Slacklines as jacklines

[Oldrig]

Lately, I've been spending my time prowling skiing websites, looking for bargains in telemarking equipment. On one site, I noticed a sale of "slacklines," which seem to be woven nylon webbing with eyes in each end that are used for a sport I've never heard of before, "slacklining."

I'm wondering if, since these pieces of webbing are designed to hold a person's weight, they could be used as jacklines. They're a lot cheaper than jacklines from marine suppliers.

Any ideas?

--Joe

[Captain Smollett]

I wouldn't.

Polyester (low stretch) vs nylon...slacklines are designed to stretch.

The lyf-safe jacklines I looked at on Defender were also coated for abrasion and chafe resistance, for what that might be worth to you.

Your choice, of course....as always.   ;)

Not saying the marine pricing is "right" in this case, but the old adage "You get what you pay for" immediately came to mind when I read your post.

[Tim]

Well I am just going to have to say that the nylon tubular webbing that I used may stretch more than a polyester but it is used on a lot of boats out there. Likewise it is used in many climbing and rescue situations.

Maybe it is not the best, but it is available for .36 cents a foot;

http://www.rei.com/search?query=bulk++webbing

[Captain Smollett]

Stretch on climbing gear is often a plus or sat least acceptable.

Stetch on jacklines can render them nearly useless for the stated purpose. I read an article a while back on the topic of drownings due to being drug by attachment to the boat, and jackline stretch figured prominently in the discussion.

Food for thought...

[Tim]

I likewise have read accounts of jacklines being too loose to do the job. Tubular webbing is not designed to stretch like dynamic climbing ropes, and like I mentioned I am guessing that the majority of cruisers out there are using it.

My own feeling is that the proper placement of the jacklines is much more of a factor in their usefulness than the difference in nylon vs polyester webbing.

But it does make for an interesting investigation and I will look around for any data. Maybe get Practical Sailor to do a test if they have not already.

[Captain Smollett]

My own feeling is that the proper placement of the jacklines is much more of a factor in their usefulness than the difference in nylon vs polyester webbing.

That's a good point.

[tomwatt]

Climbing webbing (and rope) is fairly abrasion resistant (designed with chafe against granite cliff faces in mind)... but figuring strength is always an issue, since it's rated in kilonewtons rather than pounds breaking strength... because it's real purpose is to absorb shock by stretching.
Might make an excellent anchor or dockline snubber though. Like a plastic bag, it has a limited life of stretching, too. After x-many stretches, it's really not safe for its original intended purpose.
Still, the give it exhibits is over a length of material... on a single run for a sailfar-sized boat, you shouldn't encounter that much stretch... even less if you are running a jackline mast-to-bow and mast-to-stern (necessitaties unclipping/reclipping at the midpoint).

[s/v necessity]

1 kilonewton equals roughly 225 pounds of force fwiw.  Before you spring for the slacklines I would go look at some tubular webbing, and since the price is about the same look for "climb-spec" (as opposed to mil-spec) it's a little bit nicer, and will hold up a little longer.  My biggest concern with using tubular webbing is that sunlight will have a noticable effect on it.  I suspect it would need to be replaced after a full season of exposure to the elements.  It does streatch, but it's not like a bungee cord.  And to be honest if you are hitting it with enough force to make it streatch significantly, then you probably want that streatch to keep the force on your connecting hardware and body low. 

[Oldrig]

Now I'm even more confused.

I've posted this question on another board and, just as Tim reported, I've already received replies suggesting that I get the tubular climbing webbing.

This is not, obviously, a place to skimp too much. But that's what I've been doing. I've been using some climbing rope, left over from my days in the Ski Patrol. The stuff is strong, but it's round (dangerous), and probably has way too much stretch.

I'm spending a lot on the boat this spring: I have to pull the shaft, replace the cutless bearing, send the prop for re-shaping (I hit a winter stick) and, possibly, replace the shaft as well. But it's probably time to get some decent jacklines.

--Joe

[Captain Smollett]

My comments were directed specifically to the 'slacklines' which from what I read are particularly stretchy.

Just like in climbing!, we have static lines and dynamic lines, each with their own use, I'm just saying these slacklines may not make the best jacklines.

And just like climbing ropes, you pay extra for that abrasion resistance vs el cheapo nylon from Lowes. Would you use 15 cents per ft nylon rope from the hardware store as a leader rope?

I wouldn't. That's all I'm saying. Sometimes, you get what you pay for. Sometimes, cheap != suitable for purpose.

Got a few other points but typing on phone is tough....

[Captain Smollett]

Sorry, Joe. Let try to clarify my position another way.

I'm saying I don't think slackline webbing is necessarily the same thi g as 'climbi.g' webbing.

At the very least, there's huge variation in what is used for slacklining.

Caveat emptor.

Edit: I see necessity made this and other of my points. Sorry for repeating.

[Tim]

Some data and a supply link;

http://user.xmission.com/~tmoyer/testing/Qualifying_a_Rescue_Rope.pdf

It seems as though nylon tubular stretch is somewhere around 5%

Webbing supply, polyester 5/8" @ $.41

http://www.strapworks.com/default.asp

[s/v necessity]

Sorry for the confusion, you did ask about slacklines :)  The only slacklines I have seen looked pretty much like the same type of material used to strap down loads on large flat bed trucks.  I suspect there are various arrangements out there, and I suspect it's quite strong and could possibly be used as a jackline  (however homework would need to be done)  But what is running through my mind is that 1" tubular webbing is probably still less expensive yet, and probably more suited to the task.  (one issue I see is that slacklines tend to be wide)

Also keep in mind 5% or 10% elongation may sound like alot, but that's probably calculated at or near breaking strength.  For climb spec this is about 17 kilonewtons, or 3800 pounds of force.

