchor with your new webbing.

[hawkeye69]

Using one bolt is actually stronger than using an American triangle. Do the math.

 

i used to use the merican death traiangle all the frickin time. show me all the accidents of TWO 3/8" bolts ripping aout because of all of the horrendous forces involved. i aint aware of to many. we did back in the day because we were cheap and hadnt had physics yet.

 

rapping off one bolt when two are handy is stupid unless you only have just so much webbing....or you have absolute trust in that one bolt.

[letsroll]

When the old webbing is good I use it and save my webbing, when not sure back the old with my webbing. Thinking for good Karma I am going to start clean out old webbing and leave a nice new piece this year. For trees I girth hitch them so they can grow with out growing over the webbing.

[AlpineK]

As an arborist I'm sorry to say but you're wrong. A girth hitch can also damage trees. Since you are passing a bight around the tree and then pulling it tight to set up your rap anchor you are also putting a constriction around the tree. Anything that draws tight around the main stem of a tree can damage it.

 

For the least damage running a loop over a larger branch and around the stem will cause the least damage to the tree, but even that isn't perfect.

 

I hate to say it but bolts in rock cause the least damage to trees.

Edited May 2, 2007 by AlpineK

[tradclimbguy]

Is it just too obvious or something? Rapping off one bolt is stupid unless that is your ONLY option. Why not just carry thin 1/2 webbing and carry enough of it to set a few equalized rap anchors off two bolts if you have it available along with a few rap rings or some biners. I have a 20+ft chunk of it wrapped into a very tiny ball that weighs all of a couple oz's. Enough material for a number of rappels too, no American triangle needed and no need for a single bolt rap.

 

I've always been of the mindset that the few bucks I lose on biners or sling is minimal when compared to blowing an anchor or the unlikely chance that single bolt fails while bailing and falling to my death.

 

As for falling on "one bolt". Yes I fall on one bolt all the time but NO I don't trust just one bolt. Usually there are multiple bolts or pro clipped between me and the single bolt if it fails, that or an anchor that should be bomber. Now if I rap on a single bolt and it fails, thats all she wrote, end of story. I see the point your trying to make, its just flawed.

[counterfeitfake]

This conversation... very boring.

[catbirdseat]

You aren't making it any more interesting with your contribution. I suggest that you just go elsewhere.

 

The point I was trying to make with this thread is that redundancy is important in climbing. Some people seem to not fully understand the concept while others do.

 

Don't pass up the opportunity for a redundant rappel anchor unless you have no other choice, that's all I'm saying.

 

In response to Dru, the load on each bolt is approximately 1.4 times the load on the rope, which is a modest price to pay for redundancy. If you have two shoulder length slings, naturally, you can reduce the force to 0.5.

Edited May 2, 2007 by catbirdseat

[G-spotter]

Actually you can jack it up to 4 times or more the load on the rope for high angles That's not redundancy. It's weakening the system.

 

They call it the American Death Triangle for a reason. Cause it sucks!

[ketch]

Hey CBS, I will have to look but I seem to recall the clove hitch variation you mention being brought up in Largos new book. He had some pretty good reasoning for advocating it but I don't recall it all. It may have been as simple as the clove hitch at each anchor with a little slack between bolts effectively transform the Death triangle into an semi equalized anchor. I cna look that up when I get back to the book unless you have it.

[mattp]

Do as you wish, Dru. If I have two bolts, and a piece of sling only long enough to build the death triangle, I'll use both bolts. And given my assumption that webbing does not vary in strength nearly as much as bolts do, I believe it will be safer to do so.

 

(I realize that you can generally tie a "V" anchor with an overhand at the bottom and a single line tied directly to each of your two bolts with only minimally more webbing than it would take to tie the death triangle, and I am quite sure that most here would agree that is preferable - so you need not bring up that counterargument.)

[rob]

OK, I'm a big dummy. Why would you NEED to build a death triangle? If you had a small sling, couldn't you still tie it through both bolts, use a sliding-X and just have a higher-angle V anchor? A high-angle V-anchor is WAY stronger than a high-angle death triangle.

 

 

 

forces generated V-anchors vs. triangles

Edited May 2, 2007 by robmcdan

[catbirdseat]

If your sling is made out of 5 feet of tied webbing it is 48 inches long. If the bolts are 12 inches apart that leaves 36 inches. The legs are 18 inches long if you use an American Triangle. The angle between strands is about 40 degrees.

 

If you use a sliding X, the legs are 9 inches long. The angle is now about 150 degrees. The force on the bolts would be unacceptably large.

[spotly]

I carry 15 feet of 9/16 tubular and a few rap rings. I would trust a single bolt only if I had to.

[hemp22]

If your sling is made out of 5 feet of tied webbing it is 48 inches long. If the bolts are 12 inches apart that leaves 36 inches. The legs are 18 inches long if you use an American Triangle. The angle between strands is about 40 degrees.

 

If you use a sliding X, the legs are 9 inches long. The angle is now about 150 degrees. The force on the bolts would be unacceptably large.

for the sliding X, the legs will each be ~12", so the angle will be 60 degrees, and the load on each bolt will be less than with the AT (based on the #s in the link above).

[G-spotter]

And if the legs were 9" long the angle would be ~83.5 degrees (basic trigonometry). Good thing you are a chemist and not a mathematician, CBS!

Edited May 2, 2007 by G-spotter

[catbirdseat]

I didn't do any math. I just guestimated.