MT-Propeller 11 blade propeller delivers 15% increase in static thrust

Ok, how much better is 13 blades?

Why are they only using odd numbers of blades?

I'd imagine that, just like in other industries, there are tons of metrics (or counter-metrics) that are also important. Some that come to mind are efficiency, noise, vibration, cost, maintenance, stall characteristics, RPM requirements, weight, etc etc. From some fiddling with RC quads, I remember that increasing the number of blades does increase thrust, but at the cost of efficiency and several other parameters.

Easier to balance; if everything is even, you need to balance two blades to counter one misbehaviour, and do so perfectly to avoid introducing new misbehaviours. (They’re prime for resonance reasons. I don’t remember what, specifically.)

For reference on more or less blades, aviation stack exchange has some great discussions on this subject. One of my favorites

https://aviation.stackexchange.com/questions/23009/what-are-...