[ed note: this article is also available in pdf and postscript and as a Microsoft Word document. ]
The Mongolian yurt, or ger, is a round, nominally portable, self-supporting structure suitable for camping in comfort. It does not rely on ropes or stakes to hold itself up; rather, the walls, rafters, roof ring, and tensioning bands all work against each other, in a marvel of physics and engineering, to keep the structure standing. It is thus an especially appealing structure for camping events where space is at a premium, such as Pennsic, because all of the space it requires provides useful living space -- no extended ropes are required as they are for pavillions.
SCA campers have also found other useful features that the Mongols must have designed into the structure. A yurt does not even think about moving or falling down in a storm; consider, for example, the winds out on the steppes. With a pavillion, the structure is provided by the roof canvas and ropes; if any of these gives, the pavillion comes down. With a yurt, the wooden frame provides the structure and is much more stable. The yurt frame also has a lot of redundancy built in; if a single rafter or piece of wall fails, the structure is not affected.
Because the rafters bear the weight of the roof ring, no center pole is necessary unless the yurt is very large. The Mongols would build their cooking fires in the center of their yurts, opening a smoke hole for the purpose. SCA campers faced with fire restrictions rarely have this option.
Yurts are also remarkably comfortable during the summer heat. Once you get up in the morning, you can open the flap over the roof hole and hike up the walls in 3 or 4 places. This sets up a nice convection current, and the yurt stays relatively cool all day. (Of course, this doesn't work when it's raining...) There were afternoons at Pennsic XXIV when I was more comfortable sitting in the yurt than under a canvas fly, because the yurt had a vent at the top.
For modern (and historical) convenience, the yurt collapses down into pieces no longer than 8 feet. I transport mine on and in my Mazda 323 hatchback, though I did have to install a roof rack for the purpose (much to the amusement of the auto dealer). A minivan would also suffice if you don't want to deal with roof racks.
There are additional pieces, notably the canvas and the rope that holds the cloth walls up, but they are not structural.
This article describes how to build a yurt that is approximately 16 feet in diameter. While in theory this can be scaled up, I do not know for certain how big you can make a yurt without requiring a center support. (I am told that an engineer determined that you could go as large as 30 feet, but I'm not sure I believe that.)
Note that all of this lumber will weigh in the vicinity of 100-150 pounds. If you transport it on a roof rack, make sure it's a real roof rack and not a `ski rack'; the latter will probably buckle under the weight.
I bought my canvas pre-made. The canvas for my yurt comes in the following pieces; there are many other ways to design the roof canvas, but this is the simplest to implement:
My roof comes down to the ground in the corners and has to be staked down there. Some people have built roofs that are circular and conical, and these do not require staking. Other people run a roughly foot-wide band of cloth around the outside, at the top, over the wall, to hold the descending roof canvas down. I'm not enough of a pattern drafter to be able to tell you how to do a fitted roof, however. (Note, by the way, that my roof is not under any tension.)
Each lathe needs to be drilled every foot, offset by 3 inches. That is, counting from one end, you have holes at 3', 15', 27', 39', and so on. (You should have 9 inches of lathe left after the last hole.) If you are cutting your own lathes and you have a drill bit long enough to go through a 2x4 in the 4' direction, I strongly recommend drilling the 2x4s before cutting them. (A drill press helps a lot for this.) Otherwise, you have to clamp the lathes together, hope nothing slips, and do a lot of extra work to drill the holes.
Once you have a pile of lathe boards, you start bolting them together into a lattice. Make sure that all pieces going in one direction are on top and all pieces in the other direction are on the bottom; you do not want any interlacing or weaving. (This will prevent you from being able to fold the khana.)
To apply a bolt, push the bolt through both pieces of lathe (with all the heads ending up on the same side), put the washer and nut on the other side, use the wrench to pull the head as far in as it will go, and then loosen the nut by half a turn. The last step is very important; you need to be able to move the lattices, but you also need to make sure the head of the screw is firmly seated so it can't fall out. (An advantage of carriage screws is that they effectively have the washer built in on the head side.) And, of course, you don't want the nuts to be so loose that they fall off.
You can actually make the khana with 1-inch bolts instead of 1.25-inch ones if you want to; you have just enough room to make everything fit. One of the small benefits of a yurt, though, is that you have 100+ convenient coat hooks; I used the longer bolts so I would be able to hang clothes, my cloak, hats, my drum, towels, my drinking horn, and so on from them.
The ends of the khana that adjoin the door need to be straight. This means that the last few pieces on each end will not be full-length; because you will have this problem on both ends, you can cut down some lathes to make these pieces with very little waste. (See Figure 1.)
Figure 1: One end of the khana.
You will need to break the khana into at least 2 sections for transport. To do this, pick a point approximately in the middle, remove the nuts and washers, and push the bolts out from the inside layer of wood, leaving them embedded in the outside layer. (When you assemble the yurt, you will probably want to fasten these joints together with wing nuts, which you can tighten with your bare hands.) See Figure 2 for a diagram of how the wall comes apart into sections.
Figure 2: Location of bolts to remove (to separate khana).
