Flying Captain America's Shield - RC Plane

This is Captain Nutball. She's a scratched built, easy-to-fly trainer RC plane modelled after Captain America's shield. Her name is derived from a combination of Captain America and the RC model FT Nutball. Credits to my friend Andrew for coming up with the name!

Captain Nutball is designed to be aesthetically beautiful, flyable by any beginner pilots with little to no experience (like me), and relatively easy to construct. She's also partially waterproof, so the wings are protected with a drizzle but it won't be able to withstand a rainstorm. In addition, there are optional added functionalities like a retractable landing gear and snow skid conversion for winter flying, especially here in the Great White North where I live.

I was inspired to build this after I saw Seamster's Flying Captain America's Shield project. It glides beautifully, but it does not fly nor does it return to the person throwing it. I am a huge fan of Marvel and my favourite movie series of all of them is Captain America, so in the true spirit of Captain America's shield I wanted to made it into a real flying RC shield. Given that I am absolutely in love with flying, I immediately jumped on to this project. Nothing is better than combining my passion and interests to make a marvel of a shield plane (pun intended). Admittedly, Captain Nutball looks less like a shield due to the vertical fin sticking out, but at least it can come back to me!

She took about 12 total hours to build solo. So, it's a perfectly doable project to build over a weekend and even quicker and more fun with friends and family. I had a lot of fun making this project and I hope you enjoy building and flying it too!

Plane Materials

* Dollarama(Canada) / Dollar Tree (US) Foam Board - $1.25

* Spray Paint

* Krylon True Blue - $6.49

* Rust-Oleum Glossy Apple Red - $7.88

* Rust-Oleum Metallic Aluminium - $8.37

* Minwax Oil-Based Polyurethane Semi Gloss (Not water-based ) - $9.17

* Painter's Tape - $ 5.77

* Dollar store Barbecue Skewers - $1.25

* 1/8" Plywood - $2.19 I got a small piece for free from Toose Art Store.

Electronics / Propulsion

* Transmitter/Receiver (Tx/Rx) Pair - $61.30

* 20A Brushless BEC Electronic Speed Controller (ESC) - $11.52

* 1200kv Brusless Outrunner Motor - $18.75

* 8X4 Electric SlowFly Propeller - $1.24

* 2S 25C 850mAh Lithium Polymer (LiPo) Battery - $6.81

* 2 pieces Servo Motor - $41.62 you can also get the cheaper Hextronic plastic servo motors.

Miscellaneous Items

* Stake Flags / Piano Wire for Push Rods - $2.49

* 3.5mm Gold-Plated Bullet Connectors - $2.29

* 4mm Heat Shrink - $0.75

* Nylon Control Horns - $1.75

* Nylon Clevises - $0.86

* Scotch Tape - $3.74

Total Price: 195.49 not including shipping cost or tax

Although it seems pricy, you can reuse most of these spare parts for your other RC related projects and the electronics are a one-time investment which are also reusable.

Note that, all prices are quoted in Canadian Dollar.

Tools:

* Hot Glue Gun and Hot Glue

* Soldering Iron and Solder

* Scissors

* Box Cutter with extra blades

* Set Square

* 2" Chip-Style Paint Brush

Captain Nutball is designed to for repairability, ease of flight, and manufacturability. In addition, there are many other secondary design factors that affected the design decisions for Captain Nutball such as design for aesthetics, durability, versatility, and cost-effectiveness.

* To make Captain Nutball easy to repair and construct, she is designed to be composed of only three parts -- vertical fin, wing, and power pod, all of which is made with foam board. Being fully scratch built and composed largely of dollar store foam board also makes her cost effective for many beginner flyers who will have more than their fair share of crashes.

* To tackle ease of flight, she is a virtually un-stallable plane, capable of flying slow and fast (by changing from 2S to a 4S battery) to cater the needs of both beginner and advanced flyers. She is designed with a polyhedral which allows her to self-stabilize if the pilot relinquishes control.

* She is aesthetically very pleasing, decorated as Captain America's Shield and is also water resistant. Although I would highly recommend against flying it in the rain.

* Being part of Flite Test's swappable series makes her versatile, since her power pod can be removed an transferred onto other wing designs. This also makes the electronics apart from the servo motor a one-time investments proving her to be even more cost effective!

