possibly hitting the hull?
On my 240, the rudder extends under the hull about 3" or so. When tied off, light waves sometimes cause it to "float up" and hit. It also does this at times surfing downwind.I am fitting a sleeve between the hairpin clip on the pintle and the bottom of the gudgeon (spelling?). This will take up the space and keep the rudder from hitting.Prev Owner had let boat sit a lot last year, and the top corner of the rudder actually wore/broke off and I had to rebuild it.