Over the course of the past four plus years administering Island Packet Ancestry, plus a 29 year history of working at the IP factory, I have distilled and tabulated what I feel is the definitive “treatise” on Island Packet chainplates. Some of this information has been previously released, but here are the highlights; please feel free to share:
- Chainplates prior to the 1996 model year were constructed of 304 grade stainless steel. These, to date, are the only ones that have failed (to the best of my knowledge).
- During the 1996 model year (that’s roughly September 1995 to August 1996) the transition was made to 304L, an alloy with better corrosion resistance than 304. This was a “running change” and there is no hull-number-specific documentation on what boat first received the 304L. I can only say that the 1996 model year was a “transition” year. No 304L chainplates have failed to the best of my knowledge. (Note: the 304L alloy was not as strong as 304 and the thickness of many of the chainplates had to increase to compensate. It may be possible to identify your chainplates by the thickness.)
- So, while it may be safe to say boats built late in the 1996 model year are likely to have 304L, I feel it is also safe to say that all 1997 model year boats and newer have 304L stainless chainplates (until 1999).
- GE Silpruf 2000 sealant (a superior bedding compound to 3M’s 5200 which had been used earlier) was also introduced along with the 304L.
- As the 1999 model year boats were being built (summer/fall 1998), Island Packet transitioned first to 316, and then 316L stainless, an even more corrosion resistant alloy. No failures have been reported with 316 or 316L to the best of my knowledge.
- An annealing step was added as one further way to fight corrosion at the chainplate welds sometime during late 2000 or early 2001; no failures have been reported on the new annealed 316L chainplates either.
Keep in mind, however, that the failure rate of even the oldest chainplates is still very low (less than 2%) so an immediate call for replacement may be unnecessary for well-maintained, lightly sailed vessels. But if you are headed off in an older model for blue water adventures, new chainplates are cheap insurance.
Hope this helps!
Bill Bolin, President
Island Packet Ancestry, Inc.