In praise of Lawson Glowire

[MikekiM]

1.2mm glow wire.. that's what I am waiting for.

[Intimidator]

Oh yeah

1.2mm glow wire.. that's what I am waiting for.

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[packman9000]

Does anyone have feedback with Lawson's Ironwire? It must be popular it's all sold out in the longer hanks, just wondering if it's worth the premium and what everyone's thoughts are about it. thanks!

[cmoulder]

I have a hank of it (2mm Ironwire, yellow) but have not yet used it on a tarp setup, simply because at present I'm all set for Glowire/Guywire... no new tarp in a checkout basket somewhere.

But I've played around with it, tying some knots, and the handling (tangle resistance!) and knot holding characteristics seem to be the same as Glowire/Guywire.

Stated break strength is about double that of Glowire so your tarp will shred long before this breaks. Although I think that we sometimes overestimate the required break strength of cord for tarps. Some years back in Dolly Sods our group experienced some very strong winds—sustained 35-40mph with gusts to about 50mph—but my tarp held fine with Glowire on the ridge line and 1.18mm Atwood Micro cord (rated 100lb) for the guy lines. The tiny Atwood cord was a tangled mess, but it did not break.

[uninjured]

I have a hank of it (2mm Ironwire, yellow) but have not yet used it yet on a tarp setup, simply because at present I'm all set for Glowire/Guywire... no new tarp in a checkout basket somewhere.

But I've played around with it, tying some knots, and the handling (tangle resistance!) and knot holding characteristics seem to be the same as Glowire/Guywire.

Stated break strength is about double that of Glowire so your tarp will shred long before this breaks. Although I think that we sometimes overestimate the required break strength of cord for tarps. Some years back in Dolly Sods our group experienced some very strong winds—sustained 35-40mph with gusts to about 50mph—but my tarp held fine with Glowire on the ridge line and 1.18mm Atwood Micro cord (rated 100lb) for the guy lines. The tiny Atwood cord was a tangled mess, but it did not break.

I'm so in love with my new glowire I was considering replacing my lashit tarp CRL with it but then a small part of me reminded me that lashit has double the fending strength lest projectile hit it. When a subdued color of ironwire (gray or black) comes back in stock I will probably order a 50' hank and use that.

[nanok]

you mean as in tree branch or such? i like that idea too, however there's a problem: with no stretch, double the strength might be exhausted very quickly, especially if the ridgeline is setup very flat (without any sag). a line with a bit of stretch with less strength will be more likely to protect you in the end (now, how much stretch for how much loss in strength and at what rigging angles, we'd have to figure that out, but if the glowire is half the strength, although i don't know how much more stretch it has than dyneema, it might be better for very flat setups (very horizontal rigging angles); not to mention you might be able to bring some smaller/not so healthy tress down that way, too. just something to think about

[cmoulder]

I'm so in love with my new glowire I was considering replacing my lashit tarp CRL with it but then a small part of me reminded me that lashit has double the fending strength lest projectile hit it. When a subdued color of ironwire (gray or black) comes back in stock I will probably order a 50' hank and use that.

I've given this some thought, which is hard to avoid when you're suspended beneath a couple of trees with some branches weighing several hundred pounds or more.

It's probably true that a ridge line made of 1/8" Amsteel might possibly protect against falling objects of a certain size that a comparable Zing-it or Glowire ridgeline wouldn't. But at the end of the day any falling object that could kill you has enough kinetic energy at that point that a 200lb increase in ridge line break strength wouldn't slow it down or deflect it a bunch, especially since the ridge line is already under tension and would be side loaded at or close to 90°.

Maybe there's a physics expert among us who could chime in here.

[cmoulder]

Nanok, I think we're in agreement here.

I was trying to perfect my treatise as you were posting, so there we have it!

[nanok]

indeed, there is a difference only in that i believe the ridgeline might make a difference, maybe even a big difference, if it is setup in a similar way (similar rigging angle) as the hammock suspension or there's enough stretch to the line to absorb some energy and, most importantly, soften the rigging angle when it gets hit, thus preventing overload of the line and the anchor points. the ridgeline might break and not stop or hardly deflect a falling branch of more significant size, but it might still absorb enough energy to give you a chance (so instead of being hit by a massive, free-falling object, you have to deal with a mostly static, even if still massive object. the other thing is that, so close to the ground, a falling branch that's big enough to cause trouble is also likely to prop itself on at least one side, on the ground, other trees, bushes, etc.

of course, the bad news is that there's still a probability (quite significant) that stuff would fall without ever even touching the ridgeline. oh well <shrug>

in short: i think a sturdy ridgeline might help to add some protection, but rigging angles matter a lot, and stretch helps further. (so if you rig a zing-it ridgeline taut and straight from tree to tree, forget any protection, you can probably break that easily with a fraction of your own weight, by pulling on it perpendicularly)

edit: for similar reasons, i think a structural ridgeline for a hammock, much stronger than it needs to be, is a good idea: the advantage is the SRL will most often have a lot of opportunity to protect you by bending (and coming more inline with the hammock suspension), so there it acts as built in protection, with reasonable rigging angle and all. it's also very useful for the main purposes of an SRL, of course, so accepting a few grams more to make it "full suspension strength" starts to sound more and more logical to me (i haven't yet made the switch, i'm working on myself as you can see :P )

[uninjured]

I'm certainly no physicist but I think the general formula is mgh=Wd where m is object mass, g is gravitational constant, h is height from which it falls, W is the force applied by the rope (to counter the object's momentum) and d is the distance over which the force is applied (i.e, the stretch of the ridgeline). The last point is important, just think of a bowling ball landing on concrete vs a trampoline.

As cmoulder and nanok have been arguing, there are so many variables here that it's certainly very difficult to reason about this. But for fun, let's try with say a 10kg branch falling from 10m on your Lawson glowire which has a strength rating of 250lbs (1.11kN). We're going to assume no air resistance, and that the branch fell perfectly on the ridgeline without hitting branches, the ground, etc.. first.

For lashit, https://www.samsonrope.com/arborist/lash-it-zing-it I extrapolate that elasticity goes up to 4% at 100% breaking strength. Considering a reasonable 15' CRL, that allows for 0.182m of stretch; what that allows for in vertical CRL movement, I have no idea (I'm no trigonometrist either!)

Energy of branch at moment of impact: 10 kg * 9.8 m/s^2 * 10 m = 980 N
Distance needed for the glowire CRL to travel to stop the branch: 980 N / 1110 N = 0.882 m.
Distance needed for 1.75 lashit CRL to travel to stop the branch: 980 N / 2225 N = 0.440 m.
Distance needed for 1/8" amsteel CRL to travel to stop the branch: 980 N / 11125 N = 0.088 m. (88 cm)


A few things to note:

1) I don't think applying horizontal force perpendicular to the line is the same as the 250lb determination when force is applying in the same direction of the line's fibers
2) Bowline knot at one end is quoted at retaining 60% strength
3) Trucker's hitch on the other is probably a lot less than a bowline
4) (2) and (3) significantly reduce overall strength
5) I doubt lashit or glowire would allow such a large vertical shift/stretch of the CRL

Since I'm not about to use 1/8" amsteel as my CRL, I think I'm fine with switching out lashit to glowire (and ironwire if the **** stuff ever gets back in stock).