Simple Dragonfly RC Glider

Easy to put together, simple, well documented.
Own this and print it as many times as you like for only $9.99

A reference assembly & flight video has been posted at the following link:
https://www.youtube.com/watch?v=Jo0Z-0VQf40

I have other RC planes and plane related parts:
https://cults3d.com/en/users/taciucmarius/creations
^^^ Check them here for more fun ! ^^^

• General instructions: If you want to build a good plane that flies smoothly, please take your time and read all of the below provided instructions. If you don't understand something, please don't hesitate to contact me.

Wingspan: 1400mm
Length: 860mm prop to tail edge(depending on the type of cowl you choose)
Ready to fly weight: 950g to 1100g depending on your battery and material type (the red sample in the image is 1100g).
Main wing's angle of incidence: 1°
Wing surface: 20.5 dm2 (if configured like in my pictures)
Stall speed: 30.4Km/h (if configured like in my pictures)

Recommended battery:
Li-Po 4s, 3000-4000mAh would be ideal, but other battery sizes work. Try to keep it between these recommended sizes, because it will be easier to balance the plane without adding nose weight.

Motor and propeller:
Many combinations could work, but for the reference, the sample in the images use an AEORC Brushless Motor A28L MM2216 920KV 1270KV 3.0mm Shaft Brushless Outrunner Motor
from Aliexpress. the propeller is a 9x5 foldable one. This pair can technically achieve between 850 and 1000g of thrust.
I usually fly with 30% throttle
I used a 30A ESC and 2x SG90 servos. The receiver is a 7ch RX701 from Walkera.

CG:
At 53mm as you measure away from the wing's front edge. I inserted and glued in position a couple of round headed pins (see pictures). One on each side. I balance the plane by suspending it on these pin heads with my fingers. Make it rather slightly nose heavy and you can't go wrong. More info on the attached pictures.

Main gear:
The wheels are 3" polyurethane from the online stores. Other sizes work as well. I used large ones because of the grass. The wheels are being attached with a custom made aluminum bar. You can build one out of scrap materials you might have around the house. The one in the pictures is made out of 2mm extruded alu sheet. I will add a printable support and hopefully you will be able to print that out of PLA+ or PETG. A printable wheel support might not be that resistant when it comes to bumpy runaways. If you have a foldable propeller, you can even leave it without wheels and hand launch it. The height of this wheel support is also depending on your needs, prop diameter and runaway conditions.

How it feels when flying:
It's hard not to be a little subjective here, because this is my creation after all, but it flies smooth. I would say that if the CG is balanced correctly, it's really easy to fly. It feels like a beginner's balsa trainer glider. It feels light and because of the incidence angle, it picks up altitude on it's own. It dangles sideways from time to time but it stabilizes quickly. At first, I flew it at higher speeds, because I expected it to be heavy and to require speed in order to airborne, but then I was able to reduce the speed quite a lot and still keep it floating. You can see in the video how smooth it lands at low speed. Because this plane comes out perfectly from the 3D printer, it requires no roll balancing. My samples flew straight from the first time and keep straight during flight when taking my hands off the controls.

Crashes and mishaps:
I printed several samples and some of them crashed because the plane was tail heavy. PLA or PETG don't work for the fuselage. They make it way too tail heavy and you would need to add lots of nose weight. This results in a heavy plane and all the forces and the stress in the landing gear are damaging to the whole aircraft. I saw that flying when colder than 5°C makes the plastic of the plane more brittle. Sometimes this delaminates the fuselage and breaks the wings at smaller forces. Bare this in mind. I would fly this in winter time, but with caution and performing less acrobatics.
The brand of filament that you use also plays a huge role in the strength of the plane. I printed the green version out of china PLA and that was extremely crackly and it would break easily. Then I bought some Colorfabb and I couldn't believe how strong and elastic it can be. The moisture of the filament can also impact the strength. Higher speed impacts result in shattering the entire fuselage. So at high speeds, the material is no longer elastic, but brittle. This is probably the only real downside of 3D printed planes when comparing them to balsa structures. Balsa is more elastic at high speed impacts.
Having asphalt or concrete runaway instead of a bumpy dirt meadow, can save and prolong the life of the glider. Most damages happened at takeoff or landing when touching the prop to the ground. This can result in fuselage cracks or shatters.

Print it, have fun and post pictures so that I can rejoice with you.

Fuselage:
LW-PLA is a must.
The fuselage was optimized and sliced so that you can print it in two different ways (vertically and horizontally). Previous tests showed that the LW-PLA filament is having a higher tear resistance if the printed fiber is being aligned longitudinally. However, some of the LW-PLA filaments on the market have a very high delaminating resistance. Hence, there is no problem if you print the fuselage parts vertically. The red fuselage in the attached pictures was printed vertically (with the layers perpendicularly to the longitudinal axis) and it held with no problem.
The nose comes in 4 different models. Being configurable, it allows for fitting both outrunner and inrunner brushless motors. The different cowls also have different inner sizes for accommodating various battery models.

Wings.
I printed all of the pieces out of PLA+ (for more strength), but I realized that up to 3 sections on each wing tip can be printed out of LW-PLA because they distribute less force. Each wing module is being named by the color code it has on the design assembly picture. Please check the picture for reference. At this point you will understand why I wrote some tiny letters on each wing segment and they show in some pictures (B, G, Y, W, R).
Configurable. Being a modular design, the wings can be assembled in various combinations using as many segments as you want (sort of). You can experiment with shorter wings or no second dihedral angle close to the wing tip.
The wings must be printed horizontally on the print bed and cannot be oriented vertically. For these segments, the fiber must be axial.
I welded the wing plastic segments using a soldering iron, but glue can be used as well. If you don't know how to weld plastic, check this video of mine to teach you how:
https://www.youtube.com/watch?v=_HjSz5hRb0E
Add the golden pads (LW-PLA) for more wing resistance. Normally the wings hold the pane very well, but at some point I encountered some mad lateral winds that flexed them more than expected. Other times, I just descended very rapidly or did some acrobatics that resulted in the same thing. I noticed afterwards that those particular cell walls(3 on each side of the middle line) were a little bent. The wings never broke, but I realized that they need more resistance in that area. Follow the picture instruction for more details. And of course, this step is optional. It is your choice if you need the plane to be lighter or stronger.

Tail pieces:
LW-PLA is a must in order to maintain the CG balance.
All control surfaces have print in place hinges. Normally they should withstand thousands of flex movements, but you could have surprises due to material quality, aging, UV exposure and moisture. If you don't like them and need more robustness, simply trim them off and insert regular glue in place film pieces (see the pieces that have special slots for this and the descriptive picture). Another option would be duct tape or packing tape. The control surfaces do require placing the heatshrink airfoil to them and the hinges could hinder with this. I was patient enough to tape the foil between the hinges and it came out nicely.

By the way, the airfoil can be applied and ironed on top of the LW-PLA parts with no problems.

The control horns require separate printing and gluing into position.