Prop Style

[AxeGrinder]

Is there a reason that all the Quad's I've seen only use 2 blade props? I am pondering this subject as a means to getting a little more lift/volt...

Perhaps 2 blade is more efficient, is this correct? I do understand that 3 blade will be a little heavier, however, this might be reduced by the use of smaller prop which in turn prob would effect the Kv selection also

Is there a good source for Prop Tech info?

 

[Mike]

Each blade on a prop increases drag/air disturbance and reduces efficiency. Technically, a 1 blade prop is the most efficient, but the less props you have, the longer they have to be, so you have clearance issues - also, a 1 blade prop is more complicated/ difficult to balance. Really, a 2 blade prop is the best combination of cheapness, simplicity, and efficiency. When it comes to balancing, 2 blades are much easier for the amateur since you pretty much just need to ensure equal weight on both sides. You put the prop on the balancer and sand off some of the surface on the heavy side until the prop will sit perfectly still (balanced) vertically and horizontally.

Three blade props normally used when clearance is an issue - so if you're building a smaller quad, you might want to use a 3 blade prop. This is why most props on planes are also 3 blade, except in that case, it's due to ground clearance issues.

Bottom line - you can get more lift/thrust out of an equal size 3 blade prop, but it's less efficient, more complicated, and more costly than just using a larger 2 blade prop. Also - just about every frame is designed to fit appropriate sized 2 blade props.

 

[AxeGrinder]

OK, thanks for that... I really did guess that there was a tried and tested reason for this....

PS: I could have sworn I posted a "reply" here last night, with a link to some info I found... that would have sent barking up the complete wrong tree, so good info, thanks!

 

[Mike]

No problem. There are some debates online where someone will test a three blade prop vs a two blade prop and say the three blade performs better, but most anything that is science or from real plane/copter knowledge says less longer blades are more efficient and clearance issues are really the only reason why you'd have more blades.