Model Boat Propeller

Hi,

I want to make a propeller for a model steam launch that I am building. The
propeller will be about 65mm diameter by 105mm pitch (about 2.5" by 4.25")
with 3 or 4 blades. Does any one know of any inexpensive software that can
be used to design the propeller and then generate the Gcode for my mill?

I envisage mounting the propeller blank with its axis vertical and then
milling the front and back seperately. Alternately I can mount the blank on
my fourth (rotary) axis and then mill it but this seems harder to do.

I appreciate any help with this - it is a new venture for me!

Dave.