Jordan Series Drogue chainplates

[gallatin1988]

I'm in the process of finalizing a bid to fabricate some 316L SS chainplates for a JSD. The owner of a sistership sent me a diagram of his chainplates. The measurements are Metric. His drawing specified a chainplate thickness of 10mm which is of right in between 3/8" and 1/2". I am under the impression that 7/16" is not available. The bid I received used 3/8" 316L SS. The boat in question is an Alajuela 38.

Is 3/8" sufficient or should I go with 1/2"?

Any input is appreciated.

Thanks
Sam

[shimari]

I don't think anyone can answer that without knowing the loads etc etc. Perhaps ask the previous owner who did the load calculations, and ask them.

You're going to the trouble of doing things right for a JSD with the chain plates. Maybe find out how the 10mm was calculated.

As an aside, Morgan's cloud has a number of excellent articles on JSD's. I think he even calculates some loads in one, but he also advises that a naval architect be consulted.

[glenn.225]

The area of the plate, the attachment style and the number/size of the bolts and their backing plate, and the hull material all need to be considered before that can be answered.

That said, there's a lot of rule of thumb and experience in a lot of these that are built.

[Jim Cate]

Not a big difference in the thickness (roughly 5%), and likely not an issue for such designs usually have large safety factors built in. However if you are concerned you could easily beef up the cross section by making the plate a bit wider or by going to a duplex stainless (2205) which is much stronger than 316.

Jim