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General => Beginners Area => Topic started by: DWT on June 06, 2012, 11:19:35 PM

Title: Dyneema question?
Post by: DWT on June 06, 2012, 11:19:35 PM
In a self rescue situation(your second is injured) is it safe to use dyneema to tie a friction hitch on the rope?
Title: Re: Dyneema question?
Post by: hobbsj on June 07, 2012, 08:07:30 AM
I think nylon is the way to go.  I was taught, about 6 or 8  years ago, that dyneema doesn't do well due to the friction and sliding.  As a result nylon is on most of my alpine draws (that and the fact it was cheap and I'm still not rolling in enough cash to upgrade).  That being said, materials have come a long way and I can't say compared to the stuff that's out there now.  I'm sure others have contradicting data with such and such.  But to keep it simple, I just use nylon rather than trying to keep up with all the new developments.
Title: Re: Dyneema question?
Post by: sneoh on June 07, 2012, 08:43:25 AM
But to keep it simple, I just use nylon rather than trying to keep up with all the new developments.
+1.  Simple, if it serves the purpose on hand, is, to me, always preferable.  Oh yeah, I have reverted back to Nylon.
Title: Re: Dyneema question?
Post by: DLottmann on June 07, 2012, 10:21:47 AM
Dyneema slings work great for prussiking as the thinner diameter “bites” really well on the rope. The issue of concern is it has a lower melting point than nylon. This should not be an issue on a properly tied, tested, and used prussik, as the rope should never run fast enough through it to melt/damage it. It’s slightly irrational to worry about it because it means you not addressing the true concern, a poorly tied friction hitch. Same mindset behind using a “back-up knot” for a re-traced figure eight knot.

That all being said, I find it better SOP to always carry 2 7mm nylon prussik cords tied with double fisherman knots, slightly different lengths. That, combined with one un-used 16 foot cordelette on the back loop of your harness will solve 99% of the leader/second rescue scenarios you can encounter and is a standard part of my “kit”.

If you need to use a dyneema sling, it is not considered “incorrect” in the industry, just be mindful of the low melting point.
Title: Re: Dyneema question?
Post by: old_school on June 07, 2012, 12:14:44 PM
Sound advice DMan!  +++1
Title: Re: Dyneema question?
Post by: perswig on June 07, 2012, 12:19:13 PM
I've practiced most of the belay escape/prussik stuff with Dyneema just to see if I'd die and for better or worse, I didn't.   

Holding ability was fine if you use an appropriate # of wraps relative to diameter of the webbing (obvious surface area issue) and maybe better than nylon when things got wet (?) although I'd have to go back and repeat this to be sure. 
Inspection for wear/melt was unremarkable, but as DMan says, ideally you're not greasing these things up or down a rope at a blistering (get it?) rate.  If you're looking for a means of rapid ascension, or backing up above or below your rappel device, I'd rather nylon or cord.

And for god's sake, don't get Trad started on knotting the damn stuff.
Dale
Title: Re: Dyneema question?
Post by: old_school on June 07, 2012, 01:04:42 PM

And for god's sake, don't get Trad started on knotting the damn stuff.
Dale

I thought only sport climbers knotted dyneema?   ;D
Title: Re: Dyneema question?
Post by: nuts on June 07, 2012, 11:23:17 PM
I don't even carry dyneema, it's very single purposed.  It shouldn't be hitched or knotted, as the breaking point is very low.  This includes any sort of friction hitch.

http://dmmclimbing.com/knowledge/how-to-break-nylon-dyneema-slings/

Chris
Title: Re: Dyneema question?
Post by: DLottmann on June 08, 2012, 12:14:02 AM
I don't even carry dyneema, it's very single purposed.  It shouldn't be hitched or knotted, as the breaking point is very low.  This includes any sort of friction hitch.

http://dmmclimbing.com/knowledge/how-to-break-nylon-dyneema-slings/

Chris

That is a junk article for a number of reasons...

1) It is concerned with the static nature of clipping into the anchor with a dyneema sling. You shoudn’t be doing this with nylon slings either, unless you are preparing to rappel and need to untie, so the static nature of dyneema is MOOT, the climbing rope is the energy absorber in a lead fall, NOT the slings...

2) There is no reason to knot a shoulder length dyneema sling in my opinion so that point is tossed out...

3) Article states "having any slack in a belay system is best avoided”... anyone who’s climbed sport or trad knows this is a horrible statement

The only smart statement in the article: " ideal material for slings and quickdraws. It is also more resistant to ultra-violet rays and chemical attack than nylon but has a lower melting point.”

Followed by a stupid statement: "This is an important factor to consider when abseiling – pulling a rope through a Dyneema® sling, say as in poor abseiling practice, will generate enough heat to severely weaken the sling, if not melt through it.”

That would only be true if you rappel at Mach 2... if you rappel slowly there is NO way you’ll generate enough heat to damage a dyneema sling... but if you go bounding down the cliff... well.... use a regular 7mm nylon prussik cord ok?

