Knotting dyneema

Greenheart

Greenheart

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For some reason my trapeze wires have no handles on them, just neat little crimped loops round thimbles. Nor was there any option to run a handle over the upper ends of the wires, which are likewise permanently crimped onto the mast.

So I had to fit a handle, between each wire-end and its adjustable tackle with the harness-ring on the bottom.

I chose 2.5mm Liros 'D-Pro', which seems to have a half-tonne breaking strain, but which was narrow enough to thread twice through the very narrow plastic handle...

...and I used little steel thimbles top and bottom, so there won't be undue strain on the line caused by a tight radius.

Only problem was, actually securing the D-Pro (which I think is dyneema) in a tight loop securing the handle in place.

I used a reef knot, but under great tension, I was surprised to find that the line slips, and the reef knot releases.

I hope my efforts to 'stopper' the ends by a molten heated bobble, tied tight with whipping twine, and duct-taped around, will suffice. It could all get very wet, very quickly if the trap-line lets me go when my feet are on the gunwale.

Any thoughts on whether dyneema is hard to tie? It seemed to me essentially less secure than rougher-coated line.

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I guess the best solution to my problem is to have trap-wires made with handles added before the ends are crimped. But I don't fancy shelling out £40 to replace the existing ones...especially since the last owner must have managed.
 
Dyneema is notoriously bad at holding knots. I have some lines with polyester jackets which are ok, but otherwise people generally splice it. For the relatively loosely-woven single-braid kind, there are a couple of easy splices commonly used. Even then, it's not uncommon to add a whipping, tape, or adhesive heatshrink to guard against slippage.

Pete
 
Thank you gentlemen, these are all good answers confirming what I had supposed.

Given that I'm not especially keen to spend sailing hours undoing the unsuitable knots I've tied in this slippery rope, is it possible that the reef-knots, however unsuitable, will increase in security when a moderate load, like my 70 kilos, is hung on them for a while?

Or will it appear secure, lull me into a condition of cavalier recklessness, then dump me in the drink under the bows of a ferry?
 
Add some half hitches and wrap in amalgamating tape?

Or splice pure dyneema (no sleeve) trapeze lines £13.92 for 10m of 3mm from this, that's what I used when I changed from wire.
iu
 
I 'temporarily' replaced a dyneema strop on my kicker 3 years ago using a cow hitch (apparently the knot which retains the same strength as a splice) and used an overhand knot in the running end to prevent slippage. 5000 miles later it is still in place.
 
Splice. Splicing bare dyneema is easy.

For your application, I would splice an eye into one end, then splice the other end directly onto the wire eye above the handle. Then draw the first eye down through the handle.
 
bbg said:
Splice. Splicing bare dyneema is easy.

For your application, I would splice an eye into one end, then splice the other end directly onto the wire eye above the handle. Then draw the first eye down through the handle.
Click to expand...

+1. Always splice rather than knot dyneema. Knots in it slip more easily than in other rope, and it's far easier to splice than other rope.

Splices should be quite long so that they don't tug out before the rope's tension constricts the splice tight. And as you're committing a human body to hang on the end of your creation, whip your splices too.
 
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BelleSerene said:
+1. Always splice rather than knot dyneema. Knots in it slip more easily than in other rope, and it's far easier to splice than other rope.

Splices should be quite long so that they don't tug out before the rope's tension constricts the splice tight. And as you're committing a human body to hang on the end of your creation, whip your splices too.
Click to expand...

Agreed that splicing is better all round if possible, but if it can only be knotted then there are knots which don't slip.

For full strength it's important to taper the spliced part as well, I've destruction tested non tapered splices in dyneema before, it always goes at the end of the slice as the working part bends over the other end of the line.

Doesn't go with the huge bang of steel wire rope though ;)
 
As an alternative to splicing onto the eye - if you want some extra length in order to allow for a long taper in both splices - splice two eyes, one in each end, and draw the middle of the line up through the handle.

Another alternative is just to create dyneema shackle and run that through the handle.
 
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