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Old 26-02-2021, 19:02   #106
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Re: How to fix these buried chainplates?

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Originally Posted by Sailmonkey View Post
Your chain plates are susceptible where the bolts penetrate the deck. I’ll wager that unless they’re pulled and re-bed every few years you’ll end up with corrosion on the bolts. They don’t need to even visibly leak for this to happen.

Yep! I won't argue with that. I'm now using butyl as a sealant and maybe I'll re-bed them with that as soon as I can. Thanks
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Old 26-02-2021, 19:54   #107
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Re: How to fix these buried chainplates?

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This is terrible advice!!

When stainless is encapsulated itís unable to interact with oxygen. Once itís gotten wet and starts bleeding rust thereís very high probability that the chain plates are done or near done.
I just logged in to write something very similar. A lot of people seem to have no idea what happens to stainless steel once it is sealed off from oxygen completely, either by encapsulating it in fibreglass, completely sealing it in Sika or a similar sealant, or various other ways to keep the water out, that also seals off the air.

We were taught to bed stainless 'through deck' fittings and bolts on the outside, but leave the below deck part unsealed and unpainted, even if it meant raw fibreglass with a washer or plate bolted up to the plain (sanded) glass surface..
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Old 26-02-2021, 20:17   #108
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Re: How to fix these buried chainplates?

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I just logged in to write something very similar. A lot of people seem to have no idea what happens to stainless steel once it is sealed off from oxygen completely, either by encapsulating it in fibreglass, completely sealing it in Sika or a similar sealant, or various other ways to keep the water out, that also seals off the air.

We were taught to bed stainless 'through deck' fittings and bolts on the outside, but leave the below deck part unsealed and unpainted, even if it meant raw fibreglass with a washer or plate bolted up to the plain (sanded) glass surface..

My understanding is that aluminum, stainless steel and titanium develop a surface film when exposed to oxygen. To corrode it would need sea-water, not rain water. If the deck sealant failed then the bolt/nut would corrode if it remained wet with sea water.

I have not used any sealant on the bolts/bolt holes. The deck part of the chain-plate is bolted to the embedded chain-plate.
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Old 27-02-2021, 03:28   #109
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Re: How to fix these buried chainplates?

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Originally Posted by rossdv8 View Post
I just logged in to write something very similar. A lot of people seem to have no idea what happens to stainless steel once it is sealed off from oxygen completely, either by encapsulating it in fibreglass, completely sealing it in Sika or a similar sealant, or various other ways to keep the water out, that also seals off the air.

We were taught to bed stainless 'through deck' fittings and bolts on the outside, but leave the below deck part unsealed and unpainted, even if it meant raw fibreglass with a washer or plate bolted up to the plain (sanded) glass surface..

I've used stainless steel screws to fit out the yacht. Should I expect the SS screws to corrode because they are encapsulated in timber and completely sealed off from oxygen?
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Old 27-02-2021, 04:01   #110
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Re: How to fix these buried chainplates?

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I've used stainless steel screws to fit out the yacht. Should I expect the SS screws to corrode because they are encapsulated in timber and completely sealed off from oxygen?
Air passes through or by timber (even epoxy or polyester saturated timber) relatively easily. The problem for bolts is that a sealant or uncured resin applied to the threads fills them. Or, in the case of two of my boats, some bright spark had fixed things like chainplates through a fibreglass deck (in one boat, fibreglass / plywood sandwich) then sealed both sides of the whole thing, bedding one side in Sika and sealing the other side in glass, completely sealing the bolts from access to air.

On one fitting that failed, casing the mast to drop when we changed tack, the 5/16" nuts were perfectly seated (tightly) on the 5/16" bolts. What broke, was the 1/8" diameter remnant in the middle where it was sealed in that had not corroded.

When we got back to a slipway and hauled out, I dismantled the rest of thee fitting. Every one of the set of 5/16" bolts was rotted down to 3/16" to 1/8", where it passed through the (in this case solid) glass deck.

