Replacing the Chain Leader with Dyneema--A Better Secondary Rode?

Rev. 3-20-2017
Rev. 2-12-2017
Rev. 6-10-2016
Rev. 9-19-2016 



For the primary rode the conventional answer is chain. Strong, cut-proof, fits a windlass, well proven. It requires a snubber to keep the load reasonable if you are in shallow water (not enough centenary), but other wise, pretty fool proof, and we can all use that.

But the requirements of a secondary rode are different:

• Chafe protection counts, but since the boat will not swing if set in a V, the problems are far less. It is also not our sole source of security, should it fail.
• I primarily use a secondary in very soft mud; low cutting hazard, but it must set deeply.
• Light. Must often be set from dingy or kayak and I have carry it around the boat.

After 20 years of sailing cruising boats I had an "ah-ha" moment, something that should have been obvious a decade ago. But I guess it takes time for the bits and pieces to come together. I was brainstorming through and anchoring puzzle with another sailor when the right way to use Dyneema in an anchor rode came to me.

Hybrid Rode, Trial I
a Dyneema leader, then chain, then rope

Anchor + 20' Dyneema + 10' chain + nylon to boat

The advantages are:

• Anchor sets deeper. The Dyneema is much thinner than chain, presents less setting resistance, and results in a stronger set with the same force. Limited Practical Sailor testing (February 2014) suggests going to wire or Dyneema increases holding about 25%.  Thus...
• A smaller anchor may be feasible. I'm not suggesting tiny, just eliminating ridiculous up-sizing of storm anchors.
• Better strength in wind shifts. A deeper anchor is more reliable.
• Less weight on shank. Fortress states that excessive chain weight on the shank can press the shank down into the mud, impairing setting (I've experienced this and discussed it with the factory). A pivoting fluke-specific problem, but Fortress is probably the most common secondary on the Chesapeake, since it is great in soft mud.
• Better catenary efficiency. The chain can't serve as catenary once it is underground, can it? Thus, from a catenary viewpoint, the first 10-20 feet are completely wasted in soft mud. Instead, the chain weight is place 20-30 feet from the anchor, where it can do some good. I save the weight of 20 feet of chain, which is a bunch when you are carrying the anchor in one hand and sloppy loops of chain in the other. Which brings us to...
• No need to carry the chain at the same time as the anchor. This will save a lot of scratched decks and some backs. Carry the anchor, and then make a second trip for the chain.
• Less weight to lift out of the locker. And instead of lifting with 2 hands and nothing for balance, you can lift with one and hold on with the other.
• Better safety on-deck. Instead of having both hands full, one hand is free for balance.
• Less weight when lowering. Just the anchor.
• Less weight when raising. Just the anchor.
• Less mud to clean up. Dyneema does not bring up mud.
• No additional fittings. Splice eyes in both ends (Brummel for chafe), luggage tag it to the last link of chain and use the existing shackle on the anchor (seems like a chafe point other wise). The rode can be spliced to the rode as well, if desired.

The Caveats? I don’t think this is for everyone or for every situation. It makes sense if:

• Secondary anchors deployed as a V (limits yawing, which causes causes chafe). 
• Anchor deployed by hand (easier to handle). 
• Soft bottoms with no large rocks (shells and small mobile rocks are OK).
• Chain still must be cleated during break-out.
• Still have chain to carry, although considerably less. 

It does not make sense if:

• Single anchor .
•  Deployed by windlass. Chain is better and the gypsy will not handle Dyneema. 
• Anchor is too heavy to deploy by hand. 
• Rocks or coral. All chain is best.
• Strong tide. A Fortress needs the weight of chain to get it down if there is a strong tide. May be applicable by lengthening chain section.

Finally, because the anchor sets more deeply, recovery is more difficult. We'll come back to this.

Cutting? When moored in a V the rode does not move side-to-side much, even less so when underground. It will drag forward, into oyster and rocks, as the anchor sets, but it will be  low-speed action and there will be no sawing action; I will keep an eye on this.Dyneema is also some tough stuff to cut; I've had to sharpen a lot of knives when splicing. Finally, a secondary rode is not all-or-nothing like the primary; if it cuts I am still anchored. If I were paranoid, I could go up a few sizes to something 2x as strong as the chain and still have a very light, flexible, thin rode. Overkill.

Threading webbing over the splice (the Dynema is inside) or even whole leader) would make it as cut resistant as steel cable. Because the webbing is thick, floats, and is not under load, even a sharp knife can't hurt it. If it rubs on a rock, it moves with the rock. I have tested this combination side-by-side with steel cable and found the cut resistance to be better in most scenarios. Even more important, when the webbing gets scruffy, it is $0.25/foot to replace, keeping underlying the Dyneema good as new.

Hybrid Rode, Trial II
a 20-foot Dyneema leader, no chain


If the chain only gets in the way, do we need it at all? We don't need the catenary weight with this anchor, the way I use it. Covered with a loose-fitting webbing chafe guard, the cut resistance is more than sufficient for soft bottoms.

How long does the leader need to be?

• Long enough to reach from the set anchor to a cleat to break it out. I really don't like chain grinding against the hull during recovery. That means 3(underground) + 4(freeboard) + 7 (water depth) + 2(cleating) + 4(allowance) =  20 feet. In fact, this is the thing that always limited my leader chain to 6-8 feet before; the chain need to end before the cleat, or start after the cleat, and 8-20 feet is the scrape-the-hull range.
• Long enough to extend above the ground and cover the high-chafe range where the rode will move on the bottom. Again, 20 feet seems sufficient

Longer would be OK.

Just try this with a chain rode, or even a heavy chain leader.

I still prefer chain with a good snubber for the main rode; it's durable, handles well with a windlass, and is easy to connect to other lines. But I no longer use any chain with my secondary. It serves no purpose in the Chesapeake, Dyneema is easier to work with, and the set is better. Nice.