While removing my chainplates, I noticed. some pitting and surface rust. They didn't really look TOO bad to me and still felt pretty solid. Then, I was down to two. The bow and the aft chainplate on the port side. The bow took a little time as it was flush with the surface and didn't want to lift up at first. The last chainplate on the side was another story. Each plate for the shrouds have a little block of wood for spacer. The bolts going through them stayed solid in place until I banged them out, but prying the plates from the boat was difficult because the bolts didn't budge. When I went to pull the last chainplate, it gave a little.
I thought it was odd since all the others were pretty sturdy but now I got one with a soft spot. Turns out, there was a hidden crack in it. It was hard to see at first but once I removed the spacer block, I pulled on the plate to exaggerate the bend to show the crack easier. It went right to the bottom of a bolt hole. It ended up leaving one bolt holding the half-shroud that was attached to it.
Can you see the crack?
How about now?
After I pulled a little more, the crack showed up more.
Here, you can see that with were the crack was at the bolt hole, there was only one more bolt before it went to the shroud. </IMG>
I went ahead and broke it apart altogether to show what was still holding it together. Just the little bit of metal on the left of this picture was all that held it. </IMG>
The main reason I wanted to share this is to show people why they should check them. I'm sure there's plenty around this forum or other sites online showing damaged chainplates. I wanted to share this to also inform those who are looking for older boats to consider this when shopping around. My chainplates looked ok except for some surface pits, but from seeing other owners of the same type of boat come up with cracks in their chainplates, I decided to do them for preventative measures. Turns out, there was a need for it.
My boat was built in 1981 and these straps of metal are original. If anyone has a doubt about their chainplates or they're just as old as mine are, it might be a good idea to swap them out to ensure that the whole rig doesn't come crashing down.
Previous owner of our vessel experienced a catastrophic mast failure due to crevices corrosion of one chain plate while at sea in calm conditions..However, found through metallurgical examination the SS used was not to boat spec. The Boat manufacturer, after threat of legal action, replaced all standing rigging and mast...
Good catch on the second crack. I noticed it after I saw the enlarged photos. Smaller, but still there.
I've heard the same about using round holes instead of square ones. Another owner did square with rounded corners that looked pretty good.
I don't know what grade of metal these old chainplates are but I'm going to get new ones made with 316 stainless.
I've also been looking into replacing the bolts since they have some surface rust too. Looking at 316SS bolts, they are expensive and unfortunately, they look like they come in incremental packs, like only packs of 10, so if I need 12 bolts I'd have to get a couple packs (just an example) so I'm looking around at what else I can find. I think 18-8 which is equivalent to 304 stainless may lower costs but might be easier to find too.
i had 2 cracked chainplates when i bought this boat-- and i replaced em for under 200 usd total. fabrication is the key. and i used 304, not 316 stainless, created a tad burlier than the originals that came with this particular boat
recomending 304 on here is akin to saying olive oil is the best engine oil you will get the wrath
If you go 316 go for the L variation.
know this however most stainless sailing hardware is indeed mostly made from 304, and that is because its stronger and cheaper...so more of a money maker, yes it surface rusts easier but again they are intended to be replaced regularly.
ask any stainless davit owner and ask them how brittle their 316 davits are, especially after welding...
look around for tangs, toggles, extenders etc and the overwhelming majority is 304.
Ill tell you what I did or you can look at my rebuild thread and check them out yourself
I went massive from 1/4 inch to 3/8ths, I extended my stbd plates by 5 hole legnths so it tied to the liner, I also made them wider my ports where also extended
polished to a mirror finish
I used plain old stainless bolts which I forget the grade but more than likely is 304 too
the way I see it you replace these things regularly, a bolt is a bolt not some forever piece of equipment