Hi!
Aren't you looking for scale size props for your Hercules..?? Isn't that you are after ?! Scale rpm is not realisticin our model world and at the same time have good performance.
On my Marutaka DC-3 (Scale 1:13,7) that I'm building I plane to use two OS .26 FS engines.
I know that these engines turn a MA scimitar 10x5 prop at 10000 using 5% nitro and therefore I think is possible to use 3-bladed scale props for this bird. I have been planning of making these props of carbofiber with a diameter of 9,8" and a pitch of about 5". I hope that these props will pull as good as the MA Scimitar 10x5 twobladed ones have done in my other airplanes ...only time will tell.......the first mold of a single blade was done today and it looked good. Now I only have to make two more blades and put these togheter with the centre section and made a molding of the entire prop...phuuu!
Regards!
Jan K
Sweden