An adjustable splice?

[benz]

I have a long piece of Amsteel Blue that I must splice a length of with thimbles, but can't cut the rope down. Has anyone done a bury splice with a long tail just sticking out of the rope again after the appropriate buried length? The idea is to be able to have a temporary length of rope, with a thimble at each end, and then to be able to pull the splice out and make another length, and so on as the need requires. One end of course can have a regular lockstitched tapered splice, but the 'adjustable' end brings up some concerns. Will the rope weaken where the tail comes back out of the braid? Will the rope return to its shape once the splice is taken out?
This is not for a boat, so low-load loosening of the splice is not a concern--it will only be put under a high load.
Thanks in advance!
Ben Zartman

[Bob Pingel]

I did something like this once on a small dinghy -- 470 or alike. I did a full length bury without any lock stiches or brummel -- the tail went in a came out at the end of the bury with no taper. I placed a twing ball in the end of the tail to stop it from sucking into the bury. The idea was that the length of the eye would be adjustable - I think it was a traveller like arrangement. I used probably 1/4" Amsteel so the load was trivial. It worked well in this application.

The caveat here is that without the taper you are *seriously* degrading the strength of the splice -- you'll have a massive stress riser where the tail exits. I don't how much you need to detrate the splice, but it is very significant.

You are also losing the low load security of the brummel. Your application may not have low load "flopping around", but your load may come on gradually -- the brummel takes the start of the load and then transfers it to the bury as things compress.

I think the rope will heal, and will be "resplicable", Amsteel is pretty tough.

Any chance you could splice up a series of slings that you mix and match to get your length -- or work in tackle to set the length?

Another thought, could you make up the slings as needed with multiple brummels. You can throw these in quickly with no tools. They are tough to remove and would likely distort the rope beyond more than a few re-uses.

Bob

[mikeb]

Yale has something similiar to what you ask about - they call it an "Adjustable Sling" Buy pre-done or see the splicing instructions - be sure to read the fine print about derating the strength of the rope for no taper and any angle in the legs.

http://www.yalecordage.com/html/pdf/...e/low/Pg30.pdf

http://www.yalecordage.com/html/pdf/yale_backsplice.pdf

mb

[Bob Pingel]

The link that Mike references describes what I believe that you are trying to construct...

But, the material appears to be hollow braid dacron. The coefficient of friction is higher on this material, and the tensile relative to cross sectional area is much different.

I think you can do it, but I don't think the 12% splice derating is accurate. And, those low force loads still worry me, too...

Bob

[Brion Toss]

Hi there,
You are talking about a "Whoopee sling", or possibly its cousin, the "Yippee". Both are adjustable, and both can be made in HM rope. The former has a normal eye at one end, an adjustable at the other. The latter is a grommet. We make Yippee's out of Spectra for mast lifting gear, and for temporary stays. Yippee's, I believe, are stronger per diameter, and give the greatest verstatility. Whoopee's are tidier and handier for smaller-spectrum variations in length.
The loss of strength isn't a great as one might expect; in a normal splice, the entry point for the tuck deforms the rope just as much as the exit on an adjustable splice. The difference is that the rope doesn't try to regain its original diameter immediately on the standing part side of the throat, and that it shares the load, on the eye side, between two parts.
One important detail when using a Yippee is to position the load on the doubled thickness, right by where the adjusting tail emerges. That way it becomes very unlikely that the tail can be accidentally pulled, slackening the splice.
We bury at least 72 diameters of the rope, usually quite a bit more, as a paranoia-reducing move.
Fair leads,
Brion Toss

[benz]

Thanks, everyone--these forums are such a great resource.
What I'm doing is trying to rig a tightrope between two tall cliffs (not for me to walk--I'm not that crazy), so all the materials must be light enough to carry several miles uphill in backpacks. My client doesn't want to be limited to walking just one gap, which having a rope of fixed length would do. He wishes to start small (200-foot span) and increase the gap gradually without having to buy a new piece of rope each time, since 3/4" Amsteel is hardly cheap. Hence the need for an adjustable splice. I'll do some math and see whether losing 12% of the rope's strength still leaves him the large safety margin he (understandably) wants. My own safety margin is to stay safe on the cliff, well back from the edge.
Thanks again! Brion, do your clients ever look askance when you say, "So, we'll heave it up with a whopee, then slide a yippee around the foot...."
Ben Z

[NickfromWI]

That 12% is for polyester. I am not sure if things change when you go to high tech fibers.

Where are you building these traverses? I've built a couple....

love
nick

[benz]

Nick, with the diameters we're talking (3/4--1"), we could stand to lose even 30% of the strength and still have a huge safety margin, although keeping as much as possible is desirable. There are several other options I'm tossing about.
As for the location, I have been adjured to keep silent, lest anyone go and walk my client's gap first. As though anyone would (!?)
Cheerio,
Ben

[Justaddwata]

The vast majority of splice breaks will occur at the end of the taper in the bury. (It is considered a good break when this occurs). Considering you are now removing the taper altogether I believe you are going to see a sizable loss in tensile. If you consider that a good portion of the 12 strands are going to be deviating from their normal path to allow for the exiting of the bury.

Given the fact that this is a life critical application and the rope will be taught before it is loaded (applying some high loads) I would approach Samson about having a tensile break done to an eye splice of this configuration. I am sure they would be happy to do it (it will certainly give them some valuable information) and it would certainly be better to know in advance than to have a failure occuring.

As for strength loss following the removal of the splice. I agree this should be minimal provided no damage has occurred to the yarns (and that the rope is indeed not overloaded at the revious splice points).

[Bob Pingel]

In another thread Brion mentions, "We have also begun making "Yippee Sling" grommets, which are unlocked, so need obsessive stitching, for relatively light duty things like small boat tack and head pendants"

This config is also "unlocked", and the topic of stitching has not yet come up...

Bob