Upper chainplate replacement begins

Now it's the uppers chainplates' turn for replacement. These plates anchor the critical upper shrouds which run to the top of the mast. These are the most heavily loaded shrouds on the Triton (and most sailboats) and they need a bulletproof anchor.
To start, I lashed a wooden beam to the forward and aft lower chainplates, detached the uppers, and then lashed the uppers to the middle of the beams. The shrouds aren't tight but these beams will provide enough temporary support during the work.


I knocked the old chainplates out through the deck with a hammer. Compare the original 1"x 1/8" three-bolts chainplates with the new 1" x 1/4" 316L SS plates with 5 bolt holes. These new plates are also electropolished for corrosion resistance. I did all the engineering calculations for rigging loads and then for chainplate cross section and am confident that these are robustly sized. They have tensile & yield strengths comparable to the other parts of the rig. If I get ambitious I'll post my rigging loads spreadsheet here one day. If you want to do these yourself, get a copy of Henderson's rigging book for the rig loads and any solid mechanics textbook for the tensile, bearing strength, and shear strength calculations.

This is the starboard chainplate location. I'll fill the old holes with epoxy and layup a few layers of fiberglass over the beds for reinforcement. The new chainplates will extend much farher down the main bulkhead than did the old ones.

Chainplate project progess..

A couple of weekends ago I worked more on the chainplate project. The first photo shows the port aft lower complete. I replaced the solid forks and single toggle of the old Merriman turnbuckles with two Hayn toggled forks. This fit perfectly on both sides and is a simpler system.
The backstay chainplate is coming along. I managed to create a bed of thickened epoxy for the chainplate. I covered the chainplate with electrical tape and waxed it liberally to ensure good release from the epoxy.

Finally, I dug out some rotten core around the old vent cutout in the poop deck. The area of deteriorated core wasn't large - at inch beyond the cutout at most - and was easy to fill with thickened epoxy. Soon I'll redrill mounting holes, bed the hawsepipe, and through-bolt it to the poop deck.

That ugly bucket had been sitting on the poop deck for several weeks. The chain for the stern anchor was sitting in it. To get the chain below decks, I decided it was time to install the new hawsepipe. To do that, I had to remove the old vent from the deck...
 
 
 
 

Aft lowers finished.

	On June 10th I finally got some pictures of the new aft lower chainplates. The machine shop finished all the new chainplates in late May, and I took them to the electropolishing shop afterwards. They came out looking fantastic.
	The port side. Each chainplate is bolted in with 4 3/8" bolts spaces abot 1 5/8" apart. The chainplates themselves are 316L stainless, 1/4" thick and 1" wide.
	Starboard aft lower...
	Today I worked on the backstay knee, first sanding it and then expanding the deck slot to accommodate the new 1 3/4" by 1/4" chainplate. I test fit the chainplate but left bedding for later.