How to use swivel safely
Over the years we have seen enough of them to realize that far too many boaters underestimate the danger of using an under-sized swivel, a danger that increases when the swivel is subjected to side loads. Whenever a boat is anchored there is always a risk of imposing side loads on the anchor.
If an anchored boat swings far enough when the jaw of an eye-jaw swivel is attached directly to the anchor—backward—and the anchor, for whatever reason, is unable to remain in-line with the rode, then neither will the swivel. Once this point is reached, the direction of the load on the swivel changes from a straight-line load to a side load, which is something a swivel is not designed to carry.
The best way to avoid a broken swivel is to avoid using a swivel altogether. Unfortunately, this is not always practical. There are numerous situations in which a swivel, if not absolutely necessary, is at least helpful. These include when an anchored boat is subjected to two or more cycles of reversing currents or shifting wind; when the type of anchor being used has a tendency to spin when deployed or retrieved; or when an anchor needs to be rotated while being retrieved in order to seat properly in its roller.
Fortunately, while it’s impossible to entirely eliminate the possibility of having a swivel break, by following a few rules of thumb you can greatly reduce it.
Quality: Swivels can be manufactured to any number of worldwide accepted standards. However, many are built to lesser standards or no standards at all. With the former you have some assurance as to its strength and dimensions, with the latter, not so much. If you must use a swivel of questionable pedigree, consider oversizing it.
Strength: The swivel should have a working load limit (WLL) that equals or exceeds the maximum load to which the ground tackle will be subjected. When you’re calculating the load on your ground tackle, err on the side of caution. Remember the old Maine proverb: “Nothing too strong ever broke.”
Universal movement: To avoid lateral loads on a swivel, each end of the swivel must be able to move unimpeded, up and down and side to side. The use of eye-to-eye swivels prevents a swivel from inadvertently being installed backward. Plus, the fact that shackles are needed to attach theses kind of swivels provides yet more articulation at each end. Installing a length of chain, even just a few links, between an anchor and the swivel further decreases the odds of lateral loading.
If you find yourself in a situation where a lateral load on a swivel might cause it to fail, you can:
- Remove the swivel from the ground tackle.
- Switch to a bigger swivel strong enough to carry a lateral load.
- Deploy multiple anchors, such that each will protect the other(s) from carrying large side loads.
Other things to think about
Shackles: Anchor (bow) or chain (“D”) style shackles will break under lighter loads than they are rated for—up to half—when they are side-loaded. A shackle attached to an anchor is the component most likely to experience side loads, so you should make certain its WLL is greater than the ground tackle’s calculated maximum load.
Chain: High Test (alloy) chain, also known as Grade 43 or G4 chain, presents a challenge when attempting to mate shackles to it. The problem stems from the fact that the links are too small to accommodate the pins of a regular-strength (carbon) shackle whose WLL is equal to that of the chain’s WLL. High-strength (alloy) shackles with equal WLLs but smaller pins must be used with G4 chain, or the end link of the chain must be over-sized.