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Old 16-02-2009, 13:50   #1
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Chainplate fastener stain

I have a chainplate bolt that gets a brown stain that I have been trying to stop for some time. I re-bedded the flanges on all of the chainplates and the caprail scarfs as well. I have chased the stantion plates in the area and addressed the hardware in a large area around this location but I am beginning to think it is not rainwater but condensation that is causing the problem. We have not had a lot of rain in the past couple of months but when we get a cold spell and condensation forms the tattletale stain returns. Access to the chainplate is no easy task, I would have to saw and remove a large section of ceiling, and if inspection of one chainplate is to be done then it would be prudent to inspect them all. I have no intention of ripping out the interior. If in the future challenging offshore passages make themselves available I may re-think this. Does anyone have any suggestions on sealing this in any way? Tara is a vagabond 42, are the plates threaded or do they have a clearance hole with a nut? The issue with condensation will always be present to some extent and moisture is at times going to find it's way in this area.
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Old 16-02-2009, 16:43   #2
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If this is a Taiwan boat, the problems are probably low quality material. There is nothing you can do short of replacing all the metal with 316 stainless or bronze. In the interim, Oxalic acid will bleach out the rust stains.

Are these external chainplates that are bleeding down the hull?? Whether these are external or internal, I'd be concerned with crevice corrosion. Something that you can't really detect without removing the chain plate. Crevice corrosions in the absence of oxygen but in the presence of an electrolyte (salt water) so are hidden under or behind the outside surface. Very insidious. Our Westsail 32 had very robust 1/4" thick 304 stainless external chainplates. They always looked pretty shiny and no sign of cracks. When we got back from SoPac, the insurance survey reccomended removing and inspecting the chainplates for crevice corrosion and our insurance company required it. Thought they were nuts as the chainplates looked perfect. Long story short, removed the chainplates and found crevice corrosion after 4 years in tropical waters. The surveyor said it was quite common. He'd found it so often that he reccomended an inspection no matter what the age of the boat if it'd been in the tropics for more than a year.

Aloha
Peter O.

Aloha
Peter O.
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Old 17-02-2009, 06:31   #3
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Corrosion pitting

Aloha
Thanks for the input. A Taiwan boat it is. I know that vessels built in Taiwan have a history of substandard stainless alloys and the Vagabonds are no exception, tankage being the prime example, 304 stainless torch welded is fine for the short term but time and poor ventalation take their toll. The chainplates are not external and a ketch multiplies the problem. I know raising the issue of chainplates opens a pandora's box as there is no more important structural componant in the rig. Tara's rigging is 4 tears old and one of the reasons we chose her, during the survey I talked to the man who inspected the boat about the chainplates and it was a no access issue. Personally I look at how hard any equipment is pushed be it mechanical or structural and it seems that everything in my life was by someone's standards old or worn out. This brown stain from the head of a single fastener although worrysome won't drive me to pull and inspect the chainplates but I am aware of what it represents. I would like to seal or re-bed the bolt so I don't end up damaging the Awlgrip continualy cleaning and rubbing out the stain. I hope there is a better approach than daubing marine silicon on the head of the bolt.
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