Be careful when folding, unfolding, and carrying the khana. Make sure you lift it slightly off the ground before folding or unfolding. While the overall structure is very strong, each individual lathe is fairly weak. (The good news, however, is that the weight is distributed so well that you can even replace a broken lathe while the yurt is standing, and it's ok to have 3 or 4 broken lathes if they aren't all next to each other.) It's generally a good idea to keep a few spare lathes on hand for repairs.
Making the khana is perhaps the most tedius part of constructing a yurt. Don't be discouraged that it's taking a long time to insert all the bolts. You only have to do it once, for the most part.
You need 2 pieces of 2x4 that are 6 feet long and 2 that are 3 feet long. Cut tabs in the short pieces and notches in the long pieces, as shown in Figure 3. When you put the pieces together, you'll get a door frame that's 6x3 (and 4 inches deep).
Figure 3: Notches for door frame.
My door frame has leather hinges. That is, there are sturdy pieces of leather nailed to the outside of the frame, with a `latch' at one corner. This allows me to unfold the frame while keeping it in one (long) piece; I can then fold this piece and toss it on the roof rack.
You might, instead, prefer a frame that you can take entirely apart. The easiest way to do this is to drill holes through the 4 joints (in the 4-inch direction) and put a bolt in each one. This should also make for a sturdier frame, as leather can loosen over time. (You could use metal hinges instead of leather to solve that problem, I suppose.)
The important thing is that you end up with a sturdy frame. It's going to be under tension from 3 directions, so you want to make sure it will hold.
Figure 4 shows what a single rafter looks like.
Figure 4: Rafter layout.
For ease of cutting, I recommend screwing 4-6 1x3s together and cutting them as a group. You can then remove the screws. This is much faster than cutting each rafter individually. A jig saw works well for cutting the rafters. For the notch, you may find it easier to make the two parallel cuts and just use an old screwdriver to break out the pieces.
The holes shown in Figure 4 need to be large enough for a rope to pass through. A 5/16-inch drill bit would probably work, though it would be snug; a 3/8-inch bit should provide plenty of room. You will note that the positions of the holes are not shown precisely; the left one should be within an inch or so of the notch and closer to the bottom edge; the right one should be 1-2 inches from the angled cut and closer to the top edge. Precision is not that important here -- but read through all of this article, including the setup instructions, before cutting the rafters so you understand the function of the holes.
The rounded outer edge of the rafter (at the khana end) should be sanded; your roof canvas will be pulled over this, and you don't want to cause wear on it. If the top edge of the rafter has any rough spots or splinters, you should also sand them. Other sanding may be called for depending on your tolerance for the occasional splinter. Do not sand the sides of the board at the end that will be inserted into the roof ring; it is important not to change the thickness of the board at that point.
For two of your rafters, instead of cutting the khana end as shown in Figure 4, use the cut shown in Figure 5. These rafters will rest on top of your door frame.
Figure 5: The outer end for the door-frame rafters (make a 90-degree angle).
Save the scraps from the rafters to make the roof ring.
The ring consists of two rings of plywood separated by pieces of 1x3. It looks sort of like a large wooden doughnut, 30' across and 4' high.
Start by drawing two 30-inch (diameter) circles on the plywood. In the center of each, draw a concentric 26-inch circle. Cut these out. You should now have two rings of plywood, each 4 inches from outside to inside edges.
Take 3 pieces of scrap 1x3. (Two should be 4 inches long; the third can be longer as it's only a spacer.) Take one of the plywood rings and position the 3 pieces of 1x3 together under it, such that the center piece (the spacer) points straight out. (See Figure 6.) You'll probably want to use some other 1x3 scraps to hold the ring up so it's level. Check the 3 pieces to make sure they're right up against each other (no gaps), and when you are satisfied, apply 2 drywall screws to each of the outer pieces (see Figure 7). Slide the spacer in and out a bit to make sure it can move. You can now remove the spacer.
Figure 6: Positioning the 1x3 pieces and spacer.
Figure 7: Positioning the screws.
You have just created a slot into which one rafter will fit snugly. Now do the same thing on the opposite side of the ring. (That is, create another slot 180 degrees away from the first one -- not on the other side of the piece of plywood.)
Now you have two starting points. Pick one and place 2 more pieces plus the spacer as close as you can to the existing slot, while still allowing the spacer to point straight out from the center of the ring. Screw the pieces in, and then proceed to the next position. As you add slots, you will find that the inner ends are generally right up against each other, while there are gaps between the outer edges. (It's like the spokes of a wheel.) This is normal; do not try to fill in those extra spaces between slots in the front. All rafters must point directly toward the center of the ring. Figure 8 shows a roof ring in progress.
Continue to place slots around the ring until you run out of room. Depending on luck and skill, you should be able to place somewhere between 30 and 36 slots in the ring. (You could get more in by filing down the 1x3 pieces, as shown in Figure 9, but I do not think it's worth it. 30 rafters will be plenty.)
Figure 8: Adding more slots (longer lines show where rafters go).
Figure 9: Shaving edges to pack in a few more slots (optional!).
