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Old 19-10-2009, 12:45   #1
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Wood Backing Plate for Thru-Hull Soft and Rotten

I have a Coronado 27. I recently was actuating all the seacocks valves and noticed that the thru-hull fitting for the galley sink drain was not in very good condition. When I tried to actuate the seacock the whole assembled flexed a little bit which made me notice that the wood backing plate was soft and flexing a bit. It's not leaking but it sure looks scary espcially since it's below the water line. Is there anyway to fix this without hauling out ? I hear git-rot might help but that's meant for dry rotten wood and this wood is wet-rotten.

Any ideas ?

-tavis
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Old 19-10-2009, 13:03   #2
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Two sites I have read that use about the same approach.

Seacock installation
Compass Marine Project Articles Photo Gallery by Compass Marine at pbase.com

One of Don Casey's "This old boat" amongst others has excellent directions as well.
This Old Boat - Google Books
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Old 19-10-2009, 13:04   #3
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Wow. Why would someone put a wood backing plate?
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Old 19-10-2009, 13:21   #4
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Wood backing plates were the traditional installation with a flanged seacock bolted through the hull. I guess to spread the load out. (?) Unfortunately then people just put plywood in there sometimes. Which might be ok if saturated with resin or epoxy...
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Old 19-10-2009, 13:22   #5
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Why? Cheap and Easy or ignorance. Take your pick.
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Old 19-10-2009, 13:27   #6
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Yes I googled it and it seems that people do do it. The compas site looks usefull. I had no idea about nps vs t
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Old 19-10-2009, 14:23   #7
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Quote:
Originally Posted by dubhouse View Post
I have a Coronado 27. I recently was actuating all the seacocks valves and noticed that the thru-hull fitting for the galley sink drain was not in very good condition. When I tried to actuate the seacock the whole assembled flexed a little bit which made me notice that the wood backing plate was soft and flexing a bit. It's not leaking but it sure looks scary espcially since it's below the water line. Is there anyway to fix this without hauling out ? I hear git-rot might help but that's meant for dry rotten wood and this wood is wet-rotten.

Any ideas ?

-tavis
Answer is NO, you need to haul it and repair the problem. Anything you use to try to save the rotten wood is a bandaid fix to be fixed correctly later.
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Old 19-10-2009, 14:36   #8
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I will be changing several thru hulls with the boat in the water later this year or early next year. I'll let you know how it goes.
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Old 19-10-2009, 14:48   #9
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Don't screw around- Pull it and replace it with a new one (solid timber, preferably something rot resistant- teak, cypress etc.) Soaking it with resin won't displace the water in the wood so it'll still be squishy.

Umm, it shouldn't be wet anyway so you'll need to check for seepage from your seacock or lamination problems with the hull under the fairing ring.
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Old 19-10-2009, 15:15   #10
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Wink I have to agree with Don

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Answer is NO, you need to haul it and repair the problem. Anything you use to try to save the rotten wood is a bandaid fix to be fixed correctly later.
Don is absolutely right.
Haul it, repair it properly with a new proper sea cock and move on.

Anything below the water line is too improtant to your safety to play around with. Fix it right, then splash the boat knowing your safe even if the seacock is a little hard to move next time it won't come off in your hands.

When I say "Proper Seacock: I mean a bronze one with through bolts.
Make sure you drill the holes oversize then fill in the area with new epoxy filler. Redrill the holes through the epoxy to the right size and install everything with 3M 5200 using the seacock as a drill jig.

Do it this way and you'll never have an issue again.

Need step by step directions? Buy a copy of Nigel Caulders book - it's even got pictures of how every step should look.

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Old 19-10-2009, 15:26   #11
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^^^ Everything right except the 5200- use boatlife or similar as someday, you may want to remove it.
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Old 19-10-2009, 16:43   #12
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^^^ Everything right except the 5200- use boatlife or similar as someday, you may want to remove it.

I change all the seacocks in my CSY 44 4 years ago, and i find wood backing plates , i rip off all the backing plates and made donuts with a fiberglass panel, very funy, and i use 3m 5200 because is a serious stuff in underwater fittings, another option is to make the donuts with a tick teflon panel.For me is the answer to spread the load in the tru hulls and have a free rot material. Cheers.
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Old 19-10-2009, 16:58   #13
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I also saw someone that used a glass bowl to use as a mold for a backup plate.
After sparying it with mold release they placed the bowl in the hull at the same level as the intended location. Poured in Epoxy and let it cure overnight. The next day the poped it out of the mold and presto it matched the angle of the hull ready to be epoxied to the inside then used as a solid epoxy backup plate. Looked like a great soultion unless the deadrise of the hull is too steep in the intended location. You could also use fiberglass and epoxy buildup but it would need to be out of the water longer to have everything set before your drilled and screwed everything together.

Either way you have a rot free solution that will never get soft again.

I do Like S &S comment about using something less permenent than 5200 but I don't like boat life since it turns chauky and breaks down in UV after time. Maybe 4200 would be a better choice.

Rick
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Old 19-10-2009, 18:54   #14
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Thanks for the replies. Here is a photo for anyone curious.
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Old 19-10-2009, 18:56   #15
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As another option, we can probably do without this thru-hull all together. Could I seal it up with a fiberglass plate from the inside ? Are there other good ways to permanently seal up thru-hulls. I would feel better with one less below waterline thru-hull anyway.
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