I e-mailed Blue Water to try to get some data about the elastic properties of their webbing, but i didn't get anything back from them. They said
"Do you own a load cell or dynamometer? You must determine the actual peak
load to calculate." that was all :(

Can't say i know exactly what they means, but maybe some of you guys do.

I e-mailed Blue Water to try to get some data about the elastic properties of their webbing, but i didn't get anything back from them. They said
"Do you own a load cell or dynamometer? You must determine the actual peak
load to calculate." that was all :(

Can't say i know exactly what they means, but maybe some of you guys do.

Best guess:
It means that elongation % is a curve and not just a normal % of stretch. It also means shy of having a load measuring device we're pretty much left to statics and trig (or at least as far as I know).

The elongation would be a curve, since nylon is a thermoplastic material. However, it should operate in a fairly straight line until it approaches failure. The slope of that line is the elastic modulus.

I should have qualified that with the statement that the curve is highly variable depending on factors such as environment, age (even unused web will get more static with age), usage and treatments.

Blue Water man says:
"I can supply you with elongation figures for specific loads. The "tension"
is the variable and the unknown in a slackline w/o a load cell. I figure
zero to X lbf in 250 lb. increments? Will that work? This will only apply to
BW climb spec webbing. Other webbings may vary [they]. If it out of
curiosity the figures will be of value. If it is out of need for end use I
strongly suggest using a Yates screamer as a load limiter in the system.
There are different models with different activation forces. They work"

i e-mailed him back and asked him to send all the data he could. We'll see what fun numbers we get back.

Hey slacklinejoe... want to fund a research project in exchange for the results?

Man you engineering students can take the fun out of slackline in a hurry!!!
I'm with Larry, "you guys are hurting my head!"
I'm sure this is not my kind of thread but, dynomometers have been put on slaklines before.
When Darrin did the highline between two buildings in Long Beach for Ripleys, one of the stage hands had a dynomometer and they rigged it in the set up!
Darrin told me that when he got the line walkable it read 800lbs. He also said that when he was on the line, it only increased the load to 850, I don't know about the load of a fall because Darrin never ever fell! as a matter of fact he did that walk leashless!!!

and the Blue Water man says:
"Age won't be a critical factor. You'll likely wear web out before age
becomes an issue. Wear is the biggest problem as I see it. Webbing loses A LOT of strength with small nicks [or] at the sides. The worn/ cut spots throw the web out of balance and it can lose a great deal of strength. DON'T use worn webbing!! UV is the biggest long term problem especially if the web is left set up on a regular basis. Water reduces nylon strength by 25% or so but nylon regains the strength upon drying. Wet web will elongate more. %age increase of elongation I'm not sure off the top of my head. Dampness- same as wet but not as big of a problem. The nylon produces say nylon will not mildew. But the accumulation of dirt, oil from your hands, sunscreen etc. can get attached to the nylon and those things will mildew.
I'll get my lab guy running testing this a.m. if he's caught up on regular
materials testing."

I think i love this guy.

Actually, I could have told you most of that. I believe however, that if the nylon is stretched a lot while wet that won't necessarily regain all of it's strength. It would depend if the wet nylon is strained enough.

With it being wet, it looses 25% of it's strength so it makes sense that it also takes somewhere around 75% as much of a load before it starts going static when compared to normal.

Interesting!!!! It seems that the force of him being on the line is absorbed by the stretching of the material so that it doesn't increase as much as you would expect. The elasticity of the webbing acts as a shock absorber so that the entire load isn't transferred to the anchors.

The amount of load before it permantly makes the web less dynamic than new. I.e. when wet it reaches that load faster than when dry because it's actually weaker in that state.

At first glance, this seems correct. At second glance, it seems impossible. The third (or maybe not until the 100th) time you look at it, you figure it out. If the person is standing still on the webbing, there is no way around the statics equations. The load HAS to be transferred to the anchors in the exact amount calculated via trig. It doesn't matter whether you are using a bungee cord or a chain.

The slackline tension will always be the same, given a line length, weight on the line, and angle from horizontal (or equivalently, change in height from nonweighted to weighted line). It just happens that Darrin was able to get his non-weighted line to a tension close to the tension of his weighted line. The fact that he was able to get the numbers so close is due to the large stretchiness of webbing (I think).

*Sweet: I'm a top roper.

and the Blue Water man says:
"Age won't be a critical factor. You'll likely wear web out before age
becomes an issue. Wear is the biggest problem as I see it. Webbing loses A LOT of strength with small nicks [or] at the sides. The worn/ cut spots throw the web out of balance and it can lose a great deal of strength. DON'T use worn webbing!! UV is the biggest long term problem especially if the web is left set up on a regular basis. Water reduces nylon strength by 25% or so but nylon regains the strength upon drying. Wet web will elongate more. %age increase of elongation I'm not sure off the top of my head. Dampness- same as wet but not as big of a problem. The nylon produces say nylon will not mildew. But the accumulation of dirt, oil from your hands, sunscreen etc. can get attached to the nylon and those things will mildew.
I'll get my lab guy running testing this a.m. if he's caught up on regular
materials testing."



so, sorry to change the subject a bit, with uv being a huge killer to webbing just how safe are those trad anchors. you know the ones where people have left webbing lashed around a rock years ago and expect people like me to rap off of.