ChainPlates: Inspecting Welds, Checking for Leaks and Retorquing

chainplatestarOn sailboats a chainplate system must be designed and fabricated to connect the mast shrouds to the hull or main hull bulkhead. This major connection is usually hidden behind the cabin finery and is out of sight but should not be forgotten. The photographs are of the system on a CS 33 taken from inside after the bolts (12 per side) were tightened and inspections complete.

The disassembly required removing the stereo speakers, lowering the headliner and removing the fiberglass boot that covers the cantilevered chainplate weldment attached to the bulkhead. The area in general looked OK but some water (condensation or leak) over the years had stained the veneer trim at the very bottom and inside the boot.

The starboard photo (starboard chainplate) has the headliner in place, the speaker wire is shown, and the veneer has some minor water staining. The vertical leg of the chainplate is in contact with the bulkhead (veneer cut out) and a friction connection of 6, 1/2 dia. and 2, 3/8 dia. bolts connects the chainplate and bulkhead. The vertical 1/2 thick by 3 inch wide stainless steel plate protrudes through the deck and the two mast shrouds are attached to this vertical plate just above deck level. The 4, 1/4 dia. bolts clamp a 1/8 inch thick stainless steel plate bedded to the deck surface to seal and make watertight the deck and protruding vertical plate connection.This plate and 4 bolts are to seal and do not add to the strength of the connection in anyway.

All fasteners, 12 per side were found to be loose. The starboard side bolt heads (6 by 1/2 dia. and 2 by 3/8 dia.) are behind the wall in the head and are not accessible. Fortunately the bolts ends were long enough to grip with visegrips to prevent bolt turning and the nuts were torqued up using open-end wrenches. The 4, 1/4 dia.bolts clamping the seal plate are bedded is sealing compound and did not turn when the nuts were tightened. These four do not have to be tight / tight as the sealing compound is still mobile and will start to ooze out.

Port chainplate

Port chainplate

The port side is much easier to deal with as the cedar lining of the hanging locker is cut out and the bolt heads are exposed. Using a normal socket on the bolt head and a deep wall socket on the nut, the larger bolts are tightened, and then the remaining 4 nuts of the seal plate are snugged up. After a careful check of all stainless steel welds the reassembly is completed. This is one of those jobs that brings satisfaction in the knowledge that the major chainplate connections have been closely inspected, bolts tightened and the strength / integrity restored: good for a few more years.

by Ed Sulis

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