Bottom line... Dyneema + a couple light-weight wire gates (like my favorite Petzl Ange S), create the absolute most versatile “alpine-draw” on the market. Perfect for all trad/alpine climbing... lighter than a regular quickdraw...

Really the ONLY drawback is cost... that’s it... they are more expensive... but they perform better in every other category...
Title: Re: Dyneema question?
Post by: DLottmann on June 08, 2012, 12:17:23 AM
Last thought... they actually said it is “ideal for slings and quickdraws”, but the whole article is a attack from DMM on something they must not have a patent on... reminds me of recent presidential campaign ads...
Title: Re: Dyneema question?
Post by: hobbsj on June 08, 2012, 08:06:31 AM
Dman, or anybody else, what about the texture of the dynema?  It seems a bit "rougher" compared to my slippery nylon slings.  That in itself would introduce more friction.  I remember being told that, along with the lower melting point, was the reason to use nylon for that job.  My concern would be using it as an autoblock on a rappell which seems to generate a fair amount of heat.  Maybe it doesn't generate enough but I don't stick temperature probes in my slings to know.  Anybody see anything on this?

I guess this argument has also gone past the original question.  I mean if my buddy is hurt, I'll use what I got and replace it after we get on the ground.  And to whoever asked this question, remember that this is an online forum and take the info for what its worth!  I know synthetic material isn't my area of expertise and I've heard  several times at crags "I read on such and such board blah blah x-position blah blah..." :-)  A call to the manufacturer may be your best bet.  I heard BD is great at getting back to people.  Probably quicker than waiting and reading all the back and forth on here.
Title: Re: Dyneema question?
Post by: David_G48 on June 08, 2012, 08:59:59 AM
In my opinion nylon and dyneema have both negative and positive attributes in relation to each other as well as in their use for climbing. It is your responsibility to know their proper use. I would choose the one that you have confidence in using or a combination of both if that is what gives you the confidence to climb effectively.
New studies show that static nylon actually has some stretch to it giving it greater strength in a dynamic fall than dyneema. The only instance that comes to mind where this would be applicable is by directly attaching it from you to your anchor and then standing above the anchor and falling. You should never go above your anchor while being clipped in to start with so it should be a mute point, just be aware. Dyneema should not be girth hitched to itself or nylon due to its small diameter which may cut through, always connect with a carabiner for max strength.
The reason that I like dyneema is that it takes up a lot less space on your rack per sling making it easier to organize and thus easier to set gear. I don't find the weight savings much of an advantage as the best way for many of us to lighten what we carry up a climb is to lose weight either through a diet or by climbing more often.
The issue about  friction and dyneema is covered by DMan when he states that a rappelling at a controlled slow rate as it should be keeps the melting point issue as a non-factor, again bring a small piece of cord to bring yourself piece of mind.
The bottom line is that both dyneema and nylon work when used correctly and both have some advantages over the other.
Title: Re: Dyneema question?
Post by: The other tomcat on June 08, 2012, 09:13:44 AM
I use Dyneema on my four "alpine draws", but in my experience, they are the least versatile in an actual alpine environment where you may have to sling some big blocks to bail. Even bailing from a BFT can take a few.I left several atop the Duet buttress a few years back, as I didn't know about the fixed anchor at the top of Direct. You can't knot them, so it's Dyneema girth hitched together. No I don't carry a cordelette as I climb on doubles and don't need a power point set-up either.

Based on what I have read over the years about the likelyhood of a rappel back-up actually working, which is to say tests show most people won't let go of the back-up if they just lost control of the rappel, I'd say melting is a very real issue. I would disagree that it's "ideal" for slings, maybe good for quickdraws.

And what about the texture of Dyneema? When you get it it's slick as snot, after some use it roughs up, after a little more use it's time to retire it. Based on the answers here, I could see a scenario where someone's laying on the ground sayin' "damn, it worked last time".

For everything except those four alpine draws, and yes I think it is the best stopper draw, that being the sling you put on a stopper you want to stay put, I went back to Nylon, preferably knotted Mammut 11/16 which is da bomb in my opinion.

Would I escape a belay with a Dyneema sling in a pinch, yes, have to be quite the pinch though,as I keep three prussics somewhere with me ( one in chalkbag, one as chalkbag loop, one in pocket of gear sling) at all times. Would I use one to ascend a line, or as a rappel back-up, no.

If I had to guess DMM is talking about using a Dyneema sling to make a rap anchor without a ring, then pulling the rope through it, which I'd guess it's toast at that point. Indeed we are discouraged from even doing a second rappel from a nylon sling in that scenario, but I think it happens.

We don't all get stuff pro deal either, so I think there is an inclination to use and retain skinny slings past the date they should be retired due to both the cost and their limited uses other than as alpine draws. My knotted nylon on the other hand is cycled through a few times a season as I tune up rap anhors on duffer routes hither and yon. Like I said, they have a place, but I think it's limited.
Title: Re: Dyneema question?
Post by: DLottmann on June 08, 2012, 07:16:45 PM
I think theres a reason 9/10* guides in the valley use dyneemz for alpine draws...



