Sandblasting and fairing a cast iron ballast keel.

Discussion in 'Wooden Boat Building and Restoration' started by Mohan Pakkurti, Jan 17, 2007.

  1. Mohan Pakkurti
    Joined: Jan 2005
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    Mohan Pakkurti Junior Member


    I have a ballast keel (cast iron) that is heavily rusted and I want to have it cleaned and painted. My plan is to hire someone to sandblast it, and then I can paint it with primer for now.

    But, I see that the top surface of the ballast keel, the one which interfaces with the wood keel, is very uneven. What can I do so that the top surface is level to ensure that the interface with the wood keel is even. It seems hard and messy to polish the entire surface level. Maybe I should just buy a metal grinder and get to work :)

    Is there a good material that can be placed between the ballast keel and the wood keel to the make sure that there is good structural contact between the wood keel and the ballast keel. The wood keel and the entire backbone is (swedish) oak.

    Thanks for any suggestions.

  2. PAR
    Joined: Nov 2003
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    Location: Eustis, FL

    PAR Yacht Designer/Builder

    Typically the keel bottom is reasonably "keyed" to the ballast casting. This means the keel bottom was intentional shaped to match the casting or more likely the ballast made an impression in the keel bottom, as she was cinched up on her bolts. A bedding compound, probably tar or a Dolfinite type of oil based material, was smeared on top of the casting before it was drawn up tight with the bolts.

    All this means is simply, the keel will have humps and hollow areas, which mirror the top of the ballast casting. Grinding the casting top will remove some or all of these, which will decrease the contact area, not improve it, unless similar work is performed on the keel bottom also (not recommended).

    Remove the loose rust and scale, prep, prime and paint as you desire, then bed her with the goo of choice, then jack her home again, it'll be fine. After a few hours of sailing and the keel is good and soaked, check the tightness of those ballast nuts, which should also have a bedding, gasket or wick of some sort under the washers.
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