I know what you're really going to do with this build, but I'm going to call it a "round Viking Shield" for the sake of this tutorial to avoid any licensing issues in case I win something from the Halloween contest. Whatever you do with this build after you learn how to do it from me is on your conscience as you have a Super Halloween Soldiering around with your new and lovely prop.

Step 1: Bill of Materials

The great thing about this build is that it costs less than $20 even if you have to buy the tools you need to make all the cuts. The finished product is pretty durable for a paper toy.

Here's the Bill of Materials:

Tools you will need:

1 sharp pencil
1 1-inch wide tempera paint brush (suitable for applying glue; about $4 at WAL*MART)
1 wooden yard stick trimmed back to 16" and a large thumbtack
A metal yardstick
Drill or Drill Press
utility knife (pref: the kind which lets you snap off the end to get the tip sharp)
Waterproof wood glue (if you have saintly patience and a truck box full of clamps; also used for priming the paper before painting)
Hot Glue Gun with 24 glue sticks (if you are like me and have no patience for drying glue, but you need a very precise touch)

Materials:

3 sheets, plain white mat board 30" x 40" (~ 762mm x 1012 mm) (about $7 each)
Black or Grey Krylon primer
Krylon clear coat
- Both spray paints are available at WAL*MART for Cheap

Step 2: Mark Up Your Materials

One of the benefits of this build is that the cutting is actually rather simple -- 4 circles (I have no idea why you would also want to build a star which fit exactly inside the center ring of this prop, but I had fun drawing one for you). When you have the right tools for the materials you are using, this won't take more than an hour.

In the Bill of Materials, we noted that you needed to drill a pilot hole for a tack at at the 1" mark of the wooden ruler. This is probably the most important prep step for your tools because this hole creates the center mark for your industrial-sized compass. If you have that hole too wide, or off center, or in the wrong place, the rest of your circles will be sloppy at best, or very uneven at worst.

Before we cut anything, let's look at the measured drawing of the mat board, above (picture 1)

We're not building to machine tolerances here, so we're only marked up to the nearest quarter-inch. But before you mark anything, you have to get your marking tool set up, and that means drilling the pilot holes in your marking tool according to this drawing. Notice that all the measures are of the radius, not the circumference -- that's because these will be the marking holes you make in the tool. For those who are new to this sort of stuff, that means drilling holes in the compass at these marks: 6", 6-3/4", 7", 9-3/4", 10", 12-3/4", 13", 16". See: if the center of your compass sits at the 1" hash mark on the ruler, all the other points have to be relative to that center mark -- so the radius of 5" is measured by the pooint on your ruler of 6" (6" - 1" = 5").

If you use a simple 1/8" bit, the holes should be wide enough for just the tip of your pencil to slip in and mark the board.

Before you drop the compass down on the mat board the first time, measure the board on the short edge and put down a hash mark at the midpoint. Then measure the distance of that hash mark down the log side of the board so you can create a point in the middle of the board toward one end. The point here is to leave as much scrap at the bottom of the board as possible.

Once you have the middle point marked, drop your compass in and draw the circles on the first board as noted in the measured drawing. Repeat the marking process for the second board, but trace out the circles from the second board in the drawing.

I know some of you think the star is sorta cool, and would like to make one of your own out of the scrap board in this project, so the instructions for that are below.

This may sound ridiculous to the real builders out there, but to make the star you need a protractor. Some of you are clever enough to make it with the compass, but we don't want this project to wash out anyone who failed engineering drawing in trade school. An American star has 5 points, all points the same distance from each other. If we're drawing it inside a circle, that means that each point is 72° away from its two neighbors.

Step 3: Cutting Your Marks

The final prep step before cutting is to put some sort of cutting surface under your mat boards to ensure your cuts will go all the way through the board, and not mark the floor under your cuts. I used a scrap piece of mat board underneath. If you cut these pieces on your Mom's linoleum or your hard wood floor, you will mark up the floor and you are taking your life into your own hands. Remember: Frank said to put something under the boards you are cutting to avoid this problem. My homeowner's insurance does not cover your lack of caution.

Next we can start cutting, but we're not free-hand cutters at this site. And: we want not to cut ourselves, but we definitely want to cut out circles. That's where this crazy wooden compass serves a double duty. To use it, first put on some safety glasses and ...

SAFETY TIP: if you do NOT want to cut yourself, follow my instructions below to get a sharp tip on your utility knife. If you CANNOT follow those instructions, or DO NOT READ THEM, you will cut yourself, and that will be your own fault. I can;t stop you from using tools the wrong way, and this is my warning to you: if you don't snap the tip the right way, you will hurt yourself. EXERCISE CAUTION WITH SHARP TOOLS.

... take your utility knife in your left hand. Take a pair or reliable pliers in your right hand. Set the blade to extend so that the first scored mark is lined up with the edge of the handle. While holding the tip of the knife with the pair of pliers, bend the blade at the scored mark. Crack off the old tip along the scored mark to give yourself a new, sharp tip. Dispose of the shard of blade safely and immediately so out don't step on it or worse.

