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Go Back   SailNet Community > Skills and Seamanship > Seamanship & Navigation > Splicing anchor rode
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Thread: Splicing anchor rode Reply to Thread
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Topic Review (Newest First)
04-17-2009 07:37 PM
lancelot9898
Quote:
Originally Posted by pdqaltair View Post
I highly recommend, for anyone interested in knots, that they take some light line (less than 1/8"), tie opposing anchors in pairs, and start breaking them.
.

I was considering taking a small diameter 3 strand line and comparring the back splice around that last chain length vs an eye splice without the metal thimble to determine which is better, however with the small diameter line I also need a small diameter chain length to get an accurate comparison. The weakest link will be the chain so to prevent chain breakage a larger diameter chain has to be used. If I run out of boat projects I'll get two short links of 3/8 chain and tie one chain using 3/16 3 strand nylon(1200 pound breaking)with the back splice and the other chain with the eye splice. The next step will be to pull the two chains apart and see which end breaks. A strain gage would be nice to see how close to the 1200 pounds is achieved.
04-17-2009 07:07 PM
pdqaltair
Yes, the failure is inside the knot, and always in the same spot.

Quote:
Originally Posted by lancelot9898 View Post
It was my understanding that the failure was at the U bend and not at the knot itself. If that's the case then it doesn't matter as to the type of knot or splice being used. I always thought the failure would in fact be at the knot since most books mention various reduction in strength for various knots and how a splice is better.
I highly recommend, for anyone interested in knots, that they take some light line (less than 1/8"), tie opposing anchors in pairs, and start breaking them.

Note that differing line materials matter. Don't use cotton or binders twine - different rules apply because of differences in friction.

I used to make and market rock climbing equipment, and we spent many hours breaking stuff. Always educational.
04-17-2009 06:57 PM
artbyjody Most failures would be just abrasion of the core loop around the shackle. If the shackle is suffering rust / corrosion etc - then it makes sense the weakest link is the weakest point that has the less amount of material (around the shackle). Arguments about the knot being the weakest link are only valid if the knot is one that easily becomes undone...
04-17-2009 06:52 PM
lancelot9898
Quote:
Originally Posted by pdqaltair View Post
-
If you are testing anchors until something breaks, at least go to a stronger knot, and a figure-8 loop is a good choice for this, although there are others.

It was my understanding that the failure was at the U bend and not at the knot itself. If that's the case then it doesn't matter as to the type of knot or splice being used. I always thought the failure would in fact be at the knot since most books mention various reduction in strength for various knots and how a splice is better.
04-16-2009 06:37 PM
sailingdog There's a significant difference. The reason, IIRC, knots have much lower strength when compared to splices is because they have sharp bends and also compress the fibers heavily. When that happens, it stresses the fibers far more than even the backsplice on the chain-to-rope connection does, since the backsplice can be done to allow the fibers to be stressed rather evenly, especially compared to a bowline knot. You're comparing apples to oranges... If you did a stress test of a backsplice-to-chain versus a bowline to chain or shackle, I'm pretty sure you'd fine the bowline was far weaker.

Quote:
Originally Posted by ANCORALATINA View Post
One point meanwhile is interesting, the breaking always occurs where the rope make a sharp U turn, and this U turn can be compared, with the one made by the three strands around the last chain link, BEFORE the back splice..



Perfectly right, but what about the strength of the fibers at the level of the sharp U turn?? Can we then compare them with the U turn made by the bowline knot?? Except that the U turn on the bowline knot has a bigger diameter than the one around the chain link.

Now sailingdog, I will be interested to have your comments on this specific point:

Does the reduction of strength on the U turn present on the bowline knot, be bigger than the reduction of strength present at the smaller U turn around the chain link??

Can we compare them??

Joo NODARI
04-16-2009 05:57 PM
pdqaltair
Additionally, I don't think the gypsy will pick it up dependably.

Quote:
Originally Posted by imagine2frolic View Post
Is it possible to use heat shrink about the splice, and last link to keep away some abrasion, or will it do more harm?......i2f
Maybe.

It probably won't last long.

