Steel plate between keel bolts and bilge - leakage

[Seagoon]

I have a 2002 Bavaria 38, to which the previous owner has added some stainless steel plating between the hull inner in the bilge and the keel bolt nuts - see photo at https://photos.app.goo.gl/CqvQtas3XRBQw76K2

This was due to reports that these model of Bavaria's occasionally lost their keels at sea, installation of the plates being to strengthen the site.

No major issue with the concept however a small leak appears to have developed over the past year. There is no leak at all when the boat is stationary, however a few days sailing at sea will see a few litres of salty water appear in the bilge near the keel bolt fixings in the photo. I have eliminated all other sources of leakage such as though-hull fittings and hatches, and I am pretty sure I have identified the plate in question - in the photo if you blow it up you can see what appears to be cracking around some of the sealant.

During a recent lift-out, I had the boatbuilder tighten the keel bolts to manufacturer's specifications, and put sealant around the bolts and nuts, and replaced the seal around the keel where it faces onto the hull.

It appears that what is happening is the sealant around one of the plates has failed, and when the hull flexes normally when sailing, this is enough to see water seep in. Over a period of days, this adds up.

Before I lift her out again and get the shipwrights onto the plates, I thought I'd see if anyone seen this before?

Cheers

[Spirit of Mary]

I am sorry to say, but I expect when it is seawater there is a leakage in the keel to hull connexion. This connexion should be fully watertight in order to keep the bolts away from the seawater. The bolts Bavaria uses are SS. When SS is in an enclosed environment in contact with seawater, there is a high risk for pitting corrosion, which you cannot inspect. The bolts loose its strength. To my opinion the only way to correct the situation in the right way is to drop the keel and clean everything, inspect the hull for damage (grounding of keel?), inspect bolts and reseal the connexion etc. Not a DIY job. Also the mast needs to be removed when the keel is to be removed. Expensive 3 - 5 k job.

[Symphony]

There are no reports of keel loss on that type of Bavaria. The one you hear about was a completely different design. So those extra plates are completely unnecessary and if it were my boat I would remove them.

If there is sea water coming in when you are sailing that can only come in through the joint between the keel and the hull. You say this has been resealed, but that can only be done properly by removing the keel from the boat, not just putting sealant in the external edge of the joint. Likewise putting sealant around the nuts will not achieve anything.

Suggest you have the boat hauled, rest it on the keel, check the joint externally for any sign of leakage - often there is rust streaks down the keel (if it is iron), then remove the nuts and plates where you think there is a leak past the stud. What you do then depends on what you find.

I would be very surprised if just flexing of the keel when sailing allowed water in unless the hull/keel seal has failed, so if you find seawater under that plate you may well have to remove the keel.

[tckearney]

Before you go to extremes, are you 100% sure it is seawater and coming from the keel bolts?  I had a similar problem.  It ended up being very salty fresh water in the bilge.    The only way I could think of to prove the keel bolts are not leaking was to silicone a 2” length of 70mm plastic "gutter down pipe" around each bolt.  Making a sort of cofferdam.    I still had water but not inside the cofferdam.   Turned out it was hot water boiler and the water had gotten into the hull frames picking up salt residue on the way.  It took weeks of cutting old towels and wire coat hangers inside the moulded frames to clear it all.   Just to prove it I even had two small sauce pans on a slow burner to reduce the water down to just salt, One bilge water and one seawater.   Although you could not taste the difference you could definitely see the difference in the  pan.

[Symphony]

I agree that it is unlikely to be seawater coming up the keel studs and more likely to be water flowing from the grid as the boat moves when sailing. The seal between the keel and the hull does not rely on the sealant under the plate.

The plate really needs removing and all the sealant cleaned off so the studs can be inspected.

[Ziffius]

http://bavariayacht.org/forum/index.php/topic,1216.msg6730.html#msg6730

Is the thread To read through as the reporter also thought he had keel bolt leakage.

[Craig]

Symphony is correct. It was the Match 38, a racing version, that had a few keel issues, not the cruiser version.

What I would be worried about is "Why did the previous owner put in the plate".  Was it purely a precautionary measure, or did he have a problem then do this as a repair.

It needs to be checked out professionally, probably involving a haul out and removal of the keel.

The annexure to the Cheeki Rafiti MAIB report suggests that if you suspect a delamination, then this will require investigation while the boat is suspended in slings with the keel off the ground. Delaminations are more difficult to detect if the boat is resting on the keel and the delamination is compressed. Some repairers merely tap the inside of the hull to hear a hollow sound. Others may use ultrasound to detect any delamination.

Whilst pitting of SS may occur, it is more likely that delamination will cause a keel failure. I recall the ISAF report about 10 years ago investigated about 80 keel incidents. Only 2 were the result of keel bolt failure. 

Best to get an expert, rather than a local repairer look at anything involving leaks around the keel.

Craig
"Shirley Valentine"
Gold Coast
Australia