Main plate.
the hinge bolt will pass through this plate adding extra strength.

several other holes have also been drilled in the plate and this will allow resin to form a "pin" through the plate. Once the resin has cured enough to be worked on (I'm using 7day cure resin), I'll bore 3 more larger holes (12mm) through the rudder and main plate and add timber pins which will also be resined in. These pins will be hard wood.