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Previous urban delivery drone services had trouble with noise complaints, could be related to that?

One way to solve the noise problem is a drone flying high and dropping the parcel on a long rope.

Thanks. The boat prop offers some efficiency gains in mid-range speeds and better hole shot acceleration, but I guess the benefits don't carry to smaller scales and less viscous surroundings.

With 4 counter-rotating props, that would not surprise me

Recently discovered Sharrow boat props. Apparently the guy who invented them first developed the the concept for reducing noise from drones filming orchestras. I'm surprised we aren't seeing more widespread availability yet of "tipless" drone propellers.

https://youtu.be/MNnB_50Z20I?t=553s

Previous HN discussion: https://news.ycombinator.com/item?id=33949895

Similar design MIT patented: https://news.mit.edu/2022/lincoln-laboratory-inventions-win-...

There may have been new attempts, but when I last looked into these types of drone propellers, nobody seems to have been successfully able to demonstrate they actually offer significant improvements (either noise or efficiency) over traditional designs.

To be fair, the limiting factor might be manufacturing capabilities, given most attempts were using 3d printed propellers which results in terrible surface finish, compared to injection molding.

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