This makes her a perfect airplane for beginner hobbyist who want to enter the hobby without investing a fortune, while also getting a fun-filled experience from build to flight. For me, Captain Nutball is quite a personal. I've always dreamt of flying a real plane, as a pilot, but flight school is incredibly expensive. My unending passion leads me to a path of pursing every aviation-related I get afford as I slowly work towards my lifelong goal of becoming a Pilot. Captain Nutball is the pinnacle of the objectification of my love and passion for flight and aviation and takes ever so slightly close to my dreams!

Scaling

After looking at many pictures online of Captain America's shield I concluded that all the rings are the same thickness except for the centre most ring which is twice the thickness of the rest of the rings.

To verify the scaling from my visual approximation, I copied and pasted am image to Powerpoint and used the built-in line drawing with measurements to measure the length of each ring. As shown in the image above, it's not exact, but that's likely more due to the error in the drawing and my method of measurement.

Note that the measurements are not the measurements for the paint maskings but are only there for comparison and verification purposes.

Paint Selection

After looking for the perfect colour in Home Depot and Canadian Tire for hours and experimenting I have found the following with various colours to be the best colours to paint Captain America's Shield:

* Rust-Oleum Glossy Apple Red

* Krylon Glossy True Blue or Rust-Oleum Cobalt Blue

* Rust-Oleum Glossy Aluminium Metallic Finish or Rust-Oleum Glossy Silver Metallic Finish

These designs plans are designed by Josh Bixler and provided by Flite test.

Included below are the tiled and full-size plans for Captain Nutball as well as the winter skid conversion plans. If you do not have a large format printer like most people, print out the tiled plans at 100% scale, single sided.

For taping the paper together, I used 3M Scotch tape because it is very easy to cleanly remove from paper without damaging the paper or foam board.

First, I laid out the 8 sheets of paper in order on the floor.

The circular wing and vertical fin are of pages 1-3 and 5-7. The power pod is on pages 4 and 8. The power pod is a separate piece so it does not need to be taped into a big poster. I chose to have two separate poster pieces to save space and keep it less bulky.

I find it easier to connect the vertical pieces, that is, pages 1 and 5, 2 and 6, and 3 and 7, together before the horizontal one. Align each of the vertical pieces together, focusing on the connection of the lines from one page to another. Once it is aligned, tape the two pieces of paper outside of any printed markings.

It is important not to tape over the markings since this will make cutting it easier, as there won't be an added layer of tape to cut through.

Once all the vertical pieces are taped together. Tape all of the vertical sets horizontally with the same method of aligning the black markings before taping around it. Once all the pieces of paper are taped together, tape each of the intersections. Then, tape all the places just outside and just inside of the black cut-out marks.

Make sure there are no loose paper when you pick it up. If it's loose, then tape it a large sheet of foam board.

For your reference, the black lines are cuts; the red lines are 50% score cuts; and blue marks are references.

Pro tip: The key to making smooth cuts is to use a very sharp and new blade. Hold the blade at a 30 degrees from the horizontal and use the body of the knife as a guide while you cut. This plane is quite versatile, so the cuts do not have to perfect but try to keep it aligned to the contours as much as possible.

Pro tip: I found it easier not to use a ruler to cut the straight lines since the knife can easily slip out. There's more control to the blade without a ruler and using the frame of the knife helps a lot in making precise and accurate cuts.

Wing

To cut the circular wing, focus on making small smooth cuts at about a 80% score. After all, a circle is just a series of very tiny line segments. Once you have made the 50% scores, lift up the foam board and poke the blade through the foam board and let the score marks guide the knife as you cut around the circular wing.

In hindsight, I realized it would be easier to cut the holes at the centre before cutting the outside contours, rather than cutting it after painting. While, marking the blue reference marks onto the board, so the piece of paper does not have to taped to the foam board all the time.

Vertical Fin

To cut the vertical fin, use the same technique as the circular wing by first making a 80% to 90% score with the blade, again using the body of the blade to guide the straight cuts. This will leave just the thin layer of paper on the other side holding it together. Before fully cutting it off, tape the piece of paper to the foam board so it does not come lose once it is fully cut. I taped mine on the bottom edge and wrapped it around. Like before, lift up the foam board and poke the blade through and follow the let the knife follow the pre-cut contours. Only press on it lightly and guide it around the cuts.

