Regarding the actual post topic:

For the few traverses I've done, I ignorantly hand-tightened by Bandit (Blaze) arborist's rope as best as I possibly could to eliminate a big V and thus hauling myself up the rope on the far side. Still ended up with a decent V, and obviously no TIP or rope failures occurred. That said....

OK, say I accept that I need 120deg angles in my rope to be safe. How on earth do you figure out how loose to string a rope so that you end up with 120deg once you load it with your bodyweight? Yes, I could haul a pack equal to my body weight up a tree and send it across first, but that seems like a lot of work. Other ideas?

Bandit is relatively stretchy, Moray gave the example of 3/8" Sterling HTP hand-tightened which has very low stretch. I think it would be very difficult to tighten 11mm Bandit enough by hand to make the angles unsafe.

Bear in mind that a single rope traverse is most useful for greater distances than can be done with a 150' rope on a DRT traverse. A DRT traverse is easy to set up and is very safe (if you've tied in to safe anchors).

When doing a single rope traverse you're always going to have to haul yourself up the uphill side. Very difficult (if not impossible) to do without a rope grab in the mix. Something to consider is what kind of rope grab you use to accomplish the angled "ascent" at the end of the traverse. There's a school of thought that says don't use an aggressively toothed ascender for that purpose. I have but when I do make sure to keep bouncing/thrashing to a minimum, smooth motion and soft loading is key. A rope grab with a non-toothed cam (Microcender for example) is ideal.

I've never seen anyone setting a traverse pre-test the loaded angle with weight. What I've seen others do and I've also done this is go out on the traverse line with a DRT tether far enough to fully load the traverse line and make sure everything is copasetic. 20-25' out is enough to test the integrity of a horizontal traverse setup (as opposed to a zipline).

The safest way to set a Tyrolean Traverse is use two ropes, one above the other, the climber is attached to both ropes.

Just for reference... I've set a 180' span zipline with a 10.5mm Bluewater II static, polyester cover, nylon core. The rope was tensioned with a GRCS (Good Rigging Control System) capstan winch, first person on the zip was over 200 lbs. Even with significant MA tensioning the catenary was excellent. My concern was that the zip rider would contact the ground in the middle of the zip, not that the line was too tight. The guy that wanted to go first was an experienced arborist/rigger who was not worried. As it turned out he had to run on the ground for about 15 ft. at the center of the zip, made for a good laugh. We tightened the line a bit more after that. As Moray mentioned rope construction is an important consideration especially for an MA tensioned line, the nylon core provides added safety.

Ultimately the bet way to become good at setting safe traverses is practice low and slow, figure it out, build your traverse setting skills gradually.
-AJ

It is equally as logical to presume hypothetically, from reading our posts and viewing our videos that they will get a strong impression of how risky some of these things are and that they do need to know more before proceeding - to wit - the very inquiry of this thread!

I hear your critique Moray, but I don't see you suggesting anything I haven't already stated - the 120° reference angle - I said that from my first post.

You seem to be hung up on "difficult to over tension by hand". Well, it is and your posts of how hard you have to pull is a good example of that. Even pulling 100 lbs as you stated, you still have a 5:1 safety margin. I know that doesn't include knots but again if you use tensionless connections and high strength ties, the knots become a non-factor. Which again emphasizes this discussion is no more than guidelines and rule of thumb. But there is nothing said anywhere that one should pre-tension with all you can pull.

As for your hypothetical figures, tell us how much stretch you accounted for and how much give in the knots and how much sway in the trees.

In fact tell us what our safety margin is on a limb we ascend on? I know guys that climb on limbs much smaller than I would; further out than I would. The 10:1 thing is a myth. I know of no ascender that will support a 10:1 margin.

Consider that Bruce Smith of On Rope fame, uses a 12 man concept for tensioning high lines. What that means is that with the maximum load in the center of the traverse, the line should be tensioned to what 12 men are able to pull. But, as he states in his book, two men can accomplish that with a 6:1 MA. That's with 11 mm rope. The emphasis here is with the load in the center of the traverse.

Still 12 men pulling on a rope is formidible. Let's say each one can contribute only 50 lbs. That's 600 lbs of force right there with only 50 lbs from each man. Suppose they pull as you project, 100 lbs each - that's 1200 lbs in the rope!

But, even with that, yes, some common sense must be applied to all rules of thumb - don't over tension. But then what does that mean and how do you determine whether it's gonna be over tensioned before you load the middle of the traverse? How do you pre-determine the 120° angle?

We can't pre-determine all that, might not can even after we have it tensioned. So it remains rule of thumb driven.

moss is right, all climbing discussions imply rules of thumb, risks, etc.

But if your troubled by "...difficult to over-tension a line by hand without MA" then add "...and you shouldn't attempt to pull it tight..." or whatever you want to add that you'd feel more comfortable with.

But I've done a bunch of single line traverses, and I've yet to get one too tight by hand. In fact, I usually have to re-tighten them after the first use because of too much dip. Shorter traverses are a bit touchier.

