It was the time for the putty. I used acrylic type wood putty so it would not attack the Styrofoam. After every of the three coats I sanded the hull and sealed it with white glue thinned with water.
I also sealed the inside of the tub and the deck so it would not 'drink' too much paint. Then I made the imitation of the propeller shaft housing from styrene sheet: two shaped halves plus disc for the rear of the housing glued to the keel again with polymer glue.
The rudder was made of hard 3mm PVC cut and sanded to the right profile. Then the rudder was secured to the hull with a piece of 1 mm steel tube, placed in appropriate holes. I have replaced the aftermost part of the keel with a piece of wood as the card piece was too stressed from handling. This enclosed the rudder between the hull and another piece of tubing.
I started the build by making the ribs protruding vertically from the tub to support the superstructure sides.
This task was rather time consuming as every rib was cut from 0.5mm sheet styrene and trimmed individually to fit in it's place in the tub. After they were all done I have cut two sidewalls according to the blueprints I had and glued them to the ribbing. As the glue was setting I have cut and trimmed lower front wall and two pieces of the rear wall to fit into their respective places and bent to match the cutout in the deck.