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RS600: stretchy halyard?
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bristolmustoskiff View Drop Down
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Posts: 84 		Post Options Post Options   Quote bristolmustoskiff Quote  Post ReplyReply Direct Link To This Post Topic: RS600: stretchy halyard?
    Posted: 27 Jun 14 at 2:54pm
you need the black rope with the kevlar in it 4mm last forever when you think you have pulled it up tie a loop in the halyard then tie the cunning ham to it and pull it tight that will take the stretch out of it
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Jack Sparrow View Drop Down
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Posts: 2965 		Post Options Post Options   Quote Jack Sparrow Quote  Post ReplyReply Direct Link To This Post Posted: 27 Jun 14 at 5:27pm
One thing to check if your old halyard is Kevlar.

Kevlar doesn't like tight corners and has a habit of breaking at knots. You won't realise as the the kevlar core has broken inside the outer sleeve. You could be getting slip because you are actually only tensioning the sail with the outer sleeve of the rope which then stretches under load.

Dyneema on the other hand creeps and takes a little time to bed in depending on the variety. But yes the SK78 (Excel D12 Max78) or SK90 (Excel Elite 90) minimise this to the Max and would don't the Kevlar sleeve trick as they don't mind corners.

Edited by Jack Sparrow - 27 Jun 14 at 5:28pm
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Paramedic View Drop Down
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Posts: 929 		Post Options Post Options   Quote Paramedic Quote  Post ReplyReply Direct Link To This Post Posted: 27 Jun 14 at 9:17pm
Don't buy SK90 for dinghies it has no advantages over SK78 for our purposes and is more expensive.
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Posts: 102 		Post Options Post Options   Quote NHRC Quote  Post ReplyReply Direct Link To This Post Posted: 29 Jun 14 at 10:58am
Paramedic you are completely wrong about SK90.

I have tried and tested it on a number of boats and it is the best product for no stretch applications. 

For example when testing a Laser Vang first part of the cascade in SK78 the result after a 20 minute sail in a 15 kt breeze was 65mm stretch

With SK90 it was under 20mm

20mm would have been the splices bedding in.


What I would add to this thread is that to reduce stretch/creep

a). Use a good product, might not be cheap but it will last and wont fail.

b). Work out the load that the line will carry and multiply that by a safe working factor of 4:1 to counter dynamic loading. Buy a rope diameter that will carry that Safe Working Factor

c). Splice ropes wherever possible, knots cause failures, reduce the strength of the rope and degrade it massively

d). Dont run un covered ropes through cleats as you degrade them very quickly

e). Dont use high UV sensitive ropes (Vectran or Kevlar are most common), without checking and replacing them very very regularly.
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Paramedic View Drop Down
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Posts: 929 		Post Options Post Options   Quote Paramedic Quote  Post ReplyReply Direct Link To This Post Posted: 29 Jun 14 at 9:13pm
Sorry but that doesn't bear out what the fibre manufacturers themselves claim, or what i've found on a variety of boats.

According to DSM (The fibre manufacturer who supplies Marlow and English Braids) SK90 is stronger than SK78, but has similar creep to SK75. So i don't know what was going on with your Laser kicker, but i have found that poor quality rope - even using SK78 - is a waste of dyneema. The fibre is only part of the equation, the lay of the rope and the pre-stretch process have much to do with it and cheap rope is, well, cheap.

Most dinghies will never need this extra strength, and we all want low stretch/creep.

If you want ultra low creep you want DM20 aka Dynastay - i've used this instead of Vectran on a number of boats and it's very, very good.

The rest is good advice tbf :)


Edited by Paramedic - 29 Jun 14 at 9:26pm
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Posts: 102 		Post Options Post Options   Quote NHRC Quote  Post ReplyReply Direct Link To This Post Posted: 29 Jun 14 at 11:39pm
I completely disagree with you. I am a rigger by trade and have been specing ropes for boats from oppies to the worlds largest super yachts.

Sk90 creeps a lot less. It is stronger.
I highly recommend it for all applications where you wish to have no creep in a line.

Dm20 is a good product for stays, shrouds and forestays.

Sk99 is the new product that we will be using for non creep lengths from now on.

All dyneema is produced by dsm.
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