Looking for the optimal prop:

[bleak quarry]

Hi, I am wondering how the most efficient propeller is chosen for a specific motor. (Prop length, width, pitch, airfoil etc.). If someone has knowledge on this topic, please provide me with scientific articles, formulas or any other info where I can read about it. I am very interested to learn more about this topic.

[pastel jacinth]

The most efficient prop for a motor is the absolute smallest and lightest-pitch prop you can put on it

Full-stop, that's how that works

As you can guess though, that obviously isn't going to get you any thrust to speak of

[bleak quarry]

I am watching this video but I want more specific information. https://youtu.be/jclh4U3vw3A?si=YuYqbf70urzqB_gr

[bleak quarry]

So where is the sweet spot between thrust and power consumption? Are there any formulas to calculate it? For a given motor, battery and esc, I am looking for a propeller that has the highest Thrust/Power Consumption.

[pastel jacinth]

The formulas you are looking for are not a thing that exist

Propeller loading is a highly dynamic scenario. Even full-scale propellers and jet engines aren't something that is fully "simulateable". Engineers can get a very good idea of how something will perform using incredibly sophisticated software, but at the end of the day, every design gets proven in wind-tunnel and real-world tests

[pastel jacinth]

See, now you're asking for the complete opposite of your first question. The highest thrust and power consumption is the literal opposite of "most efficient"

And as for the "sweet spot", that is entirely up to your own preference, and can be influenced by any number of factors

Picking a motor and prop is as much an exercise in preference as it is in science

[bleak quarry]

I don't understand.

So a good way to select a propeller would be to experiment and see which one performs the best

[pastel jacinth]

Generally, yes

You can pick a motor to fit the airframe, generally speaking, and then size your prop and voltage to fit. If you understand the actual performance you are wanting, it gets a lot easier because you can target specific RPM outputs

[bleak quarry]

Thank you for your help and I will also consult my professor.

Also, measuring the thrust by having the nose of the plane resting on a scale would be good? I have seen people doing this but I think it's not accurate.

"Static Thrust Measurement Static thrust model is different from dynamic thrust or advanced thrust. Calculation model for static thrust estimation is function of rotational speed, meanwhile dynamic thrust is influenced by airspeed."

also found this article here

https://iopscience.iop.org/article/10.1088/1757-899X/645/1/012015/pdf#:~:text=Static Thrust Measurement Static thrust,influenced by airspeed [3].

[pastel jacinth]

If you fully read through that paper you'll understand that their model is derived and validated from their testing

Every propeller is going to have a different coefficient because every propeller has different airfoil characteristics

It would be lunacy to calculate the static thrust of a 10" APC prop with the coefficients derived from an HQ 5" bullnose prop, for example

And even then, the coefficient represents a simplified term that is itself comprised of multiple factors determined by the propeller's airfoil characteristics

This paper reads like a couple of undergrads trying to write something up for a final project--they didn't actually contribute anything new or valuable to the area of aerodynamics research

[bleak quarry]

Yeah. I will read also the book: Design of UAS by Mohammad Sadrey. Maybe I find something.

[bleak quarry]

They created a mould for the propeller and they measured its dimensions to put inside the cfd software. Why didn't they measure the propeller itself?

Look at 3.1

page 4