Do your chainplates need replacing?
March 2022-UPDATED AUGUST 2024
IP Owners and Buyers:
Over the course of the past six 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. Like most sailboat builders of that time, 304 was regarded as strong enough for the job with decent corrosion resistant properties. We now know that 304 is good for about 20-25 years if taken care of properly. Note that any model sailboat older than the 2000 model year with 304 stainless chainplates should consider replacing them.
During the 1996 model year (that’s roughly September 1995 to August 1996) Island Packet made the transition 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. 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. Some 304L failures have been reported.
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. At that time, we were just beginning to see chainplate failure in boats that were 20 years old and older (304 stainless). 316 chainplates are thicker than 304 chainplates, as the alloy has less tensile strength than 304.
An annealing step was added as one further way to fight corrosion at the chainplate welds sometime during late 2000 or early 2001; this was thought, at the time, to extend chainplate life to 30 plus years. While no failures have been reported, we do have a report of a yard premptively replacing chainplates on a 2004 Island Packet 485 (20 yo), and one of the removed chainplates showed beginning signs of stress crack corrosion (SSC, the root cause of chainplate failure). I believe maintenace of a good seal at the caprail and proper rig tuning both play a role in chainplate longevity.
Keep in mind, however, that the failure rate of even the oldest chainplates is still very low (less than 2%). In a re-review of the records, that low number was based not on hulls with a failure, but only a chainplate with a failure. Every Island Packet has eight chainplates so one failure on a boat was considered a 1/8 of a failure. If one boat in ten had a single chainplate failure, IP's customer service team considered that as a less than 2% failure rate. That number is clearly low, as my good friend and Island Packet Ancestry subscriber Colin at Mack Yacht Services recently pointed out. Colin’s team has now performed over 250 chainplate replacements on Island Packets and only three jobs were possibly not necessary; all the rest had suffered a failure, or were about to.
While an immediate call for replacement may be unnecessary for newer, well-maintained, lightly sailed vessels, before heading off in an older model for deep blue water adventures, new chainplates are cheap safety insurance.
Hope this helps!
Bill Bolin, President