3:1 with carabiners only, any advantage?

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Re: 3:1 with carabiners only, any advantage?

Postby Stridergdm » Feb 15, 2013 12:09 pm

LukeM wrote:I string up slacklines with a 3:1 using only carabiners. It would certainly not be possible to achieve the tension needed if I used a 2:1 or 1:1.

I wonder, is any MA achieved when tying a trucker's hitch? It is a 2:1 running rope through other rope after all.


Enough that with clothesline, cheap stuff like that I've broken rope before. :-)
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Re: 3:1 with carabiners only, any advantage?

Postby PeterFJohnson » Feb 15, 2013 2:40 pm

A trucker's hitch is an interesting scenario because it does seem to produce some MA advantage. But the rope on rope friction in a truckers hitch is also usually great enough to hold the load once you have it cranked down - you don't usually have to hold the load while you secure it with a final knot. Seems contradictory? Since theoretically you would need to overcome that friction to haul your load. Animated Knots explores this a bit by talking about "surge" and how the friction essentially acts as a progress capture. But a more complete quantitative answer would be interesting.

In any case, if you are alone/short on haulers and are looking to haul a heavy load I wonder if your best bet might be to try to use a system that involves your legs which are much stronger and have better endurance than your arms.
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Re: 3:1 with carabiners only, any advantage?

Postby chh » Feb 17, 2013 6:26 pm

I also frequently set up slacklines with nothing more than biners. Though if I want it really tight I get out my two tandem pulleys and get to work. I think the advantage with biner and/or trucker's hitch combinations isn't necessarily their potential mechanical advantage, but rather the ability hold tension on the line while you use your body to reef like hell on it. Or, conversely, to release a load or capture the tension in the system for a lock off in a controlled and easy fashion.
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Re: 3:1 with carabiners only, any advantage?

Postby knudeNoggin » Feb 18, 2013 12:08 am

LukeM wrote:I wonder, is any MA achieved when tying a trucker's hitch?
It is a 2:1 running rope through other rope after all.


A trucker's hitch is 3:1. Actual MA might be around 1.6:1 ?

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