Build Props and Costume Armor with Paper, Pepakura, and Bondo

First, download and install a copy of Pepakura Designer from the Tamasoft website.

NOTE: At the time of this writing, Pepakura is available for Windows only. It is not Mac-compatible.

The software doesn’t need to be registered for it to work. But registration does unlock a few more functions, such as the ability to save work in progress. Besides, it’s so inexpensive that it’s worth paying the registration fee if only to encourage Tamasoft to keep making the program available.

Once the program is installed, the next thing you’ll need is a 3D model to print out. If you’re not a 3D modeler, never fear. It turns out you can find 3D models everywhere. The Tamasoft website has a gallery of models you can download for free, and there are countless prop and costume forums where members are willing to share models for use in Pepakura builds. If you have the appropriate conversion plug-ins, you can use models you design for yourself in freeware programs such as Blender or SketchUp as long as you can convert them to .OBJ or .STL format.

Once the program is installed, the next step is unfolding a model and printing out the pieces. The unfolding process can be tedious, but it’s also a vital part of making a paper model that can be built practically. If you’re starting with a model that’s already been imported into Pepakura and unfolded, you’re way ahead of the game. If you’re starting with an .OBJ file that hasn’t already been unfolded, there’s a bit of work to be done. As an example, Figure 2-2 shows a simple 3D model of a cube with a notch in it.

When the model is opened in Pepakura, the program will ask about flipping faces and front colors and a few other unnecessary things. Close out of this dialog box. Next, click the Unfold button at the top of the screen. A prompt will appear asking for the desired dimensions of the assembled model, as shown in Figure 2-3.

Once these values are entered, clicking OK will unfold the 3D model (shown in the program’s left window) into the flat, oddball-looking thing in the right-hand window, as shown in Figure 2-4.

As you can see, Pepakura will try to make the model into as few pieces as possible so it can be assembled as quickly as possible. The problem with this is that computers will occasionally do perfectly logical things that make no sense at all to our imperfect, meat-filled heads. Fortunately, there are tools within the software that allow us to rearrange the seams (we’ll explain those shortly). After a bit of dividing and joining edges, then repositioning the parts on the page, it starts to look like Figure 2-5.

Now that it’s been converted to pieces that will all fit onto a single piece of paper, the tabs can be switched from one side to the other side of each of the seams as desired using the Flap tool, as shown in Figure 2-6.

Once the parts have been laid out and the tabs are set up as symmetrically as possible, it’s time to print the object out and put it together.

NOTE: If you’re in the United States and haven’t been blessed by the rest of the world’s embrace of the metric system, you’ll note that the default print settings in Pepakura are for size A4 paper sheets. You’ll need to change the Print and Paper Settings under the File pull-down menu to letter-size paper. This may also require repositioning some of the parts in the 2D window so they don’t get cut off at the edges of the page. While you’re in the Print and Paper Settings menu, go ahead and click the Print Page Number box, as well. You’ll be glad you did.

The parts should be printed on the thickest cardstock paper available (Figure 2-7). This way the parts will be less likely to sag and get distorted under their own weight.

With the printing done, it’s time to cut the parts out of the sheet (see Figure 2-8). Sharp scissors or a hobby knife will come in handy. Cut along the solid lines only. The dotted lines are for later.

With the parts cut out along the solid lines, take a look at the dotted lines. These are the fold lines that indicate where the parts need to be creased. There are two types: the dotted lines indicating a peak fold, where the crease points upward, and the alternating dash-dot-dash lines indicating a valley fold, where the crease points downward. It’s a good idea to score the folds to make it easier to get a nice, sharp crease. The easiest way to do this is to gently run the tip of your hobby knife blade along the fold lines, cutting slightly into the surface of the cardstock but not all the way through, as shown in Figure 2-9.

Now the part will fold easily along the shallow cuts (Figure 2-10).

