Chain Plate Questions - September 2015

Chain Plates of 30+ year old Taiwanese sailboats might be past their useful life and could be replaced. The risk of chain plate fracture and rig failure is not something to be taken lightly. The current figure of merit on chain plate life is 20 years to be safe and 40 years is really starting to push it. When you look at the image of the STBD side main mast chain plates, peeping through the gunwale teak cap and the securing bolts below - everything looks fine.

.

Chain Plate Fracture ~ May 2106

We do not make the chain plate replacement decision lightly, but it was brought into clear focus almost immediately. While tensioning the new rigging for the Mizzen a forward STBD chain plate fractured and was pulled out of its pocket. The failure point was not in the gunwale pocket but at the top most fastening bolt. Chain plate examination on this Vagabond is difficult as the plates are behind finish teak cabinetry built onto " ply hull sheathing. Exposing them takes great care and when visible we found they had lateral 1" wide steel stringers welded to them and were fiberglass encased. The glass was removed on 3 chain pates for inspection including the sheared unit. Polishing the exposed surfaces made visible 4 lateral cracks at the top bolt its adjacent chain plate and no apparent defect on the third. We exposed another 4 chain plates and found no evidence of cracks or corrosion pitting. The boat has 12 chain plates total, this is what we knew:

The failure rate is at least 8%, but this is not the whole picture. We have no way to examine for cracks or corrosion in the section of the chain plate between its top bolt and the cap of the gunwale. This is 4"+/- in length on the Vagabond 42. If the glass encapsulation / sealing excludes oxygen flows but a wet / damp chain plate surface exists, the stainless steel will corrode in the gunwale pocket. To prevent this happening a chain plate trim plate is screwed to the gunwale cap that allow the chain plate pocket to be filled with sealant and made water tight.

Chain Plate Replacement ~ Thinking

.

This picture will make things clearer as it shows welded laterals attached to the chain plate right beneath the gunwale fiberglass overlap and teak cap. Vagabond 42 Chain Plates replacement is not easy so a lot of thought and conversation has been had with other Vagabond owners.

The Chain Plate document will open as a PDF as it is quite long - and even now not finished. I would not have spent so much time in this area were not the consequences of future failure - $10,000 to $15,000, so high.