Advice on Zipline

[10 Bears]

I'm thinking of getting my kids more interested in climbing and I have plans to buy some kids harnesses, helmets etc., but one thing I was unsure of was the best/safest way to rig a zipline.

 

My thoughts were to use a timber hitch at the base of the spar tree, send the rope up with a twist or two around the main stem for added friction, over a reasonable branch, off into the void, and something similar at the other end with enough slack in the line near the lower tree/branch to act as a brake, perhaps with a krab/rope attached as a manual brake as well.

 

Other idea was to set up whoopie slings as the anchors, but to rig it more or less in the same way. Have I missed anything obvious or is there a better/safer way that you know of?

 

I have also had some thoughts about the line itself. I was going to just use a climbing rope as there shouldn't be too much load at any given time, but presumably, a bull line would be better due to higher abrasion resistance?

 

So to recap. Could you advise on:

 

Safest zipline rigging technique, any other necessary kit you think I may have missed, best type of rope for the job

 

I hope that the collective knowledge and experience out there can help, as I don't want to make a mistake when trying to let my children enjoy something that most of us take for granted. I don't mind dropping a log, but not one of the kids!

 

Thanks in advance...

[Pete Bannister]

Ive always used static line with low stretch properties. Rope selection depends on duration and period of intended service. e.g. if you're leaving in place for a couple of years you might want a different rope that if its just for a weekend.

I wouldn’t use a timber hitch to secure the zip line because of the risk of loosening during cyclic loading.

You need a means of applying and adjusting tension but this should always be backed up by the main line, in the event of release of the tensioning rig. The line should be slackened off when not in use for long

The safe means of run-out and breaking depends on the lie of the land.

 

The list of things to consider goes on but have fun!

[10 Bears]

Thanks Pete - there's some useful things to think about there. I could add in some more details to explain further:

 

I will be setting it up at my mates farm just down the road, and it will only be left in place while we are there and using it, which may only be for an afternoon, which is why I was thinking of a quick timber hitch option (but now wont use following your advice).

 

The lie of the land is pretty straight forward, some trees slightly higher up on a bank, over an open space/field area then onto other trees which are on the flat, but with some slightly higher branches to allow an upturn in the low end of the rope - again for braking. I wasn't thinking of a particularly taught line over the distance as I want it to be relatively slow descent - my children are aged 4-7. I also wasn't planning too high or long either for the same reasons.

 

Could you explain in more detail your comment about "a means of applying and adjusting tension but this should always be backed up by the main line, in the event of release of the tensioning rig". I know if I use a slacker line this may be redundant, but Id like to know more for future reference - the kids have this awful habit of getting bigger and very quickly too!

[10 Bears]

Oh - my thoughts drifted to rope again. I saw this on another post, and it seems like a suitable candidate. Any thoughts?

 

Sirius 12mm Bull Rope | Clark Forest : Rigging Ropes

[Pete Bannister]

If the zip line is too slack the 'curve' formed when loaded is steep, so you need pre-tension to get the right trajectory for the trolley ( eg petzl tandem)

 

I tension our zip line into a grigri using a bit of m.a. to obtain the tension; then I leave it in place during use but I always tie off the slack end of the zip line very close behind the grigri, so that in the event of a failure of the grigri I dont end up with a catastrophe. If your lower anchor is a tree then a few turns and lock off at the base of the tree with a secured mule hitch is as good as anything.

If you have plenty of ground clearance and dont mind speed, then less tension may work. Bear in mind that the vectors involved in zip lines when you pre-tension them can result in high loads at anchors.

Ive always tested our run at home myself, before allowing children on it. Its not very high (in fact its not really high enough and impact with shrubs, sheds or the ground is the biggest potential hazard). If it was much higher, Id probably think about rigging a second parallel line above it as a safety and run the break line from the harness up to the safety line. The reason being, I often leave ours up for weeks or months on end but I reset everything and tension it up before each use.

How long is your proposed run?

[10 Bears]

I've not measured it at the farm, but I would estimate between 35-40 metres...

 

Of course I could potentially set up in other locations on a slightly longer run (limited only by the rope - I thought around 60m)

[benedmonds]

I have tensioned ziplines using pulleys before and it's always been a bit of a ball ache. Got my lad a slack line for chrismas which is basically a big ratchet strap. I reckon this could work well for tensioning a slack line..

[Dan Curtis]

I've set quite a few up over the last few years. My favourite method is to the the top end into the tree with a running bowline. Then I use a grigri, rope grab and pulley to make a 3:1 tensioning block at the bottom end. Make sure you put stoppers behind the grigri, they can slip. Very simple to setup and operate for the right tension.

 

I've never bothered with a brake of any kind, if your setup is long enough you should slide on the floor before coming to the base anchor. If you do find you hit the anchor, drop the top end down a bit to lessen the angle.

[Pete Bannister]

I've set quite a few up over the last few years. My favourite method is to the the top end into the tree with a running bowline. Then I use a grigri, rope grab and pulley to make a 3:1 tensioning block at the bottom end. Make sure you put stoppers behind the grigri, they can slip. Very simple to setup and operate for the right tension.

 

That's the way Ive done it of late. Agree on the grigri risk.