It’s time to start gluing the pieces together (Figure 2-11). When gluing the seams, the tabs should end up on the inside of the pieces, with the edge-identification numbers matched up evenly on opposite sides of the seams. Put a bit of glue on the flap, slide it under the adjacent piece so the edges are lined up evenly, and then hold it in place until the glue has dried.

NOTE: Every Pepakura builder will have their own take on the best types of adhesives to use when assembling paper models. They’re almost all wrong. The best thing to use is cyanoacrylate adhesive. This adhesive is available under familiar brand names such as Zap-a-Gap, Insta-Cure, and Krazy Glue. It cures fast, bonds well with paper, and can often be bought with accelerators, such as Zip Kicker or Insta-Set, that will cure even faster.

As the pieces come together, there’s no need to worry about exactly what angle they need to be positioned in. In almost every case, the geometry will work out so that there’s only one correct way for the pieces to sit together without excessively warping the paper. The end result, shown in Figure 2-12, is a completely assembled piece that’s the same shape as the original 3D model.

Chances are you’re not going to find much reason to make a simple cube. If you use more complex models ripped from video games or downloaded from any of the many forums where users share digital models and Pepakura files, though, it’s possible to make much more interesting things.

Let’s make this Hunter character’s helmet (Figure 2-13).

Based on the concept art shown here, the folks at the 3D modeling service Do3D.com were able to design a digital model (Figure 2-14). You don’t have to be an expert at 3D modeling yourself. Many 3D model websites offer custom services.

Once the 3D model is imported into Pepakura, it can be unfolded just like the notched cube. First, though, you’ll need to determine a scale factor. Usually it’s a simple matter of measuring the height, width, and depth of your head (or whichever body part the model is supposed to fit onto) and picking dimensions that will allow for a bit of extra room inside. Some trial and error may be involved.

NOTE: When choosing (or designing) your model, you have to weigh the complexity of the build against the amount of time and resources you’ll have to spend making it nice and smooth. A high-polygon model will be harder to assemble in the paper stage. A low-polygon model will take more work when it comes time to smooth it out.

After plugging in the dimensions needed for the assembled model, click OK and the whole thing will be instantly unfolded to become the stuff of nightmares, as shown in Figure 2-15.

As expected, Pepakura begins by trying to make this significantly more-complex model into the fewest possible number of parts. To a computer, that might make sense, but to human makers (and those few extraterrestrial or artificial intelligences reading this) it’s going to be a major headache to make sense out of some of these pieces once they’re printed onto cardstock (Figure 2-16).

It’s time to start rearranging the seams on the paper model. If the model being used hasn’t already been unfolded by one of the many prop-making saints who go around the internet looking for models to unfold, this can be quite a chore. It’s the same process used to rearrange the seams on the notched cube, though; it’s just going to take longer this time around.

To start with, select the Check Corresponding Face tool (hotkey Ctrl+K). Pick a readily identifiable part of the model in the left window and double-click to highlight it (Figure 2-17). This will show you the corresponding area of the unfolded template in the right window.

With a good starting point identified, it’s time to start rearranging the seams to simplify the assembly of the model. This is primarily done using the Divide/Connect Faces tool (hotkey Ctrl+N). Figure 2-18 shows the crown of the helmet separated into a few parts that’ll be easier to identify and assemble once they’re printed on paper.

While most of those parts will be easy to cut out and glue together, the big piece in the middle has a lot of odd seams that will make it a bit tricky to get right. It’s often easier to turn a big chunk like that into long strips, as shown in Figure 2-19.

NOTE: During the unfolding process, it’s also important to make sure that the pieces are small enough to print onto a single piece of paper. That saves you the trouble of having to figure out how to realign the split parts once they’re printed out.

In the end, there’s no easy way to get this job done quickly. Spending more time simplifying the build at this stage, however, will mean spending less time cursing at complicated pieces to cut and fold in the paper stage. In any case, after carefully rearranging the parts and putting the seams in places that make sense, the 2D window finally looks like something that can be built (see Figure 2-20).