Power Pod

The power pod is the piece that will be holding all the important electronic components.

Make a 50-80% score cut on the red lines. Then, carefully snap the foam board along the score cuts. Then peel off the long cuboid strip. It should come right off given your score cuts. If not, just dig in with your finger nails and peel it off until only a paper layer is left. Repeat this for both sides.

It is important that you have sharp and crisp cuts on the notches of the power pod since it will be used for attaching the power pod to the rest of the wing.

Pro tip: Do not throw out any of the the cut-out plans, even after cutting the foam board. It will be useful in future steps.

Coat both sides of the wing with Minwax using a chip-style paint brush. Leave the it on for 5-7 minutes. If you can see areas that are not dry (by looking at the reflection of light on the foam board), then the coating is to thick. Wipe the excess with a paper towel and let it dry for another 5 minutes.

Minwax is used prior to coating it with paint to prevent the foam board from warping. Dollar store foam board is made with two pieces of paper with a foam board sandwiched in between and I noticed after spraying the water-based spray paint onto a piece of foam board that the paper layer of the foam board began to warp and peel off. By using coating it with Oil-based (not water-based) Minwax so that the spray paint sticks to the Minwax and not the paper.

I also coated the power pod and the vertical wing as well even though I was not planning on painting them to make it semi-water-resistant.

Pro tip: Hot glue from a hot glue gun does not stick to Minwax. So anything that needs to be glued later on, needs to be covered with taped so Minwax is not applied to it.

Drawing the rings

Tape the circular wing onto the wall or a large flat surface. I chose to tape it onto the wall since it my wall was cleaner and less cluttered than my floor or desk. Don't worry about ruining the drywall or table paint since painter's tape does not peel it off. Then, layer painter's tape one over the other with about a 50% overlap in consecutive order downwards until the whole wing is covered. The overlap is necessary so that you can peel off the tape easily from the top with one motion.

Make a compass by tying a string to a pen as close to the bottom as possible then add a bead of glue just to the top and bottom of the pen so the string does not slip out but also not too close such that it is still free to pivot. I chose twine as the string that I used because it does not stretch. Then, cut the string to the length using your compass for the radius of each rings for Captain America's Shield one at a time (cut-draw-repeat) as specified below:

* 20 cm - Silver ring bordering red ring

* 15 cm - Red ring bordering silver ring

* 10 cm - Blue ring with metallic star bordering red ring

To find the centre of the wing / shield, use the circular plan you cut out previously and fold it to quarters to make a cone shape. Then, snip a small portion of the pointy end of the cone. Open it up and there's your centre. This is where you will glue or hold the free end of the string.

I found it easier to mark each of the radii with a ruler for multiple points of the circle as waypoint marks and sanity checks that I am marking the correct radius. Then, I used the makeshift compass to draw each of the ring.

Drawing and masking the star

Mark the top most part of the circle by going from the centre mark and using a ruler to aligned perpendicularly to one of the centre square cuts. This will be the top-most tip of the star. Then, using a protractor or a set square (mine has angle markings) mark each 72 degree point (360 degrees / 5 points of star). I connected the lines of the star the same way we were all taught to draw it back in grade school.

Cutting the masks

Once everything is drawn carefully peel off the painter's tape from the wing. To cut the different ring layers of the shield I stuck approximately half the maskings of it back onto the wall. Then, I cut perpendicularly all the way to the inner red ring. Using scissors, I worked my way around cutting the ring while rotating the parts taped onto the wall as I cut. I found that keeping some parts of it taped onto a surface since it it prevents the tape from sticking to itself, which is very difficult to pull apart.

Cutting the star is pretty simple, just follow the pen markings of the outer edges of the star and cut with scissors, unless you have a cutting mat, in which can a box cutter would be easier.

Taping the masks

Starting from the outer ring and going inwards, tape each of the cut rings onto the wing according to the order of painting. More information about this on the next step which is painting.

Pro tip: Do not throw out any of the maskings until you are done painting all the layers.

After experimenting with a combination of overlapping colours with the three paint colour selection, I learned that you can layer red or blue paint on top of the metallic paint without any noticeable difference in colour. However, a slight mixing of red and blue, even at the edges will get a deep purple colour. So this means we don't need to do any maskings for the metallic paint, but we need to mask everything for the rest of the colours.

