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Old 24-07-2017, 04:49   #46
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Re: Island Packet Chainplate Replacement

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Originally Posted by CaptRory View Post
OK, As an IP owner that has been through this, I am going to weight in. First "encapsulated" means? The three IP chainplates are made of 304 stainless, all welded to a horizontal cross member and glassed into the hull. Picture glass strands coming up from 3 feet of hull, around the over and around the cross members at each tang and back down into the hull. It is a very robust installation. The problem was, prior to '97 models, there was no way for water that made it through the bedding to escape, hence setting up anaerobic oxidation. The fix is to take the furniture out, exposing the hull and grinding out the glass, releasing the old assembly and replacing it with a new 316 stainless assembly. This is more resistance to corrosion but also more brittle so they are constructed of a larger dimension. Post '97 models and those that are properly replaced have drain holes that allow any water out of the pocket, so if you fail to maintain your bedding, your cheerios will get wet and you will know you have a problem. Mine lasted 23 years and I expect the new ones to last forever.
That is IP's take on it. But they are wrong.

Adding weep holes as an indicator is a good idea, the problem is that the only real remediation once the chainplates get wet with salt water is to pull them out, flush them with fresh water, and then reinstall them. Because any amount of salt that is allowed to remain against the metal can pull enough water out of the air to create a galvanic cell.

The problem is that chloride ions (ie salt) in a water solution can locally depassivate stainless. Then because passivated and non-passivated stainless are galvanically incompatible they will literly eat each other across the granular fault line. It's called intergranular corrrosion and it is pretty insidious.

The only thing that 316 buys you is a slower rate at which this happens and a higher temperature at which it starts. For 304 I think the critical temperature is around 0F for 316 its 40F. Or somewhere around there.
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Old 24-07-2017, 06:52   #47
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Re: Island Packet Chainplate Replacement

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A hundred years from now I see some old dude standing there holding a titanium tang in his hand. "Great chain plates but the yacht must have been a POS."


Or at least as likely, wonder why they wasted so much money putting in Ti in such an old boat Just it wasn't much more money, and that's the key to me.

I've made my living to some extent by maintaining things, I have developed an attitude of going through systems as I call it.
What I mean by that is say I blow a cooling hose, many replace the hose and drive on. I replace all hoses, flush the cooling system, new thermostat, clean heat exchanger and new impeller.
Guy who changed the hose will do everything I did, just gets to do one item every month or so, way I do it, I'm done with the cooling system except regular maintenance for at least 5 years.
That why with this old boat I started this chain plate thing with pulling the mast to remove the step to have it cleaned and hard coat anodized, then everything in the mast is being replaced, lights, antennas, wiring etc, and all running and standing rigging.
I hope to never pull the mast again, and with the Ti chainplates, never do anything with them again except maybe reseal them if they begin to leak, even if get lucky and get to stay on the boat a good long time.
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Old 24-07-2017, 06:58   #48
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Re: Island Packet Chainplate Replacement

CaptRory,
Who did yours? It looks like a single piece chainplate was put back in just like it was originally built? Mind telling us what it cost ?
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Old 24-07-2017, 07:22   #49
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Island Packet Chainplate Replacement

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Some more pics. I should add...an old boat that has been well maintained, that is regular rebidding will not have a problem.


I'd only add as to an observation that your failure seemed to be inside of the bedding, and not below deck, where the bedding will prevent the chainplate from getting worse. I don't think in your case the bedding regular replacement would have done much good?
Where yours failed would be I think worst case as the chainplate is completely in two, a failure in the tie bar should still have significant strength left from the angle and hull to deck joint. I think maybe I have a failed plate as it seems my port aft say as looser than I remember. We will know in a week or so I think.

What was the result of your failure? What were you doing when it let go? I've heard of them failing with almost no strain on them and I assume as a result if that, no damage to the boat, and I have heard of them letting go under heavy loads and being dis-masted.
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Old 24-07-2017, 07:25   #50
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Re: Island Packet Chainplate Replacement

A64 to make you feel a little better about your extra $K for the titanium, here is a 2004 IP370 that has not only replaced chain plates but all the thru hulls. Reckon he stuck the mast in a power line and left it there for a couple of weeks.

