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  • #6105
    Webmaster
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    I have just had my B30 lifted out using the SeaLift at Cowes (an excellent service) and found some small holes (30-50mm across x 10-15mm deep) in the keel bulb, presumably caused by corrosion. The boat is just 2 years old and I had a boat on the same mooring for 7 years previously with no problem. Only a small amount of erosion on the saildrive anode. When new I specified the additional anode, which is about half eroded. Does anyone know if this anode is connected to the keel as well as the saildrive? I have spoken to Opal but the only staff who would know are no longer there, and they have referred my query to Bavaria. Any ideas?

    #7389
    Webmaster
    Participant

    Things like additional anodes would have been fitted locally, not by the factory, so the easiest and surest way to check is to lift floor/bunk boards or whatever is in the way to see where the cables go from the bolts holding the anode fitting on the inside of the hull. I would guess that there is one wire going to either the engine or the saildrive, but hopefully not both, as they musn’t be wired together. If someone did a proper job, they may have included a few hull skin fittings as well, but this is unlikely in my experience. It would be an easy job to run a wire to the keel bolts, and fit an extra nut on one of the threads to capture the bare cable.

    Moonbeam
    B32

    #7392
    Webmaster
    Participant

    Thanks for your advice, Moonbeam. Last weekend I looked more closely into the problem. The anode is connected only to the saildrive – no protection for the keel.

    I talked to another who owner had cause some years ago to seek advice from MG Duff, who said that the area of a keel is too great to effectively protect by anode, and the only real solution was to physically protect with a good primer etc. I shall do this at lift-out but in the short term I will set up an external anode and connect it to the keel bolts each time I return to my berth.

    #7404
    Webmaster
    Participant

    Hi,
    I Have just read your question on the forum. I have a Bavaria 34 which when i bought her new in 2002 had a reasonable finish to the iron keel casting. Each year the keel has had rust spots when we have lifted out so i had the whole keel water jet blasted and this process removed large quantities of filler and casting slag from the keel. From your discription of the size and depth of the areas of damage on your keel i can assure you that this is not due to a lack of anodes, it is simply the casting slag breaking off the casting due to corrosion. The castings are simply not of good quality and there is no simple cure. Despite all the effort we made with water blasting followed by many coats of specialist paint systems designed for underwater metal structures we still have one or two spots that leach rust each year. Our deepest hole is approx 50mm diameter and 40mm deep so far. The slag is easy to recognise if you go to work with a hammer and chisel, it will break away from the iron and is brittle and usually contains lots of small air holes.
    If you need more info please contact

    Regards

    Alan Burns. SALOMA.

    #7422
    Webmaster
    Participant

    Alan, – Thanks for the information. That explanation looks a lot more likely than galvanic corrosion, and your description of your keel is similar to what I saw. I shall go ahead with a good layer of primer etc at lift-out, and in the meantime will keep an eye on the external anode.

    Mike Broughton
    Moon Shadow B30

    #7432
    Webmaster
    Participant

    I had a small keel corrosion problem when I first lifted my B30 a year ago, but wire brushed and painted affected areas with one of those marine aluminium primers, before antifouling. I have now lifted the boat after 5 months in the water and there is no recurrence of the problem.

    #7503
    Webmaster
    Participant

    My last boat was a Spring 25 – which also suffered from poor quality cast iron and frequent corrosion.
    The only solution I found (sic) (after having recurring corrosion for about 5 years) was many coats of keel primer over a surface as clean as you can get it. I diluted the first couple of coats with Owatrol to try and increase it’s penetration and put on a total of 5 coats. Whan the boat was lifted last year there was much less corrosion than before.
    Cheers

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