YXQ-1 Valkyrie: 3D Printed EDF Flying Wing R/C Airplane - Part 1

Hello, my name is Gus Flusser and I recently graduated from Palos Verdes Peninsula High School in Palos Verdes California. I am excited to attend California Polytechnic University, San Luis Obispo in September, but before then, why not work on a summer project?The goal I had in mind with this project was to make something that I could fly. I have recently rekindled my fascination with flight, and I wanted to experiment with various ideas I had when thinking about aviation. I thought that the best way to test my ideas was with a remote-controlled model airplane. After a lot of thought, I settled on a flying wing design with 3 small fuselages to contain the majority of the electronics.Why the wacky name? In 1962 the United States introduced a system to unify the aircraft naming designation among all of the branches of the military. I wanted to name my airplane within the bounds of this system, and I chose the YXQ designation. In this unified system, Y means prototype, X means special research, and Q means unmanned aircraft, three attributes of my plane. The 1 simply designates this aircraft as the first version. The name "Valkyrie" is already used by the XB-70 Valkyrie created by North American, but the colors I chose for this aircraft took heavy inspiration from Tessa Thompson's character Valkyrie from Thor: Ragnarok. I decided to designate my plane as "Valkyrie" in honor of this inspiration.Below I have attached all of the Fusion 360 design files for the airplane, propellers, and the assembled version of both so anyone can view them, improve them, customize them, or anything you like!P.S. Autodesk Fusion 360 has a really neat rendering feature that allowed me to capture some of these amazing render pictures. You should check it out!

This link will open a 3D model of the aircraft fullscreen.

This link will do the same for the propellers.

Materials:

2x Turnigy L2855-2800 EDF Outrunner Motor

2x HobbyKing 50A (2~4S) ESC 4A SBEC

2x 3.5mm Banana Connector Cables

1x Arduino (this is the one I used)

1x Pack of 2x 2s Compact LiPo Batteries

1x Deans Connector for batteries in series

1x package of Wire Connectors for Low-Gauge Wire

1x Pack of 683ZZ Bearings

1kg of Polymaker PolyLite PLA 1.75mm Filament

~0.1kg of ABS 1.75mm Filament

~1m of 14 AWG Wire

~0.5m of Servo Wire

Some Spray Paint

Tools:

220 Grit Sandpaper (for support material removal)

Needle Nose Pliers (for support material removal)

More Stuff:

3D Printer

Autodesk Fusion 360

KiCad

Soldering Iron

1-2x bottles of Superglue

Some Metric Hardware

While almost everyone may find it boring and time-consuming, the first step in the process of creating something is learning more about what you want to create. Without enough background knowledge or understanding of how airplanes or ducted fans work, my only chance of creating one that works is to learn. I will give some brief information on aerodynamics, propellors, and ducted fans, but I recommend doing research of your own as well. I love to watch YouTube videos when I want to learn about something, so I will link a few that I watched while learning about aerodynamics if you want to learn from them as well.

Propeller Physics:

There are two major ways that a propeller creates thrust. The simplest one is based off of Sir Isaac Newton's Third Law of Motion, and the other is based off of an equation called Bernoulli's Principle. Newton's Third Law states that for every action (force), there is an equal and opposite reaction (also a force). This means that if someone were to throw something, the force with which the object flies away is equal to the force at which you move backwards after throwing the object. This is how rockets work, they expel a force backwards through (typically) combustion of a propellant and as Newton's third law states, the rocket gains a force in the opposite direction which it uses to propel itself into the sky.

Airplane and Propeller Physics:

Bernoulli's Principle is the second way propellers create thrust, and is also how aircraft wings create lift. The principle has to do with fluid dynamics. While it may be strange, gasses are considered fluids, and air is no exception. Fluids move from areas of high pressure to areas of low pressure to maintain equilibrium. Bernoulli's Principle proves that a faster moving fluid has lower pressure than a slower moving fluid, and airfoil takes advantage of this. An airfoil is a shape designed to accelerate air on top of it and slow air on the bottom while minimizing drag. The higher pressure air from the bottom of the airfoil rushes to the lower pressure area on top of the airfoil, as the air is moving faster there, and the result is that the airfoil moves upward. This generates a force known as lift, it will help our plane accelerate and fly.

