Self-built flying wing
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.
Parts list:
- 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):
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Comment by Dwgsparky on September 7, 2012 at 6:28am -
Great looking wing, very similar to mine although my wing section is thicker to carry extra weight at a slower speed.. I see 2 small issues as it is.:-
1, A flying wing will always need reflex in the rear of the wing to create drag and provide stability, this is normally achieved by lifting the elevons about 1/4 inch each side. with your short elevons this will be difficult, you may need to extend the elevons out to the tips or cut the trailing edge and refit it raised up 1/4 approx. The problem is that there is no way to calculate the exact ammount of reflex that is needed, thats why most wings have full width elevons. Wing tips will also help with stability and protect the tips on landing.
2. the amount of elevon movement is usually very small especially in roll, if you have too much movement you will stall the wing and it will drop like a brick. You need to use the inner holes on your servo horn and the outer holes on the elevon horn..
Good luck with the test flights.
dwgsparky
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Comment by SaadTiwana on September 7, 2012 at 7:08am -
Hi. Nice wing, good job! Your wings have a shine. Did you coat them with something which gives the smooth surface/shine?
-S
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Comment by Crashpilot1000 on September 7, 2012 at 7:17am -
I always wonder how deltawing pilots give "rudder". I think they do a small roll and pull "elevator" - anyway it must be really fun to fly these tings!
Rob
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Comment by Eirik Mikkelsen on September 7, 2012 at 7:18am
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Great tips, thank you! I had initially limited the range of the aileron servos on the radio, but placing the rods like you say will of course allow full movement and resolution of the servo and should be smoother.
SaadTiwana: That is clear packaging tape! :-)
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Comment by PeteD on September 7, 2012 at 7:19am -
Why put the ESC on the bottom? I don't think it will last long there.
Have you test flown yet? Prop should be ok, the only specs I could find are here: http://www.uberallmodel.cz/index.php?id=15&lang=en.
How much does it weigh? I get the sense that it could be under powered.
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Comment by Eirik Mikkelsen on September 7, 2012 at 7:29am
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The ESC on the bottom just fits nicely with the length of the wires and the CG. I might recess it more and add some padding, but I have a few of these ESC's around so I'm not too concerned about it.
It may be slightly underpowered, haven't flown it yet. I'm waiting for the mailman to bring some bullet connectors, none of the local hobby shops have then in stock. The motor was just something I had at hand right now. With a larger motor and battery the CG should stay the same. The weight is 450 grams.
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Moderator Comment by Gary Mortimer on September 7, 2012 at 9:33am -
Get yourself a proper electric prop performance will improve, an APC thin of some sort. Add some fins as well you will need them.
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Comment by Tero Koivunen on September 7, 2012 at 12:02pm -
I have something similar:
140cm span, 10x6 prop, HK Donkey ST3007-1100kv,40A ESC, Rhino 3700mAh 3s,
about 1kg, little bit underpowered. Airfoil NACA 2412 / 0012.
At the beginning of the video you see that plane with full size elevons and depron winglets (changed to EPP lately).
http://www.youtube.com/watch?v=CZlq83C_gYI&list=UU0s8dVrhskmY4a...
I have some nose up behaviour, when applying throttle, motor is directed also straight
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Comment by Eirik Mikkelsen on September 7, 2012 at 12:34pm
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Tero, that is a nice wing! What camera was used for this video? My next project is to build a larger plane with more wingspan, I want something that flies well at slow speed, and with enough carry capacity to handle full autopilot and fpv setup.
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Comment by Tero Koivunen on September 7, 2012 at 1:18pm
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It's GoPro Hero, very nice camera, if you can stand fisheye effect ;P
I think it should be even larger than 140cm, maybe 160-180cm and specialized flying wing airfoil (quite thick, more space to equipments), 500W+ motor. Ritewing II like. In calm air not easy to launch, maybe front side of wing technique throw. Earlier I had Multiplex Xeno (120cm), and it gets quite heavy soon, when you put all load on it.
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