Chainplates

At Mack Yacht Services, we know chainplates! In our experience, they are the most overlooked piece of equipment on boats today. Chain plates are the base of your rigging system and need attention just like everything else on your boat. Barring hurricanes, chainplate failure is the number one reason spars are replaced in our area. The term stainless, says it all. They are stain less, not stain proof and are subject to stress and environmental impacts as well as fabrication and installation shortfalls. Shiny on the outside, rotten in the middle, is a pretty accurate summation of older stainless. As the top side is getting oxygen, occasional polish and fresh water rinse from time to time, it will look better and last longer than the parts you can’t see. Unfortunately, where it penetrates the deck or is glassed into the hull, it is degrading day by day. A good example which you can see first hand is in the video on this page. There are several materials that have been and continue to be used today, but the most common are 304 grade stainless, 316 grade stainless and Titanium.

In the 1970s and ’80s, 304 Stainless was the most common material as a replacement for Bronze; which was heavy, soft and had a habit of turning green. In its day, 304 was a great option although, history would prove otherwise. It’s strong, easy to work and polishes up nicely. The problem with 304 is its susceptibility to corrosion and oxygen deprivation. Generally, 304 grade stainless is good for about 20-25 years. Longer life spans are seen, upwards of 30-35 years, in freshwater boats or where the sailing season is shorter. When the chainplates are encapsulated in fiberglass much like Island Packet, Cheoy Lee, Irwin, CT, Formosa, and several others, we see cracks developing much sooner.

In the late 1990s, 316-grade stainless became the prevailing material for chain plates. It had a higher Chromium content and was less prone to rusting than 304. Due to it’s lower carbon content, it is not as strong per size and harder to fashion than it’s predecessor 304. Add that along with a higher price tag, we have seen many a boat builder use a less than adequate size for the long-term requirements of rigging. It was a common misconception that rigging failed due to the fact that the swages were work hardened when they squeezed. In the end, all stainless will fail due to age, by way of corrosion, stress and oxygen deprivation. Today, 316 and 316 L for low carbon is still considered the go-to materials for chainplates. In our opinion, they have a more than adequate lifespan for the task intended. Almost everything on your boat needs repair or replacement at one time or another and chain plates are no different. So, is there anything better?

There is a lot of Buzz about Titanium chainplates and we at MYS have done our fair share. It is a much lighter and stronger material if you get the correct alloy. Where Titanium is concerned, there are many to choose from. Some are softer, some harder, lighter and different colors as well. Little known fact, Titanium is flammable in the form of shavings and dust from machining. That said, it is believed the life cycle of titanium is in the hundreds of years, not decades like stainless. I’m sure time will tell as it always does, but it does appear the longest lasting option. Downsides include the fact that it’s much harder to machine and bend. It has a higher price tag than stainless and fewer fabricators are familiar with the material’s unique characteristics and requirements. In addition, it is more noble “Periodic table/ chemistry plug here” compared to most other alloys and will actually decay the stainless pin and toggle in your turnbuckle so other issues arise due to this upgrade. Composite bushings are the recommended solution for this issue and provide adequate isolation of the two materials.

A couple quick notes:

  • Use new 316 grade fasteners. Not the old ones you just took out!
  • Buy new cotter pins.
  • Tape traps salt and limits oxygen which promotes decay.
  • Polish and freshwater extend the life of your investment.
  • Re-bed your chain plates every 4-5 years.
  • No silicone! the vinegar smell indicates a corrosive property stainless doesn’t like.
  • We like Butyl, Uv 4000 and Sikaflex.
  • Stainless hates detergents like dishwashing and laundry soaps as well as bleach!

Mack Yacht Services, Inc.
we know chainplates

 

Mack Yacht Services, Inc.