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Old Fart
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Any advice on how to seal the deck penetrations where the SS metal members go thru the deck and connect my shrouds to the knees below deck?

I have an old teak decked boat with a balsa core and the penetrations where the shrouds go thru have leaked ever since I bought the boat. The configuration is as follows. The knees are very beefy and bring the shroud attachment inboard about 15 inches from the hull. There is a four inch wide by 3/8 inch stainless steel flat stock member that attaches to the knees and goes thru the deck and the shrouds attach to that. The hole the flat stock goes thru is far bigger than it is due to the poor boat building practice. It has about 1/2 inch clearance on all sides. I've tried the West Marine caulk and it just doesn't work. I think I need a good flexible caulking that will stick well to the metal as well as the wooden parts. Any suggestions?

Fortunately I live in a near desert climate and it only leaks when it rains. :rolleyes:
 

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You might try to fab a stainless cover plate that will fit with much less clearance.

Maybe one of wood that sheds the water away from the flat stock.

Then use clear silicone to seal the smaller gap.


I use silicone and the boat has not leaked there for 5 years.
 

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open the holes up a slight bit so you have more room. then attach a decorative plate on the underside and fill the hole from the top with suitable caulk, then put a cover over that and seal as normal.

tighter fitting holes provide less area for water ingress, but caulk works best if it has some play room, a wider strip of caulk can stretch quite a ways without splitting or tearing free. Once it splits it's a leak.
It's not a problem on stationary items, but everything bolted on to a boat moves.
stay away from caulks that dry hard.

Ken.
 

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before you even consider sealing the deck you should check to see if your core is wet and your chain-plate holes that's what those things are called. you can use a moisture meter for this as well as removing the old caulk around plates and in contact with hull material. with that much room you should be able to stick a thin blade screw driver or even paper towel to make contact with core and see if it is wet. if wet you must find out how far in it goes and dry it out (sealant will not adhere to wet/damp core or metal). then ream out core around plate holes and fill with epoxy etc. find threads on this here in archives or other sight. you should remove plates for working room and also to to make surrounding holes smaller if possible so less caulk is needed and also so plates won't move as much which sounds like your prob. if continuously leaking. and then have cover plates made to go over chain-plates with small clearance around chain-plates. i would not use silicone as it does not adhere well to anything it really only makes a gasket. you should use a poly-sulfide to fill around chain-plates and put cover plates on when poly is freshly put down to bed it i would also make an inside cover plate unless there is a wood trim piece that fits around chain-plate.
 

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first you have to find out where the water is coming from the chin-plates or the deck or both. you should without a doubt dry the core if wet or nothing will stick to it no matter how much sealant you put in the holes and silicone is not really a sealant as much as a gasket forming material so it will only work for a short while especially if you have such a large gap around your chain-plates. if core is wet you need to dry it and at the least seal the core edges with a penetrating epoxy. this would require you to remove the chain-plates for access. i would have a sheet metal or machine shop make cover plates that go over your chain-plates with a small clearance around chain-plates. so when you put them on the wet sealant(poly-sulfide) it will ooze out around the edges and in-between the plate and chain-plates. check other threads on subject here and other sites
 

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This is what I have



You might try to fab a stainless cover plate that will fit with much less clearance.

Maybe one of wood that sheds the water away from the flat stock.

Then use clear silicone to seal the smaller gap.


I use silicone and the boat has not leaked there for 5 years.
 

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Telstar 28
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Don't use silicone... Silicone caulk really has no place on a boat. What you should probably do is make the gap around the plates a bit smaller by filling the excess gap with thickened epoxy. The gap shouldn't be 1/2" all-around. Bringing it down to 1/4" would be a good idea. If the chainplates flex more than that, you've got other problems to worry about. While you're at it, checking to make sure the deck is sound in the area, especially if the chain plate passes through a cored section of the deck, would be a really good idea. If the core is exposed, sealing it with thickened epoxy would also be a really good idea.

Making a stainless steel cover for the slot is a good idea. Make it out of the same grade stainless steel as the chainplates if you can.

