So, You're Stu- I Mean in Charge of Tatamis for the Next Seminar...
I have been in charge of setting up the tatamis for seminars a few times now, and have learned from my friends (Thanks Hadi! Thanks William!) and from experience. I thought it might be a good thing to share that knowledge and allow others to complete it through their comments.
Identifying A and B
First thing to settle is locations. Where is the seminar held, and where are the tatamis? Then it becomes a three-step thing: get them to the seminar, set them up, then get them back.
A few questions to ask from the start: When is the seminar hall available to set up? When is the place where the mats are stored open? Once you know this, you can set a schedule.
Getting the Tatamis from A to B
You'll probably need a truck. But before you choose your truck, you need to know how the mats are stored. For example, if the mats are on carts, and the storing place and the seminar hall both have docks, you can then "simply" roll them in and out of the truck. This is a three-man job and takes but a few minutes.
But you need a truck that has a box with the right height (dock height). Last I checked, I don't have a driver's license for it, and we've had to use a professional driver.
If you can't get a dock-scenario, it means you'll have to load the mats in and out of the truck one by one. We've done this for years, but it's a lot more work and you'll need a lot more men and time. Count about an hour for 200 tatamis, every time... So that's two times before the seminar, and two times after the seminar.
A few times, we had a dock-scenario, but something happened: an elevator was broke, or the path was blocked by some construction, and we've had to load the mats one by one. So always have a list of people ready to come in on a moment's notice. Twice, we had to empty class and ask everyone to change and come give us a hand. Just remember to keep smiling and it's actually good for dojo spirit.
During transport, use two straps to keep the mats in place. Especially if they're on wheels. We once broke a truck door in a steep slope, as the one strap didn't hold... If you can, get 90-degree metal rods used to protect wall corners to protect the tatamis from the straps. If you don't have them, the straps are going to damage the corners of the tatamis where they press on the piles.
Have a list posted and ready. Put the hours where you'll be needing people, and feel good about twisting a lot of arms to grow that list in the days prior to the seminar. That's also aikido! You'll need four lists: to load the truck, empty the truck and set up the mats, remove the mats and load back the truck, and unload the truck back at the storage facility.
How many tatamis?
Rule of thumb... I have no idea, but start by looking at your dojo and how many people can train comfortably, then ask your Sensei how many people he expects. We usually set up 200 tatamis for a seminar, sometimes 300.
To help get a sense of the number of tatamis, I did some "napkin calculations":
(1 tatami = 1m x 2m = 2 m^2)
A basketball court holds about 210 tatamis (28m x 15m ou 26m x 14m or 420m^2)
A tennis court holds about 130 tatamis (24m x 11m or 260m^2)
A volleyball court holds about 81 tatamis (18m x 9m or 162m^2)
A badminton court holds about 41 tatamis (13,4m x 6,1m ou 82m^2)
Installing the tatamis
Start by figuring where things will be: kamiza, table at the entrance, flow of people, etc. Then decide if you want a square or a rectangular surface.
Find the center, and build from there, radiating outward (sounds very aikidoish, no?).
Talk to people at the beginning. It can get chaotic quite fast, and you don't want an error to creep and force you to undo everything. They now work for you and you need to stay merry and respectful, but you make the calls. Explain the layout, the pitfalls to avoid, how to handle the mats (two per mats, don't fold them, go slow at first, keep the mats snug), and what to do when the mats don't fit very well.
I like to have special teams: someone with a mallet, whose job is to tap the mats snug in place; someone who keeps tabs of the mats that are a little too long or a little too short (those are handy when small differences add up to an annoying inch. Get the long or the short mats, replace, and voilà!)
To keep the mats from moving during the seminar, we count on the design (see below) of mats, snug fit (hence the mallet) and adhesive on the external layer of mats. Once we reach the final layer of tatamis, we first set up two thickness of masking tape. This is to protect the surface of the hall we're renting (Thanks Karim!). On the masking tape, we use double-faced tape used for carpet. Nothing beats this, but it's not so easy to find. We also use jo sticks to unroll the tape. It helps maintain the tension.
With 200 tatamis, you end up with a circumference of about 70 meters. So 140 meters of masking tape, and 70 meters of double-sided carpet tape should do the trick.
Same when you remove the tatamis. People often stay and help at the end of the seminar. Make sure everyone understands how to handle tatamis properly. Set some teams on the tatamis stuck with the tape, for they need to be extra careful not to bend them. Also, set two people to make sure the mats are piled properly (face to face, and piled flush, or they won't fit in the truck).
Designing the Surface
The two main styles are tiles (two mats side by side creating a square) and bricks (mats are set up individually as bricks). We use both. We start with tiles in the center, then use a brick pattern for the last three or more layers. The bricks are very important, as they dissipate constraints in a different direction than the tiles. I've often witnessed tile-only patterns fall apart during a seminar, with cracks opening like crevasses, catching unaware toes with a sickening crunch (ok, maybe not that bad...). Using a mixed design, with the tape, we have absolutely no movement during the seminar. Nothing moves.
If you want a square, start with a central tile, wrapping it with more tiles. You'll get a square of 7x7 tiles, with 98 tatamis. Surround it with two or three layers of brick pattern for a total of 200 tatamis.
If you want a rectangle, you can start with two tiles in the middle instead of one, following the same pattern as before to get a slightly rectangular surface (10 x 11 tatamis, 220 tatamis in total)
If you want am even more rectangular shape, start with a square pattern as above, then add two rows of tiles (one on each sides to create the rectangle), before you lay the bricks around. You'll have 126 mats set up as tiles, with two layers of bricks for 198 mats in total (9 x 11 tatamis).
Esteemed readers, any other things to consider when setting up mats?