To make the tail wheel steer with the rudder, it is common practice to link it to the rudder either with a wire or a spring. Click this [link=http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXFV47&P=ML]Link[/link] to see what a steerable tail wheel looks like. The spring is mounted to the bottom of the rudder on one side and inserted into the top retaining collar of the tail wheel assembly on the other. Using a spring reduces stress on the rudder and servo if you hit rough ground.