we spent the last couple of days talking to a rigger in Port Townsend.
What I gleaned from his knowledge on chain plates:
The cracks start on the inside of the metal and work their way to the outside. By the time pits and cracks show up on the outside where they can be seen, the interior
matrix of the plate or bolt or turnbuckle is really in bad shape.
Lack of oxygen coupled with water
exposure make stainless steel
corrode; hence, where the plates penetrate the deck
, the above mentioned cracks and pits will be found but the exposed areas will be bright and beautiful. The moral is that proper inspection
means removing chain plates and bolts from their covered locations and exposing them to visual inspection
means it stains less but it still stains.
The cyclic loading on the plates could eventually wear them out, but the corrosion
always get the plates first.
Same issues that apply to the plates apply to the bolts that connect the plates to the hulls.
If a plate is not exactly loaded on its centerline, one side gets more stress than the other and that can cause it to over stress and crack. This is of particular importance with the less Hercie (as in Herculean) plates at the top of the shrouds where the shrouds attach to the mast
, not just to the beefy chain plates.
He showed me a few boxes of chain plates, bolts, turnbuckles, etc that are severely damaged in interesting and attention grabbing ways. He saves these items to show clients and educate them.
Best to err on the side of caution. Talk about a failure that has little running time as we call it in engineering - you want to have time to run away! when the item fails. Failing rigging
is spectacular I understand.