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Warning - chain plates on NZ built production boats


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#1 Chewing Gum

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Posted 22 November 2017 - 04:12 PM

Check them carefully

 

Apparently there have been several instances in NZ built fibreglass boats including Farr 38s, 1020s and Stewart 34s of chainplates coming loose or worse still  pulling through the deck resulting in rig failures.

 

In at least one instance the Insurance Company paid only for the mast but not the repair to the chainplates / bulkheads / deck etc citing lack of proper maintenance.

 

I guess this could also be a problem on overseas built boats or any boat for that matter as they age and water ingress causes plywood bulkhead rot and fizzing of stainless bolts and apparently can also cause fizzing of the interface between web style chainplates bonded to polyester hulls.


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PK

#2 Myjane

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Posted 22 November 2017 - 11:03 PM

What’s causing this , it can’t be the stainless
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#3 wheels

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Posted 23 November 2017 - 05:01 AM

I guess this could also be a problem on overseas built boats or any boat for that matter

 

Yes any boat.
 

 

What’s causing this , it can’t be the stainless

Causing what exactly. There are many reasons and variables for a failure. In fact there are as many reasons as there are boat designs, because each has a positive and a negative. The problems being that a metal used is prone to stress cracking and it is under enormous changing tensile loads and is then connected to or passing through a different material with vastly different properties.


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#4 lateral

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Posted 23 November 2017 - 06:50 AM

Yep, stainless has its own issues, what wheels said and crevice corrosion owing to lack of oxygen to 

form protective chromium oxide(s). Particularly in heavily stressed areas where SS goes thru a laminate where stagnate low  O2 water sits. ie chainplates, keel bolts.

And, those M16/20 bolts that go thru your bearers on your bach/whare/castle

at the beach. Started at 304, now 316, xx next. I was quite happy with greased galv. Lasted forever, done properly. (Zinc doesn't like CCA hence the grease.)

Talk crevice corrosion to building inspector and they just glaze over.

Same shite, different day.

 

Hence the duplexes, and higher Cr, Nickle, Mo alloys.

I bolted my keel on with 2205 SS, considerably better Cl resistance.

Double the 0.2% proof stress of vanilla 316. Heat sheet verified.

Hopefully they won't be the cause of me shuffling off my mortal.

Fingers crossed.


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#5 Rawhide

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Posted 23 November 2017 - 06:51 AM

havent heard of any 1020's with that issue,  a 1020 does not have the chain plate bonded to the hull, it is connected via bolts to the main bulkhead which is seperatly bonded to the hull.  only issue i have ever heard of is a couple with massive rig tension needing to go up a size in bolts if the holes slightly ovaled in the wood


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#6 Rawhide

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Posted 23 November 2017 - 06:59 AM

I also think that if you are going to put up a post warning people around certain classes of boats then you should be backing it up with some evidence.  Being in regular contact with 50% of all the 1020's ever built, and knowing the survey results from most of the sales in the last 3-5 years i dont see where you could be getting your information from.

 

​I am also aware of the cause of the rig failures that have occurred in the 1020 class int he last 5 years neither of which relate to chainplates


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#7 wheels

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Posted 23 November 2017 - 07:00 AM

The important point is that the Chain plates are part of the system called "Rigging". SST rigging has a working life on average of 10yrs. Most insurance companies depreciate the replacement cost of rigging from yr 1 progressively to yr 10 and at that point, it is no longer covered. How long rigging lasts is different for every boat. Mainly to the amount of miles it has done and in what conditions. So some rigs need replacing at the 10yr mark. A few, if pushed real hard, may actually fail before 10yrs. Many will last well out to 20 yrs or maybe more. But the risk certain goes up the older it gets.
So.....when the rig needs replacing, so should the chain plates be replaced. Or at the very least, crack tested. Which by the time you remove them and send them to be crack tested and then refit old used chain plates, you may as well just fit new ones. It is a small cost to the overall cost of replacing the rig.
Depending on how you use as a Rigger of course, but we won't go there ;-)


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#8 John B

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Posted 23 November 2017 - 07:34 AM

One of the Farrs used to lose forestays back in the day but that was down to method, set tapping the bolts into resin.
We do need to be wary of crevice corrosion on our older boats, particularly
Where a chainplate pierces the deck. They work over time and set up the leak plus oxygen formula needed to make it happen. There's been a couple of boats on this site with issues discussed at length over the years. One had leaks through the deck and the bolts into a bulkhead fried and died.
In may a p38 we were sailing with lost a chainplate and rig about 200 miles off the coast. He cut his rig away in 30 minutes and self rescued. He'd done everything except those.
So they are definitely worth inspecting. Mine are bolted through the hull and I'd need to repaint the boat to take them out. But I have polished and inspected them,beveled into the deck to sight the danger area, and then resealed.
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#9 Dtwo

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Posted 23 November 2017 - 09:50 AM

It isn't just Kiwi boats

 

Chainplate corrosion
 
Chainplate ex-bolt

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#10 John B

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Posted 23 November 2017 - 10:10 AM

It isn't just Kiwi boats

 

See thats actually quite encouraging to see that damage because its not a totally 'hidden' danger.  Thats all quite obvious and would be be showing above or below the deck line upon inspection. And that inspection has prompted the replacement ( Am I right Dtwo?)


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