Repair & maintenance: D12 stretch charastics

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D12 stretch charastics

Printed From: Yachts and Yachting Online
Category: General
Forum Name: Repair & maintenance
Forum Discription: Questions & tips on the subject
URL: http://www.yachtsandyachting.com/forum/forum_posts.asp?TID=4324
Printed Date: 14 May 25 at 4:00am
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Topic: D12 stretch charastics

Posted By: Scooby_simon
Subject: D12 stretch charastics
Date Posted: 23 Jun 08 at 9:23pm

Anyone know roughtly how much D12 (3mm and 4mm) will stretch once loaded.

Trying to make a couple of things but don't have any experience with D12 so want to know how much stretch I might get

3mm will be for trap lines, the wire is 5.9m long, how long do people think I should make them in D12 to allow for some stretch.

4mm will be used for Spi pole supports and so these will be around 1 - 1.5m long.

Many thanks

Simon

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Replies:

Posted By: Isis
Date Posted: 23 Jun 08 at 11:21pm

Dyneema doesnt really 'stretch' much at all, but it will 'creep' and it wont really stop creeping for the lifetime of the line (which is limited if left out in the sun)

For the trap lines its a good idea to put a sliding splice on the bottom so you can 'coarse tune' the trap height for different conditions so you wont have a problem there.
With the spi pole supports you may have to redo the splice every now and again but Id be surprised if you see any real difference with that length of line in that aplication before you should be thinking about replacing the line anyway.

If your worried you can overspec the diameter slightly, though what youve got sounds about right to me

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Posted By: Scooby_simon
Date Posted: 24 Jun 08 at 12:00am

Thanks

Not sure what you mean by a sliding splice?

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Posted By: Isis
Date Posted: 24 Jun 08 at 1:08am

You might have heard it called an adjustable splice? its an eye splice where the tail is burried for about one and a half fid lengths and then exits the splice and is left long.
With no tension on the line and the outside of the splice bunched up you can freely adjust the size of the loop and the effective length of the line - with tension on the line though the splice binds up without slipping. Think chinese finger trap.

The big advantage is that you can roughly set the height depending on the conditions, which means less line is needed in your main adjustment and theres less dangling around your feet on the light days.

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Posted By: Scooby_simon
Date Posted: 24 Jun 08 at 12:48pm

Originally posted by Isis

You might have heard it called an adjustable splice? its an eye splice where the tail is burried for about one and a half fid lengths and then exits the splice and is left long.
With no tension on the line and the outside of the splice bunched up you can freely adjust the size of the loop and the effective length of the line - with tension on the line though the splice binds up without slipping. Think chinese finger trap.

The big advantage is that you can roughly set the height depending on the conditions, which means less line is needed in your main adjustment and theres less dangling around your feet on the light days.

Ahh, OK understand.

Thanks

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Wanna learn to Ski - PM me..

Posted By: Scooby_simon
Date Posted: 24 Jun 08 at 1:30pm

Follow up question...

How well does D12 "go around corners" and handle knots?

Do I need to put ferrels in for high load areas ?

Can I put fig 8 knots (with bobbles against) in it to make "stopper" strops for attaching things to?

Simon

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Wanna learn to Ski - PM me..

Posted By: catmandoo
Date Posted: 24 Jun 08 at 2:45pm

I got d12 littered about the boat no probs with corners , gnotts or so , but , a man of yur means could afford some v12 , far superior for pole supports etc , used to have it on my sx and it didn't move , the d12 doing same job around pole does change length and not permantly , ie it shrinks and stretch's , but after 2 seasons I'm no longer worried by slack pole lines at times , it doesn't seem to matter .

as for trap lines folk use d12 frequently , but I'm wary of getting one wrapped round my neck if things go wrong , I know it can happen with wire , but its more unlikely and sailing solo theres no one close to get you out.

i've a short length of 3mm d12 joining the two halfs of the stealth down haul system through the clew , withbowline over a bobble one end and tied to the shackle of the blocks other end , and you know how much force goes on that , i do have a safety back up though just in case .

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Posted By: Scooby_simon
Date Posted: 24 Jun 08 at 3:06pm

Originally posted by catmandoo

I'm skint with a capital F...

just had to put 4 new shoes on the scooby. That was not a plesent experience...

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Wanna learn to Ski - PM me..

Posted By: Isis
Date Posted: 24 Jun 08 at 7:10pm

v12 is better in many respects but far worse in terms of UV degradation so you may have to replace sooner.

As far as knots go, all knots create weak points in lines... Ive heard of bowlines reduces breaking strength by about 60% whereas a really good eye splice will only reduce by about 10%?
Idealy with a stopper knot for a bobble a bulge of whipping twine might be a better option though but be surprised if you have any problems with a knot.

As for corners a thimble in the loop will spread the load and cut out any chafe if your worried and they dont cost much

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Posted By: ColH
Date Posted: 24 Jun 08 at 7:23pm

http://www.marlowropes.com/public/pageManager.cfm?page_id=155 - Linky-plinky - full spec downloadable, including load vs. extension.

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Posted By: craiggo
Date Posted: 24 Jun 08 at 8:46pm

Dont use knots on D12 or V12, and if possible splice the ends and insert a thimble, especially where trap wires connect to the hounds.

Fell of a friends RS700 because he tied a bowline at the top of the trap lines and it cost a new trapeze line and a carbon tiller extension.

My 700 has trapeze wires, I've tried D12 but it was too springy for too long. My 49er had herzog trap lines which were great but they came with the boat so were pre-stretched. My kicker is however v12 which I fitted a year ago now and its going fine thanks to my nicely spliced thimbles.

To be honest it barely takes any longer to splice modern ropes than it does to tie knots in them, and if you dont have a fid or splicing needle, any old bit of wire with a hook on the end will do, assuming it fits down the core of the rope.

Posted By: Medway Maniac
Date Posted: 26 Jun 08 at 11:21pm

Originally posted by Isis

v12 is better in many respects but far worse in terms of UV degradation so you may have to replace sooner.

My V12 jib halyard is permanently exposed to UV and is 2 years old. Maybe I should start to worry (no forestay...)

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