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Old 02-01-2015, 15:27   #1
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Missing Link

At first glance HMPE rope, available under a variety of names such as Dyneema, Spectra, and Vectran would appear to have many qualities making it especially well-suited for use as anchor rode.

High Strength and Low Weight- according to the Dyneema website there can be as much as 80% weight reduction for an equal section with the same strength when compared to steel.

Chafe Resistance- Per same diameter and same rope construction, Dyneema is more chafe resistant than either nylon or polyester.

Floats- I have heard of polypropylene used in certain localities because it floats and is less likely to foul on the bottom. Likewise Dyneema enjoys the same quality and I think it could be argued it is therefor less likely to be subject to abrasion from bottom features such as coral heads than nylon or polyester.

Low Stretch- Much like chain, HMPE rope has very low stretch resulting in less internal friction and heating when compared to other rope.

Cost- Somewhere around twice nylon but half of chain. Here's some ballparks-

3/8" (G4) Chain 16,200lbs. Breaking Strength $6.09ft.
3/8" Amsteel HMPE 19,200lbs Breaking Strength $3.44ft.
3/4" 3-Strand Nylon 16,700lbs. Breaking Strength $2.01ft.

So what's the rub?

I've done some searching around and while Dyneema is growing in use for offshore oil platform moorings for all of the above reasons, the problem with Dyneema for a yachtsman is that in addition to having very little stretch requiring the use of a snubber, it is notoriously slippery,which makes attaching a snubber challenging.

The concept of using Dyneema for a rode has been kicked around here on this forum, as well as elsewhere, and while the prevailing wisdom is that maybe using an icicle hitch or some other knot might possibly work, but that prospect seems dubious and I don't know of anyone who has tried it.

Recently, I ran across this knotless connector for tying with Spectra braid fishing line and I wonder about it's suitability for attaching a snubber to a Dyneema rode.

Most of the knots used for tying Spectra are complicated and few offer close to breaking strength of the line, and the ones that do can never be undone. This connector on the other hand is stupid simple and easy to use by any blindfolded while having buckets of water splashed in your face.

I think it's brilliant really. Perhaps a nearly ideal method of attachment and wonder if it wouldn't provide close to 100% of the breaking strength of the line? Having played around with it a bit I am quite certain that regardless of load this connection will be very easy to release.

I was able to find some prior art doing a number of Patent searches but couldn't find this one exactly so I am not really sure who to credit it to. For those who might think it too simple and somehow likely to unwind itself, keep in mind it's intended purpose is for tying lures and that many fish are known to thrash about.

I have attached some photos of a connector I formed out of 1/4" mild steel which I have paired with some 1/8" Amsteel as a proof of concept. I figure it's small enough I can break it with a forklift to get a sense of whether it slips or not.

Assuming it works as expected I would like to go full-size and I wonder if anyone out there has access to the required testing equipment who also wouldn't be interested in breaking some stuff?

I would be happy to provide samples.

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Old 02-01-2015, 15:44   #2
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Re: Missing Link

I was just over at Spencer Industries, just outside of Newark, NJ. TheY are set up to do ArmourGalv on chain. It's a hot dip alternative the Navy uses. Lower temp, less stress.

So anyway, the guy takes the chain, wacks off a few links, throws it in a tester and breaks it. Then does the same on the next piece. In like 30 minutes he has confirmed my chain is still up to spec.

Guy clearly loved his job and was a real metal geek.

They also do some light manufacturing.

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Old 02-01-2015, 18:26   #3
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Re: Missing Link

The problem is exactly as you stated. Anchor rode needs to stretch to absorb shock loads and none of these will allow for that. Chuck
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Old 02-01-2015, 18:37   #4
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Re: Missing Link

Right, chain doesn't stretch, which people use all the time. That's what snubbers are for.

Hence the knotless connector, to attach a snubber to the Dyneema.
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Old 02-01-2015, 18:49   #5
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Re: Missing Link

So your considering using this rope as an anchor rode and adding a nylon snubber? I understand this with chain but Dyneema or any of the others are not a substitute for chain, in my opinion. Other than weight, I don't see the benefit and it costs as much or more than chain. You ask. Chuck
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Old 02-01-2015, 19:05   #6
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Re: Missing Link

Cost as much or more than chain? Don't you mean cost half as much as chain but is stronger?

Yes, agreed about weight as the Dyneema weighs about one fifth of steel so you could carry five times as much Dyneem as chain of the same weight.

Substitute for chain? Well, chain doesn't float so maybe you could consider it as a potential improvement over three-strand nylon or polyester.

Speaking for myself, I just don't have room for hundreds and hundreds of pounds of chain in my life, let alone the bow of my boat. Sort of brings me down.

Maybe that puts me in a minority but I suspect I am not alone.
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Old 02-01-2015, 19:47   #7
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Re: Missing Link

In a good Sandy bottom in normal weather i dont see any con, but what about the catenary??
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Old 03-01-2015, 04:36   #8
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Re: Missing Link

Yes, I totally agree catenary effect is overrated as a benefit to all-chain rodes considering it just disappears when you need it the most! Kinda makes you wonder what is the point of dragging around all that weight during nice weather when it doesn't really do you any good in a bad storm?

Also, isn't it interesting how the 3/8" Amsteel Dyneema rope has a breaking strength that is actually 3,000 lbs. higher than the 3/8" (G4) chain? Crazy isn't it, that that size rope is that much stronger than that size chain?

What's even crazier is that 100' of 3/8" Dyneema weighs less than THREE FEET of 3/8" chain!