Turner Marine Yacht Sales, Inc. (Mobile, AL)
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Old 24-07-2017, 11:21   #51
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Re: Island Packet Chainplate Replacement

Great thread. We've been seriously considering changing to an IP31 centerboard & it's good to know what we'd be facing.
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Old 24-07-2017, 14:29   #52
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Re: Island Packet Chainplate Replacement

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Like aluminium Ti can be galvanized, and it can be done to add color at the same time, but again is a purely cosmetic issue.
Galvanized??? Did you mean anodized? Never heard of galvo on aluminium or titanium!

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Old 24-07-2017, 14:30   #53
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Re: Island Packet Chainplate Replacement

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maybe reseal them if they begin to leak, even if get lucky and get to stay on the boat a good long time.
Check the sealant once a month. When it starts to look less shiny, or has begun to appear somewhat crazed, dig it out and re-do it. It is a routine maintenance operation if it was done correctly. You might even want to take a pic when they are installed, so you have the record for comparison sake. Make sure the yard guys do it when they're doing the job.
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Old 24-07-2017, 14:38   #54
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Re: Island Packet Chainplate Replacement

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Galvanized??? Did you mean anodized? Never heard of galvo on aluminium or titanium!

Jim
Woops. Sorry, yes that should be anodized.
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Old 24-07-2017, 16:08   #55
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Re: Island Packet Chainplate Replacement

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Check the sealant once a month. When it starts to look less shiny, or has begun to appear somewhat crazed, dig it out and re-do it. It is a routine maintenance operation if it was done correctly. You might even want to take a pic when they are installed, so you have the record for comparison sake. Make sure the yard guys do it when they're doing the job.


With Ti it won't matter, the only problem with leaky plates will be my corn flakes getting soggy. Ti is simply not going to corrode significantly in my lifetime, not in salt water at ambient temps.
Or I have been sold a bill of goods
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Old 24-07-2017, 16:41   #56
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Re: Island Packet Chainplate Replacement

What is the surface texture in the bond areas?
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Old 24-07-2017, 17:34   #57
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Re: Island Packet Chainplate Replacement

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What is the surface texture in the bond areas?


I have not seen them, but as I asked for bead blasted, I assume sort of slightly roughed up, maybe not enough to help with adhesion, but likely wouldn't hurt either.
All of the strength comes from the hull to deck joint and of course the unidirectional glass, I do not think anything comes from adhesion of the metal itself.

Now it appears that IP originally put the unidirectional glass on the T bar and Mack Sails above the angle. I see no difference in the load path myself. They will be installed with the mast in so it can pull them into place, so the strands will be compressed to fill any gap if it exists between the angle and the deck.

I assume IP did it that way as it's easier to lay the glass, I do not know why or if Mack Sails does it differently, just looks that way in the video.
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Old 24-07-2017, 17:54   #58
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Re: Island Packet Chainplate Replacement

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With Ti it won't matter, the only problem with leaky plates will be my corn flakes getting soggy. Ti is simply not going to corrode significantly in my lifetime, not in salt water at ambient temps.
Or I have been sold a bill of goods
Fwiw... Titanium has been tested for crevice corrosion in sodium chloride solutions to see how long it will take to effect the metal. In order to accelerate the test they use boiling NaCl (20% NaCl @ ~1450C) and it still takes at least 10 days to initiate corrosion. At temperatures below 75C you can immerse G2 Ti in pure liquid NaCl without any concern over SCC (Stress Crack Corrosion).

In saltwater the critical temperatures (the minimum temperature for corrosion to occur) for G2 are 120C for SCC and 160C for poltice corrosion. For 304 the two temperatures are -20C and 2C, for 316 its -10C and 10C.
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Old 24-07-2017, 18:02   #59
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Re: Island Packet Chainplate Replacement

Full disclosure, Stumble more than anyone got me going the Ti route.

I don't know why on something simple like a chainplate that doesn't require a lot of machining why Ti isn't used more often.
The price is a fraction of what it once was, perhaps we are just conditioned to think it's very high priced?
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Old 24-07-2017, 18:17   #60
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Island Packet Chainplate Replacement

Here is a chunk of Ti, an AH-64 main rotor blade grip, circa late 1980's before the fall of the Soviet Union, maybe 30 lbs and is extensively machined, incredibly expensive, but the data plate that was glued on, fell off, so it is scrap. The serial number is written on it in grease pencil.
It was my door stop for many yearsClick image for larger version

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