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Old 01-01-2006, 13:43   #1
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Chainplate knees

I have a small amount of brown seepage from one of my port chainplate knees, and suspect I need to get in there and do a rebuild.

The chainplates and knees have been completely encased in fibreglass, and a previous owner (I think) has added external backing plates.

Just wondering if anyone has experience with this type of a project? I've found one site on the web (different type of knees and boat);

http://www.alohaowners.com/pages/pro...hainplates.htm

Anyone know of any other links?

Rob
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Old 01-01-2006, 14:04   #2
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Source

Have you actually found the source for the brown seepage. If it's the bolts, you may only need to replace them.

I had a similar probelm and drilled out the knees & plates with a slightly larger hole (went from a standard to metric size). It resulted in a very tight fit and while drilling the new holes, the resulting shavings showed no sign of internal deteriation.

Slightly enlarging the holes may be all that you need.

Good Luck
Roger
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Old 01-01-2006, 14:08   #3
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encapsulating SS where salt water can enter is not a good thing. If there is any wood in there, you may have a rot situation as well. SS needs air to keep the errosion from eating away at the material.

If there is bleeding, that obviously means salt water has been getting in there and doing it's job. The PO who put external backing plates, must have known there was a problem to start with. How long have you owned the vessel?

If you could post some pictures, WE here can get a better idea of what your dealing with. It may be serious or maybe minor. But we do need more details.

Personally, I'd pull out the old CP's and replace them with external plates. Which involves a little extra work for the modifcation. But, One can keep on eye on them and do inspections.

There was a big discussion on CP's a couple of weeks ago and previous to that. Maybe these may answer some of your needs.

http://cruisersforum.com/showthread....ht=chain+plate

http://cruisersforum.com/showthread....ht=chain+plate

http://cruisersforum.com/showthread....ht=chain+plate

http://cruisersforum.com/showthread....ht=chain+plate

.................................................. .._/)
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Old 01-01-2006, 14:14   #4
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Source of the brown ...

Thanks for the response.

I like that idea about checking for the condition of the bolts before planning too far ahead. I haven't looked for the source of the stain, although I've read that it often indicates rotting wood in the knee.

The encasing fibreglass has a 2-3" fine crack in it, from which the liquid has seeped. The previous owner allowed the bedding under the toerail and the chainplate cover to deteriorate, and I think water must have seeped into the knee structure and frozen.

I'm heading out to the boat tomorrow, and will try to get some pictures.

Rob
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Old 01-01-2006, 14:20   #5
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External chainplates

Thanks for the response, delmarrey. I read through the CP thread before posting, I must admit.

I will get some pictures. I'm not keen on the idea of adding external chainplates, partly for some of the reasons mentioned in the CP threads, and partly for aesthetic reasons.

I'm not sure how they would look on my boat, and I've never seen a Corvette with external CPs to get an idea.

Rob
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Old 01-01-2006, 14:27   #6
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If you own a moisture meter, check the readings at knees and surrounding deck area.
It will be interesting to hear your answers to delmarrey's questions.

Larry
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Old 01-01-2006, 14:51   #7
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We always say that Stainless requires air to create itís passive film (chrome oxide); but the film forms very quickly in any oxidizing atmosphere, such as air, fresh water, or many other fluids that contain the required oxygen.
When deprived of oxygen (or when another species, such as a chloride competes as an anion), stainless steel lacks the ability to re-form itís passive film .
In seawater, chlorides from the salt will attack and destroy the passive film more quickly than it can be repaired, unless there is also good exposure to air.
This is not necessarily the case in a fresh water environment.
Iíd look to another cause (tho' certainly examine the S/S fastenings) for the coloured seepage - perhaps rotting core.
FWIW,
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Old 01-01-2006, 19:27   #8
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No moisture meter, I'm afraid, Larry.

Gord, I've been assuming based on past DIY reading, that the source of the stain is rotted wood within the knee structure. I don't know for certain if there is a wooden core, though - anyone know if they were ever built in some other manner?

Rob
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Old 01-01-2006, 19:51   #9
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Rob - Consider buying a meter. Best way to monitor your boat, locate possible water intrusion, avoid what you already seem to have. Mine is an Aquant BLD5760 made by GE, recommended by a surveyor.
As to the knees - gotta be plywood, but I would not instantly jump to "rotten". First issue is on deck where the water is getting in - not always where we first suspect. Second is to pull a few bolts and inspect. Third might be a few pilot holes to determine if there is good wood around the plate. Bleed may be from corrosion or bedding only.
The possibility that someone already added backer plates does not sound good. Hope you get lucky.

Larry
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Old 01-01-2006, 20:12   #10
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Thanks for the suggestions

I'll post an update after tomorrow's visit to the boatyard - here's to hoping it doesn't get colder than it already is (-10C, not too bad). Nothing beats mucking about in a boat, but it does lose some lustre when you can't feel your toes.

Rob
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Old 03-01-2006, 15:41   #11
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Photo problems

I have taken some photos, but can't get the Photo Gallery upload button on my screen. I've enabled cookies, etc., but still no button.

Any suggestions?

Rob
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Old 03-01-2006, 16:36   #12
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I don't see an upload option either. This site has been purchased and new owner plans upgrade and changes shortly, so that may affect options for a while.
Did you pull any bolts or discover any additional info ?
Larry
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Old 03-01-2006, 16:57   #13
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leeway,
Try using the IMG vBcode when composing your message.

this will place the image in your message
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Old 03-01-2006, 19:28   #14
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More info

Larry, I didn't get a chance to pull the bolts, but I'll be interested in opinions once the picture is posted.

Looking at the installation now, I'm not sure but what the backing plate may be original - it's essentially an extension of the chainplate to allow it to be bolted to the knee further down the curvature of the hull.

Mario, I think the IMG code still requires the picture to be uploaded to a page somewhere.

I could email the picture to someone else to post ...

Rob
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Old 03-01-2006, 19:52   #15
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When you click to reply, down under message box there should be Options and then Attach file. If you click on the Choose File button it should let you select a photo. I usually get the photo on my desktop because it is easy to find. Larry
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