The Ultimate Guide to FPV Drone Propellers: How to Choose the Best Props for Your Quadcopter

Drone Propellers

Drone Propellers

Propellers are the essential component of any FPV drone as they determine the power, smoothness and responsiveness of the aircraft. These specialized airfoils attach to the motor hub and come in a variety of shapes, sizes, and blade counts. Understanding the basics of propellers is crucial for optimizing the performance of your quadcopter.

What’s A Propeller?

Propellers, also known as props, are the unsung heroes of an FPV drone. They play a crucial role in generating thrust that lifts the quad off the ground and enables it to move in different directions. However, many drone pilots often overlook the importance of choosing the right propellers, leading to issues such as increased noise, reduced flight time, or even motor failure.

In this tutorial, we provide a comprehensive guide to the different factors that affect the performance of FPV drone propellers, including pitch, shape, and the number of blades. Whether you’re a beginner or an experienced pilot, this guide will help you understand how to choose the right propellers for your quadcopter, enhancing your flying experience. Learn everything you need to know about propellers and take your FPV drone flying to new heights.

Propeller Directions

Propeller Direction: CW and CCW

Propellers are designed to spin in either a clockwise (CW) or counter-clockwise (CCW) direction. In a quadcopter, two motors spin CW and the other two spin CCW, so it’s important to match the propellers to the motors based on their intended direction of rotation.

On an FPV drone, the off-center placement of the propellers produces both thrust and rotation around the center of the drone. To counteract this rotation, it’s necessary to use two CW and two CCW props.

When purchasing propellers, they usually come in pairs of CW and CCW.

Fpv Drone Propeller Blade Spin Direction Leading Edge Trailing

To generate downward thrust for the drone to take off, the propellers should spin in a way that allows the leading edge to cut through the air first, with the air then escaping through the trailing edge. You can easily determine the direction of a prop by identifying its leading edge, which is often labelled as either CW or CCW on the blade.”

How to Mount Propellers?

By default, Betaflight expects the motors to spin as shown in the diagram below. This means that you should install the CCW prop on the motors at the top left and bottom right.

Pro tip: To make it easier to remember, just note that all front props spin into the FPV camera, while the rear props spin into the rear of the quadcopter.

There are three types of propeller mounting in FPV drone motors: M5 threaded shaft, T-mount, and press fit.

M5 threaded shaft (5mm) is the most common in 5″ FPV drones (and larger rigs). The propeller is attached to a shaft with an M5 thread at the end and screwed tight with a self-locking nut (also known as a “nylon nut”). There are often spikes on the motor bell, which dig into the propeller and hold it in place.

Hglrc Sector X5 Bnf Fpv Drone Motor Arm

In the T-Mount, the propeller is attached to a 1mm or 1.5mm thick motor shaft, secured by two M2 screws onto the top of the motor bell. This mounting is popular in less powerful 2″, 3″, and 4″ FPV drones.

Darwinfpv 18650 3inch Micro Fpv Drone 1103 Motor Prop

Press-fit (or friction fit) is popular in small FPV drones such as tiny whoops and toothpicks because this mounting is extremely light weight. These drones are relatively low-powered, so the props are unlikely to fly off even in crashes.

Propeller Size

The different propeller sizes

The different propeller sizes

Propeller size is given in imperial inches (1″ = 2.54 cm).

When describing propellers, there are two types of formats:

  • L x P x B
  • LLPP x B

L – length, P – pitch, B – number of blades:

For example, 6×4.5×2 (also known as 6045×2) propellers are 6 inches long 2-blade propeller and have a pitch of 4.5 inches. Another example is 5x4x3 (also known as 5040×3), a 3-blade 5″ propeller with a pitch of 4 inches.

You might sometimes see “BN” at the end of the numbers, which means “Bullnose.”

You might also see “R” or “C” after the size numbers, such as 5x3R. “R” indicates the rotation of the propeller, which stands for “reversed.” It should be mounted on a motor that spins clockwise. “C” is the opposite and should be used with motors that spin counter-clockwise, but usually, the letter “C” is ignored.

A propeller is said to be “heavier” when you increase the diameter, pitch, the number of blades, or all. It takes more torque to spin a heavier prop than a lighter prop.

Propeller Length

The length of a propeller refers to the size of the disc that it creates when it spins (or the distance from one tip of a two-blade prop to the other).

Propellers generate thrust by spinning and moving air. The faster the propeller spins, the more air it can move, which generates more thrust.

Did you know? FPV drones can’t fly in space because there is no air for propellers to move.

When the propeller pitch (explained below) and blade count are the same, a longer propeller can generate more thrust because it increases the surface area. This means you can accelerate faster, but it also requires more power from the same motor. However, longer propellers don’t necessarily mean faster flight – pitch is a more important factor (as explained below). Shorter propellers can spin up and slow down faster due to lower drag and momentum, which makes the drone more agile and responsive.

