One blade....

[Fly-n-Low 181]

I just happened across this looking for a radial air freshener.

What a contraption!!!

https://www.aopa.org/news-and-media/all-news/2018/november/pilot/singular-sensation

Oh, here is a link to one of the air fresheners I found if interested.

https://www.infmetry.com/collections/black-friday-holiday-deals/products/airplane-propeller-engine-shaped-car-vent-clip-air-freshener

[Cloud Dancer 69]

I ran across one of those for sale on Craigslist somewhere within the last 6 months. A lot of thought went into that design.

[Fly-n-Low 181]

I was always told that "physics said" one blade is more efficient. According to the pilot, such is not the case. I would be worried about an unbalance thrust because of he one blade. I know two or more isn't perfect when you take the AOA in to consideration.

It would make for an interesting conversation piece that is for sure!

[Turbo 162]

Seems to me one of the first wind turbines in the US had only one blade.  The name "Grandpa's Knob" comes to mind...