Did I mention Dyneema is also used for MODU (Mobile Offshore Drilling Units) moorings for the oil and gas industry? Must be some tough stuff!

http://www.lankhorstropes.com/Offsho...MODUOPERATIONS

Lightweight ropes for MODU and barge mooring | Dyneema «
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Old 03-01-2015, 04:53   #9
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Re: Missing Link

Take a look at these winch lines. They are dyneema with an abrasion cover. I spoke to them about using them as an anchor line. It certainly sounded possible and the per-foot pricing was reasonable. Windlass gear would be a problem. Having large spool of dyneema and then a chain leader to pick up
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Old 03-01-2015, 11:49   #10
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Re: Missing Link

That thimble could kill the deal. How would you get it throug the haws pipe?
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Old 03-01-2015, 12:28   #11
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Re: Missing Link

I'm a big fan of Dyneema and other new fibers, but I'm not so sure about using it for anchor rode. Not because of chafe or strength worries, but, yes, because of the catenary issue.

I agree that under severe conditions, chain catenary does disappear and stops being a factor in ultimate holding power. But in the (guestimate) 95% of anchoring situations where the forces are not sufficient to remove the catenary, that effect provides a large shock absorbing function. It takes a considerable amount of energy to straighten out the chain, and that energy comes from decelerating the boat as it responds to surges and wind gusts. Further, when the dread 180 degree shift comes, dragging heavy chain through the mud or sand slows the boat down so that when the chain again comes up tight there is less momentum to jerk the anchor out.

A good snubber adds greatly to the shock absorption provided by the catenary, but the combination works so well that I would be loathe to give it up... and the issue of attaching the snubber to a Dyneema rode is not trivial IMO.

We've spent a hell of a lot of time at anchor, and at times I've sat on the bow watching the rode (yotties are easily amused), and I'm convinced that the catenary of chain makes my life at anchor better.

Getting rid of the weight would be good... that's for sure! So, why don't you give it a good tryout and let me know if I am wrong?

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Old 03-01-2015, 13:21   #12
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Re: Missing Link

Jim, you may be right about the comfort of catenary. Some might suggest a kellet but to me that sounds all together too complicated. I certainly couldn't tell you otherwise because I don't know. My interest in the matter is largely academic and I not afraid to experiment a bit if that's what it takes to learn things for myself.

On the subject of learning, can anyone advise me the best way to make a 100% line-strength connection so I can test slippage on my little knotless connector?

I have access to a fork lift that should be able to break the 1/8" dyneema I have on my sample. I figure I could shackle the eye of the knotless connector with some chain to the base of the fork truck.

On the other end I wonder if maybe wrapping a dozen or more turns of the dyneema around a length of fat pipe slung between the forks would provide the best connection? Any thoughts?


I don't have any way to measure the load but I think it will be interesting to see if the knotless connector will slip before the line breaks. I don't think it will and I suspect measured testing will show it performs better than a splice. I occurs to me it could be useful for terminating standing rigging.

I doubt anyone will run out and get rid of their chain. Far from it. However, I've never been much of one for the status quo. Many believe in all-chain end of story. Yet lots have rope rides. Seems like worth playing around with. Otherwise how would you ever know?
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Old 03-01-2015, 13:40   #13
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Re: Missing Link

On my current cruising cat I've got all chain (but only 100' backed with nylon 3-strand, since I seldom anchor in over 7' of water), and on my last Kevlar cat I used A Fortress and rope. So I understand the pluses and minuses. I think the idea is not fully ready, but it certainly deserves discussion. If we didn't try new things, we'd have latenteen sails and wooden boats.

a. New England Rope WR-2 is much like that Dyneema tow cable. I have tested it against steel cable and many common ropes, and it is impressive. While not as cut resistant as chain, it is an order of magnitude above Amsteel, which is saying something. And because it is double braid, you can easily see what you've got. Unfortunately, it only comes in smaller sizes.

b. Splicing. Hollow braids are VERY easy to splice. Additionally, while Dyneema does need chafe protection in certain cases, it does NOT need thimbles for strength (this has been tested--because it is slippery it better spreads load over short radius).

c. Catenary. Valuable in deep water (where you are paying the worst weight penalty) but basically useless for wave shock absorption in shallow anchorages. Mine stretches out tight at perhaps 30 knots, and the waves start banging--a long snubber is vital in shallow anchorages with chain... though nylon works fine. Chain also aids in narrowing swing in some circumstances and in easing the anchor around when the wind changes.

d. Even harder to handle manually than chain. No combination gypsy will like it.

So what is it for?

* Drogues.
* Kedging lines, if you find one that likes winches. Lack of stretch will help.
* Rode for light racing boats. Yes sir, never use it anyway. I would have used it in a heartbeat.
* Boats with no chain windlass; possibly easier to handle manually than chain, and WAY (50x?) more cut resistant than nylon.
* Very economical per unit strength + durability.

Interesting. I will follow this.
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Old 03-01-2015, 13:48   #14
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Re: Missing Link

Two concerns come to mind: 1) you will be either going without windlass, or kludging some type of one together. 2) it floats. This can be taken care of someway, I guess, but many are the times when the wind dies and we are floating around directly above our anchor - I would hate to get all that floating rode wrapped in my prop or rudder, or those of another boat.

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Old 03-01-2015, 15:07   #15
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Re: Missing Link

Many windlasses have a capstan for rode so that makes it more acceptable for those so-equipped boats.


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