April 2014 Issue
Table of Contents
Where Credit Is Due:
Reader Workbench Update
Mailport: April 2014
Chain, Chain, More Chain
This is in regard to the February 2014 article, “Anchor Rode Report.” I have more than 100,000 miles of offshore cruising under sail and am the author of “Outfitting the Offshore Cruising Sailboat” (PS, July 2012). Here are some of my observations from a dozen hurricane anchor incidents.
When it comes to anchor chain, not much is needed except when anchoring in a good blow, poor bottom, or tropical storm conditions. Fishing boats (60 to 80 feet LOA) routinely anchor quite comfortably in hurricane conditions in the shallow Bering Sea with 1,000 feet or more of half-inch chain and 100- to 200-pound anchors. It’s the weight of the chain, not the weight of the anchor that guarantees survival. Similarly, one can get by with a wide assortment of anchors save in a tropical blow. We have bent a CQR in storm conditions and severely damaged a 55-pound take-apart popular alloy anchor. But the venerable ones, our Bruces, have never been damaged during hurricanes. We’ve consistently used 110- and 60-pound Bruces with 400 and 200 feet of 3/8-inch high-test chain during tropical storms without failure.
It’s not often realized that chain stretches under load and can break under shock loads well below its designed rating. For example, when anchoring a 45-foot, 22,000-pound centerboard ketch in shallow water in Onset Harbor, Cape Cod, during Hurricane Bob, some 200 feet of new 3/8-inch, U.S. made, G-4 alloy chain rated at 16,000 pounds stretched 10 percent, or 20 feet. We later calculated the loads at about 8,000 pounds. We were well protected from surf, and the 45-pound CQR buried itself 30 feet into the soft bottom. We replaced the chain.
Similarly, its often not appreciated that one will need one size larger shackles even when using best-grade stainless to match the alloy chain’s rating. And, that the large cast or wrought-iron large shackles typically found on anchors are rated well below the chain’s rating. However, one can with some diligence obtain “rated load shackles” from industrial supply houses of sufficient load. These rated shackles are typically not galvanized so they need to be kept painted. When buying shackles, the “name” matters greatly. No-name shackles have cost many a boat dearly in the Caribbean and elsewhere.
The real argument for chain versus wire or line is that chain is virtually indestructible if properly sized and made by a known manufacturer and that by its weight, it forms a catenary that greatly eases the vertical motion both on the boat and the buried anchor. At 1.5 pounds per foot, the common 3/8-inch, high-test chain weighs about 300 pounds for 200 feet. However, there’s no need to carry all the chain forward. A neat trick is to keep 50 to 75 feet in the bow and then lead the remainder well aft. Even when we carry 400 and 200 feet of chain for our primary and secondary anchors, almost all the chain is carried well aft. After all, most times we do quite well with one anchor and just 100 feet.
Three further thoughts. In a real blow, two anchors set out in a V are required to deal with “sailing” at the anchor. Second, its good practice to always set the anchor at full throttle in reverse to make sure it’s holding solid. For some reason, storms almost always come at night. Lastly, experienced mariners routinely put the engine in gear to take the load off the chain during a real big blow. If there’s only one anchor and it lets go when the wind is howling, the engine won’t help much—all the more reason for having two anchors at the bow ready to go. Those anchors should be big enough with enough chain to hold in a tropical storm. Of course, most of us will never have to anchor in a tropical storm, but it is reassuring that once properly set, there’s always a good night’s sleep awaiting.
Peter I. Berman