sub propeller design help
 

SmokinTep, I'm new here as a result of a Google search. I realize this is an old thread, but fascinating none the less.

This quote caught my eye:
"Propulsion is provided by a brushless axial flux motor powered by a new AlAgO battery fitted with an electrolyte management system (a low-cost rechargeable lithium ion battery is being developed for exercise use).
The propulsor itself uses contra-rotating 13-blade and 10-blade carbon fibre propellers. Top speed exceeds 52 kt."

I am designing, to build, a micro-sub. Think of it as a sub you wear.
It is most unconventional, but should be a thrill to drive/fly.
I am working on the propulsion, planning contra-rotating props
using two, axial, electric, 5kW motors. My sub diameter is only 20 inches
Can you, or someone, elaborate on what might work well for prop design?

My calculations show I should be able to achieve 15 - 20 knots providing I get 90+% efficiency from my props. I plan a very mild taperred nozzle. This is as much for aft stability as prop efficiency. The sub uses only bow planes (horizontal) to provide roll, pitch and yaw. To achieve yaw, I would first roll 90 degrees, and then give "up" input resulting in a yaw response. With no aft planes, the shroud would provide some stability without restricting roll response. Like I said, very unconventional, but there is method to my madeness. But, I digress. What I'm really looking for here is some prop design help. Please assume I know nothing about prop design, especially in the terminology department.

Thanking you in advance,

Cheers, Tom.

P.S. Drawings available

Dont know much about prop design, but a quick search shows that it uses a hollow shaft/tube for one prop with a solid shaft inside of it for the second prop. Some type of gearing is needed between the two shafts in order to get them both to rotate in opposite directions. I think the USS Albacore used that kind of design

here is a diagram showing the props

http://www.freepatentsonline.com/6702631-0-large.jpg