A thumping sound under foot

[LuckyMon]

Occasionally I will hear (and feel) a THUMP under my feet while steering, especially when sailing off the wind in a stiff breeze. It feels like the chain is falling off the sprocket, and re seating itself. We can find no sprocket teeth damage, and the chain appears to be vertically aligned. This is a 2006 Bavaria 37 with Integra auto pilot. Anyone had this situation? Advice welcomed. thanks.

[treilley]

I had a similar situation on a previous boat. It turned out to be the lower rudder bushing. It had a little bit of play in it and when sailing off the wind there was less pressure on the rudder thus causing it to thump back and forth.

[tomperanteau]

Have you checked the tension on the chain?

[LuckyMon]

Yes I had a mechanic check the chain, he tightened one side and loosened the other a bit, but it still thumps at times, seems like mostly when on starboard tack with thte spinnaker pulling hard.
Maybe I should go worry about something else? Thanks.

[MSter]

I also had a similar symptom on a slip neighbor's Catalina 470. It turned out to be a steering cable clamp had repositioned (turned) itself and was hanging up and releasing with a thud felt thorough the cockpit floor as well as in the helm.

[tomperanteau]

Have someone turn the wheel while you go below and watch the cables. Inspect where they run through the pulleys and where they attach to the rudder post.

[Sabreman]

You snagged a submerged container and it's banging on the hull.

Couldn't resist. Sorry

[micheck]

What ever you do, don't go below and open the door and let it in

[ahab211]

I hear a thumping on my 24 C&C from time to time and after checking the keel bolts and rudder I feel on my boat it's the water slapping off the keel as it happens only when sailing.