TIP: For long seams with lots of tabs on skinny adjacent seams, it’s often helpful to place the sequential tabs so that they alternate from one side to the other like a zipper (see Figure 2-21) in order to help keep the parts aligned properly during construction.

The last little things to worry about are the last little things. Oftentimes, there will be a few tiny little pieces that, while they probably made sense on a digital model, are going to be nearly impossible to cut and fold in any useful way (Figure 2-22). You should drag all of these to a separate page in the bottom-right corner of the right window. Then don’t bother printing out that page.

With all of the parts laid out in a sensible manner on the 2D side of the window, it’s time to print the whole thing out and get started. Here are a few important things to remember about printing the paper model:

• Under File>Print and Paper Settings, be sure to check the Print Page Numbers box.
• If the printer chokes on a sheet of this unusually heavy paper, the sheet can be flipped over and reused.
• Once the pages are printed, keep them stacked and in order. It’ll make life easier when searching for the next piece to cut out.

Now that the model is printed, get to building! Begin with a clean, well-lit work area like the one shown in Figure 2-23.

Then fill it with tools, as in Figure 2-24.

See the Parts and Tools sidebar above for a list of what you’ll need to build your Pepakura model.

All set? Great.

For the novice, the next logical step would seem to be to cut out all of the pieces on the sheets. This would be madness. With all of the pieces cut out at once, the whole thing morphs into the world’s most insane 3D jigsaw puzzle (see Figure 2-25), and also becomes a great reason to mock the noob who makes this mistake.

When building a Pep model, it’s usually easier and wiser to hold off on cutting out the parts until you’re actually ready to use them. Keep all of the printed sheets in order and use the Check Corresponding Face function to find the parts that are needed as assembly progresses (see Figure 2-26). With this tool selected, double-click on any facet in the model window and the corresponding facet will be highlighted in the 2D window.

Picking a place to begin can be daunting. Usually it’s a good idea to begin with the area as far as possible from the edges and work outward. It’s a lot easier to add pieces to the outside of the work as opposed to trying to shoehorn them into the middle of a bunch of stuff that’s already glued together. In this case, construction will begin with the nose area of the helmet. Start by cutting out a few pieces that will all end up glued together (as in Figure 2-27).

As each piece is cut out, use the knife to lightly score the fold lines so they’ll crease easily (Figure 2-28). It’s important to go along the center of the line and cut everything as precisely as possible.

NOTE: When building a paper model like this, errors compound, so a few tiny misalignments along the way can add up to big weirdnesses later on. Neatly scoring along the middle of the fold lines will minimize weirdnesses.

Once the pieces are scored along the fold lines, go ahead and pre-crease them (Figure 2-29).

Glue the pieces together one tab at a time using a cyanoacrylate adhesive. It cures in a matter of seconds and can be catalyzed with a separate accelerator spray if there isn’t time for waiting. (There’s never time for waiting.)

WARNING: Cyanoacrylate adhesives were originally developed for use as field-expedient sutures so combat medics could glue wounds closed on the battle field. This is why every brand has a warning label that mentions that the stuff bonds to skin instantly. They’re not kidding. In fact, versions of cyanoacrylate adhesives are still widely used in hospital emergency rooms today. Only use this power for good.

In just a few minutes, the nose is assembled (Figure 2-30).

After a couple of evenings of cutting, gluing, cursing, and peeling fingertips off each other, the paper model is fully assembled (Figure 2-31).

The fully assembled model may look pretty cool at this stage, but unless the character being built is a superhero whose one weakness is that their armor disintegrates in the rain, it’s still going to need some work. The model also needs to be reinforced so it won’t be crushed the moment someone looks at it the wrong way.

This is the time for fiberglass resin, which can be bought at your local hardware store. You’ll need a disposable container to mix your resin in, as well as a disposable brush to spread it onto the surface. Muster your tools, take a deep breath, and read the label on the side of the fiberglass resin can. It’s terrifying.