Use SikaFlex 291, 3M 4200, or butyl tape to bed the stainless steel cover and seal the hole.
 

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Old Fart
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Discussion Starter #9
Thanks guys. I'll take your advice to heart.
timebandit... If my shrouds looked that good I'd be thrilled.

Also, I've decided to refurbish my entire deck this coming summer. More to come!!!
 

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Dwayne, use butyl. You will have a much easier time removing and dealing with it. In my own experience it has not hardened in 30 years where the PO hadn't touched it. It remained flexible and well adhered. It can easily be cleaned up with a scraper and a rag wetted with acetone. Can't say the same for sikaflex. Butyl tape can be found at glass shops. Like most things your prep should take 80 to 90% of the time. Keep all pieces clean of all oil, dirt and water, and you will be well on your way to a dry bilge. There are plenty of posts outlining scenarios you may encounter as you refurbish your deck. Good luck.
 

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One challenge with some types of butyl tape is that they have a relatively low melt point, as low as 105 degrees fahrenheit. Not a big deal on a light coloured hull in northern lats, but it could be a problem on a warmer teak deck. Check the spec sheets on the tape you are thinking of using, and look for a tape with a melt point above 200 F. It will also generally be a more durable tape, with a higher elasticity rate.
 

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Telstar 28
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If you get it from an automotive glass shop, it usually has the higher melt point, since automotive interiors get far hotter than most boats do.
One challenge with some types of butyl tape is that they have a relatively low melt point, as low as 105 degrees fahrenheit. Not a big deal on a light coloured hull in northern lats, but it could be a problem on a warmer teak deck. Check the spec sheets on the tape you are thinking of using, and look for a tape with a melt point above 200 F. It will also generally be a more durable tape, with a higher elasticity rate.
 

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After reading your deck problems I thought this idea might be kewl.

6x1-- 1/2 inch thick teak with a 1/4 inch slot and round the top sides and ends with 1/2 round router.

Screws on both ends and seal with whatever.
 

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another option if the core is dry is to use a flexible epoxy to fill the gap, it should hold much better than a caulk. i found 1 that has a 50 percent flex, with a 600 psi strength. i would think it would hold and seal real well.
 

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Telstar 28
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Pretty bad idea... removing it will be hellacious... and you really don't want to use epoxy on stuff you may have to remove or replace if you can avoid it. :rolleyes:
another option if the core is dry is to use a flexible epoxy to fill the gap, it should hold much better than a caulk. i found 1 that has a 50 percent flex, with a 600 psi strength. i would think it would hold and seal real well.
 

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Ya, epoxy it, call me when you wanna get it out! Bring your VISA!
 

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I believe you should ignore ALL the advice about closing up the gap with any kind of cover plate, on the top or on the bottom! Cover plates are what CAUSE the leaks! They shear the sealant, no matter what kind, right off the chainplate as it moves. What you really want is that 1/2" thick soft sealant all around the chainplate that is able to move with the chainplate and not be stressed. That will last for the life of the sealant. Do it right and it probably won't need to done for another 20 years!

You want to pour that gap full of sealant starting at the bottom if you can so no air gets trapped. I'd seal around the bottom of the chainplate with nothing more than some putty. Duxseal, used by electricians and sold in Home Depot would probably work fine. Stick the nozzle of the caulking cartridge right down to the putty and fill the gap from top to bottom, leaving a bead higher than the deck when you are done so the water will naturally tend to run off. When the sealant has curred remove the putty and you are good to go.

You can also get the foam backer strip sold for this purpose that the guys who put store front windows in use.

Note I haven't mentioned water in the core, that's a different issue you may need to deal with.
 

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What Mike says resonates with me.

This winter, as I enter my 2nd year of ownership, I’m tracing leaks. One of which was a chain plate.

I used the butyl caulk/tape (grey in 1/2” width is available at the local home depot) around the deck entrance. It worked!

Additional notes: One of the screws that holds the cover plate does not hold; so I used a larger/longer SS screw; when thing warm up I’ll address the rotted wood issue. (Oh, that to-do list grows longer over the winter instead of shorter because I’ve been supposed to have been doing something recently).
 
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