Once you have attached all the spacers to one of the plywood rings, turn the ring over (so the plywood is on the bottom), position the other ring on top, and screw it together.
Note: you will find a drill with a screwdriver bit very helpful in construction of the roof ring.
Once you have completed the ring, drill two holes in one side, opposite each other. These are the holes for the center support (used during erection). See Figure 10.
Figure 10: Positioning of support holes (ring viewed from bottom).
Make sure the plywood on the side opposite from where you drilled the holes is smooth. If the surface is rough, sand it to avoid wear on your canvas. You don't need to sand any of the other surfaces of the ring, though you might want to sand the outside edges (plywood and 1x3s) to make the ring easier to handle.
You might want to cover the inside edge of the ring in some way, to prevent rafters from trying to push through. You can use scrap lathe for this. This is an optional step.
Another optional step depends on how you're going to be transporting the ring. You will note that when the yurt is set up, you will have a flat spot in the middle of the roof that's 2.5 feet across, and that is mostly not covered by wood. Rain will tend to collect on the canvas in the center of the ring. So far I haven't had any problems due to this, but you might want to find some way to create a `dome' in the center of your ring. One way to do this is to take some scrap lathe and form an `X' on the inside of the ring (see Figure 11). This will create a dome that prevents water from pooling.
Figure 11: A domed roof ring (optional).
During erection, the nails in the top of the support slide into the 2 holes you drilled in the bottom of the roof ring, and one person stands in the middle of the yurt holding this up while other people insert rafters (see Figure 12).
Figure 12: The center support.
Putting up a yurt works best if you have at least three people, though two can do most of it if they have to. While at least one person I've heard of has built `support gear' to enable him to set his up all by himself, I don't recommend this at first.
Here are the basic steps to putting up a yurt:
Figure 13: Positioning of belly bands on khans.
The structural parts are now done. Now you just need to deal with the canvas:
Congratulations, you now have a yurt!
There are two ways to approach this, depending on how bad the tilt is, how many rafters are already in, and how brave you're feeling. You should first try to push up on the lower side of the ring (with a spare rafter or the center support) and see if that causes it to settle into a better position. If that doesn't work, and you're feeling brave, you can toss a rope up through the center of the ring and out on the high side, take both ends of the rope, and pull down gently. (There's nothing quite so scary as standing under a loaded roof ring and pulling it toward you, but this does work.)
One obvious feature is that you have many, many places to hang things. In addition to the pegs provided by the bolts, you can hang clothes (on hangers) by hooking the hanger over any intersection on the khana. You no longer need a clothes rack. (Alternatively, you could experiment with a clothes rack that is anchored on one end at the khana and at the other by a free-standing pole, so your rack is perpendicular to the wall.)
The yurt is large enough that you can curtain off a private section and still have plenty of room in which to entertain guests. Because we aren't allowed to have open flames (let alone campfires) inside structures at Pennsic, I spread carpets over the floor. (Pillows and cushions are an obvious addition, if you do a lot of entertaining.) If you install a cross beam in your roof ring, you can hang a light from the center of the ceiling.
S-hooks are your friends; they hook over the khana and can hold up all sorts of things.
For Pennsic XXV, I'm thinking of building shelves. The basic idea is that a shelf will be approximately 1.4 feet long (the diagonal of one square on the knana), and the back corners will have hooks that are spaced to go over 2 khana intersections. In the front corners will be cords or light chains with S-hooks on the ends. These hooks are then attached to the khana directly above the intersections holding the shelf back. (See Figure 14.) I wouldn't recommend putting anything heavy, like books, on such a shelf, but it seems like it could be a great way to store clothing that has to be folded, jewelry, and miscellaneous small items. I'm not sure if a shelf twice as long could be safely used, but I may try one.
Figure 14: A khana-supported shelf.
First layer: rafters, standing on their edges (so they're 3 inches high).
Second layer: khana, bolt heads down, one layer per khana section.
Third layer: door frame and center support, to the sides of the khana; carpets on top of the khana. (The carpets help hold the khana down and protect it a little more.)
The canvas and roof ring go inside the car, as does the bag containing the wing nuts, S-hooks, ropes, stakes, wrench, and miscellaneous items like seam-sealer.
Remember when tying stuff onto your roof rack to wrap and tie down the front of the pile. The khana is light enough that the wind produced by driving at even moderate speeds can otherwise cause it to bend up and break. And if you don't know how to tie a diamond hitch, ask someone to show you. It may seem paranoid, but it would be a real pain to have to re-make the khana because it wiggled loose!
Johan von Traubenburg provided tools, carpentry knowledge, the difficult cuts,. and the realization that it was cheaper to cut our own lathes; he also helped with the first couple setups while we figured out how to debug it. Johan and Dani of the Seven Wells did a large amount of the construction work, which was especially nice because I prefer to remain far away from large power saws.
I would also like to thank Haraldr Bassi, who bravely attempted to build a yurt from a previous, informal instantiation of my description, and got much farther than I would have thought possible without diagrams.
I welcome feedback on this article, especially from people who actually build from it.