Welcome aboard! I can't help you with specs on the Yankee 30 rudder. Many older production fin keel
boats have rudder problems coming into Hilo after a downwind sail of 2000 + nautical miles. It's worth checking all the parts
and pieces that make up your rudder system and having an emergency
backup. The part that seems to give way is the tangs welded to the rudder post inside the rudder blade. I've steered a 23 foot boat with a long sweep when the rudder was damaged. I would recommend a heavy duty oarlock on the taffrail and carrying a long oar just for the purpose if you are concerned about your rudder condition. Some folks install an eye in the upper aft end of the rudder blade and lead a port and starboard line to it so they can steer using the lines through fairleads to their sheet winches in case of rudder failure.
Just some thoughts.