"Last night had a development. Normally, at 12+ knots, we have a low hum in the keel. At about midnight, suddenly there was a new sound, a very high pitched vibration, very loud, coming also from the keel. Rapid inspection of bulkheads, plus the two huge stainless steel pieces that hold the keel hinge, plus inspection inside the keel compartment, both visual and manual, feeling for cracks, or anything unusual, showed nothing. The keel could cant normally. It was not an electric sound from the motor. We have 2 half conical pieces outside the hull which are fairings for the water to flow past the hinge of the keel. In the past, we have had a corner, or piece, or nick of one of these come off, and I'm pretty sure that that is what our new sound was. The fairings are not structural. The sound was loud and insistent last night. This morning, the sound was different, not so loud, different pitch, mostly water sound, not the sound of something vibrating. Another complete inspection this morning showed nothing unusual in the structural parts, at least what can be seen. So I think we're ok, we've just lost part of a fairing."
Rich Wilson (Great American III) in his daily blog.