The starboard side and bottom plate were next covered with fibreglass cloth. Here is the cloth wetted out.
When I 'glassed the port side of the rudder I made the panel oversize so that the cloth would drape around and seal the edges and faces.
Except I did not make the panel large enough - there was insufficient cloth to go easily around the curves and onto the flat front and rear faces.
So when I 'glassed the starboard side I I made sure the panel was plenty oversize to allow this. Here you can see the substantial overlap onto the front face, sealing it up.
I will leave that to cure before 'glassing underneath the bottom plate.