WARNING: Polyester resins can be pretty nasty stuff. Before beginning this stage of the project, find an area outdoors to work or some place with plenty of ventilation to minimize exposure to fumes from the resin. Wear a respirator designed to filter out organic vapors to avoid making yourself stupid by huffing resin stink, and wear eye protection to keep from going blind if any stray splatter ends up near your eyeballs. Wear rubber gloves, and clothes you don’t care about. They will be ruined during this process. Don’t let any family pets eat this stuff either. It’s bad for them, too.

Once again, it’s time to start with a clear work surface like the one in my workshop, shown in Figure 2-32.

The model will be coated with liquid resin that will cure to form a sort of plastic. The problem is that, for a few minutes, the paper helmet will be wet. To prevent it from warping or sagging while soggy, it’s a good idea to glue in a couple of cardboard braces to help keep everything aligned, as shown in Figure 2-33.

With the struts in place, cover your work area with something disposable (Figure 2-34). Wax paper works well, since you won’t have to worry about it getting glued to the model.

Now that the work area is set up, it’s time to gather the necessary tools (Figure 2-35). It’s a good idea to have all of the tools handy and sitting on the bench. Once the fiberglass is mixed, there’s only so much time to work, and it won’t be a good idea to frantically dig around looking for tools while wearing sticky, poison-coated gloves. See the Parts and Tools sidebar above for a list of what you’ll need to cover your model in resin.

Mix a batch of resin in accordance with the manufacturer’s instructions. For something the size of this helmet, six fluid ounces (about 175 mL) will be more than enough for one coat. In any case, the resin will begin to “gel” within about 15 minutes of mixing it, so don’t mix more than can be used in that time. After adding the manufacturer-prescribed amount of hardening catalyst, use the stir stick to thoroughly blend it into the resin. Along the way, be sure to scrape the sides and bottom of the mixing cup to get the unmixed resin residue from the outside edges blended into everything else.

NOTE: The mixing instructions for most fiberglass resin will include an optimal ambient temperature for the material to cure properly, as well as the ideal amount of catalyst to use. These values can be fudged a bit. Hotter days will cause the resin to harden faster, so it’s a good idea to use slightly less catalyst. Conversely, colder days may require more catalyst to get the resin to cure in a timely manner. In fact, to a certain extent, slight (i.e., tiny, miniscule) adjustments to the amount of catalyst added can allow tailor-made cure times. This can be handy if you’re in a hurry and need more time to apply a coat.

Use the chip brush to coat the cardstock with resin (Figure 2-36), taking care not to overdo it. At this stage, the resin doesn’t need to soak all the way through the paper; it just needs to completely coat the outside.

It’s also important to keep in mind that the resin shouldn’t be dripping all over the place on the outside of the Pepakura model. A lot of work went into making the Pepakura model look as good as possible. There’s no sense drooling a bunch of extra plastic goo all over it, only to grind it off again afterward. Done right, the whole thing should have just enough resin to lightly wet the entire exterior (Figure 2-37).

Once the resin has hardened, the helmet will be somewhat waterproof. It’ll also be a bit stiffer, but it’s not all that strong. Working with materials available at any hardware store, there are two especially popular options for strengthening it. The first one that a lot of people talk about is fiberglass layup. Fiberglass mat layup takes a bit of skill, a lot of time, and generates all kinds of mess, waste, and poisonous fumes. This is not a method for the beginner.

The other option that tends to generate better results for the novice is to coat the inside of the assembled Pepakura model with a blend of fiberglass resin and an auto-body filler commonly known by the brand name Bondo. Resin on its own is brittle. Bondo on its own is very thick and hard to slush around. Mixing the two of them makes a readily spreadable composite that’s rock hard when it cures. This resin/Bondo mixture is often lovingly referred to as Rondo.

Determining the just-right mixing ratio between the two materials is largely a matter of personal preference. Lots of prop-making hobbyists will swear by their particular blending ratio. At any rate, there is plenty of room for experimentation. If a runny, watery mix is desired, use more resin. To make the mix more viscous, add more Bondo. In any case, once it’s mixed, it’ll start to harden before too long, so it’s a good idea to work in small batches.

