Splicing or not splicing Dyneema...

Kukri

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Every schoolboy knows that you can't splice polyester or nylon three strand or multiplait rope after it has been under load.

Does this also apply to Dyneema? (i.e. can I try to make soft shackles out of the undamaged end of a chafed ex halyard?)
 
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GHA

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Every schoolboy knows that you can't splice polyester or nylon rope after it has been under load.

Does this also apply to Dyneema? (i.e. can I try to make soft shackles out of the undamaged end of a chafed ex halyard?)

Don't see why not, though for splicing short strops of soft shackles single braid dyneema like marlow d12 would probably be a lot easier to splice or make a soft shackle from rather than covered dyneema halyards.
 

lpdsn

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You'll probably be using a Bummel splice anyway, so I can't see where the difficulty would be if the Dyneema wasn't brand spanking new.

Traditional splices are hard in Dyneema as they have reputation for slipping.
 

simonfraser

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not the age of the dyneema but the load it has been under.
if it has had some major stress on it i would not want to waste my time and effort using bits of it up.
push the boat out and buy a meter or two of new stuff and practice making shackles etc.
 

lw395

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The core of a random bit of dyneema-cored rope may not behave exactly like Marlow D12 or whatever, so if you're trying to follow instructions or do repeatable work, you can do yourself a favour by knowing you've got the right stuff, at least while learning.
Old dyneema seems to splice OK in smaller sizes FWIW. Maybe less pretty than with new rope, but it does the job IME.
 

thinwater

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I found used single braids of all types easy to splice. A number of times I've re-spliced Dyneema because I got the length wrong, after the construction stretch settled in. No worries. I've even strength-tested re-spliced sections.

If not, woopie slings wouldn't work. (I bet you'll have to Google that)
 

thinwater

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Remember that it is NOT the brummel that creates the strength, it is the long tail bury. Brummels with short or no bury fail at lower loads. On the other hand, most larger Dyneema is simply burried and lock stitiched, no brummel. The brummel is ONLY to prevent loosening at zero load.
 

zoidberg

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The Technical Manager at Marlow Ropes advised that they recommend a bury of at least 40x diameter when splicing loops.
Yes, I'm sure someone here will have a different idea, so 'just sayin'.......
 

GHA

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The Technical Manager at Marlow Ropes advised that they recommend a bury of at least 40x diameter when splicing loops.
Yes, I'm sure someone here will have a different idea, so 'just sayin'.......

Lots of load testing to destruction in here >
https://web.archive.org/web/20160715154948/http://www.bethandevans.com/load.htm

Seems to get to full strength with a shorter bury but under a static load can slip slowly. Tapering the tail is important to get to full strength.
Regarding bury length . . . quite short bury's will carry full strength. Under a slow 'static load' 18:1 will slip, but 27:1 will hold. I tested 27:1, 37:1 and 46:1 bury's under a significant drop load (50lbs falling on a 4' 1/2" dia Dyneema line as the 'fall line'). All three samples slipped about 3 diameters, which I take to be the "constructional take up" of the splice (without any stitching), but then all three held. Extra bury length is of course always a nice thing and double 27:1 = 54:1 (which is near the typical bury recommendation) would seem to be conservative, but these results do suggest you can 'get away' with a shorter bury if it is necessary to make the piece.

I've load tested 6mm dyneema on fast winches before, double brakes hard on to simulate loss of power at 6m/s(11.7Kts or 13.4mph) descend with a 500Kg load & a 50:1 bury splice but no brummel and a tippex mark across the splice - none slipped enough to crack the tippex. Test load bounced about a bit though :eek:
 
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