I'm not saying 15° isn't safe for you, nor anyone else for that matter. But, 15° does put twice the climber's weight on the rope. You alone, at 140 lbs, won't be a problem, but a number of our members weigh 250 lbs and more. To say 15° is safe and let it go at that, might be a bit misleading.

Plus, if you ever had to 'help' another climber on a traverse, that 140 lbs is now at least double that.

All that criteria you listed is conditions that are extremely important. We just saw a rope failure in a traverse recently.

But of all the criteria you listed, assuming a sound rope and anchors, the tensioning is the key. We can't measure angles of rope easily, sometimes not at all. So it is important not to over tension. If one is using non-flexing anchors, e.g. back tied trees, tensioning becomes even more important.

But yes, a 140 lb climber can get by with a more tightly tensioned rope than a heavier climber.

It's important when we start making 'safe' statements that we include the whole picture, i.e. what conditions make it safe. Safe is not always safe.

And the standard disclaimer/reminder... when any of us post we're stating our opinion. Anyone considering doing anything on rope has to take full responsibility for their own safety and perform due diligence/research to determine the safety of any climbing techniques or rope configurations they are considering.
-AJ

That disclaimer is not a license to state seems like I remember somewhere, somebody said something about 15° and let it go at that. There's a lot more to it than that.

Part of the 'research' is seeking knowledge from more experienced and knowledgeable tree climbers and one way they do that is on boards like this.

So when we give advice about a specific question, it needs to include a little more than one parameter that purportedly makes it safe for everyone.

Hey man you're getting all legalistic on me. This is what I said first on the subject:



Here's what I said next:


That's very conditional, not certainty "I think..." ie: my opinion, my guess, as I recall etc. Also urging low tests first.

Here's what I said next after showing a photo of a very respected and experienced climber on a traverse with a roughly 15° or greater angle. Note: the rope he's using is 6000 lb rated and was brand new at the time.



Note the constant reference to "test low" and language like "15° or greater".

I feel very comfortable with all of my comments above on the subject.

I guess I have to search and find the old discussion and see what folks said about optimal angles at the time.

Even as a flyweight I would not feel comfortable with a 15° angle on a 5000 lb. rated rope, would not do it.

Even on 10mm HTP I felt pretty squirmy about it, I like margin of error.
-AJ

Well that wasn't too difficult to find, the previous discussion is here:

Tyrolean Traverse Anchor Loads

Very similar to the current discussion except Moray took the role of warning "Watch what you say guys!"

I found the source of the minimum 15° angle recommendation, I quoted it from the TAG safety page with the catenary force calculator, here's what they say:



I believe TAG is a reliable source of high angle rope safety information.
-AJ

Clearly rope strength rating is key, assuming the anchor quality is good. With a 5000 lb rated rope the 15° angle is not so great but with the 5900 lb. or better ratings typical for ropes widely accepted for tree climbing use a 15° minimum angle is looking good.
-AJ

The safety of the traverse is not in what looks good. We just saw an accident report on a traverse line that must have looked good.

The minimum angle should be based on a desired margin of safety, not an angle. The angle is only one factor. The strength of the rope, the angle, and the weight of the climber are all equally significant to the safety of the climber.

It is a natural reaction to a sagging line to take up slack before the next rider crosses. That can lead to over tensioning. I got taken to task by saying that if a person only tensions with his hands, no MA, he can't over tension a line. Tell you the truth, I'm not sure he could over tension a rope with a 2:1 MA, but that's untested and unconfirmed. Anyway the guy said people's strength varies too much to go by that.

And he does have a valid point. What if the 300 lb guy is on the ground and puts his entire weight into tensioning the line with his hands?

All I'm saying is we have to be careful making sweeping statements about only one aspect of a technique and suggesting that one thing makes it safe.

Ya, zips are a whole 'nother matter. Setting a zip line for a bunch of people to ride requires upping the safety margin for all aspects of the setup waaaay up. That's a huge responsibility, not to be taken lightly.

Never did see any detail of that accident as far as what kind of rope or cable was used on the zip, who set it, etc. etc.

Setting a traverse line for yourself is not to be taken lightly either but at least you're in control of the variables.
-AJ

I haven't heard any details either. I meant to ask Bruce to see if he had heard anything. I'm sure we'd all like to know some details.


We can be in control only if we know all the variables and the significance of each.

ok, let me see if i have this straight-- regarding the weight difference between a 15° traverse and an SRT ground anchor, the traverse might put more weight on the rope, but it is no more weight on the limb than the ground anchor, yeah?

i have been using a 32 kn rope for traversing, which feels pretty pretty pretty pretty safe. i also think safe practice involves lanyarding out onto the traverse line and fully test weighting it, before hauling yourself back to unclip and commit. recently i went across a 100' traverse set by someone else, using 1/2" california truck rope (WLL 420 lbs, tensile strength of 3,700-4,000 lbs). it had already been used so i assumed it was good to go, but somehow the far end of the rope had gotten caught up on another small branch in the process. i slid out on my pulley and after about 20' the rope finally pulled free from the snagged branch and i felt myself free fall several feet and then catch. the drop happened so fast that i didn't have a chance to react and then it was over and all i could think was "well, i am still here". i traversed across and as soon as i got clipped back onto the tree the adrenaline rush finally surged.



20-30' feet. which was barely closer than i was high. it would've been easier if i was higher, actually, since then i could've let out more slack on the throwbag to make it an easier snag. on two trees i was just barely close enough to reach it on my tippy toes stretched out perpendicular from the trunk. if it ever quits raining i want to try again in some tall doug firs.

32kn rope sounds excellent. First time I set a high traverse solo I also went out on a long lanyard first to test. If there was a failure it still would have been bad swinging back into the tree but it helped with my confidence. Now that I have a good handle on what works for me configuration-wise i don't do the long lanyard test.

I hear you on the "too fast to react" situation when dropped a couple feet on any rope system. It's happened to me a couple of times on remotely set DRT traverses, some twig breaks or the rope moves down over over a nub when I'm out on the traverse, it happens so fast you can only get an adrenaline rush in retrospect, if you get one at all. Same for partial TIP breakouts on SRT ascent. I now try REALLY hard not to create the conditions for that to happen when setting any rope for any purpose (traverse, ascent, whatever).
-AJ

What's the deal on "truck rope"? I have a friend who did some tree sitting to protect old-growth Coast Redwood, they rigged all their traverses with truck rope. Is this a "standard" in the PNW for environmental action folks? I can imagine it's a cost issue. It's quite the challenging test environment, must be lots of history/stories behind the use of that rope over the last 15-20 years or so! Have you heard about rope failures with that stuff?
-AJ

The 15° traverse doubles, well actually, 1.93 times the climber's weight on both the rope and anchors. So, yes, what you stated is the idea.

yes, if you ever go to the mckay tract in humboldt you will see close to 60 trees tied in with truck rope traverses. it is truly awesome. cost is probably the main factor, but also longevity in the elements. the truck rope has a uv sensitive orange tracer strand. it can be hard to keep track of how long rope has been in use, but if the orange fades to white, you know to replace that rope.

http://efhumboldt.org/2011/06/tree-sit-music-video/

Cool video! Thanks for posting that, Sinthome!