NOTE: Bondo and fiberglass resin cure via an exothermic chemical reaction. This means that the mixture will generate heat as it cures. The bigger the batch, the greater the heat, and the faster it will cure. It might be tempting to mix one big batch to do all of the layering in one shot, but it’ll likely just end up becoming a useless lump that’ll need to be chiseled out of the mixing container.

Before mixing the Rondo, gather up your tools, shown in Figure 2-38. See the Parts and Tools sidebar above for a list of what you’ll need to make your Rondo.

NOTE: The gallon-sized cans of resin and Bondo are way too much for a project of this size, but it’s always nice to have more on hand for the next project.

Once all of the tools are handy, it’s time to put on some rubber gloves and mix up some goop. Here’s how Rondo is made.

STEP 1

Scoop some gray goop out of the Bondo bucket. This should not be done with the same tool that will be used to mix or spread the Bondo. That way, there’s no chance of contaminating the rest of the can of Bondo with hardener and have it slowly turn into garbage. A helmet this size should only require a couple of blobs the size of golf balls. Or one blob the size of a baseball. Or two-thirds of a blob the size of a soft ball. It’s not an exact amount, but balls are involved somehow.

STEP 2

Add slightly less of the Bondo hardener than the instructions call for. The reason for skimping on the hardener is to allow a bit of extra mixing time before the material cures. Remember, you’ll have to mix up a batch of fiberglass resin, too, so you don’t want the Bondo to harden too quickly.

STEP 3

Blend the hardener into the Bondo (Figure 2-39).

 

Secrets of BondoIf your workshop is as well equipped as mine, you have a retired auto mechanic father who stops by whenever he gets bored with his antique car restoration projects to tell you what you’re doing wrong. If you don’t have such help, here’s what Dad usually tells me when I’m mixing Bondo: 

• Keep everything neat and clean.
• Let the Bondo touch only one side of the putty knife so you can control where it goes. If it ends up on the backside of the putty knife, it’ll trail little ribbons along the top of your work and it’ll be impossible to spread it smoothly.
• While mixing, periodically scrape the Bondo off the working side of the putty knife so it can be blended back into the rest of the material.
• Scrape the Bondo off the mixing surface from time to time, as well, to make sure the stuff on the bottom gets mixed in, too.
• Continue mixing and scraping and folding the Bondo back into itself until it’s all one uniform color.
• Make smaller batches. When you sand it all off, you won’t waste as much time and money filling the workspace with pink dust.
• Get a job.

That last one is apropos of nothing. It just comes up a lot when my Dad visits.

STEP 4

Once the Bondo and hardener are thoroughly mixed to an even, homogeneous color, mix up a batch of fiberglass resin (in accordance with the manufacturer’s instructions) that’s about the same volume as the blob of Bondo. Then scoop the Bondo into the resin (Figure 2-40).

STEP 5

Using a tongue depressor or other flat-sided mixing tool, mix the resin and Bondo together until it has an even color and consistency, as shown in Figure 2-41.

When it’s mixed thoroughly, it becomes a blended goop with a viscosity somewhere between milk and mayonnaise, depending on the mixing ratio. More resin equals thinner goop. More Bondo equals thicker goop.

This goop is RONDO!

STEP 6

Pour the Rondo into the Pepakura helmet, as shown in Figure 2-42.

STEP 7

Tip the work piece from side to side and front to back so the Rondo slushes around and coats everything on the inside. The goop will eventually cure to a solid, almost rock-hard mass. The object is to keep moving the helmet around in order to get the goop evenly spread over the interior of the paper. Otherwise, the Rondo will drool its way down to the bottom of the helmet as shown in Figure 2-43 and solidify into a big, heavy, thick area that will never sit right and make the helmet lopsided and unbalanced. This can be prevented by continually keeping the whole thing in motion while letting the Rondo slosh and splatter around the interior until it gels and hardens into a shell of uniform thickness.