Now make sure the center of your compass is set correctly, and set your knife on the measured mark of the ruler corresponding to the widest-radius mark on the board. Press down firmly so the tip of your knife bites into the paper, and the edge of your knife bites into the wooden ruler. If you set the blade properly, you can simply pull the blade along your guide mark and the compass will assist you by keeping the blade at the correct point on the circle's circumference. You can see this in Picture 1, above.

Pull the blade toward the ruler, on the guide mark, and press down at the same time, You may need a helper to hold the center pin of the compass in place as you cut, and you may need to make more than one pass to cut all the way through the mat board. You can see this in picture #2, above.

Continue for each guide line until you have something left which looks like Picture #3, above.

Those of you who are still with us and not dreaming of other things will notice that this picture has some circles on the right which are not in the measured drawing. They are optional for the final step of this build. When you are done, you should have the 4 circles on the left. If you are extra patriotic or in search of a pentagram for some weird reason you will also have a star cut out of the scrap.

This cutting step can be completed in less than an hour if you are anywhere near handy with the knife and the compass.

Step 4: Making 2D Parts Into 3D

Let's be honest about something: stacked up mat board is not very impressive as a viking shield. Right? Just circles on a disk, like Picture 1, above. And that's fine when it's 1974 and all you have at your disposal is a refrigerator box, watercolor markers, a steak knife, and a tattered copy of Cap #111. (but we are not building a Captain America shield, right? We're buildinga viking shield to avoid any potential Trade mark infringement issues) But we have all of the fire power of being middle-class nerds in 2014 who understand that it really doesn't cost that much to transform those paper disks into something a little more dimensional.

If we are marginally clever, we can see that we don't have to make the surface of the shield one continuous curve. We can actually build it like picture #2, above.

Which is really a stack of straight lines, each one as you move out from the center set at a more-steep angle. The way we get that steeper angle is to take each pre-cut circle and tighten it up. This is a very clever technique users of Pepakura understand and the rest of us are just going to catch up right now.

Let's begin with the largest circle, which is the outer circle of the shield. Take the utility knife and the yard stick, and cut the circle on the centerline marking left over from when you measured the board ON ONE SIDE ONLY (see image 3, above)

A neat, straight cut is your best friend. Next, lay the yardstick down and place the circle over it. Have a helper keep the uncut end of the circle at the center mark on the "zero" end of the yardstick, and you begin to cinch up the circle, overlapping the cut ends on top of each other until your outer diameter (OD) is 28". When you have that diameter, your circle will no longer be a flat piece: it will have a very distinct slope. Mark the place where the top overlapping piece ends for reference, and then break out the glue and the clamps.

Make sure when you clamp you are getting good bond lines (right to the edges) on the inner diameter (ID) and outer diameter (OD). In image 4, above, on the left, the clamps are allowing the outer diameter to gap, and if it dries that way you'll be stuck with a lousy appearance. On the right, above, the clamps are getting good pressure without marking the paper, and the edges are all sealed.

You want to repeat this process on all 3 outer circles. You're going to draw the middle circle in so the OD is 22.5"; the inner circle gets drawn in so the OD is 14.5". When you do this, the three circles will each have a different slope.

Step 5: Priming and Painting

When the glue sets up under the clamps, take the waterproof wood glue and mix 4 parts glue to 1 part water (not an exact recipe - just don't mix it with more water than glue). Mix it well so it is very runny, very smooth. Paint the tops of the rings, the center circle, and the star with the watered down glue. This mixture will take about 1 hours to dry in a sunny place, or about 3 hours to dry indoors. When it sets up, your rings will be ready to take paint.

Without any exaggeration, there is simply no other way to make a paper part ready to receive enamel paint except to have it adequately primed, and the only method I have found to do this is with the waterproof wood glue mixture recommended in that post. The only thing you have to be careful of is overcoating the paper so that the glue isn't flaking off after it dries. You want the glue to saturate the surface of the paper, dry with a water-resistant seal, and also not cause the paper to buckle or warp. The second thing you need to paint well at this scale is one of those plastic triggers for your spray can, as in Picture 1, above.

Personally, I don't care about the brand you use -- they are all about the same thing. I prefer one like the item pictured above as it has an open space around the spray can nozzle rather than a closed dome. But the point of using one of these is to have proper control of your spraying, which the classic single-finger technique for spraying from a can simply doesn't give you.

Next, you need to master how to use the trigger for even coating. The key to spray painting is using as little paint as possible while also using enough to get a fully-covered surface. You accomplish this by spraying lightly and quickly over the area to be painted, using strokes in the same direction. There are about 100 videos on YouTube for painting technique, but this one from Ace Hardware, frankly, is brief and the most helpful.

