One of the glass fibre arms of my quad shattered after repeated hard landings on a hard-wood floor, so I have some carbon fibre replacement arms on order. Meanwhile I thought it would be fun to experiment with foam cutting and trying to build a plane from scratch. With inspiration from MyGeekShow I decided to build a flying wing design using XPS insulating foam. One of the advantages of living in the cold north is that thick foam mats (6 cm) is widely available, so there is no need to glue plates together to get the required wing thickness.
The wings were cut using a 26SWG nichrome wire, with a 7 A 12V ATX power supply. The wire didn't get quite hot enough, so the cutting was very slow and I was worried that the uneven progress from tip to root would ruin the airfoil, but I think it turned out pretty nice. I designed my own airfoil with a flat bottom, quite similar to Clark-Y but I made it much thicker because I was worried about the rigidity of the tips of the wings. Turns out that isn't an issue, and I would probably go for a thinner air foil such as MH32 if I should do this again. I would also make the root chord longer to get more wing area. I have more foam laying around, and I'm waiting for a 32SWG nichrome wire which should cut nicer, so we'll see...
In the centre I added a rectangular piece of XPS which i rounded at the tip. I also cut out compartments for battery, receiver and speed controller, and found a nice way to mount the motor. The motor is pointed straight back, not slanted upwards like I see on many models, and I wonder if that is something I need to change.
The wing span is 123 cm (about 48 inches), and the take-off weight is 450 grams. The center of gravity is calculated using the flying wing CG calculator, and if I was to expand the battery compartment to accomodate a larger battery, the CG would not be affected very much.
This is my absolute first attempt at foam cutting and plane building, and I'm quite happy with the outcome. Of course I still don't know if it will actually fly... If it does, and has some lift to it, I might install the APM and a camera - but my gut feeling is that it will be too small for that, and I do have a Bixler kit on order for that purpose.
- One 6 cm thick XPS foam mat
- Foam safe glue
- One glass fibre rod
- Two HS-55 servos for ailerons
- Two aileron control horns and aileron rods
- One Nippy Black 0808/98 motor
- Propeller (haven't decided on the right one yet, pictured is a 8x6 RAM)
- 1300 mAh Lipo
- Turnigy 8 ch receiver
- Skywalker 20A ESC
Bottom side (yes, the antenna is too close to the ESC):