The wings of the propeller ensure the aerodynamic lift of the Kotpers and thus that the multicopter can actually fly. The six most important criteria for a propeller are:
The first two criteria can usually be found in the name of the propeller in inches. For example, 9'' x 5'' means the propeller is 9 inches in diameter and moves 5 inches forward during one revolution. Occasionally you will also find designations such as 1038, which then means that the propeller has a diameter of 10 inches and a pitch of 3.8 inches.
The larger the diameter of the propeller, the slower it can turn to move the same amount of air. As a result, larger propellers tend to be more efficient and also quieter. With many multicopters, however, the maximum size is predetermined by the distance between the motors of two adjacent arms. This means that 9 inch propellers can still be used on a DJI Phantom, whereas the tips of 10 inch propellers would touch. Another limitation on size can come from the maximum RPM of a propeller. But more on that later.
The slope also has an effect on the amount of air moved and also on the compression of the air. The greater the incline, the more air is moved and the faster the multicopter becomes. However, a high gradient also reduces the maneuverability of the copter at the same time, because even if you let a propeller run out, it still transports a lot of air. Smaller pitches therefore make the multicopter a bit more agile in flight and they also make take-off and landing maneuvers easier, since the air can be better dosed by propellers with a small pitch. A good mean value for multicopters is:
Material
There are now propellers on the market in a wide variety of materials. The material has a not inconsiderable influence on the flight characteristics of the copter. For example, soft propellers generate more vibration than stiff propellers. But the material also affects the price, durability and balance. The following materials are currently common:
When it comes to propellers, you usually think of propellers with two blades. There are also propellers with 3, 4 or even more blades. There are also so-called single-blade propellers, which only have a single blade. However, these are only used at extreme speeds and are unusual in the multicopter area. Two-blade propellers
are used as standard on multicopters. They represent the best compromise in terms of flight behavior. They offer solid flight times, decent thrust and relatively smooth flight characteristics. Basically, you should therefore use two-blade propellers on copters. However, three-blade propellers are also used again and again
used on multicopters. These make your own multicopter stand out from the crowd of other copters, mainly because of their different look. In addition to the visual aspect, a three-blade propeller offers another advantage. It distributes the buoyancy over a larger area and thus generates less vibration. The flight becomes a little calmer and also audibly quieter. However, you also buy a lot of disadvantages. With a three-blade propeller, for example, after a third of the pitch, a blade returns to a place where a blade had been shortly before. This reduces efficiency and thrust, which is reflected in reduced flight times and reduced carrying capacity. In addition, three-blade propellers are difficult to balance and they are also usually more expensive due to the 50% more material.
Blade shape
There are many different types of blade shapes in propellers. Basically, however, it can be divided into the following types:
In practice, the transitions between the blade shapes are fluid. so that you can only try out what best suits your own requirements.
Direction of rotation
If all the propellers of a multicopter were to rotate in the same direction, the copter would also start to rotate and thus reduce the lift of the propellers again. To prevent this from happening, 50% of all the multicopter's propellers rotate clockwise and the remaining 50% rotate counterclockwise. Of course, the propellers must be designed precisely for this direction of rotation. A distinction is therefore made between the following directions of rotation:
- diameter
- pitch
- material
- sheet count
- leaf shape
- direction of rotation
The first two criteria can usually be found in the name of the propeller in inches. For example, 9'' x 5'' means the propeller is 9 inches in diameter and moves 5 inches forward during one revolution. Occasionally you will also find designations such as 1038, which then means that the propeller has a diameter of 10 inches and a pitch of 3.8 inches.
The larger the diameter of the propeller, the slower it can turn to move the same amount of air. As a result, larger propellers tend to be more efficient and also quieter. With many multicopters, however, the maximum size is predetermined by the distance between the motors of two adjacent arms. This means that 9 inch propellers can still be used on a DJI Phantom, whereas the tips of 10 inch propellers would touch. Another limitation on size can come from the maximum RPM of a propeller. But more on that later.
The slope also has an effect on the amount of air moved and also on the compression of the air. The greater the incline, the more air is moved and the faster the multicopter becomes. However, a high gradient also reduces the maneuverability of the copter at the same time, because even if you let a propeller run out, it still transports a lot of air. Smaller pitches therefore make the multicopter a bit more agile in flight and they also make take-off and landing maneuvers easier, since the air can be better dosed by propellers with a small pitch. A good mean value for multicopters is:
- pitch = diameter / 2
Material
There are now propellers on the market in a wide variety of materials. The material has a not inconsiderable influence on the flight characteristics of the copter. For example, soft propellers generate more vibration than stiff propellers. But the material also affects the price, durability and balance. The following materials are currently common:
- Wood: The biggest advantages of wooden propellers are the low price and the high rigidity. Overall, however, the disadvantages of wood outweigh the disadvantages. As a naturally grown material, wood does not have a homogeneous structure, which is why there can be large differences in quality between otherwise identical propellers. In addition, wood can be influenced by the weather like no other material. Moisture stretches the wood, sun exposure causes it to dry. In both cases, the leaf structure and the force changes. Also, wood is not a particularly stable material, so that propellers often break, splinter or tear after falls. Even high speeds cannot be achieved with it. The bottom line is that wooden propellers are not recommended.
