Hi John,
I believe that the plans show the prop so that will give you the diameter. This type of vessel would have been fitted with a three or four bladed propeller. Look at the D & A type brass props here: **LINK**
As far as the rudder support is concerned, you will need to fabricate this yourself. The simplest method would be to bolt a section of flat brass bar to the after section of the keel which extends beyond the propeller to just beyond the rudder post above. This can then be drilled to accept the bottom bearing of the rudder. My usual practice is to cut the heads off brass bolts and glue them vertically into the exterior of the keel with a small amount protruding Then you can drill the brass bar to fit over them and use nuts to secure it in place before painting everything over. This method allows you to dismantle the bearing and remove the rudder at a later date for servicing and to withdraw the propshaft.
The photo below shows you the general idea.
Hope this is clear!
Colin

Edited By Colin Bishop, Website Editor on 27/06/2014 14:21:14