Ducted Propellers:

Now that we know about creating thrust with propellers and lift with airfoils, why do EDFs have a duct around them? The simplest answer is that they require this duct to minimize wingtip vortices. Wingtip vortices are a phenomenon in which high pressure fluid at the bottom of an airfoil moves to the side and around the wing to reach the low pressure zone. This decreases the lift force the airfoil can produce and reduces the amount of thrust that the propeller creates. To get around this, we will create a duct around the propeller to nearly eliminate the wingtip vortices.

This duct will also be used to constrict the air coming out of the EDF into a cross-sectional area. A second statement of Bernoulli's Principle is that a fluid moving through a smaller cross-sectional area will do so faster than if the same amount of fluid was moving through a larger area. This will slightly reduce the amount of thrust we create but it will increase the speed at which our EDF can expel air and make the airplane go faster.

If you want to learn more about aerodynamics or ducted fans, these are a few videos I found interesting and useful:

Wyman's Workshop: How to apply ducted fan theory to real world fans

The Efficient Engineer: Understanding Aerodynamic Lift

Designing the body of the flying wing took me almost 6 months. During this time I was able to look online at dimensions for the various electronics that needed to fit inside the plane, and with these measurements I was able to work through the design process until I finalized my design.

I started by creating a sketch of the top view of the airplane. This allowed me to scale the fuselages to the right dimensions as well as give me a general idea of how large this plane would be. I came back to this original sketch several times (as I did with most of my early sketches) to make small adjustments to the outer fuselages and fan ducts.

Next I created a canvas of a flying wing airfoil from The University of Illinois Urbana-Champagne's Airfoil Database. I traced this canvas and ensured that the scale was correct so that it could be the outer fuselages of the airplane. I created two offset construction planes perpendicular to the airfoil's direction of flight, and followed similar procedures to create the smaller airfoils at the center of the plane and where the body meets the wing. I then used Fusion 360's loft feature to create a solid body out of these 3 airfoils.

I then made my original sketch visible and revolved the fuselages around their center points to bring them into three dimensional space. After I had the final size of the outer fuselages, I began to model the propeller duct. I knew I was going to design a 70mm propeller to fit inside of the duct, so I simply grabbed my caliper and the EDF motor created a motor mount using a few sketches and extrusions. I had to 3D print, adjust, and 3D print a test part of the motor mount where the motor would screw into until I had the correct dimensions, enabling the motor to fit properly.

After I had a general shape of the body I turned my attention to ensuring that the electronics I had would fit inside of my plane. I stared at the wing, and created a cavity for a 9g servo to fit in. I then cut out some of the space between the servo and the outer fuselage so I could later attach the servo to the flight computer. I also created a path from the outer fuselage to the inner one for all of the wires to reach their destinations. After settling on a location for the servo, I sketched where the center of rotation was and cut out a section of the wing to connect to the servo and serve as an elevon. I made sure to create a hole at the other end of the wing for a bearing.

I then began to work on the landing gear servos. I took the sketch that I made earlier of the servo and pasted it into the outer fuselage. I then created several vertical beams to connect the servo to the fuselage and reinforce the servo, which could snap off of its connection places due to vibration damage from landing. I created a hole in the reinforcement beam for another bearing.

The middle landing gear servo mount was a little trickier because I did not have as much space, as the fuselage diameter was smaller. After following similar procedure to the outer fuselage servo mounts, I had completed the left half of the plane. I mirrored all of my work over the middle of the center fuselage, and the airplane was complete.

I began the design of my EDF propeller by again gathering images of propeller aerofoils from UIUC's database. After making a hub for the propeller, I then took our airfoil image and overlayed it on a tangent plane to the hub. I rotated the canvas around its center to create the pitch (angle) of the propeller. I then traced the airfoil image using the spline tool, accurately creating a sketch of the airfoil canvas. To make the outer airfoil I used a similar method, overlaying a canvas of a propellor airfoil on an offset plane, and rotating it around its center. I then again traced the canvas using a spline. After the inner and outer propellers were sketched, I used the loft tool to create a solid propeller blade from the two airfoils.

