Chainplate bolts: OK?

[wesley]

Hi folks,

I've recently checked out a Nicholson 32 to maybe buy, and I'm scratching my head over these chainplates:





It looks like the bolts go straight into the hull, rather than being bolted through a bulkhead or something. It's clear from the second pic that the hull is reinforced with something (just thicker fiberglass?) to support the chainplate bolts. But still, is this a maintenance nightmare waiting to happen? If the chainplates are bolted into a metal plate that's bedded in the hull's fiberglass lay-up, then I shudder at the thought of dealing with a potential corroded backing plate.

Thanks in advance for any help and insight you can offer. Seller claims the boat was built in 1979. He says it was built by Camper & Nicholson but because the build year doesn't match the Mark X or XI Nicholson 32s being built in '79, I suspect its an Australia-built Mark VI.

-W

[UNCIVILIZED]

Chainplates being bolted directly to the hull are nothing new, nor anything to worry about if it's done correctly. It's the being done correctly part that may or may not be a concern here. And to be able to offer up more than speculation about said point, we'll need more pictures in order to determine as much. Including ones showing the outside of the hull where the chainplates are attached, etc.

As to their possibly being a piece of metal buried in the laminate there. Such could be the case. Though odds are it wouldn't be overly much trouble to grind down the laminate & remove it. Followed by significantly beefing up the laminate in that area.
Although I'm not sure why the builders might have considered burying a piece of metal in the hull there to be assistive in terms of carrying the chainplate loads.

It's not uncommon to have chainplates externally bolted to the hull, & then to have full sized metal backing plates on the hull's interior, or sometimes vice versa. Which, such large backing plates have obvious advantages. Though strictly speaking aren't a necessity. But if you look around at some other boats with external chainplates, you'll see a few boats which are built thusly.

[wesley]

Wonderful help, @Uncivilized. Thanks. The boat's a 1.5 hr drive plus 30 min dinghy ride away, so the pics I have are what I will have, alas.

I did make sure to look over the hull outside of the chain plates though, and it all seems fair and smooth, no sign of trouble.

-W

[GordMay]

Greetings and welcome aboard the CF, Wesley.

[tkeithlu]

Uncivilized is being very civilized. The cross tees and rectangles under the fiberglass look too regular the be fiberglass as well - I'm betting on steel. My concerns are the first photo, which includes rusty nuts or bolt heads, and the evidence of water intrusion, and then the two small cracks in the second photo. I think it's time to grind off a few test spots in the interior fiberglass to determine the condition of the reinforcement.

[appick]

I agree the condition of the plates and bolts in the first photo is cause for concern.

[Suijin]

Any of the chainplates that look like the one in the first photo will need to be removed and replaced, along with the backing plate, bolts, and associated hardware, whatever it's made of. Where there's rust, there's fire. Replacing the chain plate is cheap compared to a dismasting.

The second photo looks like it's been painted over. I'd open it up too to investigate. In fact, I'd open them all up and proceed on the assumption that all of them need to be replaced. You have water intrusion on at least one where the bedding failed, and there's a high degree of probability that there's intrusion on the rest of them but you can't see it. Chainplates invariably fail right where they go through the deck, where water has been trapped against the stainless in the absence of oxygen and caused crevice corrosion. So just because you don't see any signs of water intrusion below decks does not mean it has not happened.

While it's not a enormous project, it can be expensive; new chainplates themselves will cost $50-100 each at a machine shop, depending on size, thickness of the stock, and whether you have them polished or not. I have 8 and I'm looking at about $800 for new ones this coming month. Yours are obviously complicated by the embedded backing plates. The glasswork involved is not that complicated and would in fact be a good introduction to fiberglass repair if you don't have prior experience with it.

As to whether it's worth it or not for this boat, that's your call. That said, if there are other signs of neglect that mirror the condition of that one chainplate I'd consider walking if I was not prepared for the time and cost of a major refit.

[brownoarsman]

My understanding is that painting over chain plates can be bad for them. As Suijin mentioned, it can hide rust, but I believe it can also trap water/moisture, which would accelerate the damage seen on the other, non-painted one.

[UNCIVILIZED]

FYI, when replacing chainplates, one's better off to replace them with titanium, or (distant) 2nd place, duplex stainless. As both materials are much, much better at resisting corrosion, & stress cracking than is regular stainless. Such as 316, or 304/306.
I say as much, as both the material costs, & machining costs are only slightly higher. And titanium don't rust.

[Suijin]

Originally Posted by UNCIVILIZED

FYI, when replacing chainplates, one's better off to replace them with titanium, or (distant) 2nd place, duplex stainless. As both materials are much, much better at resisting corrosion, & stress cracking than is regular stainless. Such as 316, or 304/306.
I say as much, as both the material costs, & machining costs are only slightly higher. And titanium don't rust.

When was the last time you got a quote on titanium chain plates? I think "slightly" is an understatement. The material price has come down to be roughly on par with 316, and it fluctuates, but the fabrication cost, where most of the cost of new chainplates lies, is much higher. Hold your breath if you want them polished. And you have other issues to consider such as the fact it is more noble than stainless, ie. using titanium bolts, which is no biggie.

New well cared for stainless chainplates should last another 35 years. Titanium would be a waste of money on this boat.

[Stumble]

Originally Posted by Suijin

When was the last time you got a quote on titanium chain plates? I think "slightly" is an understatement. The material price has come down to be roughly on par with 316, and it fluctuates, but the fabrication cost, where most of the cost of new chainplates lies, is much higher. Hold your breath if you want them polished. And you have other issues to consider such as the fact it is more noble than stainless, ie. using titanium bolts, which is no biggie.

New well cared for stainless chainplates should last another 35 years. Titanium would be a waste of money on this boat.

No idea of current prices, but a few years ago I was quoting G2 Titanium plates pretty regularly. Our prices probably averages about 20% more than 316L plates.

Unlike stainless which must be polished for marine use polishing titanium is a purely cosmetic option. And yes polishing titanium is very difficult, but since it isn't necessary why bother. I normally recommended a sandblasted finish because millstock was a little to industrial for most people and was cheap, a mirror polishing job could cost more than the plates themselves.

Yes titanium plates should be mounted with titanium bolts. But their cost isn't terrible either.

[wesley]

Ooo titanium. I am already imagining the additional speed we'll develop by dropping the weight of steel, lol. It had never occurred to me that Ti was an option, but it makes a lot of sense. I'll certainly look into the option.

You've all been very helpful. I am definitely not afraid of removing/replacing chainplates (this boat's rigging has to be redone anyway), I just wanted to get an idea of whether the builder had made a terrible mistake with this construction method. It sounds like they made a reasonable choice (even if not ideal), so I'm reassured.

You all are wonderful!

-W

[Cheechako]

I assume you mean they are not thru bolted/no exposure to the outside of the hull?
It appears if that is the case that they embedded plates in the layup and tapped them for the bolts. I would probably want to remove, rebed and inspect all that but it seems like a good method, and loos like decent access also.

[Orion Jim]

Is there some reason why silicon bronze is not being considered? It would have been my first choice.

[wesley]

Originally Posted by Cheechako

I assume you mean they are not thru bolted/no exposure to the outside of the hull?
It appears if that is the case that they embedded plates in the layup and tapped them for the bolts. I would probably want to remove, rebed and inspect all that but it seems like a good method, and loos like decent access also.

Whoops, yes, I should have been more clear. That's exactly right - there is nothing on the outside of the hull, everything is interior or embedded in the glass.

-W