tow rope from looped rope?

[aeveling]

just wondering... I've got some 2 tonne poly rope. If I knot the 2 ends to create a loop and then double the rope up so that there are two thicknesses of rope at each end does the breaking strain of the whole thing increase? I'm assuming that any load is now distributed through the 2 thicknesses of rope rather than one. Obviously the knot is the weak point. I'm thinking if the whole thing were then pulled out with the knot in the centre and then twisted to form something that resembles a bow string the knot might receive less stress than if the rope wasn't twisted. I realise I might be completely wrong on this and this is for a one off situation for dragging a tree stump (our lifting chains have been nicked). The location isn't suitable for pulley systems etc. I want to use several thickness of rope so eye splices etc are not viable.

Many thanks,

Andrew.

 

[Wook]

The problem would be when you went round corners you would tension one side but not the other. To turn several strands into a true single unit, they need to be properly braided.

Such a setup might even end up increasing the opportunities for breakage compared to just using one rope by itself.

 

[bilmo-p5]

Buy some bigger rope!

24mm polypropylene will give you a BS of about 6 tonnes once you've spliced an eye in each end, and won't cost much.

 

[Teepee]

I've done similar. I had some 10mm poly rope to attach to a 5 tonne Tirfor winch. Used 10 thicknesses and made it into a continuos loop. Bound the rope with gaffer tape and zip ties.


It pulled out 25 hawthorn trees

 

[awarner]

Personally I avoid poly rope far too unreliable and can burn though itself with friction.
You are correct about the know, you can lose a lot of strength with knots depending on the knot of choice it can easily be a drop of 40% etc. As Ian said above splicing would be the best option.

 

[asemery]

This is the sort of problem that the folks at the International Guild of Knot Tyers (IGKT) love to discuss. Tony
http://igkt.net/sm/index.php

 

[mrcharly]

Two tonne? Should be adequate to tow with.

If you loop the rope round the whole thing twice (like a bowstring) then seize the ends, you'll have a stronger system than using one rope. Not twice the strength though and as said the bend is the weak point.