1) Not sure what you're trying to accomplish, but you can candy-cane rebar by taking two poles, sticking the rebar into both of them (end to end) then folding one pole over until the poles are touching, the rebar should bend over nicely.
2) Blue tarp is loud, flimsy, not particularly good at blocking light, and it doesn't "breath". Cotton parachutes are among the best covers, though any silverized fabric works pretty well too.

1) another solution for the rebar issue: leave them straight, and buy caps for them when you buy them. You can buy 2', 3' and 4' lengths of various diameters of rebar at Home Depot (as well as other, locally owned stores too, I'm sure), and orange "mushroom" caps that are one-size-fits-all. If you drive the rebar at an angle (such that the rebar and the rope make approximately a 90-degree angle), you can take a couple of wraps of the rope around the rebar and it won't slip. A pair of big vice-grips or channel-locks, along with possibly a sledge hammer to knock the rebar around a bit, are usually all it takes to work the rebar back out of the playa. And the bonus is that the stack of straight rebar is re-usable the next year, and isn't such a snaggy, space-taking up mess to transport back home. The mushroom caps are mostly just to keep people from impaling themselves on the ends of the rebar-- dolls and stuffed toys work well, too.

2) Blue tarps will work and are relatively cheap, silver tarps are a little more expensive and will work about as well as the blue-tarp, both in terms of structure, shade and ventilation. Parachutes also work. All of these are ventilation-limited-- without being well-ventilated (as you suggest your design is) all three will accumulate heat underneath. You don't mention if your tensegrity structure will result in the shade panels needing to curve. If so, tarps of any color will be difficult to pitch tightly, which will result in the dreaded flap-flap-flap noise as well as (if the flapping gets out of hand) failure. Here's a suggestion: aluminet. It's only negative is that it's not 100% shade (but you can get weaves with up to 75% shade). I've been using it for several shade structures lately, and its advantages are that it's light, it's shady, and since it's knit, you can pitch it tightly over curved surfaces. Therefore no flapping (ahhh! quiet!). It's strong as hell, and it's also pretty. It's also "relatively" cheap-- I think it's running somewhere around $0.40/square foot right now, and you can buy it in widths up to 15-20 feet if you look (google Aluminet for a variety of sources, widths, densities and prices). And since you can re-use it for other structures that may have other dimensions, that brings the price down.

have fun!

Chris

I considered a hexagon and went with a pentacle. In retrospect, I think a square, or Diamond, might be the best configuration and is what I am doing for our second structure (to shade a martial arts training area).

Pictures of first attempt are in my question-post here:
tribes.tribe.net/shadegeek...9c74f0f320

Do you have any design sketches or descriptions of your proposed structure? I'm struggling with balance of cost, reliability and performance for our structures. Hint that might be obvious, but Harbor Freight sells bright-orange ratcheting cargo straps that come-out to less than $3/piece. That's almost cheaper than one can buy rope! Excellent for tensioning-up the structures and very visible. Cheap enough that I can keep a few spares to make up for iffy quality.

-B.