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 Post subject: Our boat is sinking (slowly)
PostPosted: 15 Apr 2023 19:22 
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Navigator

Joined: 06 Sep 2020 10:08
Posts: 99
In February we were in the boatyard for a bottom job and decided to check out the centerboard. We found that the hinge and its bolts were badly corroded and needed to be replaced. Most of the old bolts broke off and left enough stainless in the keel that I had to drill and tap new holes (on a different hole pattern) for the new hinge. When I drilled those holes, they all started dripping water. Looking around the centerboard trunk I found some pretty big cracks and voids as shown in the pictures (bottom paint inside the trunk was a messy job).

We've also noticed since hooking up the bilge pump to a Cerbo GX digital input that the bilge pump turns on very regularly about once every 10 hours. I thought this was backflow from the pump's outlet hose refilling the sump. So I changed the bilge pump setup to eliminate backflow. But the float switch still triggers the pump every 10 hours.

Careful inspection shows all the seacocks and stuffing box are dry. The bilge sump has saltwater in it. Looking more closely I found water slowly seeping through hairline cracks in the floor of the bilge just aft of the sump (between the sump and the companionway). This is the source of the water that keeps activating the bilge pump.

So, the big questions are: is this a "normal" thing for our 40 year old boats? Is it unusually bad that we have water inside the keel? Has anyone found a good way to seal up the bottom of the keel and keep the interior dry?

Thanks in advance as always.


Attachments:
File comment: port side of the forward end of the trunk
forward port.jpg
forward port.jpg [ 2.06 MB | Viewed 0 times ]
File comment: starboard side of the forward end of the trunk
forward starboard.jpg
forward starboard.jpg [ 1.69 MB | Viewed 0 times ]
File comment: Another view of the aft end of the centerboard trunk
aft end 2.jpg
aft end 2.jpg [ 1.95 MB | Viewed 0 times ]
File comment: Aft end of trunk showing cracks
aft end 2.jpg
aft end 2.jpg [ 1.95 MB | Viewed 0 times ]
File comment: new hinge with new hole pattern
new hinge.jpg
new hinge.jpg [ 2.03 MB | Viewed 0 times ]
 
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 Post subject: Re: Our boat is sinking (slowly)
PostPosted: 15 Apr 2023 22:17 
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Skipper

Joined: 29 Dec 2006 09:38
Posts: 656
I am sorry that I can't really be an expert on this one because I have the deep fin keel version. But if you are absolutely sure this is not coming from a through hull or stuff box fitting, I would be worried--especially with a crack. I hope someone with centerboard experience (there used to be a bunch of them following this site) might be able to advise. I once had a tiny pinhole leak in the sink through hull that I chased for years as some keel boat leak--the rivulet was so freaking small and well hidden by the furniture that I missed it and it caused me to replace all the through hull fittings. Now dry everywhere except when it rains down the mast.
You might try going over to the Tartan email group and seeing if someone there could help. Joe Palmer is there and he worked for
Tartan for many years and is a fount of technical information.


 
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 Post subject: Re: Our boat is sinking (slowly)
PostPosted: 15 Apr 2023 23:37 
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Navigator

Joined: 06 Sep 2020 10:08
Posts: 99
I'm really sure the water isn't coming from a seacock or thru-hull. This photo doesn't look so great, but it shows a crack in the bilge just aft of the sump. At the bottom of the photo you can see the two wires going to the float switch. On the rightmost edge is the inlet hose to the manual bilge pump. Above the crack is dry; it looks wet in the photo, but that's just shiny paint. I can watch drops of water seeping out of the crack and dripping into the sump.

Does anyone have a good idea of how the centerboard keels are constructed? I'm guessing the outer surface of the keel was molded with the hull and then lead is placed inside. Is it lead shot potted in resin like the centerboard?


Attachments:
File comment: Crack in the bilge just aft of the sump
seepage in bilge.jpg
seepage in bilge.jpg [ 332.78 KB | Viewed 0 times ]
 
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 Post subject: Re: Our boat is sinking (slowly)
PostPosted: 18 Apr 2023 08:22 
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Skipper

Joined: 29 Dec 2010 10:24
Posts: 191
Mike,go back ten pages in General Maint. To Jan 2018, a long post by Zac Duncan on Holiday,(zdunc) about this topic and repairs his boatyard did.

_________________
Hull #6


 
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 Post subject: Re: Our boat is sinking (slowly)
PostPosted: 22 May 2023 19:51 
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Navigator

Joined: 06 Sep 2020 10:08
Posts: 99
Follow-up:

For navigation ease, here's the link to Zach's 2017 keel repair. I'm convinced we have the same situation, except our visible seepage is at the aft end of the keel instead of the forward end.

viewtopic.php?f=4&t=1338

Interestingly, the leak rate has been gradually slowing down. There's some yellowish gunk solidifying where the water has been dripping into the bilge sump. No idea yet if it's marine growth or some kind of goo coming out of the resin in the keel, but the flow rate is tapering off. We hauled the boat in February for bottom paint, internal halyards, partial centerboard rebuild, and some other stuff. Splash day was Feb 24. The bilge pump was running about once every 4 hours at first. I started tracking it carefully on April 10 when it was triggering once every 10 hours. Now it's only in the once per week range. Screenshot of the bilge pump counter attached below.


Attachments:
bilge pump run count.png
bilge pump run count.png [ 9.94 KB | Viewed 86 times ]
 
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