Medieval-style pavilions that you can buy commercially are very nice, but they are expensive. They're generally made of cotton canvas (not hemp, which would be more authentic), with all the problems that come with it: leaks, mildew, weight, and so on. Making your own is also expensive, and is very labor intensive, to boot.
Many people simply give up and buy a modern tent, or even huge portable carport from Costco. Those are light weight, waterproof, rot-proof, and completely modern.
Isn't there an option in between?! A big tent that can be quickly and cheaply made? A tent that may be made of modern materials, but at least has an authentic silhouette?
Well! I have recently discovered what many of you must already know: that tarpaulins of enormous size (up to an astounding 60 x 120 feet!) are now available at little cost. What's more, although they are woven polyethylene, they are not always an obnoxious blue. In fact, the heavy-duty ones are generally white.
The large size makes it possible to create a pavilion that is, as it were, cut from whole cloth. A single huge piece, with only a few darts to shape it.
What's more, tarps already have many of the features you would want in a tent: A reinforced hem, grommets all around, etc. With careful layout, for example, a 13' x 20' octagonal pavilion could be cut from a single 30'x30' tarp, with only six seams in the whole project, and nary a hem. Total cost, including decoration, under $200, and finished in a day.
The trick is to design the tent to use up precisely as much fabric as the tarp provides. I used this spreadsheet to specify all the measurements, and used Excel 97's "Solver" feature (which is essentially a linear progamming module, for those of you who are mathematically inclined) to maximize the floor space while maintaining the correct size and shape.
Here is the pattern that I used to make our first pavilion. To preserve as much of the factory hem as possible, the doors end up being on the ends, the way they are on some medieval French belled wedges, instead of the long sides. Oh, and vertical side walls also help to preserve the hem and avoid seams.
Out of a 10' x 10' tarp I made a prototype with four foot poles two feet apart. Here's what it looks like (before applying the contrast striping). You may be able to see two tall finial poles on top, ready for banners.
Although the original plan called for an internal frame at shoulder height, that worked out about as well as internal frames ever do: poorly. So, instead I salvaged grommets from the cutting room floor, hemmed them, and sewed them into the shoulder seam on the ends.
Shoulder guys, following the roof pitch, then held the tent open. Why am I ever surprised when the historic solution turns out to be the most practical?
For tent stakes, I used huge nails, 10" long, from the hardware store. They only cost about 33 cents each, and they are tough as--well, tough as nails.
The model tent was a big hit, especially with my kids!
Here are some of the parts I used to make the pavilion.
The poly tarp fabric is stiff, and bigger than you would expect. I had to set up the sewing machine outside on a sawhorse-and-plywood table. Putting most of the stripes on the fabric in advance definitely helps you to line things up and keep track of which is the inside and which the outside.
However, the woven poly fabric isn't hard to sew. I used heavy upholstery thread and a heavy duty needle, but my little home machine had no trouble penetrating the layers. I did have to increase the thread tension to get even stitches. The biggest problem was that the tarp fabric was slick and heavy, so the little feed dog that normally scoots your cloth along couldn't work very well. I had to pull it through by hand, which made for uneven stitches. It's a good thing I plan to cover the seams with tape anyway.
I used French seams on the big tent, which are much easier than the flat-felled seams I used on the scale model. Then, I applied Seam Sealer to all the seams.
When pitching the tent, it helps to have stakes right at the corners of the octagonal footprint. I ended up adding several grommets there.
For the woven poly tarps, I found this outfit that sells mail order. Their prices are really great, but they never had the right size in stock. So, I ordered from Party Tent City in Houston. Brian Nelson is a nice guy, he had what I wanted (or in one case got it the next day), and he shipped immediately.
Some vendors carry tarps that are UV coated or flame retardant, but not all. The way we like to play with fire in the SCA, that could be important. If your tent burns down, don't say I didn't warn you.
Large canvas tarps are available, too, although they cost more and weigh more. Harbor Freight sells bigger canvas tarps than I have seen elsewhere. Maybe plastic isn't the only way to get a one-piece pavilion. It's a trade off: Canvas breathes and looks better, but it's also heavy and it rots. I hate the smell of mildew. The biggest problem is the color: mud brown. Yuck!
You can also find big tarps sometimes on eBay.
Here is what happened when we took this tent to the Pennsic War.