The new chain-plate material arrived today. The material is a special form of stainless steel called Duplex 2205. It has superior anti-corrosive qualities over the more common 316 stainless steel widely used in the marine industry.
Duplex 2205 material for new chain-plates
A certification letter came with the material attesting to the origin and quality of the material. When friend, Tim gets a drill press on site, we will begin the arduous process of drilling holes and grinding edges. For some inexplicable reason, I mistakenly ordered four long pieces where I only need two for the major shrouds. Makes me think I am in for another surprise and will be happy to have the spares in future. I ordered all new 316 stainless steel fasteners to secure the chain-plates. Realizing the shear strength of stainless steel is about half its tensile strength (lengthwise) I did a quick calculation and determined four 3/8″ bolts do not provide enough shear strength for the size rigging and loads on the major shrouds, but is OK for the minors going to the middle of the mast. So I decided to increase the size and number of bolts securing the majors to five 1/2″ bolts and one 3/8″ bolt. I am retaining one 3/8″ bolt to simplify the bonding wire connection. Cost of the new 316 SS bolts, washers, lock washers, and nuts came to about $72 including shipping. This includes a few extra to keep as spare parts.
Old 3/8″ Chain-plate Bolt ready to break!
The picture at right is one of the old 3/8″ bolts securing the chain-plates. You can clearly see the wear spot where the chain-plate was trying to shear the bolt. It is good to correct this now before losing the mast at sea.
All materials and supplies are on hand now to complete the chain-plate replacement. I still need to make the mold for raised landings at deck exits. The fibreglass landings raise the deck where the chain-plates exit and a metal trim covers the caulking. Raising the cover plate off the deck helps prevent water intrusion onto the knees and the securing bolts, preventing or reducing hidden corrosion. It is an extra step to insure longevity and trouble free maintenance of the new chain-plates. The landings must be bonded to the deck prior to installation of the new chain-plates. I will be sure to include photos of that process.