Join Date: Feb 2000
Location: Annapolis, Md
Thanked 140 Times in 113 Posts
Rep Power: 10
Bolt on cast iron keels are slighly more maintenance than a bolt on lead keel, needing prompt touch up to any damage to the fairing materials and barrier coat when ever the boat is hauled out.
Encapsulated iron keels, and especially encapsulated iron set in concrete keels should be avoided like the plague. My direct experience with them and my conversations with marine surveyors regarding them is that it is simply a matter of time before water gets through the encapsulation envelope, usually from the bilge, and that the rusting iron will slowly damage the bond between the encapsulation envelope and the ballast. Also over time, once rusting starts it will pry the matrix of concrete and iron apart so that the ballast keel is no longer a single casting. It would be nice if there was a proper concrete cover as Billpjr suggests but that cover would be required to be 3" (which is the concrete cover required above the steel for concrete in contact with moisture). Most boats that I have seen, do not have any concrete cover on the steel as the steel and concrete are mixed together in a cement mixer and simply dumped into the encapsulation envelope. This is a poor way to build a boat as the concrete shrinks as it cures and breaks the bonds with the envelope. Bristol used to cast its concrete and iron ballast in a separate mold and use polyester slurry to glue it in place. That is a better system but one that is rarely used in boat construction these days.
Once the bond between the keel and the encapsulation envelope is broken and once the iron starts to rust, there really is no econmical and good way to restore these critical bonds.