Mast Stability while replacing chainplates

[GrahamHO]

Originally Posted by billdre

GrahamHO 5 years ago I rebedded my chainplates and there was some surface rust and a few pits on the plates where they pass through the deck. A month ago I noticed that water was once again seeping around the plates into the cabin, so I know the plates are getting wet where they shouldn't. So it's time. After 37 years I think it's reasonable maintenance.

That seems reasonable. They should last you another 37 years after you redo them. As you probably know, SS needs air contact to help prevent corrosion.
Moisture and lack of air makes for corrosion in SS which can be crevice corrosion.

If you can't find a new spares, a SS workshop should be able to copy your old ones if you can't or don't have time to do it yourself. I guess they are not identical, rather mirror images, port and starboard.

For my replacements, I drew full size sections on thin card and cut out the pieces of stainless with a hack saw. I bought 316 flat bar; from memory mainly 75 mm X 4 mm so it mainly needed cutting to length and drilling. I used a drill press in a friends factory firstly drilling small pilot holes for accuracy and later the final diameter. I clamped the segments together with bits of wood and screws in the holes to get the correct angles. I took them to a welder who tacked the bits together. Then I tried them for fit in the boat before final welding. After that, to a metal polisher. Hopefully my design eliminates the leaks so the inevitable lack of air through the deck shouldn't lead to corrosion. 316 grade SS is the best reasonably available. Cheaper 304 grade is more easily worked but more prone to corrosion and should be avoided. Possibly your old ones are 304 grade.

When I earlier replaced my keel I had the new keel bolts made from 2205 grade SS round bar which is recommended as suitable for use in high temperature cooling systems in nuclear power stations.

My chainplates should last me at least another 30 years until I'm 107 when I'll probably want a smaller boat without sails. Maybe?

[UNCIVILIZED]

A cost saving tip. When you go to have them made, find a machine shop that's not associated with Marine or Boat work. They'll be a Lot cheaper. And, of course, do a little research to ensure that you're dealing with a quality shop.