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20 votes

Why are larger propellers generally more efficient than smaller ones?

Thrust is proportional to the change in momentum of the air passing through the prop - i.e. how much the prop speeds it up. The power required to do this is proportional to the kinetic energy of the ...
Robin Bennett's user avatar
17 votes

Why are larger propellers generally more efficient than smaller ones?

An explanation for why this is can be found in this Aviation.SE answer: Why aren't large, low-speed propellers widely used?, which I'll paraphrase here. The thrust a propeller generates is a function ...
ifconfig's user avatar
  • 6,008
6 votes

Why are larger propellers generally more efficient than smaller ones?

Comment number 7 at this link is an excellent source (and fairly trustworthy as it was written by Joshua Bardwell). The main reason specified for the efficiency is that for a given amount of thrust, ...
Drones and Whatnot's user avatar
6 votes
Accepted

Does the sharpness of a propeller blade affect efficiency?

Rounded leading edges are better for subsonic aerofoils. Props and wings have to work at a range of angles of attack. The airflow has to split to pass either side of the aerofoil, and a rounded ...
Robin Bennett's user avatar
5 votes
Accepted

Do flexible propellers affect multirotor efficiency?

It's really a challenging question to answer because flexible and stiff propellers both have their advantages and disadvantages in terms of efficiency. Flexible propellers are typically lighter ...
Schome1's user avatar
  • 1,226
5 votes
Accepted

Influence of propeller blade shape and tip shape on its behaviour?

The main thing the designers are trying to achieve is reducing tip losses by making the chord of the tip of the prop small relative to the rest of the blade. Tip losses are due to air moving around ...
Robin Bennett's user avatar
3 votes

If AUW is 90 grams, will 4500Kv motors be better than 7500Kv?

Lower kV motors will spin more slowly but with more torque. Spinning more slowly (with the same prop) will give you less thrust and less power (and thus lower current) at full throttle. However, a ...
Robin Bennett's user avatar
3 votes

Do flexible propellers affect multirotor efficiency?

Multirotor propellers with too much flex can actually negatively affect thrust generation efficiency, but not in the way you might suspect. During high throttle punches, the propellers experience ...
ifconfig's user avatar
  • 6,008
3 votes

Why are larger propellers generally more efficient than smaller ones?

The easiest way to think about this is to remember that drag increases with the velocity squared. A smaller propeller will have to spin faster to achieve the same thrust as a larger propeller, and ...
Fraser Steen's user avatar
2 votes
Accepted

Error in the explanation of Ingenuity: The Mars Helicopter by NASA members?

The thrust being the same, a coaxial design is going to need some 15% more power than a single-rotor helicopter. This increment in power is due to the aerodynamic interference among the upper and ...
sophit's user avatar
  • 271
1 vote

I am confused on how to measure thrust for a propeller and would like some help

Yes, you'd use a watt meter. It's possible to measure volts and amps separately and multiply them together to get watts, but it's convenient to have a device that does it automatically. Additionally ...
Robin Bennett's user avatar
1 vote

Is 1 large propeller more efficient than 2 smaller propellers (if both cover the same area)?

Propeller momentum theory is only concerned about total area, so you can split the area up over any number of propellers and the maths works out the same. It calculates the mass of air moving through ...
Robin Bennett's user avatar
1 vote
Accepted

Should I use a tandem wing for my RC aircraft?

An "endurance plane" is best built like a glider. Nice long high aspect ratio wings. For "convenience", do what the Navy does, use foldable or removable wingtip for storage. ...
Robert DiGiovanni's user avatar
1 vote

How to choose the most efficient (thrust per watt) motor+propeller setup for a drone?

The most efficient propeller is infinitely large. However, that would give you a zero top speed, like this human powered helicopter: To fully optimise this, you need a target top speed, and to know ...
Robin Bennett's user avatar

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