"Encapsulated" chainplates

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"Encapsulated" chainplates

Postby Duncan » Sun Jan 28, 2007 8:35 am

I linked in this photo from the thread about Rachel's Alberg 30. I have roughly the same sort of forward lower chainplate installation on my Eastwind 25 (and I guess many boats do).

Image

Two questions:

1) What does it look like inside - I doubt there are any mechanical fasteners, are these simply glassed to the hull?

2) Should I be grinding the glass off to take a look this spring? The boat is forty years old, and always been used in salt water. Am I right in thinking there are risks of crevice corrosion and metal fatigue?
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Postby David VanDenburgh » Sun Jan 28, 2007 10:14 am

Duncan,

I know that the chainplate knees on the Alberg 30 are plywood encapsulated in glass and bonded to the hull, the underside of the deck, and shelves in the v-berth, hanging locker and head. The chainplates - stainless straps - are through-bolted to the knees.

As to your question about whether or not it's necessary to dig into yours, I'll let those with more experience answer that.

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Postby Rachel » Sun Jan 28, 2007 10:24 am

It does look like the chainplate itself is inside the knee in that photo, but it's actually bolted to the outside of the knee. Here's another photo of the same chainplate that I didn't post, because it's slightly blurry, that shows it more clearly:

Image

That being said, they look kind of small to me - and I have heard of A-30 owners having trouble with the forward lower chainplates, so I will no doubt look into it more before I do any boisterous sailing.

If your chainplates are stainless steel, and are encapsulated, I'd probably dig in and have a look-see, and possible move them "outside." But then I'm not a fan of stainless (the world should be bronze!), so I tend to be suspicious of it. As I understand it, stainless requires air (or flowing water that contains some oxygen if underwater) to form the protective coating that makes it stainless, so when it's in an oxygen-starved environment, it can develop nasty things like crevice corrosion, and subsequently fail.

I'll probably take the paint off the chainplates on my boat, at the very least, just to give the stainless a bit of air (perhaps it can get some through the paint, but I'd like to be able to see them anyway).
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Postby Shoalcove » Sun Jan 28, 2007 11:41 am

I have a similar set-up on my CheoyLee and re-did the chainplates two years ago. I took mine off to check the bolts and when I removed the chainplates themselves they were in poor condition. They looked fine on the visible side but against the knee were very corroded. The bolts were also ready to be replaced. To add to the pleasure, one knee had leaked and the core was completely rotted so I got to open it up to recore and reglass. Another skill (?) aquired. : ) I am completely aware that CheoyLee is known for cruddy Stainless Steel and new chainplates were to be expected, but if I had any 30+ year old boat with SS chainplates I would want to take a peek. Best regards.
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Postby Duncan » Sun Jan 28, 2007 4:14 pm

Thanks very much for the replies.

Rachel, it's very kind of you to blame the photo, but I had mis-interpreted it and never even noticed the fasteners. Now I understand the A30 setup much better, thanks. I don't have a photo of mine, but my recollection is that there's no knee, and that there is a block glassed straight onto the inside of the hull.

That doesn't sound right, though, so I'll have to take a closer look when the time comes (its too cold to work on the boat up here right now - bbrrr).
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