After I finished the solid outer propeller, I created an inner propeller designed to push air through the motor to keep it cool. I did this by creating a hole in the propeller hub and extruding a secondary hub where the motor shaft will be attached. I then extruded the first airfoil sketch into the new hub to create the inner propeller. Then all there is left to do is separate the bodies of the inner hub, inner propeller, outer hub, and outer propeller. I used the body separation tool for this task. I then duplicated the outer and inner airfoils around the center point of the propeller using the circular pattern tool. I settled on 12 blades for the outer propellers and 6 blades for the inner propeller. I then created a hole in the inner hub for the motor shaft and my model was ready to print!

After I had finished modeling the difficult parts of the airplane, all I had left to do before printing was the landing gear. I had already created holes and covers for the landing gear to retract back into the fuselages, so I knew what dimensions the landing gear had to be.

I started by creating a rounded rod that would act as the landing leg. I realized that while this simple design would work for the outer landing gear, the middle module would have to be modified. To compensate for the tight space and the size of the servo, I created a slight bend in the middle landing leg. I had already designed wheels for my previous Instructable, so I followed a similar procedure when designing the new wheels. I created a circle, extruded it, and filleted the edges. I then created a notch in the wheel to aid in traction, and circular patterned that notch around the wheel. I then created a hole in the wheel for a screw to fit in, and placed a bearing hole in the landing legs. I was finally done modeling my plane!

At over 800 millimeters long, I knew that I could not even come close to printing the body in one piece. I started on the process of splitting my plane into sections. I created a left and right wing partition as well as a left, right, and middle fuselage partition. I then subdivided all of these zones into printable pieces, and began to export.

I used Fusion 360's Print feature to export the parts of my plane quickly into my slicer. While slicing I knew I needed to reduce weight as much as possible, so I minimized the amount of wall layers and filled it at a 4% triangular infill. This gave me the maximum strength for the least weight.

After I had printed most of the pieces, I began to superglue them together. After joining a few pieces I began to get the hang of it, and I was able to glue together the parts faster and with more precision. After I had created larger sections of plane from the smaller ones, I spray painted the fuselages and elevons and assembled all of the pieces I had into a left and right section. After carefully lining up the two halves, I glued them together and had finished realizing my 3D model into a physical plane!

With the physical plane ready for electrical components, I grabbed my soldering iron and sat down to connect everting. I first mounted the landing gear servos in their respective areas and glued the wires to the inside of the fuselage to prevent the beginning of a tangley wire monster. I then glued the ESCs in place and used solder butt-joint tubing to connect them to the power source and the motor leads. I then extended the elevon servo wires so I could glue them to the fuselage and give them enough length to plug into the flight controller. I again mirrored my procedure for the other fuselage, and all that I needed to do was power the ESC's and create a flight computer.

I layed out all of my flight computer components on a breadboard, and began wiring them to the Arduino. After a few attempts, I was able to get all of the electronics responding properly, and I was ready to create the PCB. I started up KiCad, a PCB software, and designed my flight computer to fit inside of the central fuselage and communicate to all of the components. I did not use Fusion 360 for designing the PCB because I am not as familiar with it as I am with KiCad, but I plan on learning how to use Fusion 360 for designing circuitboards in the future as it is a much more powerful program. After double and triple-checking the connections I had made I placed an order for a custom PCB and waited for them to arrive.

I received the circuit boards and soldered all of my components to them. I ran the same code I had when everything was connected through the breadboard, and everything worked properly! I then began to mount the flight controller to the middle fuselage, and realized I had forgotten to model a stand for it to rest on in Fusion 360. I opened up my Fusion 360 file and created a platform to mount my flight controller to. I then glued some heavy-duty velcro onto the mount and flight controller so that it would stay stable in flight, but would also be removable in the case of a software update or a bad crash.

After I had secured the flight controller in place, I removed it and uploaded a program that would allow me to control the plane with my remote. I tested the landing gear retraction, elevon control, and throttle, and everything went smoothly.

In my next Instructable I will complete my aircraft and follow up with afterthoughts and what I would do differently if I was to design and 3D print another airplane. Will my Valkyrie fly? We’ll soon find out!