tensioning highlines

[tree-fancier123]

I haven't yet set one up, but was wondering could it be tensioned with a smaller tirfor style winch using a bowline on a bight, or similar.

 

I can of course go into the woods on a rec climb and just experiment, but am first asking for ideas about

1.sensible minimum thickness of stem at the fork, probably species dependent

2 how much sag there is, I know there are variables, say if the line was at 60' and trees 100' apart - climber in centre nearly on ground due to sag or suspended at 50'?

3 Using a small tirfor in the way described I was asking because obviously the line wants to be tight, but could tensioning it snap rope, tree top, or even start to lift the root plates. I guess the root plates and tree tops are more a consideration than the rope, if money were no object (apart from 80k for a tracked mewp) the rope could be tensioned using one of those load cell gadgets to keep tension way under the ropes SWL

 

The people who have posted high line stuff don't seem to have any dramas, but just thought the tirfor idea may allow a bit extra tension.

 

If I do have a go at setting one up 14mm sirius bull rope and a hitchclimber is all I have currently. I guess the 14mm rope can be pulled pretty tight if the trees can take it?

[Alinicoll]

I don't know if I would use a tirfor. When you hang off a high line the forces generated are surprisingly high. If you are super tightening the line to remove sag then you will be over loading everything. I think with a horizontal high line you would be putting 5x the weight of the climber on EACH end of the high line so 10x on the line itself, thats static load, if you are bouncing around then the forces are even higher. So it's better to have some sag.

 

Ideally you want the anchors well above where you are working to leave plenty of sag in the line and still be able to work off it.

 

Some kind of smaller hand winch would be better. We've used a hobbs but you could use a 3:1 or similar.

[tree-fancier123]

thanks, pity about the overloading thing, was thinking about situations where there are neighbouring trees, but not much higher than the intended work position

[Alinicoll]

They are useful in certain situations but I think like zip lines they either work or are they don't. It is a technique worth playing around with. I see you're already aware of the beech highline thread, there's some useful stuff in there.

[BenR]

Food for thought:001_huh:

[tree-fancier123]

nice diagram - I guess half a ton pulling sideways at the top of a tree is a fair amount of leverage at the rootplate, but obviously not too much or no one would use highlines.

I can see now that pulling the two trees together with the tirfor on the highline may be a bit much, unless each tree was guyed at 180 to the highline, by which time it would be getting dark

[scotspine1]

I've worked off 3 highlines on different jobs in recent years and it would never occur to me to use a tirfor to tension the line, it seems excessive.

 

I think I posted this pic in the Beech highline thread, we just use a variation of a 3:1 block and tackle system for removing the slack and making the highline taught enough to support the climber. Equipment wise we just use what's easily available and works.

 

David Humphries has posted good pics of highline setups following the beech highline thread which are more refined than what I've used.

 

Some people like to use two lines to create the highline with one of those rigging hubs in the centre as an anchor point.

 

 

 

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[scotspine1]

another tensioning setup (this one is taken from an old Treebuzz thread). That's the original Buckingham Port A Wrap 1 being used in that setup.

[Darrin Turnbull]

Here's something as well.

[scotspine1]

tree fancier, this thread/vid may be of interest to you -

 

High-line improvisations | The BuzzBoard

 

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