On my next boat I knew what to look for - and it had the same problem, except to a lesser extent. It was the first job I tackled after the osmosis blisters were tidied up.
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Old 27-02-2021, 04:26   #111
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Re: How to fix these buried chainplates?

I finally got out to the boat and looked at the chain plates. I chipped some glass off a nut but I didn't want to get berserk with no vacuum. Only some rusty crud.

The plates look to have 2 T-sections.

Damn I wish I could just move the boat up north then I'd have plenty of time to work on them. At the moment I'm on a temporary mooring in Sydney and just parked the car and trailer sailer next to a park back where I want this boat to be.

I don't know how structural this glass over the plates is.

It's not easy to just tear it off.

Here's some pics:



Worst looking one but the paint is a complete different colour. Someone has to have done this outside factory.



Best looking ones. I chipped of the bottom left nut which was full of rust.



Super awkward.



Also bad.



Back stay.



Plates go through the gunwale. There's some sealant on the top.



Outside bolts look clean.
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Old 27-02-2021, 04:26   #112
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Re: How to fix these buried chainplates?

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Originally Posted by coopec43 View Post
My understanding is that aluminum, stainless steel and titanium develop a surface film when exposed to oxygen. To corrode it would need sea-water, not rain water. If the deck sealant failed then the bolt/nut would corrode if it remained wet with sea water.

I have not used any sealant on the bolts/bolt holes. The deck part of the chain-plate is bolted to the embedded chain-plate.


Rainwater will eventually cause this as well, just takes longer.
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Old 27-02-2021, 19:29   #113
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Re: How to fix these buried chainplates?

Coopec 43 the one trouble with polyester is the smell, particularly when you are working in confined spaces. Also I love epoxy with slow hardener as it gives you plenty of time to get the job perfect.
WaldPinkler I think you really need to slip the yacht, drop the mast and repair those chain plates. You could do it in the water but I don't know any marinas that allow that type of work to be done.
Manatee I think your mates were a bit shocked about your anti glass grinding stance? It is very nasty stuff but with the correct training and PPE the risks can be greatly reduced. The other day I observed a guy grinding fiberglass and his offsider was holding a large dust extraction hose next to the grinder. Both were wearing full PPE and I doubt either were getting much dust on them at all.
Cheers
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Old 27-02-2021, 21:20   #114
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Re: How to fix these buried chainplates?

These are just my thoughts on the problem if she was my yacht:

Looking at those pictures, my first order of business would be to start replacing the bolts and nuts on ALL the chainplates one set at a time. That is, do one bolt/washer/nut at one (same) position at every chainplate until you have done one on each of them, then start on the another bolt/washer/nut at another position on each chainplate.
Continue until they are done all the way around the deck/hull one at a time.

The job could be done in bits, days or even weeks apart, as long as one or more 'round' is COMPLETED at a time.

I would do them in sets, like say number 2 position all the way around, then number 4 position all the way around, then number 3 then number 1 depending on how many chainplates with how many bolts in each that you have.

Sort of like the old way we used to tighten cylinder head bolts.

By then you would have got a pretty good idea of:
The condition of the bolts in the areas you couldn't see.
How much corrosion and where it is (if any) on the actual chain 'plate' part of the fitting.

From there, you at least have peace of mind that the bolts are not going to start popping any time soon, dropping your mast :-)
And you have a repair plan if there is corrosion damage to the fittings.
And a further repair plan should the fibreglass of the hull, or the timber of the deck and gunwhale strakes be damaged.

My guess is that if it is like my last two, the bolts will be corroded, but the fittings might clean up ok.

After replacing the bolts/washers/nuts, and seeing the damage to the stainless plates / through deck fittings, I was able to rig bridles to one shroud or stay at a time to take its strain, while I removed the chainplate and fitting (some of mine looked identical to those in the photos) and cleaned them up.
NOTE:
DO NOT use any 'Rust Converter' products on Stainless Steel !!

