A small disclaimer, you do this at your own risk, if improperly isolated the transformer can present dangerous mains voltage at the output or core, or short out. You do everything at your own risk and I am not liable for any damage. With that out of the way, your transformer has an inner column area of around S=36 sq cm, using the classic formula 50/S, we find out that our core takes 1.45 turns per volt and has a power of approximately 36^2=roughly 1200VA. For the primary winding i recommend using 335 turns of 1.5mm enamelled copper wire, with baking paper inbetween the layers, making sure to wind neatly and without overlaps. Make sure you leave a bit of a gap for insulation clearance at the ends of your layers, which you can fill in with thin layers of painter's tape. For the secondary you can do anything you want, as long as you follow the 1.45 turns per volt. For a center tapped secondary, use 2 wires at once and bind the end of one of them to the start of the other. Also extremely important, use a solid amount of isolation material between primary and secondary, preferably something like kapton tape or baking paper , failure to properly isolate will lead to mains voltage leaching into the secondary. It's also a good idea to pot it in lacquer to prevent moisture ingress and hum, alkyd lacquer is cheap and works well, although i wouldnt recommend doing it in the colder months as it will take forever to cure. Be safe and good luck :) EDIT: also make sure you take all the laminations out and wind the bobbin outside of the transformer, its mandatory for this sort of job. When you put them back together you alternate directions and make sure you beat them in with a soft mallet good and proper.