Are double ropes always needed ...

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GBM
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Are double ropes always needed ...

Postby GBM » Thu May 31, 2007 8:42 pm

Hi guys

Girlfriend and i started doing the low grade adventure climbing thing about a year ago. We've built up a handy set of gear however recently find ourselves taking the 35m Beal rope on outings more and more and leaving the 60m at home.

Is it necessary to get another 35 m for double roping; the 60m number is really heavy and a bit of a mission to drag along with (bearing in mind that girlfriend hauls the Energade only) all the time ... i am a bit concerned however that doing any multi-pitch stuff with a solitary rope is probably not to smart.

Any suggestions?

Drifter
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Two ropes are better for trad

Postby Drifter » Fri Jun 01, 2007 6:43 am

I have been told by someone you should use two half ropes for trad climbing or if you want to climb with one rope in trad then you must use a 11mm rope. It is not advisible I believe to climb with one rope as with two ropes you can put in more protection. Someone correct me please if I am wrong. I don't know that much about trad to be honest.

MarkM
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Postby MarkM » Fri Jun 01, 2007 7:59 am

Hey GBM using two ropes in SA is really due to most of our trad lines not being dead straight so you tend to scatter gear around. With two lines you can more or less keep your ropes running straight which goes a long way in reducing rope drag, which can become significant on longer pitches. Also the half ropes are skinnier than single lines (make sure your 35m line is a single line, if you're using it as a single rope) which means that when/if you fall they stretch a lot more, which reduces the load that the piece of gear holding your fall has to carry. So Drifter's idea of a single 11mm cord is wrong since you'd ultimately be putting much more force on the piece of gear you're falling onto.

If you are heading out doing multi-pitch routes you should seriously consider using half ropes or at least you 60m single line because if you have to bail on your 35m line, you're going to be leaving a lot of gear behind (since your raps will only be 12.5m per rap). However that would make someone else very happy, collecting booty every 10m or so :wink:

Go spend some time on a couple of the rope manufacturers sites as they tend to explain stuff quite well.
Open hand, open mind...

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fanta
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Postby fanta » Fri Jun 01, 2007 8:13 am

Ideally for trad you want to be using 'two half ropes'. For mulitpitch trad I don't think you should be using 35m (its a bit short!!). Buy the best you can afford! I use two 8.6mm 60m Cobras from Beal and I can highly recomend them!! Sometimes even 50m ropes can be a bit on the short side, however with that said. I have 2 by 50m ropes which have 5m chopped of the ends which are great for shorter crags.

11mm rope on trad gear is not a good idea! Nor is it a good idea to clip two half ropes to the same piece of trad gear!! (I have seen this all to often, even by experienced climbers!!!!) People do it for good measure especially on the first piece of gear off a stance. You could be doing more harm than good. The less dynamic the rope is the more force exerted on a piece of gear. Not good!

Also, please not the difference between half ropes and twin rope systems.

mokganjetsi
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Postby mokganjetsi » Fri Jun 01, 2007 8:36 am

Beal ropoes have a great little booklet advertising their ropes and explaining all the stuff regarding half, twin and single ropes; lines for sport and trad; impact force etc etc. You should be able to get it from any Beal dealer.

most single ropes have a max impact force of around 8-9kn and the smaller pieces of trad gear is guaranteed at a max impact force of 6kn i.e. on a single rope you can generate enough impact to break your protection. for some reason the impact force on half ropes is much much less but only if you use it in a half-rope configuration (haven't figured out why).

nosmo
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Postby nosmo » Fri Jun 01, 2007 12:05 pm

GMB wrote:bearing in mind that girlfriend hauls the Energade only


Hmm, is that the sound of a big whip I'm hearing? :wink:

mokganjetsi wrote:for some reason the impact force on half ropes is much much less but only if you use it in a half-rope configuration (haven't figured out why).

MarkM wrote:half ropes are skinnier than single lines which means that when/if you fall they stretch a lot more, which reduces the load that the piece of gear holding your fall has to carry

mokganjetsi
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Postby mokganjetsi » Fri Jun 01, 2007 12:46 pm

OKeh, but here's some numbers:

the Beal Joker is both a single, half and twin rope. its published max impact force is around 8kn as a single rope and slightly below 6kn used as a half rope (probably due to using an 80kg load in the single test vs 55kg for half). one rope but different imapct forces when used in different configurations. anybody has an idea what the logic is? surely your full weight is on the one rope only when taking a fall on a half rope configuration?

Drifter
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Postby Drifter » Mon Jun 11, 2007 6:47 am

Is max impact force worked out like this 80kilograms falling 27 and half meters will reach the full ropes breaking point if the ropes breaking point is 2200kilogram(2.2tons)?

80kilogram x 27.5meters(the fall)=2200kilograms(breaking point of rope)

If the object fell 13.75meters then max impact force( what weight the rope could take) would be 160kilograms before it broke.

Max impact force=weight of person

Breaking point=max impact force(persons weight on rope) x height person falls.

Is this right?

Hector
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Postby Hector » Mon Jun 11, 2007 12:49 pm

No Drifter, I'm sure you started a thread about this somewhere else. Anyway, the inpact force depends on how quickly the climber comes to rest when the rope stops his/her fall. I.e. it depends on the climbers upward acceleration caused by the rope. Inter alia this depends on how much rope is out, the length of the fall, the stretchiness of the rope, how much slip there is at the belay, the response time of the belayer, the weight of the belayer etc etc. So there's no neat formula to calculate impact force. But as has been said elsewhere, the rope snapping is the least of your worries if you generate 2,2kN. With that kind of force I'd be way more worried about my gear ripping. Instead of harping on about strength of gear etc, just learn to use it properly. A bit of common sense goes a long way.

nosmo
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Postby nosmo » Mon Jun 11, 2007 3:20 pm

Hector wrote:the rope snapping is the least of your worries if you generate 2,2kN. With that kind of force I'd be way more worried about my gear ripping.

On the other hand, if you're on a sport lead, well-placed bolts should handle 2,2kn - but with that kind of force I'd be just as worried about my back breaking clean in half.

If you go look at the product page for the Beal Top Gun on MMO http://www.mountainmailorder.co.za/index.php?act=viewProd&productId=218 you'll see the max guaranteed impact force is 7.4kn - a force more or less around the limit of most trad gear, but again, the amount of force being enacted on your body will make you wish the rope broke.

A more understandable way to analyse the force generated is fall factor. http://www.southeastclimbing.com/faq/faq_fall_factor.htm

Thank you for the handy hints on great books, have you read them?


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