Is there any way to make a simple, moveable shock absorber for climbing?

                    I'm trying to put a multi-purpose platform about 90 feet up a very large tree.  The first 25 feet or so from the ground is completely devoid of branches, so I threw a rope around some branches higher and then prusiked up it.  However, the throwing-the-rope-up-and-prusiking method will be ineffective higher up, as the dense braches would stop a rope thrown from getting anywhere.  So I was thinking that I'd do a via ferrata type system, where I had multiple slings attached to my harness and would attach them progressively to branches as I climbed, so that I could clip in, climb a few feet, clip in again, unclip the previous sling, and repeat this.  However, a short fall onto normal webbing or rope would cause serious injury.  I looked at buying a via ferrata kit, but the only ones I can find are one-time tear versions.  I really don't want to have to pay ~ 100 USD every time I fall, so I was wondering if anyone knew how to make a simple, reusable energy absorber, preferably from webbing, carabiners, etc. (i.e. the kind of stuff the average climber has lying around).  Thanks!

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Here's something i found that I'm going to build

http://www.oldnewspublishing.com/climbing/vflanyar...

Jayefuu7 years ago
So you just want to get the up the last bit that's full of branches? Could you do the prussiking with a rope tied to you and then just get someone to belay you up through the branches, placing slings as protection as you go? That would be much safer and cheaper since you're not relying on just two contact points, one of which may be unattached as you're moving up and the other may(or may not) be wrapped around a branch that could break. Cheaper because you're more likely to have a spare rope and a dozen slings and crabs already.

If you still want to do it your way you can buy a via feratta stitch plate and thread your own with your own carabiners.
mad magoo (author)  Jayefuu7 years ago
Honestly I've never really lead climbed, so leading up the tree with a belayer would be a little hard.  I mean, I know the techniques (Freedom of the Hills FTW!)  but it would still be a little dangerous.  I think the best option is something like that stitch plate you mentioned earlier.  Know any nationwide retailers that sell them? (REI and MountainGear don't).  By the way, what were the "damper" and "screamer" mentioned earlier? 
A screamer is a sling bunched up and stitched in a certain way. When you fall on it the stitching rips and you fall on the sling. Some of the force from your fall is absorped by the ripping stitches.

I'd still advise that you lead it. Or if you don't have the experience yourself ask around and see if one of your friends knows how. Might be worth a few beers (after! :p) for you to get him/her to lead up it and place a static rope for you to prussik up. 
gmoon Jayefuu7 years ago
A screamer is designed to absorb more energy than a dynamic rope would on it's own (for marginal pro), but it's not to be used in place of a dynamic rope.

A screamer by itself with a static rope or sling wouldn't soak up enough force to make it safe.

"Construction" lanyards are a combination of dynamic sling and screamer-type technology. Probably not cheap, though. And one-time use only, like a screamer.
Jayefuu gmoon7 years ago
Ahhhhh yeh. When ice climbing you've got the springyness of 2m or more of dynamic rope to help.

On that point.... perhaps leading IS the only safe way to do this. I've done via ferrata and we were strongly warned that while the lanyards they gave us would stop us breaking our backs if we fell, it WOULD hurt. A lot.
gmoon Jayefuu7 years ago
Right. When "on belay," the climber has all that length of dynamic rope that leads down to the belayer to help absorb the fall. The higher the climber goes, the more the total length of rope, so the lower the "fall factor"--assuming everything else is equal (length of the fall, distance above the protection, etc.)

Some considerable energy is also absorbed in other ways. The friction of rope running over the 'biners; the knot tightening on the harness; the rope running over rock if it passes through several pieces of gear, etc.

Several years ago, Petzl used to run a graphic about falls on static lines.

If I recall correctly, a "factor two" fall on 0.6m of static line is considered fatal--that's a fall of just over a meter on approx a 1/2m of cord. Either your back would break, or the harness, or both.
I wonder if the roped access guys have something suitable ? I seem to remember seeing something with a damper in it.
A screamer with screwgates on either end instead of snap gates? Not resetable like the stitch plate.

I still thinking finding a belayer's the best/safest option.
gmoon7 years ago
Good call on realizing the danger of falling on a static anchor.

Jayefuu is on the right track. You'd be "lead climbing" the tree.

So approach this like any lead climb. Enlist a belayer, set "pro" (protection) every few feet by slinging the branches (ALWAYS use a carabiner, never run the rope through a sling itself.) Periodically you'll have to climb above the pro, but that's what makes it a lead climb.

Obviously, you need a "dynamic" rope for this. Forgive me if you know this already, but there are two types of climbing ropes--dynamic and static. Static ropes are used when the rope itself is climbed (ascender) or for hauling.

Static ropes have little or no "give." They are much more durable, and don't "bounce"--why they are used with ascenders.

Dynamic ropes are the "shock absorber" you're looking for.

Done carefully, the largest danger here will be hitting a branch below you in the fall. This could potentially be very dangerous.

The severity of a fall isn't measured in total distance, it's measured by "fall factor"--the ratio of the length of the fall, to the length of dynamic rope that's "payed out." The most severe fall is a "factor two.": falling twice the distance as the rope length. It doesn't matter if you fall 2 meters or 200 meters, the severity is the same.

You could "solo self-belay" yourself--something like what you describe. But that's tricky.  Do it wrong--"hard"anchoring the rope at each branch--and each fall will be a factor two.

The correct way would be to anchor the rope at the base, then give yourself just enough slack to get to the next anchor (branch), by tying a temporary knot in the rope on a locking 'biner and clip that to your harness. Then climb up, set the pro (sling with a biner) clip the rope and get your self to a "safe position" (clipped in to an anchor, most likely) where you can add more slack. Then repeat.

To be honest, if you've never lead climbed before, you might want to think twice about doing this... Lead climbing isn't rocket science, but there are so many potential mistakes you could make as a first timer (like "back clipping" an anchor), I'd try to enlist someone with experience.
I've seen ones made from an accordion-folded flat metal tube around some webbing, but there is absolutely no way I'd trust a bodged-together DIY rig. Well, not without extensive R&D and testing, anyway.