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Laskadog · 08-01-2022, 15:43

Hi all,

I'm going to be adding a staysail chainplate to my boat this spring and need a little advise in order to properly protect the core.
The 2.5" x 1/4" stainless bar will be attached to a bulkhead in the chain locker and come up through the deck. The deck is plywood cored and I want to protect it from rot in case of leakage. I was thinking of cutting the rectangular hole for the chain slightly oversize and filling it with thickened epoxy. In order to make a nice tight fit I was going to wrap the chain plate in packing tape and leave it in place so I can poor the epoxy around the chain plate. I am hoping that when the epoxy dries, the tape will prevent the epoxy from adhering on in and back it out, thus leaving the perfect hole. Does this sound feasible or will the chainplate be stuck there?

Cheers,

Bowdrie · 08-01-2022, 17:45

Sure, that's doable.
You'll want to cut the rectangular slot with at least a "fat" 1/8th or so clearance all the way around and apply some coats of un-thickened epoxy to seal everything up.
Then, with the part mounted you pack the surrounding space with a Polysulfide, 5200 can be used but real Polysulfide is a better sealant against metal, especially against a polished stainless surface, (the miracle product Dolphinite can also be used, and provides easy re-do if there ever is a leak).
You'll want a stainless plate with a slot cut in it that matches the cut-out but has less clearance, (perhaps a 1/16th,) with a couple of screw holes to secure it to the deck.
That plate will go down on top of the packed-in caulk in the same operation, screwed down to the deck, with the wet caulk squeezing up, and you'll end with making a neat fillet of caulk from the plate to the strap.
You can use some thickened epoxy but seal the deck opening first with the un-thickened stuff first.
You still need a good clearance for the caulk, don't skimp on that, small caulk lines fail, there has to be enough "mass" of caulk in the joint for flex.

**Jim Cate** · 08-01-2022, 19:55

Quote:

Originally Posted by Bowdrie

Sure, that's doable.
You'll want to cut the rectangular slot with at least a "fat" 1/8th or so clearance all the way around and apply some coats of un-thickened epoxy to seal everything up.
Then, with the part mounted you pack the surrounding space with a Polysulfide, 5200 can be used but real Polysulfide is a better sealant against metal, especially against a polished stainless surface, (the miracle product Dolphinite can also be used, and provides easy re-do if there ever is a leak).
You'll want a stainless plate with a slot cut in it that matches the cut-out but has less clearance, (perhaps a 1/16th,) with a couple of screw holes to secure it to the deck.
That plate will go down on top of the packed-in caulk in the same operation, screwed down to the deck, with the wet caulk squeezing up, and you'll end with making a neat fillet of caulk from the plate to the strap.
You can use some thickened epoxy but seal the deck opening first with the un-thickened stuff first.
You still need a good clearance for the caulk, don't skimp on that, small caulk lines fail, there has to be enough "mass" of caulk in the joint for flex.

If you choose to go this route, make the cover plate in two pieces so that in the future you can check or renew the caulking without having to detach the rigging from the chainplate.

Jim

CSY Man · 08-01-2022, 20:42

I sealed my thru-deck chainplates with flexible West System epoxy. Also tried ways of sealing but they all started leaking after 3-6 months.
Never tried 5200 but it is a good idea.
Under deck I wrapped rags or paper towels around the plates so as to detect any leaks after heavy rains.
It was a constant battle until I discovered the flexible epoxy.

bcboomer · 08-01-2022, 21:37

Bed-it butyl tape is more forgiving of movement than polysulphide. I'd undercut the plywood another 1/4 inch and fill that with thickened epoxy.

**roverhi** · 08-01-2022, 22:42

Epoxy is a brittle medium and could be subject to cracking if stressed. You want to be sure the core doesn't get wet. Plywood wicks moisture and rot will expand rapidly over a large area if it gets and stays wet. Use a Dremel 199 bit to rout out the core all around the opening. Fill the void with thickened epoxy after first sealing everything with straight epoxy. Seal the chainplate with Butyl or some other good sealant. The key to any caulk sealing is having an 1/8" or more around the chainplate so there is a donut of caulk that can expand and contract when it works in service.

FWIW 5200/4200 are polyurethanes, LifeCaulk is Polysulfide.

**GordMay** · 09-01-2022, 00:57

Quote:

Originally Posted by CSY Man

I sealed my thru-deck chainplates with flexible West System epoxy. Also tried ways of sealing but they all started leaking after 3-6 months...