- Plastic: Propellers made entirely of plastic are very cheap to buy. They can be produced homogeneously and are therefore of good quality. However, plastic propellers lack rigidity. Like no other propeller, they therefore generate vibrations that spread to the entire multicopter and quickly lead to the notorious Jello effect during camera flights. They are also not suitable for high speeds due to their mediocre stability. The propellers are still recommended for beginners, as they forgive many mistakes and small falls due to their softness. And if they do break, they can be replaced cheaply.
- GRP: These propellers are made of glass fiber reinforced plastic . Just like pure plastic propellers, they offer a relatively low price and a homogeneous manufacturing quality. However, they have better rigidity and stability due to reinforcement with glass fibers. This usually allows use on higher-revving engines.
- CFRP: These are also plastic propellers , but they have been reinforced with carbon fibers . Since carbon is more complex to produce and therefore more expensive, CFRP propellers are usually a little more expensive than pure plastic propellers. In return, they offer very high rigidity, very good stability and high manufacturing quality.
- Carbon: Pure carbon propellers are extremely complex to manufacture. Each propeller has to be formed individually and then baked in a lengthy process. On the other hand, high-quality carbon propellers also offer very good flight characteristics thanks to their extreme rigidity and excellent stability. At the same time, the carbon propellers are very light, which reduces centrifugal forces and makes them usable for very high speeds. Last but not least, the black carbon propellers offer a distinctive, high-quality look.
When it comes to propellers, you usually think of propellers with two blades. There are also propellers with 3, 4 or even more blades. There are also so-called single-blade propellers, which only have a single blade. However, these are only used at extreme speeds and are unusual in the multicopter area. Two-blade propellers
are used as standard on multicopters. They represent the best compromise in terms of flight behavior. They offer solid flight times, decent thrust and relatively smooth flight characteristics. Basically, you should therefore use two-blade propellers on copters. However, three-blade propellers are also used again and again
used on multicopters. These make your own multicopter stand out from the crowd of other copters, mainly because of their different look. In addition to the visual aspect, a three-blade propeller offers another advantage. It distributes the buoyancy over a larger area and thus generates less vibration. The flight becomes a little calmer and also audibly quieter. However, you also buy a lot of disadvantages. With a three-blade propeller, for example, after a third of the pitch, a blade returns to a place where a blade had been shortly before. This reduces efficiency and thrust, which is reflected in reduced flight times and reduced carrying capacity. In addition, three-blade propellers are difficult to balance and they are also usually more expensive due to the 50% more material.
Blade shape
There are many different types of blade shapes in propellers. Basically, however, it can be divided into the following types:
- Slow-Flyer: This leaf shape is rather thin, but convex (bulky) on the front and back. Due to the thinness of the material, a slow-flyer propeller cannot be used at high speeds. Therefore, before buying, it is necessary to compare the maximum speed of the propeller with the maximum speed of the engine. Slow flyer propellers are very effective as long as you don't fly fast or frantically, as they tend to vibrate during fast maneuvers.
- Thin-Electric: With this leaf shape, the front is rather straight, whereas the back has a clearly bulbous shape. The propeller is also thicker overall, which also makes it usable for high speeds. The blade shape offers increased agility and speed in flight. However, it is less efficient.
- Electro-Props: A blade shape, which became known mainly through the Graupner E-Props. It is rather straight both at the front and at the back. Compared to the others, this shape is quite thick and can also be used for higher speeds. They offer high rigidity and greatly reduce vibrations. In addition, the shape is very suitable for fast flight maneuvers. However, since offers noticeably less lift than other blade shapes and thus a shorter flight time.
In practice, the transitions between the blade shapes are fluid. so that you can only try out what best suits your own requirements.
Direction of rotation
If all the propellers of a multicopter were to rotate in the same direction, the copter would also start to rotate and thus reduce the lift of the propellers again. To prevent this from happening, 50% of all the multicopter's propellers rotate clockwise and the remaining 50% rotate counterclockwise. Of course, the propellers must be designed precisely for this direction of rotation. A distinction is therefore made between the following directions of rotation:
- cw : The abbreviation stands for clock wise , which is English and means "clockwise". Corresponding propellers are also referred to as "clockwise rotating".
- ccw : This means the English counter clock w ise, whichmeans something like "counterclockwise" . These propellers are also called "left-handed".