During this stage of the project, it’s absolutely guaranteed that at least a little bit of liquid Rondo will drip out somewhere. Be sure to cover the floor with the finest antique Persian rug available, let it soak up any spills, then leave it where it is until the Rondo has cured and it glues the rug to the under-lying floor. Actually, that’s a bad idea. The better idea is to lay down a bed of newspaper or wax paper over the work area so it can all be rolled up and disposed of when the project is done.

STEP 8

Mix up another batch of Rondo and repeat the coating process as many times as needed to make the helmet nice and strong. After enough iterations, it’ll be pretty sturdy (Figure 2-44). How sturdy? That depends on how many coats you layer on. I may have overdone it with this one.

There is no trickery involved in this picture. That’s all 175 pounds of me plus steel-toed boots, heavy coveralls, and pockets likely filled with sanding dust and used rubber gloves standing on top of this paper helmet. I may have overdone it with the reinforcement, but it gives you an idea of what’s possible.

So all it takes is some paper and hardware store materials to make a nice, strong helmet. It’s not safe to wear for motorcycling, or hockey, or getting shot out of a cannon, but it should be more than adequate to hold up to the rigors of costuming. The next step is to smooth the outside so it stops looking like a multifaceted 3D model and starts looking sleek. This, too, is a job for Bondo body filler.

Remember all of the guidelines mentioned above about mixing and working with Bondo? They still apply. All of the required “body shop” tools are shown in Figure 2-45.

If you’re paying attention, you’ll notice that these are basically the same tools that you used in the Rondo phase, minus the fiberglass resin, tongue depressors, and mixing cup. The only new tools are the files, sanding blocks, and sandpaper that will be used to shape the cured Bondo.

With the tools gathered up, it’s time to set up the workspace. This step is going to take a lot of time and generate a lot of dust, so it should be done somewhere that can deal with that kind of mess. Since the aim is to take the faceted, digitally generated paper model and smooth out all the surfaces to make them look like the original character design, it’s also a good idea to have all the available reference images close at hand. (Your workspace should look something like what you see in Figure 2-46).

Now that everything’s ready to go, it’s time to get to work. I usually start by using a wood rasp to grind off the high corners of any area that’s going to need to become curved. Then the first layer of body filler goes on. If the initial 3D model was already fairly smooth, it shouldn’t need very much filler to fine-tune the shape. If it started as a low-polygon model, it’ll need more filler to round out the facets. In either case, resist the urge to pile on a lot of material. It’ll just need to be ground down as soon as it cures. Instead, it’s easier (and less messy) to build up several small layers and cut down on the amount of sanding time and material waste along the way.

With the first coat of Bondo on the Hunter helmet, it looks like Figure 2-47. Note that there’s not just a huge glob piled on willy-nilly that would then need to be carved back down. As the Bondo cures, it will become progressively firmer, allowing the user to do some rough shaping with the putty knife. At this stage it’s a good idea to shape it as close as possible to the finished form, but don’t fret if it’s not perfect. There will be plenty of time for perfect later.

After about 20 minutes, the filler will harden to the point where it can’t be smooshed around with the putty knife any more. After another 20 minutes, it can be carved and sanded to knock down any high spots or rough patches that may have come up during the smooshing. The best tool to start with is called a Surform shaver; it’s the little cheese-grater-looking widget with a bright yellow handle shown in Figure 2-46. They come in a variety of shapes and sizes, but the little rounded one will remove a lot of material in a hurry at this stage (Figure 2-48).

This is the tedious stage of the project. From here the next step is to continue filling in the unwanted low spots and sanding down the unwanted high spots. There will be curves that need to be made straighter or flat, and faceted areas that need to be evened out to create compound curved areas. The general progression of sanding and filling with the Hunter helmet is shown in Figure 2-49. Get comfortable and settle in for the long haul. Unless you’re some kind of sanding savant, this is the stage that will consume the largest number of hours.

