I do not have any idea how to create any design or even use a computer for drawing 2D things, I am an oldschlool guy and I draw everything on to paper with a pen if I ever need any drawings, I mostly just machine my things, mechanics, parts, gears rocket motors etc. from 3D plans directly in my head.
I have got this into .stl by my friends help who made it with a half million dollar 3D Scanner. I did not design it so I can not make any changes either into the file, I am sorry :(
But new info from the actual prop, I have mixed props at my home. This is perhaps a Formula 4 prop originally 19p and for 60hp outboard.
The real prop I sold away, I have one 24p Semicleaver I will ask my friend for 3D Scan it too.