I have dropped the rudder on our Tartan 30 a couple times while in the water. The shoe on the bottom of the skeg is held on with two screws. All you need to do is remove those screws, and wiggle the shoe loose. It might take some gentle prying with a flat blade screw driver to get it started. The shoe will slide down while you lower the rudder.
A couple of cautions: The rudder is heavy. When removing the rudder in deeper water I secure it with some line to keep it from plummeting to the bottom. Also I think that if your keel is resting on the bottom, you will not be able to get the rudder completely out. It has to go lower than the keel to clear the lower end of the tube.
s/v Stap Isi
Madang, Papua New Guinea