NOTE: It can be tempting at this stage in the project to use some sort of power tools. At first this might seem like a great way to save time and effort, but inevitably it will also mean removing too much material. Shaping and sanding by hand will allow for a lot more control and a lot less waste.

Somewhere in the seemingly endless loop of smoothing and shaping and filling and sanding, it’ll eventually reach the “zit stage.” This is the point at which continuing to mess with it will only make it worse. It’s important to recognize this stage when it is reached; otherwise, it’s easy to get lost in a hellish, dust-filled downward spiral that will take over your life like some chalky, time-sucking leech.

It may even require the timely intervention of friends and family and possibly the occasional mental health professional who can, after a lengthy and emotional intervention, somehow convince you that it looks “pretty good.”

At this point (or much sooner probably), it’s a good time to spray on a coat of primer to identify areas that need a little more attention (Figure 2-50).

While things may have looked “pretty good” when they were all sorts of different colors and covered with dust, a coat of primer will take away any deceptions caused by the different colors and show all of the remaining flaws and problem areas. Now it’s time once again to set off on the long cycle of filling, sanding, filling, sanding, and filling, and sanding.

During the course of the sanding, filling, and priming process, there will likely be places where the original paper bits become exposed. When these areas are sprayed with primer, they’ll likely end up soaking in a bunch of the primer and looking fuzzy and weird. Not to worry. Once the primer dries, sand these areas lightly with some fine sandpaper (220-grit should be good) and then spray on another coat of primer. A couple of rounds like this and it should be good to go.

When all of the little problems are finally fixed, prime it again. If it’s smooth and straight and there’s no more visible fuzzy paper showing, it’s time to move on to detailing.

Now that the basic shapes are smoothed out and curved or flattened as needed, it’s time to add details. There are usually at least a few bits and pieces that need to be added to the physical model that weren’t present on the digital model. This is especially true of a lot of the models that were originally designed to render characters or props in video games. In most cases, developers would rather not waste rendering power on tiny seams and details when they can just be painted onto the skin that’ll be visible in the game.

Small seam lines and grooves can be carved in with a triangle file or, just as well, with a loose jigsaw blade. Use a straight edge and a hobby knife to lightly scribe a mark where the grooves will be. Then go back over the scribed lines with a small file or saw blade to make them deeper and wider as needed (Figure 2-51).

Not all of the details will be this simple, though. If there’s a raised edge that wasn’t present on the model, more Bondo can be used to build up an area. On the Hunter helmet, the cheek areas are covered with a bunch of ridges that were not present in the model. In order to ensure that they all have the same cross-section shape, a contour gauge was carved out of the end of a mixing stick (Figure 2-52).

Then the cheek area was covered in Bondo and shaped by dragging the contour gauge through it. This leaves a series of matching ridges (Figure 2-53).

TIP: If the design calls for bolts or screw heads to be visible, the easiest way to simulate them is to pick them up at the local hardware store and just drill holes to mount them onto the assembled piece.

These final touches can be added after the bulk of the shaping and sanding has been done, but there will still be occasional flaws to fix. Ideally, the bigger problem areas have been fixed with Bondo. Most of the flaws at this point should be fixable with glazing and spot putty, another automotive product available at the local hardware or auto parts store. It’s designed to fill in pinholes and tiny scratches before you spray on your paint. It dries on contact with air and will shrink slightly as it dries. For this reason (and the fact that it costs money) spot putty should only be used to fill in the tiniest of tiny holes (Figure 2-54).

Once the holes are filled in and the putty has dried, sand it smooth with 220-grit sandpaper. Then spray the whole thing with yet another coat of primer (Figure 2-55).

If the plan is to just make one helmet to wear around and look awesome, you can move on to painting and weathering. If you have reason to make more than one, you can make a copy of the assembled helmet without going through this entire process again. For guidance on both of those processes, check out my new book, Make: Props and Costume Armor.