Gotta say, since my boat is in the roughest marina in the SF Bay Area (Pier 39), this slapping noise is a very tuggish thing I do not remember from my days on a sailboat. The semi-planing hull, when rocked, exposes the hard chine to waves, which then tuck into and under the boat and make nice slapping noises. But they make them irregularly, so yes, you wake up thinking someone is beating on your boat. I average about 80 nights a year on our boat in the dock and on the hook, so I have grown acutely aware of this consequence of a semi-planing hull. Our contemporaries who have more gentle marinas or don't anchor out a lot have no idea what I am talking about.
The other great noise that we noticed on our classic R-27 was fuel sloshing in the tanks. In our year (2011), they did not put baffles in the tank, so it thumped a bunch in rough stuff in the marina or on the hook. Also on the water.
But I gotta say, after a while, this is just boat noise and as long as you have a memory foam topper on the rock they call cushions, you are good to go. Except this week when the King Tides were rolling through San Francisco (including tonight) and big storm waves were pulsing through the Golden Gate and into my sketchy marina. Even the veterans in my marina were cranky. That and the stretched dock lines.
As you can see, this thread hit a timely nerve!
Jeff
