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Lower Chainplate replacement (photos)

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Jonathan Cuff
Navigator

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Cayman Island
173 Posts

Initially Posted - 07/26/2004 : 11:54:58

Hi guys

Some of you may remember I had a lower chainplate failure about a month ago. The new chainplates arrived from CD. It seems my boat already had the new style 1/2" chainplates as we did not have to drill out the holes in the deck. The deck did not appear spongy when we checked. What I'm hoping the photos show is that although the chainplates may look ok, particularly below decks, corrosion takes place inside where the air can't get at it. When we tightened the existing chainplates as a way of testing them 2 of the 3 remaining ones failed, and were almost complately rusted through. I'm just glad they all didn't go when one went.

Cheers JC

Pie Sees 2 C25 #5686 1987 SR/WK

Edited by - on

Leon Sisson
Master Marine Consultant

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USA
1893 Posts

Response Posted - 07/26/2004 : 18:54:43

Jonathan,

Great photos, excellent advice, and a fine example of why stainless steel needs fresh air to work right.

-- Leon Sisson

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Frank Hopper
Past Commodore

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Pitcairn Island
6776 Posts

Response Posted - 07/27/2004 : 20:21:33

I would like to steal these picts for the tech tips.

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lcharlot
Master Marine Consultant

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Antigua and Barbuda
1301 Posts

Response Posted - 07/28/2004 : 08:33:33

I have never seen corrosion this severe on stainless steel! What alloy are these eyebolts made of? I would have assumed they are marine grade A-316 (18% chromium / 8% nickel), but perhaps they are A-304, a cheaper alloy with less corrosion resistance than 316. Is there a widespread problem of failure of these bolts on Catalina 25's, or is this a rare, once-in-blue-moon occurance?

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Tony Dillon
Navigator

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USA
168 Posts

Response Posted - 07/28/2004 : 10:36:14

I was at Brion Toss's place in March. He had several examples of this kind of chain plate failure to show his clients.

The problem results from water (especially salt water) getting into the area where the chain plate passes through the deck and being trapped there. Making sure that all of the chain plates are properly bedded is the best way to prevent this kind of failure. The lower ends of the stays and turnbuckles are also higher failure areas where salt tends to build up. About all one can do there is to check them closely and rinse them with fresh water to remove as much salt as possible.

In the photos there are a few clues. There is a fair amount of corrosion on the top of the flange (which does seem odd for 316) and some rust stain on the deck. It looks as thought the nut had some corrosion visible just under the backing plate.

At any rate it is good that no one was hurt and gives us all (including myself) insentive to give the rig a good close inspection.

A piece of brown 3M scrub works wonders for cleaning up the stainless to make any cracks more visible.

Removing riggers tape is a good plan also. I pulled all the cotter pins from the turnbuckles on Mental Floss and replaced them with a piece of stainless TIG welding rod shaped like a "U" threaded from the upper to lower cotter pin hole with the ends on the inside of the rig, then tucked back into the center of the turnbuckle.

Edited by - Tony Dillon on 07/28/2004 11:06:07

Jonathan Cuff
Navigator

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Cayman Island
173 Posts

Response Posted - 07/28/2004 : 10:40:32

Hi

The chainplates were definately stainless, but of what grade I couldn't tell you. My boat is a 1987 SR/WK, and already had beefed up backing plates and 1/2" bolts through the hull. I guess the tropical climate the boat has lived in hasn't helped. Whether an old owner has retrofitted chainplates of a lesser quality I don't know.

Cheers JC

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Frank Hopper
Past Commodore

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Pitcairn Island
6776 Posts

Response Posted - 07/28/2004 : 17:12:12

I wonder if he used his rig for an antenna, any signs of current being directed through it? Any short to grounds/mast in your mast wiring? Something ate that rigging and I would be very nervous about my swage fittings if I were you.

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Jonathan Cuff
Navigator

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Cayman Island
173 Posts

Response Posted - 07/29/2004 : 10:36:35

There is a short in my mast wiring as the lights flicker and go and half power depending on what combinations I use. The power is all getting to the deck socket ok, and I have replaced all the nav lights themselves. Any ideas on where to check next?

Cheers

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Notice: The advice given on this site is based upon individual or quoted experience, yours may differ.
The Officers, Staff and members of this site only provide information based upon the concept that anyone utilizing this information does so at their own risk and holds harmless all contributors to this site.