The diving plane switch is considered one of the most important mechanisms in the N.  The switch activates the rear motor which in turn, turns the propeller and makes the sub go!  Pretty simple idea to make a 2 channel sub go forward, dive down and turn at the same time!  Some diagrams below: 

 

   The rudder mechanism is simple yet effective.  Most submarine models have linkages to operate their rudders and diving-planes located on the outside of their body.  For the Nautilus, the thin tail space is quite impossible to make linkages invisible if I decide to run them inside the space, if they were outside, they would be visible and and won't create the streamlined realistic look anymore.  So I thought of installing a small motor at the end of the tail piece, the motor shaft is attached to the rudder top, all I have to do is press the right/left buttons on my transmitter and activate the motor which turns rudder. 

 

   However, this creates another problem,  after you've turned the rudder left/right, it stays like that, not returning to the center position.  I thought about using a spring system like in RC cars but with the small space that you have to work with, this was a bit too difficult.  The simplest way came through me by some weird phsychic way...... :P  I decided to use the amazing elastic band!  when the motor turns the rudder left/right, the elastisity of the band will simply pull the rudder back into its original position!  Some diagrams below: