Step 1: The Nozzle
thin, bendable sheet of plastic or any other material that can be used to build a cone
two boards of MDF or any other sturdy material
For the nozzle we chose an arc with a radius of 61cm made of a thin and bendable sheet of plastic. The angle depends on the size of the stand for the nozzle but it is helpful to have sufficient material overlapping as this makes the procedure of taping/gluing the cone much easier. In our case, we decided to use tape as it was quicker to apply and seemed to be stable enough to keep the cone in form.
The stand for the nozzle was made out of 1.8cm thick boards of MDF. The dimensions we used can be taken from the photo below but can also be modified. If choosing different dimensions it is important to note the following:
- the greater the inlet area, the better as it catches more wind
- the smaller the outlet area in comparison to the inlet area, the greater is the difference in speed (the outlet velocity is greater than the inlet velocity) which leads to an increase in kinetic energy the rotor is able to catch
- the diameter of the outlet must be slightly bigger than the rotor diameter ensuring an optimum distribution of the wind at the contact surface of the rotor blades including the tips
For a better fit of the cone into the boards it is helpful to sand the edges of the circles at the appropriate angle.
The next step is slotting the boards onto the boards and gluing it. If the outlet seems to be too small, it will be easiest to trim the nozzle at this point.