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Many C&C boats have external ballast affixed to the hull by bolts.
The bolted-on keel is required to deliver the entire righting moment to the fiberglass keel stub across one half of its width. The narrower the keel attachment is, the greater the forces required to produce that moment. The tension members are the keel bolts, and the compression member is the outer periphery of the keel/hull joint on the side to which the vessel is heeled.
Net result is that the keel will move a little under the influence of these large forces and any rigid fairing material gets heavily compressed. To some extent this also applies in a fore and aft direction, but to a much lesser degree.
That's the cause of the C&C smile, and the flexible fairing solution suggested previously by using 3M 5200 or the like to fair the cracked joint is perhaps the only way to reliably avoid repeat cracking in the fairing area. An additional benefit is that, if carefully done and placed between the keel and the fiberglass, the flexible material helps to distribute the compression loads along the keel side, and that is a good thing.
Some will prescribe tightening the keel bolts. I'd be cautious. Excessive bolt tension adds to the compressive loads on the keel stub. Unless there are leaks or unusual gaps or movement, it might be wiser to leave well enough alone.
Last edited by Goodnewsboy; 01-03-2007 at 08:49 PM.