Johnn
Not to worry too much - it seems that you have installed the rudder bearing tube with Epoxy (thats what it looks like)
I'm assuming the problem is that you installed the rudder tube with the rudder shaft in place, and its all epoxied up?
Leave the rudder shaft tube in place (its glued in, right)
Can you get the rudder shaft out of the rudder tube? - if so carry on as below
Epoxy is a plastic - drill or ream it out to the right size for the rudder to turn in it.
You have a nice fillet round the outside of the rudder bearing tube, but you do need to add a support for the top of the tube - I will sketch on your photo what I would suggest - basically a "shelf" about 30 mm wide (balsa, styrene, or liteply) that runs across the boat
at about the level of the top of the tube to support it against the side loads.
If your rudder shaft is permanently epoxied into the tube than you need to extract the whole shebang (rudder, rudder shaft and rudder bearing tube) from the boat (I would attack from the outside with a knofe, or possibly a hot soldering iron tip)
When you have it out - salvage all the metal parts by heating the rest - if the beariing tube is plastic it will soften and melt, and so will the epoxy on it. Then obtain a styrene tube (or nylon, or other plastic, or brass ) which is a good fit on the rudder shaft.
Patch the hole in the bottom with a bit of scrap styrene - redrill to fit the new tube and refit the rudder tube (without the shaft in place, and without using too much epoxy
Still fit the support shelf for the top of the rudder bearing tube!
Please ask anything else you need help with - someone knows the answer, often several someones
Sketch follows tomorrow
andrew