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My bobstay chainplate needs some work. When I hauled out, I noticed water dripping from the chainplate for a few weeks. When I finally took the mast and rigging down almost a year later, even more water started coming out of it. It definitely needs to be sealed up so water doesn't get in there, but after inspecting it I am now worried about serious crevice corrosion and am considering replacing it. However, I have no idea how to get it out. Most things on the boat were pretty self-explanitory to disassemble, but this one has my head scratching. The fittings on the interior are glassed in, and I am hesitant to start grinding it away until I get some advice on how to proceed. Here are pictures of the exterior and interior:
Notice the crack/gap around the edges, that is where the water came out of
The interior attachment is somewhere under all of that glass:
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The question is whether or not the chainplate is compromised… Why not first test the chainplate
before starting another area of boat deconstruction.
Try rigging some means of applying directional pressure to the chainplate to simulate actual tension.
(Maybe with a come-along.) Carefully tape or paint the exposed portion of the chainplate beforehand to discern any
movement under load, and also observing any retraction once the load is released. If the results
of the test indicate acceptable tolerance, then clean as deep as you can probe around the chainplate,
use a dryer, and the apply acetone to dry the cavity. Then inject successive layers of epoxy
in the deeper sections and MarineTex in areas toward surface. Just make sure of the proper angle
and alignment of the chainplate before rebedding.
(PS- From the interior photo that you posted, the water stains would indicate that the primary
source of the water intrusion is above the chainplate [upper stem, deck, cap rail,?] ).
A series of interior weep holes first at the top the chainplate, and then below, may assist in mapping
out water retention and source, and could be used to later inject epoxy through.
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Thats a scary one... Your never going to really know unless you take it out and inspect it. Crevice corrosion is evil stuff, and from the look of it that is a great place to get annoxic water that will cause crevise corrosion. Personally if I thought there could be serious crevice corrosion I would pull it and inspect and repair or replace. My ideal replacement would be a marine grade bronze fitting but stainless is a proven solution also. When putting it back in I would NOT glass it back in like that. Instead I would reinforce the inside where you cut out the fiberglass to pull that unit and use lots of 5200 to bond the replacement to the hull. I know why they did it the way they did as you are pretty much gauranteed that you wont get a leak into the hull while sailing. If replacing the unit I would go to a slightly bigger backing plate so that I had more surface area for the 5200 to bond to since it wont be fiberglassed back into place.
🙂 after having said all that though.. this looks like a pretty good solution just the way they did it given that it has lasted 30+ years.
scott
wow.. I said a lot without commiting to a single thing... I'm feel like im ready to run for office now. 🙂
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For those interested, this is what the bobstay chainplate looks like when removed:
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it looks pretty good in the low resolution pictures. Do you see any cracks in it anywhere or pitting?
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Scott Carle said:
it looks pretty good in the low resolution pictures. Do you see any cracks in it anywhere or pitting?
Hard to tell, it was covered in rust. I'm going to have a replacement made regardless. I just had all of my chainplates made, might as well go the distance with this one. This piece is the worst looking one of all the rigging parts, and I'm going for a full standing rigging replacement.
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Sounds Wise.. Wish I could afford to do that. Valkyr's rigging actually mostly looks in good shape.
I heard of someone, not sure where, that was replacing a bobstay fitting that sits under water all the time and I thought they had one made of titanium. They said it was expensive but not as expensive as you would think 🙂 lol. but didn't tell me how much that was. It's about as non corrosive as you can get I guess. Also strong. Monel might be another great choice. For something that lives glassed in like that with exposure on the other side to salt water it would be good to go away from stainless that is prone to anaerobic crevice corrosion.
Flip side is that stainless lasted 30 years or so there so should last for another 30.. if you make sure that it is a high quality 316 stainless used again. In the last few years I have all kinds of issues with stainless parts I have purchased, they have been made of much cheaper and lower quality stainless.
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