Posted by Darrell Nicholson with Jonathan Neeves at 07:36AM - Comments: (11)
What length, diameter, and type of snubber do you use? What do you need?
The main purpose of a snubber is to reduce loads on the the anchor and boat by adding elasticity to the rode. Usually made of three-strand nylon, the snubber joins a strong point on the boat—usually a cleat or a bit—to a link in the anchor chain. In between these two points the chain is slacked to allow the snubber to stretch. If a boat uses a mostly nylon rode, a snubber can still be used to reduce chafe at the bow roller, hawsehole, or chock.
You can use a variety of hitches for attaching the snubber to chain, but a hook makes it easy to attach and detach. As wind and waves lift the anchored boat, the snubber stretches to reduce, if not eliminate, any shock loads that might jerk the anchor free of its holding or rip a cleat from the deck. In theory, the snubber sounds simple. In practice, there’s a lot more than meets the eye.
Over the years, Practical Sailor has been collecting information on boats that have dragged anchor and wound up lost or in peril. The results of many of our anchoring studies can be found in our ebook on anchoring and mooring, as well as in our online archives. To anyone who has spent a night pitching in an exposed anchorage, it would be no surprise to learn that in many dragging incidents the snubber parted, or was stretched to its limit—allowing the chain and boat to absorb some teeth-rattling shock loads before something finally gave.
Based on the information we’ve gathered, PS testers have devised a series of tests to explore the topic of snubbers in greater depth. Some of their findings run contrary to popular assumptions regarding snubbers. In the March 2016 issue of Practical Sailor we look at two of these assumptions.
The first assumption is that an eight to twelve-foot long snubber is more than enough to absorb the loads when a squall rolls through an exposed anchorage. The second is that using a snubber hook has no effect on the strength of the chain. It turns out that both of these assumptions can lead to trouble.
The topic is one that interests me personally. One of the most harrowing nights I ever spent aboard my 32-foot ketch Tosca was when she diving into steep chop among a small fleet of squid boats in an exposed anchorage near Thailand. Sustained winds blew well over 25 knots, gusts blew much higher. One after the other my snubbers snapped.
On two separate occasions, squid boats, straining under their own anchors, bore down. Being able to adjust the anchor rode, yet still absorb the shock loads in the shallow (less than 20 feet) anchorage became a round-the-clock job. I finally settled on a length of 3/4-inch diameter three-strand nylon used for a kedge and deployed about thirty feet (Tosca weighed in at 12 tons). The engine ran through the night.
How long should a snubber be? What material? And what about diameter?
The upcoming issue will answer these questions in greater detail, and I think even long-time subscribers will be surprised what we find. For the moment, I’m hoping that you can tell us about the snubber arrangement you use for your own boat, and how it has performed. (You can leave your comments below, or send your comments to me at email@example.com) Here’s an example of the snubber used by one of our contributors Jonathan Neeves, who carries out many of our anchor and rode tests. Neeves uses this setup on a seven-ton, 38-foot catamaran that he sails in Australia.
After some rough calculation of loads, Neeves concluded that a snubber of about 30 feet long was the minimum he would need to absorb predicted loads at anchor. While it is hard to envision the idea of a 30-foot snubber extending forward from the bow, it need not extend 30-feet forward of the bow, as he describes below.
On most catamarans, the snubber is a bridle that extends outward from the bow cross beams and attaches to the anchor. Our bridle is formed using two 50-foot long lenghts of lightly used 11 millimeter climbing rope (selected for its abrasion resistance and elasticity) and attached to horn cleats on the stern. (The equivalent would be 12-millimeter nylon three-strand braid or eight-strand plait, either of which would serve well.)
We run the snubber up the side decks, through the stanchion bases. The legs of each bridle then pass through swivel blocks shackled to pad eyes that we have installed at each bow. Although each snubber is fifty feet long, we only use about 30 feet; the rest is in reserve.
The individual snubber legs are joined at a shackle with scaffold or halyard knots (climbing rope is impossible to splice). The only tricky part of the installation is reinforcing the area where the pad eyes are located. An alternative to the pad eyes is to fit the blocks to the forward horn cleats. (We used to do this, securing the blocks with a length of nylon webbing so that they hung outboard.)
The same system can easily be adopted for a monohull that uses a single snubber. The main variable is how to direct the snubber from the side deck to the chain hook. This will depend on the individual yacht, but fairleads would be an attractive option, probably requiring some form of chafe protection.
If you have a beamy or heavy monohull, a bridle can be more effective at reduce yawing, and yawing can exacerbate snatch loads. The amount of time, you invest in developing a sensible system will depend on how much time you spend at anchor. We can be at anchor for three to five months each year so we wanted something permanent.
Look for a complete report on snubbers and chain hooks in the March 2016 issue of Practical Sailor.