Need some expert prop help

[skydawg]

Here's the deal: I am putting a Chevy V8 on a C172 (don't ask). The engine is limited to 210 HP by RPM limiter (2700 engine RPM max) and will be attached to a PSRU capable of a 1.7 to 1.2:1 reduction ratio (depending on best RPM for performance), so prop RPM can be anywhere from 1600-2250 max depending on what gears I install. Max prop diameter is 78". Cruise speed 140 MPH.

Would like the lowest prop speed that makes sense (to keep noise down) in terms of performance. I spoke with a couple of prop manufacturers but most say they don't have anything for that low RPM or it would need 5-6 blades (weight is an issue), and some say 2 blades best. So, here's my questions if anyone can chime in:

- when does 3 or more blades make sense?
- am I better of with 2 wide blades or 3-4 narrower blades?
- There's plenty of torque (360 ft lbs at 2700 engine RPM) so pushing blades at larger pitch shouldn't be an issue, but does this matter with more blades? I expect more blades would more easily distribute the HP, but a 2 blade wood prop should be strong enough.
- what's best method to design such a prop on paper or online calculator?
- would prefer an ground adjustable at first for test flights.

Thanks

 

[TFF]

 

[Dana]

 

[N8053H]

 

[bmcj]

 

[kent Ashton]

 

[Dan Thomas]

 

[Jan Carlsson]

 

[clanon]

 

[skydawg]

 

[kent Ashton]