The SkyersJet EDF system is designed to provide more efficient thrust than other existing EDF systems. In order to achieve this, the fan is much larger in diameter than other EDFs. To spin a fan this large requires a lot of torque. Normally a fan or propeller of this diameter would be mated to an outrunner motor. However, I chose an inrunner motor (A) because they have a higher power to weight ratio and greater efficiency. Unfortunately inrunners don’t provide high torque, hence the addition of a reduction gearbox with high-performance steel gears (B).
The fan blades (C) are 3D printed from high strength PETG and firmly attached to a precision machined aluminium hub, which in turn attaches to the output shaft. This composite design results in high strength yet light weight. As the blades are removable, the fan pitch can be adjusted to suit the needs of the user. EDFs are generally not seen as suitable for VTOL partly due to their high pitch blades. As a result, the base design uses low pitch blades for maximum static thrust efficiency for VTOL applications. Higher pitch blades are recommended to be installed for fixed-wing flight.
As well as the ability to change the blade pitch, the duct casing (D) is a modular design to which various intakes and nozzles can be attached depending on the application. The duct casing consists of two concentric segmented rings that are screwed together. One incorporates the stator vanes which straighten the flow and further improve efficiency. These vanes also act as the frame of the entire EDF. This combined design saves weight. At either end of the duct casing, holes are provided for the attachment of intakes, nozzles or diffusers.
A crucial part of a VTOL lift fan is its intake. It has two purposes; firstly to smooth the incoming airflow and hence prevent turbulence within the duct and secondly to provide additional thrust by creating low pressure over the lip surface. The SkyersJet EDF intake (E) is designed with a large lip for maximum thrust and a smooth gradual curve for minimum turbulence. It is constructed from thin 3D printed PETG hoops that are glued together. This screw-less construction reduces weight. As stated earlier, the intake is simple to remove and replace with a more aerodynamic variant for forward flight.
Thank you for your interest in the SkyersJet project. Here I will discuss some of the design ideas behind it.
Typically, the manufacturing methods used to produce EDFs are 5-axis CNC machining, injection moulding or carbon fibre laminate forming. These methods are all very expensive, which is why any EDF of size 200 mm and above tends to cost thousands.
Fortunately, low-cost consumer 3D printing machines are available nowadays which are capable of printing most complex shapes including fan blades. Unfortunately 3D printed parts are not known for their strength. However, a range of new high-strength engineering plastics are now available to 3D printers such as PETG, which is what is used to construct SkyersJet.
When I first had my ideas for this project and researched 3D printing an EDF this large, the general consensus was that it couldn’t be done. However I decided to try anyway.
There are multiple benefits to using a large size. Firstly, SkyersJet has much lower disc loading than other EDFs. Secondly, the gap between the fan and the duct does not have to be as small. Finally, much more power can be put through a larger fan, which enables it to be used for more serious applications such as large fixed-wing or VTOL drones.