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Warning - chain plates on NZ built production boats


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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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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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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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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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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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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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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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316 does not mean it is "better" that 304. SST is made to meet a specific requirement for use. 316 offers better protection from Chorides than 304 for example. Which is why 316 is considered better for Salt Water immersion than 304 is. But 316 is also a lot more brittle than 304. This means that 316 can crack due to vibration etc. 304 is a little better and does not work harden as easily. That is why Bolts used to be only available in 304, because cutting threads was really hard work in 316. However, threads are no longer cut. They are rolled into a bolt and hence why you now see 316 just as commonly as 304. Although 316 is often sold at a premium because they can.
Above waterline, 304 can have some big benefits due to being less subject to cracking.
The really big issue the Boating industry has, is the want to have shiny bling for rigging. If only everybody was happy with Galv. If looked after, it can last a life time.
 

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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

 

 

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

 

 

It isn't just Kiwi boats

 

Good to hear there have not been many issues with the 1020s. You guys would likely have more idea than me. But all of these boats are quite old now and my source of info is definitely reputable. The reason for my post is just to hopefully save at least one boat owner a lot of hassle and possibly risk. The post from Dtwo is a good example of what to look for ie the staining caused by leaking through the deck. In regard to chainplates bolted to plywood bulkheads - all good unless leaks have rotted the ply or the ply is coming away from the hull. A good look around for staining, rot or even the slightest movement of the chainplates is probably reason to further investigate. Somebody else on this forum is likely more qualified on what to look for.

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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?)

It's a known issue on KP44s, built in Taiwan and the quality of the 1977 stainless is shite.  Combine that with a f**kknuckle of an owner who thought that you seal things from the underside, using 5200 liberally coated on everything.  All that did was keep the water from draining away... However, nothing showing anywhere as the chainplates pass through the deck, with all the corrosion happening at deck level, which is about 30mm thick.

 

The bolt that broke was the very first one that I pulled, it made me replace all 30 of them but it was the only really dodgy one, go figure.  I'll ppost a photo of the bolts holding the rudder shoe on in a minute.

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Just had a 1/2" 31600 stainless bolt fail after 10 years of cyclic'ish loading, went just below the nut and looked suspiciously like fatigue that had propogated from a small crack in the thread root. Time to replace the other 15 in the spirit of preventative maintainence ????

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...another important factor with chain plates is "The leading angle" ,

that is ...That the line of the chainplate is in line with the stay.  As the cyclic loads come on and off , the small amount of deflection in an out of true chainplate can cause it to let go with out any warning. You will find this even more often with Tball fittings. Particularly where they sit in the mast, they often dont allow the wire to run true and it will fail at the point of exit from the swage.

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