Metallic Aluminium Paint and Masking

Naturally, start by painting both sides of the wind with the metallic aluminium-coloured paint. To paint it, first shake the spray can for about a minute, then hold it approximately 30cm away from the surface and make 4 to 5 light coatings or until it looks like a nice even metal finish. It took a lot of practice to get just the right feel for the spray paint so I recommend practicing with a scratch piece of foam coated in Minwax until you get the hang of it. Practice it with all the spray cans since each brand behaves a little differently.

I chose to only paint top side of the wing with the Captain America star and the other as used metallic look (mainly because I did not want to make another mask for the other side). Let it dry for about 10 minutes.

Blue Paint and Masking

Next layer is the blue paint. Mask all the layers except for the blue ring with the maskings you made in the previous step. Again, apply 4 to 5 light and even coatings at approximately 30cm away from the surface with the blue spray paint. This just takes practice to master. Let it dry for another 10 minutes before coating the red layer.

Red Paint and Masking

Lastly, the we will paint the red rings. Again, mask all the layers except for the red rings and apply 4 to 5 light and even coatings, then let it dry.

While the paint is drying, you move on to the next steps.

Power Pod Assembly

Fill the empty cavities on each side the power pod with hot glue. Do this one at a time so hot glue does not dry out. Once filled, placed the side layer on top of the bottom layer of the power pod. This is called an A-fold, A for above. Then, use a set square to keep the sides perpendicular as the glue dries. Do not touch the paper layer with your hands as it gets very hot, so only use the set square to align. If there are excess glue seeping out, take a scrap piece of foam board and scrape it off before it dries.

Repeat this for the other side of the power pod.

Pro tip: Always keep an extra stick of hot glue handy.

Attaching Power Pod to the Wing

Glue a small popsicle between the two small oval holes just below the centre of the wing and loop a zip tie around the two hole as shown in the picture. Test fit the power pod onto the bottom side of the wing. It should fit snuggly. Then, poke a hole through the back of the power pod with a skewer as marked in the templates and tighten the zip tie. Cut the skewer to size.

Cutting and Drilling

Cut the motor mount guide on the template and tape it onto the 1/8" piece of plywood. Then using a bandsaw cut the motor mount, also known as the firewall, to size accordingly.

Again, following the template, drill the holes for the motor mount with a drill press as shown in the picture above. I did not have a large enough bit for the centre but the hole did not have to that large for my particular motor's shaft so I just used the largest bit I had.

Motor and Propeller Mounting

Screw the motor onto the motor mount using a threaded bolt and tighten the nut against the firewall. Two screws on opposite sides are enough but you can also use for to be safe. Cut the excess bolt using a hacksaw.

I first attach a prop adaptor ring onto the propeller since the bore was too large for the motor mount. Then, place the propeller into the motor shaft and screw the collet on top of the propeller. To tighten it, I inserted the stake flags into the holes and used it as a lever to tighten it. You can also use a vice grip.

Mount to Power Pod

Then, glue the motor mount onto the front (flat-side) of the power pod with the two top holes of the firewall aligning with the wing. Take two skewer push and into the foam board with a twisting motion. Remove it from the foam board with a similar twisting motion but in the opposite direction and add a bead of glue into the hole and twist the skewer back in for both holes. Do not glue the skewer onto the firewall so that the firewall can be removed for battery charging purposes. In addition, this power pod can be removed and transferred to other RC planes.

ESC to Motor

Connect the three wires of the ESC to the motor. A particular does not matter in this step. All you need to know is that switching any two wires of the ESC-to-motor connection will reverse the direction of the motor.

ESC to Battery

The two sets of wires of the ESC connects to the battery. Here, order does matter since there is a polarity. My ESC came with bullet connectors but the battery only came with JST connector, so I cut each wire of the ESC and soldered a male jumper cable to connect to each female pin of the JST connector on the battery, as shown in the picture. Connect black to black or negative or negative and red to red or positive to positive.

ESC to RC Receiver

The three thin wires connected together is the signal pin of the ESC. This connects to port labeled channel 3 of the receiver. Different companies have different standards but for a Turnigy or FlySky Receiver, the throttle control is channel 3. The white white is the signal pin, black is ground, and red (which is always the middle pin)is power.

