Working on the Chain Gang

Thoughts on anchor rode chain length and Danforths

Article by Jonathan Lewis

There are so many opinions on anchors, types of rode and chain length and it seems that these discussions predate Moses’ papyrus basket in the bulrushes on the banks of the Nile. How could that infant had been better tethered? Should the chain have been the length of his craft? There are so many factors and variables that go into determining a proper setup, and so many techniques employed in securing our vessels to the bottom. I’m certainly not going to enter into the fray on the best option, but I do want to suggest a remedy for a particular type of anchor that is regularly maligned and yet ubiquitous around the globe.

Danforth anchor

A “Danforth” style anchor does have its drawbacks, but many of its faults are the result of operator error and not the hook itself. There are thousands of stories, tests and videos berating the setting capabilities of fluke, sand, plate, Danforth and Fortress anchors. Those five are all essentially the same type of anchor with similar characteristics, although variations in materials and design may make a significant difference in their respective holding power and setting abilities. The crown, stock, flukes and shank that make up its various components can be of different proportions and sizes that also affect performance.

However, the underlying design characteristic that is present in this style mandates a proper chain size and length (therefore weight) for it to function properly. An all-chain rode doesn’t work. The crown controls the angle to the seabed and the angle of the shank but this “regulator” is overridden if the chain attached to the shank is too long, which negates the mechanical aspect that forces the flukes into sand or mud, the preferred botom for this style of anchor. A long length of chain causes the anchor to drag horizontally along the bottom until a fluke point digs in by happenstance. A short length of chain (follow the manufacturer’s recommendations), which is never as long as a boat length, BTW, allows the shank to be angled while setting and allows the flukes to penetrate the bottom at the prescribed degrees dictated by the crown, or close to it.

I learned this lesson the hard way. While at a slip in Florida, before jumping off for the Bahamas my first time, the captain on the adjacent boat remarked about the 5-foot length of chain on my Hi-Tensile Danforth. He suggested I at least quadruple the length to protect against abrasion from unseen neighboring coral heads. He was a salty sort with a beautiful Sparkman & Stephens yawl, so I followed his advice and replaced my short BBB segment with 25 feet of galvanized proof coil. While it behaved reasonably well in the soft sand, the harder substrate areas were a problem. It wasn’t until we were returning to New England and making our way up the East Coast, that I noticed setting the hook in places where I’d anchored before was noticeably more challenging. My mate and I discussed the predicament. What had changed? An epiphany…the chain length. After returning to our orignal setup the setting ability of the Danforth improved immensely.  

There are situations where a short length of chain may be detrimental and result in chafe caused by rocks, coral or debris, but you’re likely to benefit more from a properly set anchor in the long run than the additional chafe protection afforded by too long a chain.

This being said, I prefer to use a Danforth or Fortress as a lunch hook, a stern anchor, a beach attachment, a kedging hook, or a second bow anchor to inhibit swing. I’m not as comfortable or confident using it as a primary anchor because of its resetting characteristics. And with tide changes and wind direction changes I don’t sleep as well on that style of anchor.

An anchor such as a Rocna, Mantus, CQR or plow anchor, is considerably less concerned about rode weight and the catenary curve produced by a lengthy chain is absolutely beneficial to its function. On the other hand, a Herreshoff or fisherman style anchor performs well with no chain at all.

Of course proper scope is essential, remembering to include the distance from the surface to your deck and add it to the water depth. At that point, your 5 to 1, 7 to 1 or other ratios are calculated by existing and predicted conditions. Other boats moored or anchored nearby must be considered as well. If they were there first, you must make suitable accommodations.

But I digress. After determining the properly sized anchor for your craft, please take note of the manufacturer’s recommended “support hardware,” which includes the chain type, size and length for your chosen anchor, the shackles, and the correct line. Fortress suggests 6 feet of chain if regularly anchoring in water depths of 25-feet or less, and three strand nylon. Danforth recommends 4 to 6 feet depending on your anchor choice, irrespective of depths. Remember that oversized line also inhibits stretch and the rode’s ability to compensate puts increased load on your hook. You’re better off using a chafe guard at your chock than depending on greater diameter line for security.

I hope my thoughts benefit some of you with regard to the age old question of anchoring and its intricacies. And to close the circle, I beseech thee, don’t do as David did when being informed of the deaths of Saul and Jonathan and “kill the messenger.” •SCA•