Same here, I rarely get it tight enough on the first set, ergo why I once had to kick my way over a chain link fence testing a zip. So far all the danger I've experienced setting zips is not tensioning enough (by hand). I've never set a short traverse w/single rope, I have no reason to.
-AJ

LOL - while I haven't had to kick my way over a fence, and I'm smiling as I visualize you doing that, I have wound up with some pretty deep Vs.

I did one very short single rope traverse, proabably around 10 - 12 feet, to get into a position to take a pic of a limb. I had no choice. I was to the point in the tree where there were no reliable TIPs that were high enough to support a DDRT traverse, so I used the trunks as the TIPs and set up a short single rope traverse.

Jack, good point about bounce. Were you thinking of something like this?

I've never been tempted to bounce on a horizontal traverse, or zip for that matter. I think most technical tree climbers know (or should if they don't already) that they can seriously magnify forces by bouncing. I'll bounce a vertical rope to verify the strength of a TIP, otherwise bounce is verbotten!
-AJ

LOL … well sorta … if I tried a split like that, I'd split in half all the way up to my chin. However, I think that by the time my feet got a meter apart, I'd simply do a face-plant into the grass … LOL … he was good, though … but he was at a safe low-'n-slow height.

I would be interesting to have one of your peak-load testers in that line he was bouncing on, wouldn't it? To specifically address the OP and the ensuing discussion, it would be an interesting experiment to setup a 10-20 meter traverse with typical static and dynamic line; tensioned 'hand-tight' (50kg?); then measure the tension and angles at the anchors with a 100kg load in the center; then bounce the load from different heights to measure the tensions at various excursions. It might be useful data to have properly documented.



I never doubted it for a moment, Andrew. The caveat about bouncing was offered simply as due diligence for those few who may not have known about the risk already. I sincerely hope neither you, nor anyone, took offense.

I, too, use the magnification of vertical forces to bounce test a TIP. I even have an anecdote about those forces that may be of interest. A few years ago, while climbing with a sit-stand type system, my ascent rhythm was apparently the same as the natural frequency of the tree which resulted in a large harmonic oscillation with the tree itself. Each bounce of the ascent got larger and larger until the excursions approached a meter. It was fun but, fortunately, I recognized it as a potentially dangerous condition and modified my style to stop the oscillation and avoid getting into trouble. Just hope the concept will be helpful to pass-on.

Since the title of the thread addresses anchor loads, lets go to an expert that teaches this stuff and has one of the highest rescue certifications you can get and trains rescue personel - Bruce Smith, co-author of "On Rope".

When a caver was trapped in a deep cave in Franklin Tennesse, Bruce was called for the rescue. The significance of this is that Franklin in much closer to Nashville, the capitol of TN than Chattanooga, but no one in that area had Bruce's level of certification.

Then, last summer, Bruce showed me the rigging they used to rescue an injured man and they had to set up a highline with a long drop down to the man. The rigging required pretensioned backties, high tension tie offs, etc. The very things that Bruce teaches in his advanced rescue certification classes. He even uses load cells to demonstrate forces generated to the trainees.

In fact, I hope to get in on one of his rescue training classes he performs at Fall Creek Falls (FCF). FCF has a waterfall in a gorge and they set up a highline with a drop to the floor. I'd like to do that.

But, quoting from the book, "On Rope", here's what Bruce says about tensioning a highline, and I'll relate that back to a tyrolean traverse:

"Before actually tensioning the highline with its full payload, it is important to pre-tension. Pre-tensioning should take place with two people pulling on the mainline. This can actually be done easily with one person using a 2:1 tensioning system. Curiously, when the full payload hangs from the center of the expanse after pre-tensioning, the proper tensioning only needs to be fine tuned."

So how does pretensioning a highline relate to a tyrolean traverse? Remember I said it would be difficult (not impossible, but difficult) for one man to over-tension a traverse line? Well here's Bruce saying a line should be pre-tensioned by two people pulling on it before it is loaded. But lets keep in mind that is totally unnecessary for a tyrolean traverse and should not be attempted. But it does speak to the issue that even on a tyrolean traverse, it would be difficult for one man to over tension the line.

Bruce uses 11mm nylon rope, EzBend to be exact. So I'll stick with my statement based on Bruce's experience and my own that it would be difficult, not impossible, for one man, wtihout using MA or some other method other than just arm force, to over tension a traverse rope.

But, it is important to keep in mind that when Bruce, et al, sets up a highline, which is different than a tyrolean, they use multiple pre-tensioned back ties on the anchor tree.

For a tyrolean traverse, the back ties would not normally be needed and it is unnecessary to bust a muscle trying to tension the rope. OTOH, as both moss and myself have repeatedly found, the tension often, if not always, needs to be tightened after one use.

But all of that has to also be considered at the anchors also. The forces in the rope are applied to the anchor points as well. And as I alluded to it in a previous post, there could be enough force with a long lever arm to be problematic at the root system of the tree.

Not all, you'll have to work waaaay harder to offend me I just wanted to point out that bouncing on a traverse line is not something that's in the normal range of activity for people who create their own settings. I can imagine someone bouncing on a steel cable line at a commercial zip facility. Majority of the time even on commercial zips people just ride, not bounce.
-AJ