Propeller Pitch

Propeller Pitch refers to the distance a propeller travels during one revolution, and it’s measured in inches. Essentially, it’s how far the propeller would move forward if it were moving through a solid medium instead of air.

A propeller with a higher pitch moves more air with each revolution, which can create more thrust when the aircraft is traveling at high speeds. However, it also means that the propeller generates less thrust when the aircraft is not moving.

A higher pitch propeller can also create turbulence and prop wash, which can affect the performance of the aircraft. It also spins slower, which can make the aircraft less responsive. On the other hand, a lower pitch propeller is more responsive and can spin up and down faster, making it better for manoeuvrability.

Blade Count

emax rs2205 2300kv 2600kv motor propeller thrust test

Adding blades increases the surface area and hence creates more thrust. This is similar to making the propeller longer, except you can fit it in a smaller disk area. By increasing blade count improves grip in the air, but it also makes it less efficient and puts more strain on the motor.

For FPV drone pilots, both two and three-blade propellers are popular for racing and freestyle flying. Most pilots prefer three-blade propellers as they are a great balance between efficiency and power, they provide more grip in the air due to the extra surface area compared to two-blade. On the other hand, two-blade is more efficient as they creates less drag and draw less current, hence great for long range flying.

There are propellers with even more blades, such as quad-blade and hex-blade propellers. Quad-blade propellers are said to be great for indoor tracks and cornering, but they are less efficient than tri-blade and spin at a lower RPM at the same specs. Hex-blade propellers are not recommended for normal flight due to its extreme inefficiency, but they can be used to put on a show due to their unique appearance. These props with more than 3 baldes are more common on micro quads, where space is limited and you can’t simply make the blade longer to increase surface area.

 

Weight

When it comes to propellers, weight is an important factor to consider. In general, lighter propellers tend to perform better. Heavier propellers have more mass on each blade and require a more powerful motor to spin them. This can lead to higher torque loading, making the motor work harder and possibly decreasing overall performance.

Lighter propellers have less moment of inertia and can change RPM faster, making your drone feel more responsive. They also work better with a wider range of motors because they require less torque to spin up.

The weight distribution of the blades also makes a difference. Propellers with the blade’s center of mass closer to the hub are better. However, this means the tip of the prop gets thinner and easier to break. If the center of mass is further away from the hub, there is more drag and the propeller is harder to speed up and slow down.

What Propellers To Use on an FPV Drone

It’s important to choose your propeller size first because it determines the size of the frame you can use.

The propeller size you choose also depends on the type of flying you want to do. The 5-inch propeller is the most popular because it’s versatile and can be used for racing, freestyle, and even carrying a full-size GoPro camera. The 7-inch propeller is better for long-range flights because it can carry a much larger battery.

Thrust

Thrust is measured in grams. For your drone to hover, the propeller needs to produce at least 1 gram of thrust for every gram that your drone weighs. To perform stunts, or even just to take off or fly forward, your drone needs more than 1 gram of thrust per gram of weight.

Propellers produce more thrust when they spin faster and less when they spin slower. The speed of the drone also affects the amount of thrust produced. Some props perform well when the drone is stationary, but not so well during a cruise, while others perform well at high speeds but poorly when hovering. You want a prop that balances these factors and can create a good amount of thrust at different speeds.

To find the best prop for your drone, look up motor thrust tests to see what prop size work best with your motor. Keep in mind that props perform wildly differently when strapped to a thrust stand in a static setting compared to when they’re actually flying through moving air. Props can produce 20-30% less thrust in the air than on the ground.

To accurately assess prop performance, it needs to be tested at the speed your drone normally flies at. However, few people have access to wind tunnels for this type of testing. So, take performance tests with a grain of salt as they may not be an accurate representation of real-world use.

Smoothness

In the hobby, people often use the term “smoothness” to describe the quality of a motor or propeller. It’s not something that can be measured quantitatively, but more of a feeling that pilots have. In my experience, lower pitch props tend to be smoother because the motor can change RPM more easily and quickly. This allows the drone to respond faster to correct errors and reduces something called “prop wash”.

Speed

A propeller that creates lots of thrust with high pitch doesn’t necessarily make a drone faster than a lower pitch propeller that generates less thrust. As the propeller’s speed increases (which is measured in rotation per minute – RPM), so does the drag, requiring more torque from the motor to turn.

The theoretical maximum speed of an aircraft can be calculated using the equation:

Max Speed (in inch per second) = Max RPM * Propeller's Pitch / 60

In real life, factors such as air resistance, head wind, and angle of attack etc can all affect a drone’s speed.

Thrust affects acceleration and angle of attack, while RPM affects top speed. To achieve the best speed for your FPV drone, you need a balance between thrust and RPM.

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