Kittrina - dismasted.

[geem]

Same with my even older Golden Hind. However unlike many designs (such as the tri in this thread) all the chain plates are external bolted through the topsides with stainless backing plates inside rather than passing through the deck. A disaster waiting to happen unless the seal through the deck is perfect and the attachment below is not hidden or embedded in a knee or a bulkhead. Many 1970-1990s designed boats fail in this respect - and the chain plates fail through a combination of crevice corrosion and stress, just as in the photo in post#34.

Probably little to do with the quality of the material - even the best 316 is susceptible to crevice corrosion.

Design of shroud attachment has come a long way since then with first through deck tiebars down to the keel through such things as internal structural bulkheads or dedicated webs to the keel load bearing structure or more recently back to external chainplates bolted through to laminated internal structures and even composite laminated into the hull structure.

Yep, mine are bolted through with numerous M10 bolts through substantial bulkheads. We pulled a couple of bolts on the chainplates and the bolts were,perfect. Let's hope they were typical of the rest

 

[Chiara’s slave]

Same with my even older Golden Hind. However unlike many designs (such as the tri in this thread) all the chain plates are external bolted through the topsides with stainless backing plates inside rather than passing through the deck. A disaster waiting to happen unless the seal through the deck is perfect and the attachment below is not hidden or embedded in a knee or a bulkhead. Many 1970-1990s designed boats fail in this respect - and the chain plates fail through a combination of crevice corrosion and stress, just as in the photo in post#34.

Probably little to do with the quality of the material - even the best 316 is susceptible to crevice corrosion.

Design of shroud attachment has come a long way since then with first through deck tiebars down to the keel through such things as internal structural bulkheads or dedicated webs to the keel load bearing structure or more recently back to external chainplates bolted through to laminated internal structures and even composite laminated into the hull structure.

The other factor is as Geem implies. A very robust fitting helps eliminate any flexing, which, when the material is well known for work hardening, and subsequent fatigue failure, can only be a good thing.
We pulled 30% of our bolts to check, and re sealed it all. No issues at 20 years.

 

[Tranona]

I was surprised at those bolts failing with no visible signs of corrosion. However without knowing the exact material and what the bolts were doing difficult to come to any meaningful concluson.

 

[billskip]

Looks to me the bolts cracked in tensile and over time corrosion in the cracks created the end result....

 

[geem]

I was surprised at those bolts failing with no visible signs of corrosion. However without knowing the exact material and what the bolts were doing difficult to come to any meaningful concluson.

I have seen cheap Chinese s/s bolts fail in the same way. We bought an led floodlight to use a a powerful deck light. I used the shiny s/s bolts that came with it plus the bracket. Everything rusted and the bolts seized. Undoing them snapped M8 bolts like toffee. They looked identical to the ones in the OPs photos

 

[Tranona]

Highly unlikely they were "cheap Chinese" from the early 90s - OP says they seem original.

 

[Chiara’s slave]

Highly unlikely they were "cheap Chinese" from the early 90s - OP says they seem original.

Indeed. Built in the USA, pretty sure everything possible would have been American, preferably Californian.

 

[geem]

Highly unlikely they were "cheap Chinese" from the early 90s - OP says they seem original.

We had a problem getting bolts of the right quality for the hinges on our foredeck locker. They rusted for fun. Eventually sourced some that don't rust. They were all specified as A4. Who knows where stuff comes from or to what quality.

 

[Rum_Pirate]

I was surprised at those bolts failing with no visible signs of corrosion. However without knowing the exact material and what the bolts were doing difficult to come to any meaningful concluson.

The bolt head (external location an 12” above waterline) looked perfect.
The bolt end, the bolt and the washer (located internally) looked absolutely perfect.

However, the bolt head end sheered off flush externally at where the bolt entered the fiberglass hull.
Note that there was a plastic washer under bolt head to isolate it from the aluminum folding bracket mechanism.
Also the bolt sheered off internally off flush at where the bolt came through the fiberglass hull.
There was a section of bolt that remained stuck fast in the hole through the hull and had to be hammered out (used a large screwdriver and hammer).

I would unreservedly recommend regular removal and inspection (and replacement as required) of these structural fittings and fixtures.

 

[srm]

The explanation for pitting corrosion that I was given after finding it on the Waverider hull was that ss exposed to aerated water was fine but when part of the surface is covered and deprived of oxygen, (as with barnacles or in fibreglass) an internal electrolytic cell is formed on the boundary causing the corrosion.

 

[Kelpie]

Interesting thread, and sightly scary.
We pulled all of our chainplates last year, replaced one which was showing pitting. They're pretty substantial and there was only very slight damage but for €70 to get a new one made up there was no point putting the old one back in.
The bolts all looked fine.
I don't know old all of this stuff is, but the boat is from 1978.

Mast tangs are another story- relatively easy to inspect, of course, but much less substantial than the chainplates.

Do the tangs lead an easier life, since they see a lot less salt spray?

 

[Rum_Pirate]

Interesting thread, and sightly scary.
We pulled all of our chainplates last year, replaced one which was showing pitting. They're pretty substantial and there was only very slight damage but for €70 to get a new one made up there was no point putting the old one back in.
The bolts all looked fine.
I don't know old all of this stuff is, but the boat is from 1978.

Mast tangs are another story- relatively easy to inspect, of course, but much less substantial than the chainplates.

Do the tangs lead an easier life, since they see a lot less salt spray?

The tang in this instance was on the coachroof.

It could be that rain and some spray entered and made it's way vertically down into the recess, subsequently causing the damage.

The other three support fittings/tangs for the shrouds will definitely be removed and replaced.

Just to ensure confidence and importantly safety.

 

[Tranona]

The explanation for pitting corrosion that I was given after finding it on the Waverider hull was that ss exposed to aerated water was fine but when part of the surface is covered and deprived of oxygen, (as with barnacles or in fibreglass) an internal electrolytic cell is formed on the boundary causing the corrosion.

That is a good basic description of crevice corrosion. It is the damp oxygen deprived environment that is key. Good example is when boats are left in the water for long [periods without the prop shaft turning there can be build up of deposits inside the cutless bearing that fills the flutes so removing aerated water. Not only is there crevice corrosion and pitting, but when the shaft is turned under power it can wreck the bearing and score the shaft.

 

[Rum_Pirate]

Remember that there is no way to spot any such damage without removal and proper close inspection.

 

[Tranona]

That is true, but in some cases there are indicators such as failure of sealant around stainless items that go through decks. Tell tale signs of rust weeping out underneath fittings. Of curse you can only really see when you take things apart.

 

[zoidberg]

Remember that there is no way to spot any such damage without removal and proper close inspection.

From the little I know, yours is exactly the right kind of boat to benefit from replacing s/steel chainplates with far better carbon-fibre ones bonded in. That's a DIY job, with just a little 'handholding' from a couple of specialist firms on 'what and how'. Yes you can!

 

[zoidberg]

Hello, Rum_P

You could start looking here....

 

[Rum_Pirate]

Chasing up the boatyard for the repair quotation tomorrow.

 

[Chiara’s slave]

Chasing up the boatyard for the repair quotation tomorrow.

Best of luck with that. I hope it all comes to a satisfactory conclusion.

 

[Rum_Pirate]

Best of luck with that. I hope it all comes to a satisfactory conclusion.

Well it seems like repair (labour and materials) cost may likely equal or exceed insured value.

Sister and daughter telling me not to repair (due to safety ) but to sell instead.