Servo Motor to RC Receiver

Connect the servo motor to the RC Receiver channels 1 and 2. Channel 1 for the rudder and channel 2 for the elevator. The wire colours are consistent to that of the ESC wires and plug in the exact same fashion as the ESC except in a different channel.

Once tested remove the battery connection and before proceeding to the next step.

The polyhedral is a component of an airplane's wing that is angled away from the horizontal axis of the wing outside of it's centre line. If it is angled from it's centre line, it's called a dihedral. If you've ever seen a Boeing 787 Dreamliner, you will notice that the wings are angled outwards from the centre line or fuselage, that's a dihedral. If you've ever seen the Corsair F4U, also the same Corsair from Disney's Planes. that wing is called a polyhedral.

The polyhedral is added to make the plane more stable. Granted, it makes it look slightly less like Captain America's shield but it also makes it the perfect aircraft for any beginner RC pilots to fly.

To make the polyhedral, score the red lines from the template for the wings and fold it along the lines. Then place the power pod on top of the wing where the shield is painted and let the the polyhedral shape droop down. If it does not droop down, push it down to make a crease. Then, fold it along the score lines again and fill it with hot glue and place it back on a level surface with the power pod facing down. Repeat this for both sides.

If you would like to perform aerobatic manoeuvres or are an expert pilot and simply want the aesthetic of Captain America's shield, then you can skip this step. Since I'm not an expert pilot I went ahead and added the polyhedral.

The rudder is moving component of the vertical fin. It is used to control the yaw motion -- moving the nose from side-to-side laterally -- of the airplane / shield. Whereas, the elevator controls the pitch -- moving the nose up-and-down -- of the airplane / shield.

Bevelling the Rudder

Following the templates, make a 50-80% score cut for the aft section of the shield and the vertical tail. By now, you should be an expert in making these score cuts. Then, hold your blade at a 45 degree angle from the horizontal and make a bevel cut to allow the control surfaces to move in both directions as shown in the image.
You can also use a sanding block, but I found it to be less precise and take more time.

Gluing the rudder

Ensure that the rudder is perpendicular to the wing with a set square and then glue the rudder onto the hole at the aft section of the wing with hot glue. Add extra hot glue on both sides of the rudder once it is inserted to further secure it.

The push rods are used to control the throw of the control surfaces (rudder and elevator) of the airplane from the rotary motion of the servo motors by pushing or pulling on a control horn attached to a control surface.

To attach the push rods to the servo motor, we need to make Z-shaped bend or more commonly known in the RC community as Z-bends. This will ensure that the push rods do not slip off the servo motors.

To make a Z-bend, bend the stake flag 90 degrees for about half a centimetre using pliers. I broke my pliers during this build (lesson learned: do not buy cheap dollar store pliers) so I had to resort the wire cutters that came with my pliers to make the bends so they are not very crisp bends. Then, bend orthogonally from the previous bend by another 90 degrees to get the shape shown in the picture.

Do this for two different stake flag rods. I found piano wire to be a lot easier to work with, but I could not find them in any local hardware store so I had to resort with the thicker stake flags.

You can either buy ready made control horns from hobby shops, but if you do not want to make the trip or do not want to wait the long shipping times or pay expensive shipping fees, you can make your own using old plastic ID card. I wrote an Instructable a while ago about this here.

Once you have made your control horns, simply insert it onto the appropriate cut mark on you elevator or rudder, filling the cavity with hot glue like shown in the picture.

If you want to use the ready made control horns, trace out the outline onto the control surfaces and make a very shallow cut using your box cutter and dig out some foam enough for the control horn to embed onto the control surfaces. Glue the bottom of the control horn onto the shallow hole you made with hot glue.

Insert each of the clevises into the top most hole of each of your control horns and snap it into the clevis ring to lock it in place as shown in the picture.

When installing the control horns make sure to put the rudder control horn on the opposite side as the elevator. Do not make the mistake I made in the picture, since I had to redo it and leave an ugly hole on my rudder because the only one servo is mounted per side.

Connect the servo motor and ESC to the receiver and the ESC to the battery as outlined in the 'Electronics' step. Then, turn on the transmitter; it should automatically bind to the receiver. If not, connect a jumper wire from the ground pin to the signal pin of channel 6. This will centre the servo motors.

