Swivels are used to attach an anchor to the chain with the purpose of preventing chain twisting as the boat moves around in the anchorage. Swivels also help the anchor come up in the correct orientation into the bow roller on retrieval.
- In the practical sense swivels are often unnecessary unless you intend to anchor for a long time in one spot, further twist usually gets undone as the chain is retrieved with the windlass. If anchored in one spot for an extended period or if designing a mooring system swivels do solve a problem.
- Swivels are generally considered to be the weakest link between your anchor and the boat. One issue is swivels often fit directly into the shank and if so can be side loaded (when the anchor is stuck in rocks for example) and fail at much lower loads than the SWL they are rated for. To solve this attach a shackle or a shackle with some chain to the anchor first and then the swivel this will prevent the above mentioned problem with side loading. Further it is often hard to size a swivel to match the strength of the HI TEST chain, though some well-designed products are available on the market they are often really expensive.
- It is generally recommended to use a short pieces of chain attached to the anchor via a shackle and then attach the swivel bridging chain to chain. This will prevent both swivel jamming as seen above and the side loading issue.
- There many brands available on the market and one should pay attention to the SWL (safe working load) rating on the swivel as compared to the chain. Further if using a stainless steel swivel on the galvanized chain, try to isolate the two materials with insulating tape to reduce the galvanic interaction between the two dissimilar metals.