[Captain Smollett]

If you look at the pictures of folks slacklining...just standing on the webbing, they sure seem to dip mighty deep....lots of stretch there.

It does not take much to make the difference between being drug under water at five knots vs staying on the boat.

Getting on after going over, jackline plus tether or not, is darn near impossible.

Maybe I am fretting over nothing, but it just seems to me that there are ways to save money and things to avoid using...it's about personal margin of safety.

'Slacklines' are not designed or manufactured with 'life on the line in harsh environment' in mind.

[Tim]

If you look at the pictures of folks slacklining...just standing on the webbing, they sure seem to dip mighty deep....lots of stretch there.

It does not take much to make the difference between being drug under water at five knots vs staying on the boat.

Getting on after going over, jackline plus tether or not, is darn near impossible.

Maybe I am fretting over nothing, but it just seems to me that there are ways to save money and things to avoid using...it's about personal margin of safety.

'Slacklines' are not designed or manufactured with 'life on the line in harsh environment' in mind.

I am not sure what pictures you are talking about and whether that would all be attributed to stretch and likewise I am not advocating using "Slacklines. 

Without a doubt all you say about getting on a boat is true but the data I see on "tubular webbing" indicates a stretch of 5% at breaking point.  Which if properly placed on the boat would not be a problem.

I do think that exposure and abrasion are factors to consider and regular inspection of anything would be important.

[Captain Smollett]

the data I see on "tubular webbing" indicates a stretch of 5% at breaking point. 

5% stretch is a linear, tensile spec.  That does not speak to the stretch characteristic perpendicular to the tube axis.

But, aside from that, different tubing has different properties.  It's not all created equal. 

Both dynamic climbing ropes and static lines are made of nylon...same basic stuff, very different stretch and strength characteristics.  Nylon tubular webbing designed for climbing applications is different from "others."

I don't know where slacklines fit in exactly.

But, here's one of the pictures I was talking about.  Think about having that jackline on the windward side of the boat, stretched that much with a regular 6' tether....how wide is the boat at the cockpit?



I'd say with this particular setup, there is a VERY good chance you are going over.

It's no skin off my nose one way or another.  I am not "condemning" the use of tubular webbing for jacklines on a boat.  I am merely saying to do homework regarding a PARTICULAR webbing and not assume it's all the same...that it's all climbing/life critical grade.  There's a reason these things get such certifications and not everything carries it.

The other thing I'm saying is to look  beyond price per foot.  A good deal on quality stuff is a good deal.  A low price on poop still buys poop.  Are jacklines where you want to save a few bucks merely for the sake of saving a few bucks?

The OP was about slacklines use for jacklines.  My opinion, and mine alone, is that *I* would not use such for jacklines on my boat without very careful research into what they are made of and how they are constructed.

[SeaHusky]

But, here's one of the pictures I was talking about.  Think about having that jackline on the windward side of the boat, stretched that much with a regular 6' tether....how wide is the boat at the cockpit?



I'd say with this particular setup, there is a VERY good chance you are going over.

I,m not disagreeing at all but would just like to point out that the picture may be missleading. The slackline is set up with "slack" and then you walk on it. What you are seeing is not all stretch.

[Oldrig]

Thanks guys, I think John is right about the stretch factor--I had never even heard of "slacklining," and when I got an e-mail about a special discount on slacklines, I thought they might be useable.

--Joe

[Captain Smollett]

I,m not disagreeing at all but would just like to point out that the picture may be missleading. The slackline is set up with "slack" and then you walk on it. What you are seeing is not all stretch.

Perhaps sometimes they are "slack," but they are spec'd to set up to 4 TONS of tension...they are not ALWAYS slack, but pretty much all the pictures I've seen of them have significant transverse deflections.

From Gibbon's web site on 2" lines, a couple of comments:

(1) The "Funline," the beginner series, mentions specifically that it is atypically NON-stretchy.  This suggests that the others are 'stretchy.'

(2) The "Travelline" says "Perfect as a fitness tool or for the slackliner on the go. The TRAVELLINE is made of thinner webbing for a lighter, more compact kit and a "stretchier" feel."  There's one that is specifically marketed as being "stretchier."

(3) Similarly for the "Ladies Line," the marketing copy says: "a lightweight, compact and an ideal fitness tool. The thin webbing has a "stretchy" feel perfect for yoga, tricks and staying fit. (Elastic style webbing)"

The parenthetical is on the page; I did not add it.

(4) From the "Jibline," even more interesting terminology:

"Thinner webbing and much more dynamic, the JIBLINE is ideal for tricks and jumps. This line takes balance to a new level!


  -Thin, flexible webbing provides a trampoline like effect"

Again, all quoted from the page, not added or edited by me.

Now, all this simply goes to show the two points I have been making:

(a) Not all webbing is created equally

and

(b) Know what you are buying; look beyond price.

Some of this stuff is very much NOT suited to jacklines on a boat.  

Given that 5 out of 7 of this particular company's 2" lines specifically mention stretchiness, bounciness or "trampoline effect," I simply conclude, for my own purposes, that the slackline market line of webbing products lies squarely in the "not suitable" category.

[tomwatt]

I'd just like to add that milspec webbing, as I've seen it used by the military, is ordinarily either a) built into a complex harness with a lot of supporting material, or b) used once (e.g. aerial delivery out the back of the plane) and then discarded. Just in case anyone's pondering that.