The reality is that a rope-chain splice is really an easy one to learn and should be re-done every few years anyway, to check the link. It is probably the simplest splice to learn and to do well. However, I would practice on some scraps. Just remember to taper it so the gypsy picks it up smoothly.
04-16-2009 05:54 PM
pdqaltair
If it were simply the turn, a splice and a knot would be the same.

Quote:
Originally Posted by ANCORALATINA View Post
Once more I have to apologize for not speaking a perfect English...

It has never been my intention to COMPARE splices and bowline knots, I was only answering Lancelot9898s question



One point meanwhile is interesting, the breaking always occurs where the rope make a sharp U turn, and this U turn can be compared, with the one made by the three strands around the last chain link, BEFORE the back splice..



Perfectly right, but what about the strength of the fibers at the level of the sharp U turn?? Can we then compare them with the U turn made by the bowline knot?? Except that the U turn on the bowline knot has a bigger diameter than the one around the chain link.

Now sailingdog, I will be interested to have your comments on this specific point:

Does the reduction of strength on the U turn present on the bowline knot, be bigger than the reduction of strength present at the smaller U turn around the chain link??

Can we compare them??

Joo NODARI
Not the case at all. The turn where the rope breaks is not where it crosses the shackle. Also, all knots would be the same. As SD pointed out, a splice is ~ 90-95% efficient. A bowline is ~ 40-45% efficient. A figure-8 loop is ~ 80-90% efficient, depending on the finish. If you take a length of line and tie a figure-8 at one end, a bowline at the other, and pull, the bowline will fail EVERY TIME. If you tie a figure-8 at each end and tuck the free end back in such a way as to pad the first turn ON ONLY ONE OF THE KNOTS, the other figure-8 will fail every time.

The key is that ALL of the fibers carry the same load. A splice does that. Breaking a laid or braided line into smaller parts does that. Webbing is inherently good over an edge for that reason.

If you are testing anchors until something breaks, at least go to a stronger knot, and a figure-8 loop is a good choice for this, although there are others.
04-16-2009 08:52 AM
knothead
Quote:
Originally Posted by sailingdog View Post
Comparing a bowline to a splice is pointless.

Bowlines reduce the strength of the rope about 40% IIRC or so.... depending on the type of line, etc... splices generally only lose about 10-15% of the strength of the rope.

That doesn't make sense to me either.
If you are testing anchors, why would you want the failure to occur in the line?

That would be like testing shackles with a swl of 1000 lbs. using a line with a breaking strength of 500 lbs.
04-16-2009 08:49 AM
ANCORALATINA Once more I have to apologize for not speaking a perfect English...

It has never been my intention to COMPARE splices and bowline knots, I was only answering Lancelot9898s question

Quote:
Originally posted by lancelot9898 Oh....Anchoratlantia, do you have some photos for the failures of the splices in your anchor tests? Thanks.
One point meanwhile is interesting, the breaking always occurs where the rope make a sharp U turn, and this U turn can be compared, with the one made by the three strands around the last chain link, BEFORE the back splice..

Quote:
Originally Posted by sailingdog View Post
splices generally only lose about 10-15% of the strength of the rope.
Perfectly right, but what about the strength of the fibers at the level of the sharp U turn?? Can we then compare them with the U turn made by the bowline knot?? Except that the U turn on the bowline knot has a bigger diameter than the one around the chain link.

Now sailingdog, I will be interested to have your comments on this specific point:

Does the reduction of strength on the U turn present on the bowline knot, be bigger than the reduction of strength present at the smaller U turn around the chain link??

Can we compare them??

Joo NODARI
04-15-2009 09:18 PM
sailingdog Comparing a bowline to a splice is pointless.

Bowlines reduce the strength of the rope about 40% IIRC or so.... depending on the type of line, etc... splices generally only lose about 10-15% of the strength of the rope.

Quote:
Originally Posted by ANCORALATINA View Post
When doing our anchor tests, we usually use a line done with about ten meters of chain and Nylon rope,

We do not make a splice to connect the rope to the chain, we use what you call a Bowline knot ; and in 100% of the cases, when we broke the line, it has always been at the level of the bowline knot, where the rope make a sharp U turn..

Sorry, we didnt take photos of the rope as the purpose was to test anchors, not the rope.

Joo Nodari
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