Hello amijo, I have looked into this idea and found it cost prohibitive. You could check out fabric guru, they have lots of different fabric and sometimes you can find a deal on outdoor fabric. Currently they have awning fabric for $10/yd. Then you would need to figure a way to put in grommets and have a structure to tie it to. A big patio umbrella might be best.

Here is a link that might be useful: Fabric Guru

place i used to live 'arcosanti' uses lots of these. they recently received one from a company called sunami.

architecturally, these are known as 'tensile structures' which may be good to search for.

and gee, that's the url for sunami..
www.tensileshadeproducts.com/Sunami.php (i haven't visited the site to exercise caution with the link)

i've also built several such structures using regular shadecloth from eg. home depot.. i'd say d.i.y. can be a good route, but for high winds you really want to make sure it's as taut as possible.. with really strong seams. using those double ended screwy tightener things for sails or stuff.. should be able to grab some at ace hardware.

tight/less play is good.. more play = more breakage.

if you design your own, maybe consider some way that it can be drawn up so you only expose it to the elements when you want to use it.

I highly recommend putting up your own structure using 4 X 4's and getting a shade made of cooloroo. We found this method cost effective, attractive and effective as shade for us, the pooches and plants. Arizona Bag on W. Buckeye is where we got ours. They have a wide range of colors. They will cut material to fit what you've got, seam it and install grommets for a fraction of the 'sails'. (I thought I wanted a sail, too, till I investigated the cost!)

I misspelled "Coolaroo" but you can find more about it here. I have no association with this company, but I found that it's a great resource for gardeners wanting shade or a greenhouse or even tools.

Here is a link that might be useful: @ Coolaroo

I have not used a sail, but have attached the Coolaroo shade cloth to a pergola and lattice structure to provide additional shading and it makes a world of difference.

tomatofreak's suggestion about puting up a 4 x 4 structure and getting the shade cloth at AZ Bag sounds like the most cost effective solution for your situation.

I have one I use in the garden, under the %50 shade cloth during the hottest months. I love it..got it a local Walmart for about $40, it's a triangle. Will get some more, same reason, some spots don't have good tree canopy yet. And I also use umbrellas, but have to run in and out due to winds, lol...I have also used just cheap sheets from the thrift store, work fine, just not as pretty and they die pretty quick, not made for weather outside. But work fine as a quick save.

for your replies to my sail question...
have given up on that due to cost...
still pondering.........

Consider building a pergola. Not cheap, but easy to do, attractive, long lasting and you can train grape vines up it (and maybe kiwis) to replace the shade cloth after a couple of years. Can build benches into them for sitting or just park a bench or two under them for contemplation.

I'd search images for "pergola" to get some great ideas.

http://www.woodworkersworkshop.com/resources/index.php?search=pergola

http://canadianhomeworkshop.com/6349/project-plans/pergola#projecttabs

http://www.popularmechanics.com/home/how-to-plans/pergola/4294348

http://www.popularmechanics.com/home/how-to-plans/pergola/3352816

http://www.ronhazelton.com/projects/how_to_build_a_free_standing_pergola

Here is a link that might be useful: Build a Pergola �