Rust stains coming from my hull to keel join

Puggy

Puggy

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Hello All,

I am seeing rust streaks coming from the keel to hull join on my Nauticat 43 ketch. The hull has a Cuprotect covering that was applied after treatment for Osmosis in 2008. The boat has been out of the water since December and was steam cleaned about 3 weeks ago, but the weeps are still damp. I am not sure whether the keel is iron or lead, and as my boat has deep bilges there are two large water tanks on top of the keel bolts so I can easily inspect them without major surgery.

Anyone got any thoughts what is causing this, how serious it is and thoughts on remediation? I have attached a couple of photos showing the forward section of the keel where the ballasted part joins the hull moulding.

Thanks in advance

Piers
 
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The rust is coming from inside the joint between the keel and the hull. The sealant between the two has degraded to allow water to penetrate. It would be worth checking the areas adjacent to the keel bolts internally to see whether the rust has come right through.

Renewing the sealant without dropping the keel off the hull is really not worthwhile. If you injected it as the boart is now it would not adhere due to the water and the gap will open as soon as the boat is not standing on the keel. The only proper answer is to lower the keel, clean it up and rebed it. If water is not getting into the boat you will probably be able to leave the job until next winter but I would check that keel bolts are tight, in which case it is probably worth doing the whole job in view of having to remove the tanks.
 
Veli Kärjä

It would be worth speaking with Veli Kärjä at Nauticat in Finland as they'll have the yacht design drawings and could advise on build of the keel. They may have experience of other yachts experiencing similar issues. I have Veli's contact details here but won't post them on the public forum - PM me if you would like the details.

rob
 
Simply solution would be to let it fully dry out then clean back an inch or so above and below the joint then glass a 2" strip GRP over the joint. Might do this with mine next year.
 
It seems to be pretty common with iron keels. We noticed the same thing with our boat when she was out the water last winter. I read around and got a lot of advice and in the end decided to leave it till the following lift-out so we could do some sailing. Sealed it all as fully as possible from the exterior and dunked it back in, having checked all the bolts etc.

I also read an article on the Westerly website about someone resealing their keel having only dropped it an inch or so - just enough to dry it fully, prepare the surfaces, and apply the primer and sealant. Rather an easier and less costly job than removing the whole keel, and no reason it shouldn't work as long as you can *definitely* get sufficient access to the mating faces to do all of the above thoroughly.

From reading around it also seems likely that cast iron keels of a certain age may well need this doing every so often...

Our surveyor, btw, regarded it as evidence of movement between the keel and the hull, and assured us it meant that the GRP lay-up in the keel boss was insufficient, and that we needed to reinforce it internally with extra floors and stringers. A lot of people disagree with this in the case of our particular boat (which happens to be a fin-keeler and not a bilge, which is also relevant), but it's worth bearing in mind.

Best of luck,

Steve.
 
Thanks Steveparker and daveyw. I think I am coming to the conclusion that a keel drop and reseal/new keel bolts is probably on the maintenance list for next winter. My original post had a typo: I *can't* access the keel bolts easily as they are under two 250 litre water tanks sat on the keel, these tanks are located by some sort of industrial expanding foam.... So checking bolts is a big project and I might as well do the whole lot at the time.
As regards your surveyors comments, I can't see any evidence of movement (no cracking in the hard Cuprotect layer covering the join) and almost to a fault the Nauticats seem to be over engineered: 24 tonnes on 46 feet on the deck..., so I am fairly sure that strength is not an issue. There is no evidence of hard impact however I suppose you just don't know in a 25 year old boat.

Interesting idea daveyw, and very cost effective, i just wonder whether I would be sealing in the moisture though, what do you think?

Best wishes
Piers
 
daveyw said:
Simply solution would be to let it fully dry out then clean back an inch or so above and below the joint then glass a 2" strip GRP over the joint. Might do this with mine next year.
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This is something I've also bee considering as in a few places there are traces of rust at the joint. I think the bolts are fine and dont want the expense of dropping and rebedding the keel.

Anyone else got any thoughts on this approach?
 
SvenglishTommy said:
This is something I've also bee considering as in a few places there are traces of rust at the joint. I think the bolts are fine and dont want the expense of dropping and rebedding the keel.

Anyone else got any thoughts on this approach?
Click to expand...

It's the 'I think the bolts are fine' bit that's the problem. If there is water in the joint there is a good chance that it is reaching the bolts. I assume these are stainless so they will be OK but the keel iron around them will corrode more rapidly. Seems unlikely that this would penetrate enough to weaken the joint but when you eventually remove them there might be a significant hole there that would need to be treated somehow. If you know that the bolts are bedded in sealant in the keel this is less of a concern, and I doubt it is a major one anyway, but it could cost a bit when you finally do the job.
 
I dont think there is water in the joint, it's not weeping like in Pierscovil's pictures, and my suspicion is that this is just the very edge of the keel rusting (well apart from the rest of it but that's another story).

I guess I should probably pull a bolt in the most suspect area and have a look first.
 
SvenglishTommy said:
I guess I should probably pull a bolt in the most suspect area and have a look first.
Click to expand...

They may not be bolts but studs with nuts on the top. In that case it is extremely difficult to remove them without dropping the keel. If you think your rust is just at the edge - quite common - then clean it back, paint it and put a bead of sealant in the exposed joint. This will slow down the rusting.
 
Finally 4 years after I first started looking at this, I have got the water tanks out and can confirm that my keel bolts are leaky. So looks like a keel drop project which won't be trivial as I have to take my engine out to get at the rear keel bolts, but a good opportunity to replace the 30 year old fuel tanks and rebuild the engine and gearbox. Any helpful advice welcome as I can't find an owner who has done this before, and Nauticat tell me that their keel bolts have never leaked on a Nauticat 43.... Mine is an early hull so I suppose I am the guinea pig.
 
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Puggy said:
Finally 4 years after I first started looking at this, I have got the water tanks out and can confirm that my keel bolts are leaky. So looks like a keel drop project which won't be trivial as I have to take my engine out to get at the rear keel bolts, but a good opportunity to replace the 30 year old fuel tanks and rebuild the engine and gearbox. Any helpful advice welcome as I can't find an owner who has done this before, and Nauticat tell me that their keel bolts have never leaked on a Nauticat 43.... Mine is an early hull so I suppose I am the guinea pig.
Click to expand...
So its lasted 4 years and no deterioration? I would do a bit more thinking
S
 
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