chainplate relocation help! (old ones FIBERGLASSED IN!) - SailNet Community
 
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post #1 of 9 Old 08-09-2009 Thread Starter
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chainplate relocation help! (old ones FIBERGLASSED IN!)

On my new to me hurley 22, the chainplates are fiberglassed over on the inside of the hull. Two of these are leaking. I have concerns that the others may be sitting in a nice fiberglass cup of water corroding away.

As I understand, the usual approach is to grind off the fiberglass covering the chainplates in order to unbolt and replace.

I have a different idea and would like opinions--

Can I simply cut of the tops of the old chainplates fill the holes in the deck with epoxy. Then, install new chain plates immediately next to (either fore or aft of) the old chainplates. Would this relocation by an inch or two adversely impact the integrity of my standing rigging. My hope is such a slight change shouldn't matter much? Opinions/advice appreciated
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post #2 of 9 Old 08-09-2009
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Such small changes in location will not alter thr integrity of your rigging. Another alternative might be to install the new chainplates on top of you old ones. After closing the gap on top of your olda chain plates, you might drill holes through the sides of your old chainplaes ant attach the new ones to the old ones.
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post #3 of 9 Old 08-09-2009
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Have you got a picture? I would suggest taking the current chain plates out and refitting them back where they originally where designed for. It is not that difficult a job. I had to do this on my islander. But without a picture it is hard to say.
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post #4 of 9 Old 08-09-2009
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Why do you think they are deteriorating and need to be replaced? I would expect the chainplates to be made of stainless and the water they have been sitting in is probably a mix of fresh and salt and whatever stuff has leached out of the glass laminate. I (like Sailking1) had to address an issue with the lower chainplates on my Islander. After reglassing one lower chainplate I addressed the others (and that one as well) by simply:

1) drilling a small drain hole into the void at the base of the chainplate from inside the boat. This will drain any accumulated water.

2) making a best estimate of where the centerline of the chainplate was and drilling thru the chainplate and installing stainless bolts along that centerline. This basically made the bolts the effective holding of the chainplate and the fiberglassing the backup. Nice clean straight lines and carriage bolts, set in Sikaflex, with polished heads visible on the outside of the boat. Inside nuts are polished acorn nuts with stainless washers.

3) removing the stainless collar around the top of the chainpate (this is the finish cover where any difference between the original hole and the chainplate was hidden) and digging out the old caulking and recaulking with Sikaflex; then re-installing the covers.... gluing them with the Sikaflex.

4) leave the small hole open at the bottom on the inside of the boat so that you will see if you ever have to re-address the sealing issue.

This has worked well for me for many years. Hope it helps,

Wiley
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post #5 of 9 Old 08-09-2009 Thread Starter
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Weily1,
How can you tell if your chainplates are in good condition under the frp? As I understand water without oxygen is the perfect environment to rust stainless...
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post #6 of 9 Old 08-10-2009
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Mkrautha,
Well, in my case I physically got to examine the one chainplate that I reglassed. It was very good condition. As for the environment "water without oxygen being the perfect environment to rust stainless". I had not heard that and would appreciate a link to a site where that is stated to be a problem. Here is a link to a site which, although not exhaustive, covers the basics of corrosion of stainless steel and the conditions creating corrosion. Stainless Steel - Corrosion Resistance

I do not know the dimensions of your chainplates are nor of the alloy of which they are made but I would suspect they would most likely be type 304 or 316 stainless both very common in the industry. If you feel that they are patently unsafe and pose a danger to life or limb or property by all means discontinue use of the vessel until you are satisfied by whatever means that they are safe.

I will say I think perhaps you are over-thinking the problem. It's a 22 ft boat not a America's Cup racer. Stainless is quite strong, and the loads in this case are not phenomenal. Good luck with whatever you decide to do.

Bests,
Wiley
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post #7 of 9 Old 08-11-2009 Thread Starter
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stainless will corrode if conditions are right

Weily,
You are probably right-- I am likely overthinking this.
Nonetheless, stainless will and does corrode. Generally corrosion is prevented on stainless because oxygen combines with chrome in SS to form a protective layer, but in the absence of oxygen, esp. in an electrolyte like salt water, this is not possible.
I believe its called crevice corrosion and fbrglassed chainplates are just about perfect for this. You can do an internet search and find many people who have had this problem.
To learn more about SS corrosion check out this site:
Corrosion, stainless steel

I will wait until this winter or next to tackle the chainplates. I'll keep you posted.
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post #8 of 9 Old 08-11-2009
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While I agree that the boat is small and the loads are not very high, crevice corrosion is a very real problem with stainless steel in marine environments.
That's one reason why you seldom see stainless through hulls (and shouldn't use if you do find them). Here's a pic of the results of this type of corrosion and a link to the article it came from.
Google Image Result for http://www.passagemaker.com/DesktopModules/Galleries/thumb.ashx?id=5148&maxDimension=425

Brian
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crevice corrosion.jpg  
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post #9 of 9 Old 08-11-2009
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mk, fiberglass work on something that small isn't much of an ordeal. Check out West Systems Epoxy (Gougeon Bros.) they'll probbaly have a detailed PDF of the project on their web site, and they will gladly talk you through it if you call their tech support number. Right down to estimating the amount of materials and the cost of them, at retail price, to give you an idea how expensive the job might be. (You are free to buy them locally and discounted, of course.)
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