Also, I cannot stress this enough: when you use any spray paint, SHAKE WELL BEFORE USING. The standard line is, "shake for 60 seconds before spraying," but most people simply have no idea how to shake well and thoroughly, or how long 60 seconds is. When you pick up the can, hold the can at the top with the cap in place. Take the can and wave the bottom of the can until you hear that rattling noise. That sound is a large bearing which is dropped in the can to assist you in mixing the paint well. When you wave the can, the bearing will start to wander around the inside of the can, and now you're ready to shake well. To get a good shake on, grasp the can with two hands, and shake it at least the distance of the height of the can up and down. You will have a good shake on when you are shaking at 4 shakes per second. Until you are confident in your ability to count to 60 at the right pace, use a timer to let yourself know when you're done shaking.

Now: why the kindergarten primer on how to shake a can? Well, because spray paint is not some magic liquid: it is a chemical mixture of pigment, a solvent (and other balancing chemicals) which is the evaporating medium that carries the pigment to the object and assists in curing the pigment to the object, and a propellant which is what causes the mixture to fly out of the nozzle. In order for you to use it properly, you need to get the mixture coming out of the can as close to what the chemist who refined this stuff intended as possible.

Before you start spraying, CLEAN THE AREA YOU ARE SPRAYING IN; wipe down the parts with a damp cloth to remove all dust. Every hair in the air will immediately cling to damp paint. Every stray dead leaf of grass will fly toward your project like a lemming trying to hurl itself over the precipice of your hard work. Every grain of dust has waited since the beginning of time to fly onto the paint on your project in order to make it look like sandpaper instead of coated Vibranium, um, I mean Viking Steel, and your job is to remove them all from your work space before you start painting.

Also: it is easy to want to paint as soon as possible, but every paint has a temperature range recommended for application. If you apply it when it is too cold, your paint will take too long to dry and it will puddle or run. If you apply it when it is too hot, it may not stick at all as the solvent evaporates too quickly. If you apply it when it is too humid, you may actually get paint taffy which will never dry but will always be sticking to something -- like hair, grass and dust (or worse: your costume). Pick a time and place where you have the right temperature and humidity.

Last: as you spray, cross the painted surface in ONE DIRECTION ONLY. The best result in this case comes from painting in strokes from the center of the circle out past the outside of the circle. When you have painted as much as you can reach, move to the next section. Work hard not to overspray because every drop of paint you overspray will be a teardrop of regret your shield will always wear.

When I painted mine, I painted with silver because: shiny. The silver parts got 3 coats of silver, and when finished before assembly they were as shiny as the shiny side of tin foil - like picture 3, above.

Step 6: Assemble & Glue

Before we do this next step, let me say this as clearly as possible for those of you in a hurry here:

PAINT BEFORE YOU GLUE. You might have made different color choices than I have recommended in this Instructable - which is a great idea. Be creative. PAINT BEFORE YOU GLUE. If for some reason you are using 3 colors instead of 1 color, PAINT BEFORE YOU GLUE.

This next step takes about 90 minutes if you have a helper and are extremely competent with hot glue. Also: you will be very well served if, after all of the previous steps, you set the whole project aside for 24 hours to let the paint not just dry, but to actually cure so that the silver paint doesn't do spectacularly bad things when you touch it. Anyway, the idea at this point is to assemble the pieces as in the picture above.

And that seems so obvious, right? Just stack them up, and away we go.

Some pointers:

Assemble from the smallest ring up to the largest ring.
Set the smaller piece inside the next-largest piece, and make guide marks on the INSIDE of the piece to make sure your rings are getting glued where you want them glued.
Apply hot glue to the edges on the INSIDE of the project where all mistake are going to be forgiven. Your best bondlines will be very fat, and overlap the piece you are gluing for the best hold.
DO NOT try to seal the edges tightly as you glue. You will create a ripple of the slack in your piece, and you won't be able to work it out because: hot glue.
Work slowly. The worst thing that can happen to you at this point is that you don't keep the pieces centered and they get misaligned toward the center.
Have cookies and kool aid at the ready because when the kids in the neighborhood see you assembly this shield, they will want to watch.

Step 7: Optional: the Back Side

The shield you have built is now totally suitable for saving NY City from alien invasion or strapping to the side of a Viking ship on its way to war. However, you may find it hard to carry and maybe a little less sturdy than you hoped for.

If that's the case, cut a flat circle of mat board with a radius of about 12". From your scrap board, cut 4 industrial "C" shapes as in picture #1, above. The way I did it was to draw 2 more 12" radius circles, draw 2 x 2" wide diameter lines which are perpendicular to each other inside the circles, and then square off the centers at about 6" from the center of the circle. You are cutting out 4 so that 2 can go inside the center circle for extra strength.

Lay out the circle as pictured, above, and drill holes for the screws. Glue the pieces together and then add the bolts. Add straps.

And you're done.

If you want to go crazy with spray paint, you can get something like I got, where I varied the colors in the outer rings and put that star I keep talking about in the center of the shield on the front.

http://3.bp.blogspot.com/-vutrZKKs6OA/VByPeufohvI/...