Too much sun? Make yourself some shade! This instructable comes from an idea I had about a way to make simple, fast, and cheap shade structures out of spandex (Lycra) fabric. This method lends itself to experimentation since it doesn't require sewing or permanently altering your materials. It'd be great for a temporary display for an event that needs a splash of color and some relief from the sun.

Step 1: Tensile Structures

There are two main categories of forces that a material can experience: tension and compression. Think of tension as a pulling force and compression as a pushing force.

Most permanent buildings are made of materials that work well in compression, like brick and concrete. The weight of the building itself and the stuff inside it push down and compress the walls to keep it standing. Buildings that are made of compression materials are usually heavy. The Romans used a lot of stone. They were fans of compression.

A structure like your average camping tent works via tension - the space is enclosed by fabric that is stretched between a lightweight frame. You put stakes in the ground to pull on the fabric so it stays more or less in the same shape. When you think tension, think ropes and fabric. Some of the best rope-structure builders were the Incas. They built suspension bridges that spanned canyons and terrified their European visitors.

Wikipedia will tell you more about tensile structures.

One of the advantages of tensile structures is that you can span a very large distance without using a lot of material. This is why the longest bridges in the world are suspension bridges with a deck hanging from cables in tension.

Step 2: Materials

You will need:

Spandex Fabric - This is the tight-fitting stretchy stuff that swimsuits and cycling clothes are made of. Your local fabric store should have some. Get enough to cover the area you're looking to shade. I bought 9 yards for the structures you'll see in the pictures and it cost about $40.
String - A spool of medium gauge synthetic string from a hardware store should work fine. Avoid cotton; it'll break down in the rain and sun.
Zip ties - Part I of the super secret no-sew connection system. A pack of 100 short (3") ties will do. Look for UV resistant ones - they're usually black.
Pennies - Part II of the super secret no-sew connection system. Go to your bank for a roll, or break open the ol' piggy bank. A dollar's worth will do.
Scissors - If you want to cut your fabric into different shapes (optional), you'll need some scissors. These will also come in handy for clipping the ends of the cable ties to make things look neat, but a pair of nail clippers or wire snips work better for that.
Extending curtain rods (optional) - If you want to push the fabric up where there is no existing support, a curtain rod works great. You can get twist-locking adjustable ones at a hardware store. Extending paint roller poles also work well, and they're useful if you take the structure down. Other non-adjustable poles will work and are cheaper, but they're harder to experiment with.

Step 3: Play Around

Stretch that fabric! See how it behaves, how far you can stress it, how much force it exerts, what shapes it takes etc.

You'll notice that the fabric never takes on a form with straight lines. It also never will be completely flat. In fact, the flatter the fabric is, the more it will flop around with the wind. The best forms for tensile structures are ones with double curvature - which means the fabric is bending in two different directions (a dome and a classic circus tent both have double curvature, a vault has single curvature).

Do a Google image search to get some ideas on forms you can make. You'll see that the physics of working with this kind of material lead to a certain style of structures - no boxes or straight lines allowed!

Step 4: Reinforced Connection Points

After playing around some, you probably realize the best way to shape your fabric is by pulling on it. To free up your hands, you'll probably want to tie it back in various places. Usually a tensile structure's fabric will have sewn-in reinforced connectors or grommets for wires or ropes to grab onto. These stop the fabric from ripping due to a concentrated force from the rope. Think of the metal grommet holes in a tarp or on a flag.

Putting in grommets is an option, but it's tough to do in stretchy fabric and it requires permanently altering the pieces you have. Instead, try this:

Take a penny and push it through a corner or edge of the fabric
Twist the penny to make a narrow "neck" in the fabric
Cinch a zip tie around this neck, trapping the penny inside the fabric
Tie a piece of string around the fabric neck.

The penny should stop the string from slipping off even if you pull on it very hard, and since you didn't have to cut the fabric you can pull much harder before it rips.

That's the secret. Simple, right? You can even use this to connect two pieces of fabric together, like a stitch (as shown in the pictures).

Step 5: Stretch, Tie, Experiment

Try tying the fabric to different structures around the area you want to shade. Trees work well, as do fire escapes, pipes, or other things sticking off nearby buildings. Since the fabric is mostly hanging from these things, you'll want to find some supports that are high up, but try bringing it down to the ground as well.

If you want to take the fabric in a different direction, just add in another connection point! Try to keep the whole piece taught - it will flop around less - but you might have to relieve the tension some to push another penny through.

Step 6: Push It Up

If you need to raise the roof in a spot or two, use your curtain rods or adjustable paint roller poles to push up on the fabric. The elastic fabric will push back and hold the rod down to the ground without any additional support if you push hard enough. Try this in the center, edges, and corners of the fabric. You can also run the string over a pole to make a high tie-back point.

Step 7: Add On

Connect different pieces of fabric together to extend your structure and make different shapes. No need to sew the pieces - just connect them with pennies and zip ties at a few points. The more "stitches" you use, the smaller the gaps between the fabric will be, but there will always be some space. I think it looks nice that way! Who needs straight lines?

Step 8: Enjoy the Shade

Keep playing until you've got something you like that shades the area you want. Remember that the position of the sun will change, so keep in mind where the shade will be at different times of the day.

Then sit back and enjoy the shade!