Zero stretch rope

[stuckinthemud]

I need a 2 metre length of rope or cord able to repeatedly winch 200kg with zero stretch. The 10mm braided nylon I am using isn’t up to the job. I have some linen thread I could make up a length with but it’s not cheap and I would rather use it for other projects. I hear good things about spectra dyneema. Anyone used it? Would I need winch rope or braided?

 

[Yojevol]

Wire?

 

[ChaiLatte]

Please view some old episodes of Star Trek, particularly Mr Scott and his 'ye cannae change the laws of physics'. No material invented by man has an infinite Young's modulus, thus nothing on this earth will have zero stretch.

Dyneema is very good and is low stretch. As it is 'slippery', you cannot tie knots in it. It needs to be spliced. It needs a good bury (40 to 50 times its diameter) to achieve best results. Clearly, the diameter is increased over the length of the splice, so anything over which the rope passes needs to accommodate this extra girth.

AFAIK, all dyneema is braided.

https://atlanticbraids.com/dyneema-brummel-eye-splice-1-end/https://www.premiumropes.com/splicing-rope/splicing-instruction-videos
Watch those and 'Mobius brummel' will trip off your tongue in no time.

 

[Jacob]

I need a 2 metre length of rope or cord able to repeatedly winch 200kg with zero stretch.

What for?

The 10mm braided nylon I am using isn’t up to the job. I have some linen thread I could make up a length with but it’s not cheap and I would rather use it for other projects. I hear good things about spectra dyneema. Anyone used it? Would I need winch rope or braided?

What about old fashioned hemp or sisal etc?

https://www.cheaprope.co.uk/flax-hemp-rope-c-1000_254.html

 

[mwinfrance]

chain...the kind you lift engines out with.

 

[stuckinthemud]

I had no idea hemp rope still existed , that’s perfect!

 

[Sideways]

Cavers and arborists use low stretch polyamide (?) ropes whereas climbers use nylon ropes.
Climbers fall on their ropes so need them to stretch and reduce the shock of the fall.
Cavers and tree surgeons climb up and down their ropes so they don't want to be fighting an elastic rope.
But the climbers are getting in on the act and using even lower stretch aramid fibres - spectra and dyneema for slings and for thin but super strong cord loops that are attached to their fall protection gear.
These cords are either ready stitched or knotted (triple fishermans knot) into loops, not spliced, but 2 m long is readily available.

 

[sometimewoodworker]

I had no idea hemp rope still existed , that’s perfect!

Virtually all natural fibre rope it still available

need a 2 metre length of rope or cord able to repeatedly winch 200kg with zero stretch.

However there is no rope or cord with zero stretch. The closest will be a Kevlar. though if you use a low stretch rope with a test strength of 20,000kg you will get minimal stretch.

 

[profchris]

I've winch launched gliders on Dynema and you can definitely feel the stretch. Noticeably more than the steel wire we used to use. But definitely less stretch than polypropylene rope.

 

[stuckinthemud]

True to the zero stretch, but, I do need to minimise it. I have a heavy lath set up in my bow press. The press has 14” of travel, the nylon rope in there at the moment pulled the tip on the lath for the first 6 inches of travel, the next 6 inches of travel were all stretch on the rope
I have jute cord I could twist up but jute fibres are quite short. The hemp rope looks good, correct for period too (14th century) when I need to make a stringer

 

[sometimewoodworker]

True to the zero stretch, but, I do need to minimise it. I have a heavy lath set up in my bow press. The press has 14” of travel, the nylon rope in there at the moment pulled the tip on the lath for the first 6 inches of travel, the next 6 inches of travel were all stretch on the rope
I have jute cord I could twist up but jute fibres are quite short. The hemp rope looks good, correct for period too (14th century) when I need to make a stringer

Unfortunately nylon is probably the worst possible material, as it shown by its use by climbers and as a mooring, what is the floating population. both of these rely on the stretch. For your needs woven polyester or Kevlar are the choices

 

[ChaiLatte]

I've winch launched gliders on Dynema and you can definitely feel the stretch. Noticeably more than the steel wire we used to use.

It is easy to take that statement out of context and end up comparing apples and oranges, a sure route to detention when I was at school.

If you look at the specific modulus (Specific modulus - Wikipedia) - sort the fourth column of the table high to low, dyneema is way above steel.

Given that this is sometimes a woodworking forum, what is interesting in the second table (again sort the fourth column high to low) is how close wood comes to steel.

 

[profchris]

It is easy to take that statement out of context and end up comparing apples and oranges, a sure route to detention when I was at school.

If you look at the specific modulus (Specific modulus - Wikipedia) - sort the fourth column of the table high to low, dyneema is way above steel.

Given that this is sometimes a woodworking forum, what is interesting in the second table (again sort the fourth column high to low) is how close wood comes to steel.

True about the comparison - the wire was a twisted cable, the Dynema was braided, so I suspect that explains the difference in elasticity. There was definitely more lag between the cable tightening and the glider moving, and in 'bumpy' air the Dynema gave a smoother climb.

I doubt the OP wanted single strands though, so the proper comparison is whatever cord formats are available. Looks like hemp is the answer for him, more period correct as well.

 

[bourbon]

I'm a 15 century re-enactor with The Ferrers household (the ones with the fences!) We use Polyhemp for guy lines and our pole lathe turner has used the thinner stuff for his 'drive' rope. You should get it easily enough. I know Bernie the bolt had some a couple of years back at Tewksbury.

 

[Stuart Moffat]

My Dad was in the navy for the last couple of years of ww2, and on a destroyer he was on they were using steel wire to tie up the ships in dock. One of those steel cables gave way, and the flailing cable took off the legs of a couple of deckhands. The story was you got no audible warning of failure of a steel cable, but you could hear the rope ones groaning! ProfChris, having driven the winch at little grands and learnt to fly there, I’m curious what your experience was of the man made ones? Do they break less often than the steel ones? And if /when they break, can they be repaired as quick as the steel ones?
Stuart

 

[stuckinthemud]

Bourbon, I’m trying to workout the draw weight of the Skane Lillohus crossbows.

 

[pe2dave]

I had no idea hemp rope still existed , that’s perfect!

And it stretches.

 

[gmgmgm]

Thicker rope will also stretch a bit less. 10mm rope is probably 1.5 tonne breaking strain, so at 1:6 (or similar), your 200kg is close to the limit.

Try 18mm rope? I seem to use "polysteel" rope for a lot of applications (it has low stretch), and it's easy to get a few metres on ebay.

Dyneema is great, but ludicrously expensive and as mentioned, you can't tie a knot in it easily.

 

[spanner48]

Your existing nylon rope is the worst possible for stretch. As others have mentioned, climbers use it BECAUSE it stretches so much.

Better, in order:
• Polypropylene
• Polyester
• Manila hemp [but beware when wet]
• Aramid
• Steel wire rope [preferably galvanised; not stainless]
• Chain

 

[Jones]

Spectra / dyneema halyard rope from a chandlers should work. No need to splice most knots will hold, bends will tend to slip though.