Once the servo motors have been centred, mount the servo motor onto the square hole in the middle of the wing and secure it in place using hot glue.

Then, insert the Z-bend onto the outermost holes of the servo motor pointing to the left or right for the rudder and elevator respectively looking from the tail towards the nose of the aircraft. For me, push rod did not fit the hole, so I enlarged the servo horn with the hot tip of a soldering iron. Then, rotate the wire 90 degrees so that the 2nd perpendicular bend of the push rod is mounted on the servo horn.

Keep the elevator flat along the surface of the wing and mark the length of push rod needed to fit into the clevis. I found it easies to remove the push rod from the servo motor and then cut it at the marked location and then placing the Z-bend side back into the servo horn. Push the free end onto the clevis. If you are using the stake flag rod it should fit snuggly, if not add a bit of glue and push it in place. Repeat the same step for the rudder.

Pro tip: It is important that the control surfaces as flush to it's respective surface as possible so no extra trimming of the controls is necessary in the future. Having nicely aligned control surfaces makes your job a lot easier in the future.

I briefly mentioned trimming in the previous step. Trimming is a way of levelling the control surfaces by programmatically defining a new centre point for the servo motors. However, the amount of trim we can make is quite limited.

If you're control surfaces are levelled you can skip this step. If they are not levelled, use those trim buttons -- the ones right below or beside the joysticks, to adjust the surfaces until they are levelled. If it is still not levelled you will need to either adjust the length of the push rods or relocate your control horn. Pick your poison.

Dual rates adjusts the controls linearly. The effect is that it makes the servo move less or more in relation to the stick. Expos adjust the controls by fitting it in an exponential curve. The effect is that it gives you more precise control of the controls surfaces but still allows you use the full throw.

For beginners I recommend a 15-30% expos setup on your transmitter. This will prevent you're fingers from overcompensating on the controls when you are flying it.

If you feel that the controls are twitchy adjusts the duals value. This will depend on the throw of your airplane and how twitchy it feels. Start with 50% and play around with the values until you get a throw that is controllable based on your skill level.

* Check rudder and elevators and make sure they are not reversed. Moving your right hand horizontal joystick left should move the rudder left looking from the nose to the tail and vice versa. Moving your right hand vertical joystick up should move the elevators up looking from the nose to the tail and vice versa. If they are not moving in the correct direction, simply change the settings on the transmitter to reverse the appropriate channel.

Remember, rudder is channel 1 and elevator is channel 2. Traditionally rudder is connected to channel 4, but since this is a 3 channel aircraft it defaults to channel 1.

* Check the direction of propeller. If you turn up the throttle (left vertical joystick in mode 2) you should feel the air being pushed towards the back of the airplane. If the direction is reversed, simply switch any two of the three wires from the brushless motor to ESC connection.

* Check the battery voltage with a multimeter and ensure it is at full charge at 4.2V or close to 4.2V. As a rule of thumb, do not go 80% of the full charge voltage per cell. That is, 3.36 per cell and 6.72V of a 2 cell battery.

* Check the centre of gravity (CG) of the aircraft by putting both your things on the blue reference marks or just behind the notch at the bow of power pod.

This is because the battery drainage is non linear and once a cell is drained it cannot be revived safely.

Take it for a spin. Captain Nutball is quite friendly to beginners allowing you to learn by trial and error. Some tips to get started though, get your throttle up to around 40-50% for a 2 cell battery, angle it upwards and launch. You do not need to throw it hard, just let it fly. If you feel like you are losing control, remove your hands from the stick and since it has a polyhedral it will self-stabilize. Then bring the throttle down gently to land it. Captain Nutball also likes to fly at a high angle of attack so don't worry about it wanting to fly nose up.

My first attempt flying Captain Nutball failed miserably. I was using a very small battery and ESC with a powerful motor and propeller combination so I over-drew current and the safety override of the ESC kicked in shutting my motor down at over 75% thrust.

It was already lifting at around 50% so the lesson learned is to add the a throttle check from 0 to 100% to the preflight checklist. And given that it did not need full throttle, I could have bounded the throttle channel to 75% so I won't accidentally go higher and crash like I did.

I'll give it another try tomorrow, weather permitting!