Swappable 65mm EDF (electric ducted fan) powerpod
The whole foamboard and powerpod thing has certainly done a lot to make building planes less mysterious and more approachable, for me at least, and I think for loads of other people too. But even better, it is a great platform to allow people to design their own planes.
I wanted to try designing a jet, and have now built and tested a Messerschmitt ME262, which I will post separately in the near future. But before I did, it seemed like a good idea to take advantage of the benefits of being “swappable”, and that means I needed an EDF powerpod.
EDFs, or electric ducted fans are little round fan housings with super high KV motors. I quickly found out they are a little complicated, but I still managed to make one without actually learning very much, so they can’t be all that complicated. Below I have posted the plans and some instructions to build a EDF Powerpod for a 64mm EDF, a common middle of the road size unit that could power a small jet or, as I did, a rather large twin. This could also be scaled up easily to make a 70mm unit, which is a common size for single engine EDFs.
But I want to point out that I have gone for maximum flexibility here, so the unit is very simple, generic, and deliberately uses the same overall design as the FT Powerpod, and even some of the same dimensions. So if you wanted to try something crazy, you could turn a stock FT Flier in to a jet just by “swapping” in one of these units, and taping it on. Not sure if it would fly...but I hope someone tries!
-64mm EDF unit (I used this one):
-Foamboard frame (see plans)
-Plywood front wall (see plans)
-small foambaord spacers (a few pieces about 0.5X1.5”)
-Tape and glue gun
1. Cut out a plywood front wall according to the plans. Drill the main hole about 65mm and centred as indicated (or drill a smaller hole then cut out the circle). Drill two skewer-sized holes 1” apart, like in the FT Powerpod.
2. Cut out foamboard frame and make two score cuts on one side where indicated on plans. Peel off the paper between these two score cuts, exposing the foam. Now flip this over, and with the exposed foam side down, slowly pull it back and forth over the edge of a desk or table, gently bending it down as you do. This induces a nice smooth curve in the foamboard with the paper side out.
Peeling back the paper where the foam will be curved.
3. To keep the shape of the foamboard the same at the rear of the powerpod as it will be at the front, you can either make another “back wall” out of foam (but without the top tab with the skewer holes), or what I did was simply glue the cardboard roll from a used-up roll of packing tape into the end (it happens that most rolls are about 85mm, which is an ideal size), and then tape it into place on the top to keep the shape.
Use an empty tape roll to keep the backside in shape.
4. Now glue the leading edge of the foamboard to the plywood, being careful to hold the foam tight while it sets to ensure it maintains the rounded shape of the front wall. Once it is set, tape the outside of the front wall to the foamboard to make a solid bond.
Glue the front wall onto the foam frame.
5. The EDF I used has a flange in the front, so I used some foam scraps to create spacers, and also a nice slot to lock the unit into place. I simply removed on side of the paper, bent it a bit, and glued it to the bottom of the inside about 3mm from the front wall. If you are using a different EDF, you will have to adapt it to the space, but because it is pushing forward against the inside of the front wall, it only has to be held down to stop vibrating or spinning.
Glue the spacer into the bottom - forming the slot between the spacer and front wall.
6. Your EDF will need an exit cone to control the rate of airflow. I did a bit of reading and decided a diameter of about 400mm was ok for mine. To make the cone, I cut paperboard (see plans) then taped it to the outside of the EDF housing, leaving a slot for the wires, then taped the inside and outside of the joint so the exit hole was 40mm.
Taping the exit tube onto the EDF unit - start at the wires and work your way around.
7. Lastly, I cut the tape roll (to allow the exit tube to be inserted from the top), and placed the EDF unit into the slot behind the front wall so the flange sits in the slot between the wall and the spacer. Put another foam scrap on top, and tape the whole top of the EDF securely to the sides and front wall so it can’t vibrate much. Lead the wires out the back, and add a little velcro tab to attach to the ESC so it does not get in the way of the exit tube and disrupt the air flow. Lastly, tape the cut you made in the tape roll at the back to make it solid again.
That is it - your EDF Powerpod is not ready to mount.
You can get creative about how to mount it. On the ME262 I made half-rounded nacelles that make a nice tight fit with the two alignment skewers protruding from the wing and a skewer through the sides locking the EDF Pod into place. This is a nice set up, because you can swap it out for props if you want (because the alignment skewers are spaced the same distance in both pods).
Underwing twin EDF powerpods - attached much like normal powerpods.
Detail of wing-mounted EDF powerpod.
Underside - powerpod slides into nacelle
I will finish by saying that there are probably hundreds of ways to do this better, but it seemed like a good simple plan for a starter,and it does work, and is swappable. I hope someone works out a better swappable EDF unit and posts it, or modifications on this one, and I also hope people try this out on different planes in different configurations (like an EDF FT Delta, or maybe an EDF Blender...). Have fun.