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Go Back   SailNet Community > Skills and Seamanship > Seamanship & Navigation
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Seamanship & Navigation Forum devoted to seamanship and navigation topics, including paper and electronic charting tools.


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  #11  
Old 04-10-2009
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Quote:
Originally Posted by lancelot9898 View Post
.....a splice thru the last link of the chain (making a U turn) will reduce the strength of the line by 50%.
I don't see how this splice is much different than an eye splice over a thimble with the line making a U turn around the thimble rather than thru the chain link
.
The secret is very simple: “RADIUS

- modern fibers don’t like to be bended following a very short radius – a “U” turn around the last link of the chain has a radius = the diameter of the chain: much smaller than the radius around the thimble...

When doing anchor tests, we often broke the rope and in 100% of the cases the failure occurs at the level of the knot, where the fibers make a small radius curve...

João
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Old 04-11-2009
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Quote:
Originally Posted by ANCORALATINA View Post
The secret is very simple: “RADIUS

- modern fibers don’t like to be bended following a very short radius – a “U” turn around the last link of the chain has a radius = the diameter of the chain: much smaller than the radius around the thimble...

João
If this is true then one of the methods on the referrenced website shown for splicing the line to chain also has a small radius.


http://www.samsonrope.com/site_files..._RopeChain.pdf
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Old 04-11-2009
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One point that Ancorlatina fails to mention is that the backsplice used to attach three-strand laid lines to an anchor chain separates the three strands of the laid rope and bends them around the chain, but it isn't as bad as trying to do that with the rope as a whole, since each strand is smaller and the radius is relatively much larger for the strand as compared to the entire rope.

He also neglects to mention that the fact that the lines often broke at the splice point could also be due to chafe.

The backsplice is the preferred method for connecting a line to an anchor chain if you use a windlass. All of the windlass and rope manufacturers pretty much agree. Using a thimble can be far more dangerous, because it requires you to manually handle the rode on retrieval.
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Old 04-11-2009
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Quote:
Originally Posted by sailingdog View Post
One point that Ancorlatina fails to mention is that the backsplice used to attach three-strand laid lines to an anchor chain separates the three strands of the laid rope and bends them around the chain, but it isn't as bad as trying to do that with the rope as a whole, since each strand is smaller and the radius is relatively much larger for the strand as compared to the entire rope.

.

Good point dog about the radius issue. I still like keeping that line intack when passing it thru the last chain link rather than separating the three strands. I do think chafe is the potential problem for failure regardless of the method used and I do keep an eye on that eye splice. FWIW That is the type of splice I used when anchored during a Cat 1 hurricane some years ago. Used 5/8 inch 3 strand nylon line spliced to 80 feet of 3/8 BBB chain. Had somewhere around 200 feet of total rode out and that 5/8 inch line looked like a banjo string. Never will stay aboard the boat again during a hurricane if i can help it and that was only a Cat 1.
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Old 04-11-2009
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Quote:
Originally Posted by sailingdog View Post
the backsplice used to attach three-strand laid lines to an anchor chain separates the three strands of the laid rope and bends them around the chain, but it isn't as bad as trying to do that with the rope as a whole, since each strand is smaller and the radius is relatively much larger for the strand as compared to the entire rope.

He also neglects to mention that the fact that the lines often broke at the splice point could also be due to chafe
.
CHAFFING is the main concern for a rope, on the seabottom (use some chain) at the level of the splice and also at the cleat or Samson post...

I can’t see how (or why?) the fact to separate the three strands or splicing the whole rope will change something; the radius is still the diameter of the chain link... (at least for the inner fibers, and not that much bigger for the external ones..)

This is why, my favorite is the elongated splice described in BlueMoment - Articles

This splice will also go easily through the deck pipe and the windlass...

João
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Old 04-11-2009
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A Shovel Splice.

Quote:
Originally Posted by ANCORALATINA View Post
CHAFFING is the main concern for a rope, on the seabottom (use some chain) at the level of the splice and also at the cleat or Samson post...

I can’t see how (or why?) the fact to separate the three strands or splicing the whole rope will change something; the radius is still the diameter of the chain link... (at least for the inner fibers, and not that much bigger for the external ones..)

This is why, my favorite is the elongated splice described in BlueMoment - Articles

This splice will also go easily through the deck pipe and the windlass...

João
I understand this is a mess in terms of bringing up mud, but I have no experience. I tried it once to see how it went through the windlass...it did not. Jumped right out of the gypsy. Perhaps my windlass is fussy, but the only thing that feeds well is a standard last-link splice, with the ends tapered the last few tucks.

Radius makes all the difference - it changes the % of fibers carrying load. Consider climbing ropes and round-slings for crane work; neither are laid or braided in their working parts. the interiors are a collection of very small ropes in order tot maintain full working strength over small radius edges.
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Last edited by pdqaltair; 04-11-2009 at 03:09 PM.
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Quote:
Originally Posted by ANCORALATINA View Post
CHAFFING is the main concern for a rope, on the seabottom (use some chain) at the level of the splice and also at the cleat or Samson post...
Yes, chafe is a concern. But, with regular inspection, it isn't a serious issue.

Quote:
I can’t see how (or why?) the fact to separate the three strands or splicing the whole rope will change something; the radius is still the diameter of the chain link... (at least for the inner fibers, and not that much bigger for the external ones..)
If you think about the rope as individual strands of fiber, when you bundle them together in a thick bundle, the ones on the outside of a tight radius bend are under a lot more tension than the ones on the inside of the bend, due to the fact that they have to go a further distance. By separating the rope in to three laid strands, the fibers are now being stressed more evenly than they are when you do an EYESPLICE with the entire rope. By spreading the tension on the fibers more evenly, they're far less likely to break.

Quote:
This is why, my favorite is the elongated splice described in BlueMoment - Articles

This splice will also go easily through the deck pipe and the windlass...

João
From what I've seen, very few windlass manufacturers recommend this type of splice. IMHO, it probably causes more chafe on the line IMHO as the chain and rope move against each other. The single point of contact between the rope and chain on a properly done backsplice is generally tight enough that movement is almost non-existent, which limits the amount of chafe possible there.

Also, the elongated splices are going to collect more mud or sand and the galvanizing on the chain is going to wear faster because of that. The backsplice is generally tight enough that not a lot of mud or sand will get in, and because it is fairly limited in its movement, it won't wear the galvanization as much.
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  #18  
Old 04-11-2009
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SD,
I guess that on a tri, you need to keep the weight down, but when cruising, would a 6mm short link chain and long nylon snubber be more effective than 200' nylon ? If you have a shoal draft vessel, do you need to anchor in areas which need 200' of rode?

A long splice is the only way to join the lines, but if the splice is being used (>30m of rode out), can he rely on his splice. Only about 3 or 4 turns is required in the splice, but tensioning each turn is very important and if not done correctly, will weaken the line at some point.
back to you
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I did the above splice 5 or 6 years ago. It was used hard and even drug across the barnacle encrusted boat bottom. There were numerous chafed areas.
There is no question that the more you deform a piece of line, whether by knotting, splicing or simply turning, the more you weaken it. However, there is usually more than enough safety margin built in that it becomes a moot point.
As with most other pieces of rigging, failures usually result from chafe or corrosion. Both of which are evident in the photo.
With proper use and inspection, These types of failures can most always be avoided.
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knothead,
looks a beaut splice. I couldnt agree more with what you said about maintenance. I would put a stainless link between the galv and nylon. Then again, I personally just use 10mm chain and would be very rusty at splicing.
DC
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