What is the best number of blades for propeller?

Question

Could anyone explain me the best number of blades for propeller with reasons?

Answer 1

I couldn't explain the physics of it; but from observation 3 or 4 seems to be the optimum.  I've been told that Navy subs use propellers with numerous blades - typically 7 or 9 - because it reduces noise.

Answer 2

General rule, fewer blades means less drag therefore more efficient, but having less surface area, robs you of torque.

And, adding blades generally means more bow lift, all else being equal.

Answer 3

So far a lot of good answers, but I'd like to add a couple, on most sailboats they use 2 blades of very low pitsc, because when not in use, they offer less drag, and the boat's top speed is only 10-14 mph so higher pitch is a waste of touque.   The other think I want to add is that Duoprop by Volvo uses 3 blades, but a total of 6 (2 props per shafts) and they get great proformance, So props are more an art than a science.  It's application and results that matter.

Answer 4

what's the boat size & powered by and what's she primarily being used for (cruising, fishing, skiing, tubing, etc). We'll all need to know before an answer can be given

Answer 5

2 blades extreme high speed racing> 3 blades all purpose> 4 Blades hole shots and smooth running> Less high speed> 5 Blades power smooth running less top speed>