Changing all the Bolts BEFORE removing fittings makes budgeting a bit easier and you would give yourself anywhere between days and years of breathing space depending on what you find..

Again, I am not a shipwright, nor do I really know anything 'technical' about all this stuff.
It is simply my thoughts based on what worked for me on two old yachts built in the late 70s, with the same problem that the photos show...
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Old 27-02-2021, 21:29   #115
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Re: How to fix these buried chainplates?

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Originally Posted by Fore and Aft View Post
Coopec 43 the one trouble with polyester is the smell, particularly when you are working in confined spaces. Also I love epoxy with slow hardener as it gives you plenty of time to get the job perfect.
WaldPinkler I think you really need to slip the yacht, drop the mast and repair those chain plates. You could do it in the water but I don't know any marinas that allow that type of work to be done.
Manatee I think your mates were a bit shocked about your anti glass grinding stance? It is very nasty stuff but with the correct training and PPE the risks can be greatly reduced. The other day I observed a guy grinding fiberglass and his offsider was holding a large dust extraction hose next to the grinder. Both were wearing full PPE and I doubt either were getting much dust on them at all.
Cheers

My biggest worry when using Polyester in confined spaces is not the smell but the heat build up (and possible flames) do to lack of circulating air. (I always have a bucket of water handy)


Of course you can always slow down polyester by using less catalyst. The epoxy I have always used is quite slow and gives plenty of time to work.


As far as grinding f/g is concerned I have a proper dust mask. If outside I wait for a strong breeze to blow the dust away (onto the property next door )


A bit off topic but I was not aware that you can gets different catalysts for polyurethane(?) finish coat: one for spray painting and slower ones for rolling in either hot or cold weather. In Australia I am sure it is illegal to spray Isocyanates out in the open due to there toxicity.
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Old 28-02-2021, 01:36   #116
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Re: How to fix these buried chainplates?

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Rainwater will eventually cause this as well, just takes longer.
Is that why you never see stainless steel water tanks?
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Old 28-02-2021, 03:05   #117
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Re: How to fix these buried chainplates?

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Looking at those pictures, my first order of business would be to start replacing the bolts and nuts on ALL the chainplates one set at a time.
I'm liking this advice. I'm procrastinating now. This gives me a way forward.
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Old 28-02-2021, 04:14   #118
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How to fix these buried chainplates?

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Is that why you never see stainless steel water tanks?


Stainless water tanks are not encased in an oxygen deprived environment. Itís the anaerobic environment that prevents the stainless from being stainless.

Besides that, do you never plan on having any seawater on the deck?
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Old 28-02-2021, 04:24   #119
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Re: How to fix these buried chainplates?

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I finally got out to the boat and looked at the chain plates. I chipped some glass off a nut but I didn't want to get berserk with no vacuum. Only some rusty crud.

The plates look to have 2 T-sections.

Damn I wish I could just move the boat up north then I'd have plenty of time to work on them. At the moment I'm on a temporary mooring in Sydney and just parked the car and trailer sailer next to a park back where I want this boat to be.

I don't know how structural this glass over the plates is.

It's not easy to just tear it off.

Here's some pics:



Worst looking one but the paint is a complete different colour. Someone has to have done this outside factory.



Best looking ones. I chipped of the bottom left nut which was full of rust.



Super awkward.



Also bad.



Back stay.



Plates go through the gunwale. There's some sealant on the top.



Outside bolts look clean.
From the last picture, it seems it would be a fairly simple and inexpensive job to just fabricate new external chain plates and leave the internal ones as backing plates (once you've removed the fiberglass covering them). As they are now, they're so close to the hull that moving them a few centimetres out won't affect your sheeting angle at all. The advantages of external chain plates are many- easy inspection and no leaks being the main two. I also don't think it will be a detriment to the already "salty" look of your boat.
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Old 28-02-2021, 09:46   #120
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Re: How to fix these buried chainplates?

Some talking as if stainless steel is immune from rust. I have replaced glassed in chain plates that on the surface appeared fine. Ever hear of crevice corrosion?
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