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Any rocket science to re-bedding chainplates


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I'm planning to re-bed my chainplates because a couple are leaking. It doesn't seem like rocket science - remove chainplates cover, clean, wrap chainplate with some butyl tape, re-attach cover and watch butyl tape goosh out, clean up. 
 

I haven't done it before so it seemed worthwhile checking to see if I was missing anything.  
 

Any information is appreciated. 

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If the deck is cored, and you or previous owner has not done it before, dig out the core at the opening and fill with thickened epoxy.

Add a little bevel around the opening so the caulking has some width - gives it more sealing bond as the chainplate is loaded.

image.thumb.png.df35ba2381d3fedf085ca69ce25f6a18.png

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^ This.

The chamfer Zonk details is the "square" equivalent of chamfering a bolt hole with a countersink - it creates an O ring effect and hugely improves the reliability of the seal.

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55 minutes ago, DDW said:

I don't speak butyl tape. Hate the stuff.

That is surprising, Captain. Too clean? Too convenient? Too inexpensive? Too elastic after decades? No concern for the contents hardening between uses? 

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No, it oozes out of the joint. And oozes out of the joint. And oozes out of the joint. For decades. I had a 20 year old boat and the stuff was still oozing. I have a 10 year old RV and it is oozing still. When it gets warm out, still more ooze. Did not prevent leaks in either case. I have a dinghy that has the hull fastened to the flotation tubes with butyl. A line of ooze all around, bits break off and get tracked everywhere on deck. Going to take a couple of hours to clean that ooze off, and it won't end there.

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Are you using MaineSail's butyl? I've had the problem you describe with hardware store butyl but I haven't with his stuff.

It also helps a lot to put a heavy chamfer around fastener holes and limit application to a ring around the fasteners at the interface. I try to have enough butyl to seal the available volume but not much more and I want the path of least resistance to flow to be the chamfer and the clearance around the fastener, not out to the side. 

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What Zonker said but I'll add to seal the top of the bulkhead with epoxy wherever you can readily access it (e.g. around the tang on the chainplates that sticks through the deck) if it is not solid glass.  Our port bulkhead delaminated from inside the marine plywood that was sandwiched / tabbed in between sheets of glass.  We caught it before the bulkhead completely blew up, when the top layer of veneer about a foot away from the real rot started to bubble up... but it still wasn't cheap.  Lesson learned... 

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Depending how deep one wants to go ...

One idea I have seen put to good use is to add a "plinth" to each chainplate.  This is say 1/4 - 1/2 inch preform FG plate, nicely tapered smoothed etc, epoxied where the existing top plate goes.  This effectively raises the entry point for the water a bit above the deck, and adding some "caulking" length to the seal, both leaking to less leakage.  The original caulking, etc is as before, the top plates attach just as before, just now screwed into the plinth.

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^^^ And have a fillet of sealant going up the exposed edge of the c-plate. Anything to get the water away from the joint quicker will help

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23 hours ago, IStream said:

Are you using MaineSail's butyl? I've had the problem you describe with hardware store butyl but I haven't with his stuff.

It also helps a lot to put a heavy chamfer around fastener holes and limit application to a ring around the fasteners at the interface. I try to have enough butyl to seal the available volume but not much more and I want the path of least resistance to flow to be the chamfer and the clearance around the fastener, not out to the side. 

I'll confess I have never applied butyl caulk to a boat. I have cleaned up a ton of butyl caulk applied by others. My last production sailboat and my camper were both built in Canada, they seem to love the stuff. I've cleaned bucket fulls of it off, either 'cause it oozed out or I had to reseal the failed joint. I don't know what brand they used. The Bullfrog dinghy on the motorboat was built in Bellingham, butyl is oozing badly from the joints top and bottom. I scrape it off (leaving an oily stain) and 6 months later there is more. 

18 hours ago, jamhass said:

Depending how deep one wants to go ...

One idea I have seen put to good use is to add a "plinth" to each chainplate.  This is say 1/4 - 1/2 inch preform FG plate, nicely tapered smoothed etc, epoxied where the existing top plate goes.  This effectively raises the entry point for the water a bit above the deck, and adding some "caulking" length to the seal, both leaking to less leakage.  The original caulking, etc is as before, the top plates attach just as before, just now screwed into the plinth.

The idea of a plinth or land at any planned deck penetration is a sadly underused design feature. We've known since Newton that gravity is dependable, and for the most part water runs downhill. This was amply demonstrated to me when I was a young lad building a shed from used materials. All I had for the roof was some used corrugated iron, full of nail holes from its original use. My father said just turn it so the nail holes are on the top of the corrugations, it'll be fine. Looking up at that roof it looked like a sieve, bright pinholes of sunlight everywhere. Only in the heaviest of rains, every so often a drop would bullseye one of the holes and there'd be a fine mist from it. Other than that completely dry. If the deck had a plinth and the chainplate had a gaiter or drip collar, you probably wouldn't need sealant at all. 

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On 4/23/2021 at 11:02 AM, Zonker said:

If the deck is cored, and you or previous owner has not done it before, dig out the core at the opening and fill with thickened epoxy.

Add a little bevel around the opening so the caulking has some width - gives it more sealing bond as the chainplate is loaded.

image.thumb.png.df35ba2381d3fedf085ca69ce25f6a18.png

This

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I thought that was what happened in the person of Rob Ford and that after he was gone, it would be the perfect country. Alas, they apparently can't do without a Ford in power up there. Maybe they just need to lose Ontario as a whole.

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Ontario is a pretty big piece of land to condemn as a whole. But Toronto in particular is probably my least favorite part of Canada. Followed by Saskachewan in the winter.

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Well, the phenomenon started in Toronto with Rob but now it's spread to all of Ontario with Doug. At this rate, if you don't amputate immediately you'll lose the patient. 

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