replacing U bolt chain plates

[BlueCanoe]

My standing rigging needs to be replaced being between 20 and 36 years old. I don't like the U bolt chain plates. With the west marine bankruptcy I scored a bunch of rigging parts at about 20% of the original price from my local west marine including enough 1/2" toggles and turnbuckles to use at every rigging position. I am considering making a custom chain plate for these in one of the designs shown below. These initial designs are to illustrate the concept and I would do some further refinements to make them easier to produce. Most likely I would use either 316 SS or titanium (I have a big block of titanium that I obtained from a surplus store). I would also replace the inner aluminum chainplate blocks probably with 303 SS.

Before I do any of these I would make sure that the component I would me making is at least as strong as the rigging using finite element analysys in cad.

The reason I am bringing this to the forum is I am wonder if maybe I am re inventing the wheel.

My cost to make them is maybe an hour each, I am still justifying the CNC mill that I bought off craigslist in 2009.

 

[Prairie Schooner]

My standing rigging needs to be replaced being between 20 and 36 years old. I don't like the U bolt chain plates. With the west marine bankruptcy I scored a bunch of rigging parts at about 20% of the original price from my local west marine including enough 1/2" toggles and turnbuckles to use at every rigging position. I am considering making a custom chain plate for these in one of the designs shown below. These initial designs are to illustrate the concept and I would do some further refinements to make them easier to produce. Most likely I would use either 316 SS or titanium (I have a big block of titanium that I obtained from a surplus store). I would also replace the inner aluminum chainplate blocks probably with 303 SS.

Before I do any of these I would make sure that the component I would me making is at least as strong as the rigging using finite element analysys in cad.

The reason I am bringing this to the forum is I am wonder if maybe I am re inventing the wheel.

My cost to make them is maybe an hour each, I am still justifying the CNC mill that I bought off craigslist in 2009.



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Well, yes, you're reinventing the wheel. But it might end up being a better wheel. As I understand the chainplate system, the force is lead to the structure below the deck. These might lock the deck in place more, perhaps adding more stress to the deck than intended. When you do the FEA, will you try to recreate the entire assembly in CAD, including decking?

Is there galvanic compatibility between SS and titanium?

But the CNC mill, heck yeah. That was a good move.

 

[sdwnav]

I’d like to see results of fea, should be an interesting comparison if you model both original and the new design. The backing plates below deck secured by the rod are loaded in a similar way to your new design. I suspect that getting a big enough fillet radius at the intersection between the tang and base plate is key. I would also check out of plane loading; rigging isn’t perfect. Deflections are also probably important. The fiberglass deck is going to be along for the ride and won’t absorb any meaningful load; if deflections are too high you will crack fiberglass or have leaking.