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11 votes
Accepted

Do propellers layered on top of each other have twice the thrust of one propeller?

At least at the small/model scale, the answer is no. There is significant efficiency loss due to the stacked propellers not receiving the same clean air as they would if they were horizontally ...
ifconfig's user avatar
  • 6,008
6 votes

Do propellers layered on top of each other have twice the thrust of one propeller?

TLDR: The thrust would not double. You can get close but it won't be easy. There are a lot of factors affecting this but in my experience the distance between props dominates. I once built a push-...
slebetman's user avatar
  • 161
4 votes
Accepted

How do I calculate thrust for a quadrocopter?

The usual way to calculate exact thrust is actually experimentally, through testing on a thrust stand. There are countless factors that may influence the performance of your particular motor and ...
FlashCactus's user avatar
  • 2,997
4 votes
Accepted

How to determine the minimum thrust to weight ratio for a fixed-wing aircraft?

I'm afraid it's not that simple. As you mention, planes can fly with a fairly low thrust to weight ratio. Obviously gliders can fly with no power at all, so there's no critical lower-limit. The other ...
Robin Bennett's user avatar
3 votes

Building a personal helicopter, I have a 5kw electric hub motor, how big will the rotors need to be?

If you are asking this question here, like this, then I humbly suggest that you probably shouldn't be attempting this. This is life or death stuff, and without years of professional aviation knowledge ...
strepto's user avatar
  • 356
3 votes

Can an extra 300s glide upside down and backward?

The maneuver you describe is called a "tailslide" -- I've seen it done in full size aircraft, but it virtually always ends in a "whipstall" (the alternative is advancing power ...
Zeiss Ikon's user avatar
3 votes
Accepted

Can an extra 300s glide upside down and backward?

The plane would be extremely unstable in reverse - like trying to throw a dart with the fins first. It's not really the same thing, but some indoor models with reverse thrust do manage to fly ...
Robin Bennett's user avatar
3 votes

How useful is knowing the torque generated by a motor prop combination?

Not very useful. If you're designing at the absolute limit of what a frame can handle, such that it's as light as possible, then maybe you'll want to know the maximum torque, but you should be ...
Brydon Gibson's user avatar
3 votes
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How do thrust requirements change as a multirotor leaves ground effect?

To fly above ground effect, you need thrust equal to the weight of the aircraft (or slightly more, as you want to climb). Ground effect doesn't hold aircraft down, it just makes it easier to fly when ...
Robin Bennett's user avatar
3 votes

What impact does a shroud have on the torque produced by the prop(s) of a multirotor that incorporates a properly designed shouded propeller?

There are two possibilities, depending on how ducts increase efficiency, but the end result should be the same. It could reduce torque required to spin the motor at a given RPM and thrust, or it could ...
Luca Scheuer's user avatar
3 votes

What impact does a shroud have on the torque produced by the prop(s) of a multirotor that incorporates a properly designed shouded propeller?

Ducts and shrouds reduce tip losses; the reason we don't see them more often is that a well designed propeller should not have large tip losses. Tip losses are greatest when there's a large pressure ...
Robin Bennett's user avatar
2 votes

How do I calculate thrust for a quadrocopter?

Many common motors will come with a data sheet for a range of voltages and propellers, such as the data sheet at the bottoms of the description for these motors: https://www.quadcopters.co.uk/iflight-...
Drones and Whatnot's user avatar
2 votes

Datasheets for lift of a 27x12x2 inch propeller?

There are too many factors to be able to give you a precise plot. All the below have major impacts on propeller performance: Activity factor A blade with a thicker chord will generate more thrust, ...
Kenn Sebesta's user avatar
  • 1,892
2 votes
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Do propellers at different angles work the same? And do intersecting flows of air work the same?

The motors would still generate the same amount of thrust, however it would be aimed in a different direction. Think of the thrust as horizontal and vertical vectors. You can work out the ratio of ...
Drones and Whatnot's user avatar
2 votes

Do propellers at different angles work the same? And do intersecting flows of air work the same?

The amount of force generated remains the same, however it is applied in a different direction; you therefore get an effective reduction in force for a given axis. To use the two extremes: If the ...
Kralc's user avatar
  • 6,046
2 votes

EDF Simplified Thrust Calculation?

The problem you have found is that you are trying to calculate the efficiency and lift coefficient of your fan, which isn't possible. There's no simple calculation to convert power to thrust because ...
Robin Bennett'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

Building a personal helicopter, I have a 5kw electric hub motor, how big will the rotors need to be?

A helicopter needs the highest power in hover. As a first approximation we can use the momentum theory which estimates the thrust as: $ T = 0.5\sqrt[3]{2 \rho A P^2} $ Where: $A$ is the rotor area; $\...
sophit's user avatar
  • 271
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
1 vote

How useful is knowing the torque generated by a motor prop combination?

The torque a brushless motor is capable of producing is particularly important when dealing with control loops. The torque is directly proportional to the rate of change of RPMs, which is directly ...
QuadMcFly's user avatar
  • 1,200
1 vote
Accepted

How useful is knowing the torque generated by a motor prop combination?

I am a fan of "More information is better". I believe that torque can be used to calculate system efficiency. I just do not know what those calculations are. I have seen one commercial ...
HansenJC001's user avatar
1 vote
Accepted

How do ducted fans impact drone performance?

There are a number of performance differences between open-blade quadcopters and ducted fan quadcopters and they may depend on the shape of the ducts. In theory, the most notable difference in ...
Jacob B's user avatar
  • 5,792

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