*number is a educated guess.  Look around, many guides do use them. Really use what you want and know the limitations. "Safest" is not always best or required.
Title: Re: Dyneema question?
Post by: MJShove on June 13, 2012, 07:04:37 AM
The reality is that just because it works doesn't make it the best for any given situation.  Do your homework outside of this website as some of this info isn't true.  Google up some test results to see dyneema sling strength reductions after being used for friction hitches.  Besides, who wants to hang on something that looks like a shoelace anyway?
Title: Re: Dyneema question?
Post by: DWT on June 13, 2012, 05:15:57 PM
  Do your homework outside of this website as some of this info isn't true. 

That's a grenade.  Could you be more specific? :)
Title: Re: Dyneema question?
Post by: MJShove on June 13, 2012, 09:07:56 PM
Good stuff here.

http://www.geir.com/mythbuster.html (http://www.geir.com/mythbuster.html)

Pull tests on friction hitches for sling/webbing at Misty Mountain.  The highlight with the yellow smiley face is scary.  Also, a review of the test results indicate erratic and inconsistent behavior of the hitch/material interface.     


Full report here http://www.docstoc.com/docs/115249971/MMT-Testing         
                 
19   Pull test Kelmhiest       1/2" Nylon Runner   No   slippage at 650   6 wrap
   (10.5mm Dynamic Rope)      1/2" Nylon Runner   No   slippage at 460   6 wrap
         1/2" Nylon Runner   2020   slippage at 1850   6 wrap
         1/2" Nylon Runner   No   slippage at 1170   6 wrap
         1/2" Spectra Runner   No   slippage at 1330   6 wrap
         1/2" Spectra Runner   No   slippage at 610   6 wrap  :(
         1/2" Spectra Runner   No   slippage at 1180   6 wrap
         1/2" Spectra Runner   No   slippage at 750   6 wrap


A colleague on mine in NC pulled the nylon and dyneema slings after the friction hitch tests, and the dyneema failed at a substantially lower loads than the nylon.


The bottom line:  It might be better to have some nylon slings on your harness as well.  I always carry at least one.  It certainly can't hurt. 


More interesting info here.  http://www.mountainproject.com/v/105876750 It is around John Sherman's incident, but some of the comments revolving around testing are interesting. 


My intent is not to discredit DMAN (he's credible and we've even shared a rope at one point).  It's to be sure that you, as a climber make your own informed decisions that are not based on generalizations.  I find that DMM video to be eyeopening, and although the test is harsh, and would be difficult to recreate on the cliff, it's not impossible.  I try to stay objective and take the test data for the science it is.



Title: Re: Dyneema question?
Post by: DLottmann on June 13, 2012, 10:03:12 PM
No worries Matt, I wasn’t feeling discredited. But here’s my revised official stance, and how I use dyneema.

1) Carry two prussik cords made from 7mm nylon tied at different lengths

2) Carry 1 cordelette (I use a 16 foot 5.5 mil tech cord)

3) I rack all my gear on a regular nylon sling for transport

4) Carry 1 or 2 double length nylon slings

Armed with the above there is almost no need for me to ever use one of my 8 or 10 alpine dyneema draws for anything but draws. However, if I needed to, I wouldn’t have a problem using it with due caution. But as is being pointed out, there are better materials to have on you for these contingencies...

And the ultra-light combination of Petzl Ange S carabiners and dyneema is really the coolest draw setup in my book. I hate having should length slings dangling over my head so this system works great for me. YMMV.

Title: Re: Dyneema question?
Post by: DWT on June 13, 2012, 10:12:17 PM
good stuff indeed.  thank you.
Title: Re: Dyneema question?
Post by: tradmanclimbz on June 14, 2012, 07:02:05 AM
I have seen folks with pre knotted skinny dynema equalet type setup for belays.  Also seen data that indicates that a slip onto the belay / rapell anchor with the anchor loose but at your waist may be enough force to break a knotted  dynema sling? 
Title: Re: Dyneema question?
Post by: NY Climber on March 12, 2013, 07:34:02 AM
I think nylon is the way to go.  I was taught, about 6 or 8  years ago, that dyneema doesn't do well due to the friction and sliding.  As a result nylon is on most of my alpine draws (that and the fact it was cheap and I'm still not rolling in enough cash to upgrade).  That being said, materials have come a long way and I can't say compared to the stuff that's out there now.  I'm sure others have contradicting data with such and such.  But to keep it simple, I just use nylon rather than trying to keep up with all the new developments.

I agree. I persoanlly don't care for Dynemma much and use all nylon slings. Deeme is too stiff for me and way too expensive IMHO - esp if I ever have to LEAVE sling(s) behind on raps!