Did you use West System G/Flex 650 Toughened Epoxy?
➥ https://www.westsystem.com/specialty...ughened-epoxy/

sailcrazy · 09-01-2022, 03:23

When we replaced our chainplates we initially sealed them as you propose, using 5200. We put a bead (maybe a thin 1/8") of 5200 around the in-place chainplate, then screwed down the cover plate, cleaned ithe edges and the ooze up, and called it good. 2 years later we moisture below deck, where the chainplates bolted to f/g structure....not good! I removed each chainplate, enlarged the rectangular hole until I was in dry, solid teak decking and deckcap, and sealed and refilled the edges with epoxy until I had about 1/8" around the installed chainplate. Then tapered the hole edges to about 60* (so the deck-side was wider than the bottom, reinstalled the chainplate, and stuffed the angled opening with butyl. Reset the cover plate, cleaned up the ooze top and sides....and have not had a leak since! That was 8 years ago. Chainplates do move under load, epoxy will crack, but butyl remains soft and flexible. Use butyl!
PS. I used the same process for my 2 deck prisms, too. The leaks stopped, the headliner remains dry, and no issues.

Searles · 09-01-2022, 03:47

Cut the slot at least 1 inch in all directions of the intended c/p taper the slot widest at the top ,if possible fit a grp doubler under the deck where the penetration is ,fill area around the fitting with the chosen epoxy ,bolt in and seal with g/ flex ,have found this product v/ good for s/s to grp sealing .⛵️⚓️

Bobby Lex · 09-01-2022, 04:39

I think that this link would be a useful guide for you on your project.

Chainplate Rebedding - TKRonaBoat

This boatowner followed what appears to be a sound method of replacing/rebedding his chainplates. And I especially like the excellent photos, step-by-step guide, and clear explanations as to what he did and why he did it.

Bob

Davidhoy · 09-01-2022, 05:23

Quote:

Originally Posted by bcboomer

Bed-it butyl tape is more forgiving of movement than polysulphide. I'd undercut the plywood another 1/4 inch and fill that with thickened epoxy.

+1 on the Bed-It butyl tape. That's exactly what I used when rebedding my chainplates, stuff is truly the best thing for sealing anything that attaches to, or goes through, your deck. I have never had that stuff leak after installation.

phorvati · 09-01-2022, 05:26

Quote:

Originally Posted by Bobby Lex

I think that this link would be a useful guide for you on your project.

Chainplate Rebedding - TKRonaBoat

This boatowner followed what appears to be a sound method of replacing/rebedding his chainplates. And I especially like the excellent photos, step-by-step guide, and clear explanations as to what he did and why he did it.

Bob

In my experience, there is not enough butyl there in that link. Also the deck hole is too small. Chain plate is making contact with the deck in the hole. As the hull flexes, it will push chainplate around and create cracks. There needs to be a larger void between chainplate and deck and it needs to be loaded with butyl. Along with good bevel on the surface of the deck around the holes. Butyl needs to remain in the void to be able to squeeze and expand, but in those pics there is almost no void.

Bobby Lex · 09-01-2022, 05:41

Quote:

Originally Posted by phorvati

In my experience, there is not enough butyl there in that link. Also the deck hole is too small. Chain plate is making contact with the deck in the hole. As the hull flexes, it will push chainplate around and create cracks. There needs to be a larger void between chainplate and deck and it needs to be loaded with butyl. Along with good bevel on the surface of the deck around the holes. Butyl needs to remain in the void to be able to squeeze and expand, but in those pics there is almost no void.

I get what you're saying, but....

This owner's boat was about 15 years old when he undertook his project and the photos show no cracking after all those years of flexing, despite the narrow slot.

Bob

phorvati · 09-01-2022, 05:50

Quote:

Originally Posted by Bobby Lex

I get what you're saying, but....

This owner's boat was about 15 years old when he undertook his project and the photos show no cracking after all those years of flexing, despite the narrow slot.

Bob

If there is no leaks or cracks, that is very fortunate, cheers to that. And by cracks, I didn't mean cracking in the deck, I meant cracking in the slot or whatever void there is between chain plate and inner walls of the deck. Metal chainplate will flex differently than the deck going up and down, bulging and stretching. So something has to stretch and compress to fill that. In my experience lifecaulk did not do it. I re-did my chainplates with butyl rubber and its working very good after one hard season.

https://www.cruisersforum.com/forums...-202415-2.html