Yang Xiao Long's Robotic Arm

Hello Trident Fans!

It's Stephen here. Today, I'm going to go through the steps it took to create Yang Xiao Long's robotic arm from RWBY. 

Now, to start off with, the materials used were some EVA foam, hot glue to attach it together, Worbla (optional), acrylic paint and some elastic. In addition, a long black glove was purchased to serve as the basis. You'll also need a sharp knife, such as an Xacto Knife, to cut out the foam, as well as a heat gun to form the foam and Worbla, if you are using it. 

We also made use of some plastic wrap and duct tape to create an arm form to make our templates. This is completely optional as well. You can very easily just free-hand your templates onto your foam. Tutorial for the arm form will be posted at a later time. 

Most of the materials were purchased from our local craft store, with the exception of the elastic which was sourced from some cheap hair ties that BubblyWaffo already had, and the glove, which was purchased on Amazon. 

First, we drew out the basic shapes of the individual pieces of the arm on the EVA foam and cut them out. Be very careful, as the Xacto blade is very sharp. 

After cutting out these pieces, we used them to trace the shapes onto the Worbla, making sure to leave enough space around the edges to allow for the thermoplastic to be folded over the edge of the foam. Assembly of any pieces of foam would need to be done at this point. For this build, there were only two pieces that needed to be attached together, but depending on the project, it could be more. 

We used Worbla Finest Black, although the original Finest Art will work just as well. FB simply has a smoother surface initially, so makes for a shorter build/finish time as it doesn't have to be sanded down to have a smooth surface. Bear in mind, using Worbla is 100% optional; we used it to give the arm a more rigid shape to hold up to wear and tear better.

Once the templates were traced onto the Worbla, they were cut out using scissors. Heat up the Worbla with the heat gun so it becomes pliable and place the foam onto it. Be sure to not overheat the Worbla, as it can bubble and potentially fall apart. Fold the edges up and over the back of the foam, making sure to smooth out the Worbla as you go. Alternatively use heat and a smooth object (the flat side of your cutting blade makes a great tool for this) to form the plastic onto your foam. 

If, like in our case, you have multiple pieces that need to be attached together after having the Worbla put onto them, it's actually very easy to do so. If you heat up the pieces individually (not to as high a temp as when you put the Worbla on the foam), you can just press the pieces together. Once the Worbla cools back down, they'll be bonded together similarly to if you would have glued them together.

You'll continue this process until you have all your pieces covered. If you opted against using Worbla, you can skip to the priming step.

Also of note for this build, the fingertips and rings were made entirely out of Worbla. There are no pictures of the process unfortunately, but I'll attempt to explain it as best as I can. Basically, we cut strips out of the Worbla and heat formed them to the individual finger segments, 2 per finger, with only 1 on the thumb. For the fingertips, we used a roughly half circle shape and formed it over the end of the finger. BE VERY CAREFUL doing this, as the Worbla can get VERY hot, and it can burn you. We were using a long glove as the base for the arm, so we were able to form the pieces over that, and eliminate a lot of the direct skin contact.

Once you have all your pieces shaped and attached to each other, the next step is priming for paint. If you didn't know already, most paints will eat through EVA foam or just wrinkle after drying if painted directly onto the foam. The most notorious for this is regular old spray paint. Something in either the paint or propellant actually destroys the foam, even if it doesn't immediately look like it's doing any damage.

For this reason, my recommendation is to always use acrylic paint, and always prime your surface. Acrylics give a nice smooth finish, but can be applied with different techniques to give texture if you want. I won't be going into those techniques in this post, however. Also, priming the surface will protect your base pieces from anything in the paint (so you could use spray paint if you really want to), as well as give a more even final color.

For foam work, I generally use Plastidip in either white or black to prime my completed pieces. Plastidip is fairly cheap and can be found pretty much anywhere you can find spray paint. It's a rubberized paint and comes in many different shades, so it could be used to paint your projects if you want as well. The reason I like it for foam work, however, is the fact that it allows the foam to bend and flex without having to worry about the paint cracking.

First off, you need to do this in a well ventilated area, outside if possible. You'll want to lay down something to cover the surface you are painting on to protect it (I usually use old cardboard boxes) and place your pieces on that. Then, with smooth, even passes, spray a light coating of your Plastidip on the pieces. Spray from about 12-16" away. Let dry, and repeat. I usually put 3 or 4 coats on, but your mileage may vary. 

Something to note here, don't spray your coats too thick. There are a couple reasons for this, but the main one is that if you spray it on too thick, the Plastidip will start to bubble as it's drying, and you'll end up with small pockmarks in the finish where the bubbles pop. Unless that's a look that you are intentionally going for, it isn't recommended, as it's pretty difficult to cover up.

The second reason for not spraying too thick is that your pieces can and will get stuck to your painting surface. I generally pick up and move my pieces slightly in between coats, and if the layers are too thick, that can actually make it difficult to get off your surface, as well as make the primer peel off the pieces. More thin coats are infinitely better than a few thick ones.

After your final primer coat has dried, it's time to paint! As stated before, you can use spray paint if you want (if you've properly primed the pieces), as it is cheap and can give a nice smooth finish. However, pieces that may flex while being worn, can still crack if you aren't careful.

By far, my favorite type of paint to use for foam pieces is acrylic paint. And after a recent impulse buy at my local craft store, I can safely say my favorite type of acrylic paint is FX, from a company called Plaid. They make quite a few other crafting things, but that's for another post entirely. FX as a paint does a lot of the same things that Plastidip does. It's flexible and allows your pieces to bend without having to worry about your finish cracking. In fact, just as a test, I'd used it on a smaller project for BubblyWaffo's niece and painted it directly onto a thin foam piece. I was able to bend the piece completely in half and roll it around and there were no cracks. At all. I was incredibly impressed.

For this particular project, I used Fools Gold, which is a nice vibrant yellow, in a Smooth Satin finish. Simply brush the paint on in several thin coats with a brush. There's not too much needed to say for this other than make sure you're using the paint in an area with good ventilation, as with all paints.

Once I'd laid down 2 or 3 coats of the Fools Gold and allowed it to dry, it was time for some detailing. Depending on the details you want, you could use a number of different methods, including permanent marker or other paints. I used PlaidFX Carbon, which is a nice black color. Using a thin paint brush, I put down the detailing that was needed.

After that dried, we attached some thin pieces of elastic to the fingertips to allow them to stay on the fingers. You could also glue to tips and rings onto your glove using a little bit of hot glue, and depending on the finger pieces, that may actually be better. We did have some issues with the tips falling off in the middle of the photo shoot, and we'll probably remake the tips and attach them permanently to avoid that issue in the future. Elastic straps were also made to hold the arm pieces onto the arm.

After that was all done, all that was left to do was put it on!

Starting from the upper arm and working down, we put the pieces on over the glove. Upper arm, forearm, hand and then finally the fingers. The rings were slipped on like, well, rings, and then the tips were the final touch. Note the image used was from before the detailing was done, as Bubbly couldn't wait to try it on!

The whole project took roughly 2-3 days, accounting for the time it took paint to dry, and was surprisingly easy to do. I credit Jedimanda for their work on the robot arm, as I based this build loosely off their tutorial. Their tutorial gave me a good starting point for this project, as well as a couple other future projects.

And with that, I will end the tutorial. Hopefully, it will help all you lovely Tri-Hards (name I'm trying out for Trident fans, which I snagged from Neptune's gun) make your own robotic limbs for cosplay. Keep an eye out in the future for more tutorials and tips.

We'll see you all next time!

-Stephen

*BubblyWaffo's Yang cosplay is based on fan art done by Babsdraws