PVC - How far does it bend?

[griffin]

Does anybody have any figures on the bending ratio of PVC tubing? I'm wondering how far the different thicknesses of PVC can be bent before they snap, or just stop bending. For example, a 10' length of 1/2" PVC will ben almost in half, whereas a 2" thick tube will hardly bend at all. Another example: last year I used six 10' lengths of 3/4" pvc to make a large circle. This circle supported the outer edge of a parachute that was hung from a 12' tall center pole. I think I could have used thicker pvc for the circle. If anybody has facts or figures on this subject that can save me the time of buying a bunch of pvc just to see how far it will bend, I would appreciate it.

[bareman]

if you want to bend PVC to a small arc , fill it with dry sand , plug each end, and gently heat with a space heater. the sand will prevent the tube from collapsing. you can make a form to bend the tube around if you are bending more than one. when the tube is cool, dump out the sand. take your time and don't get the tube hotter than it needs to be to bend.

[Icepack]

Interesting to see this thread started. We've been planning to build a dome this year out of metal conduit. However a recent trip to the local Home Despot has somewhat surprised me on the cost. Also, the weight of the metal. The PVC is so much cheaper. However, will it hold up in the wind? Is the money and weight (while driving it to Black Rock) saved worth it?

Experienced dome builders please clue me in.

Thanks.

[robotland]

If it's a SHADE dome, I've seen many successful designs for PVC. If it's a SHADE/HANG HAMMOCKS/CLIMB ON dome, 3/4" EMT's Da Bomb. A 19' dome weighs less than most passengers, if that's the issue, and the conduit for a 2v shouldn't set you back more'n a C-note.

[naga brain]

I second Robot on the cost. But if you don't have access to a lot of metal working gear, it takes a good amount of time and a good vice to build a metal dome. We went through two of the ones from the local discount tool store. It's a bit weighty, I think ours (a 15 ' 2v) weighed in at over 200lbs.

But the most important thing is to remember to bring all of the dome struts to the Playa. Otherwise, you look kinda stupid to the neighbors... (I speak from experience on this.)

Finally, I don't think you can build a higher interval dome outta PVC can you? Your six point junctions would be over seven inches thick!

[robotland]

I've seen examples of PVC dome junctions made by heating and then squashing the ends, thus reducing the thickness of the vertex....I'm just too lazy to try it. Also seen 'em joined by cutting a slot in the end of the PVC and sliding it onto a metal disc with a retainer bolt. Maybe a high-frequency dome made of 1" PVC would work, but I still wouldn't climb or hang on it.......

You don't need a vise to squash EMT, either. I've always used a 3 lb. hammer and an anvil. MUCH faster than squishing in a vise. Half-dozen whacks per end and you're done. REAL anvils are hard to get aside from ordering a new one (wanna pay shipping on THAT?) or finding one at an auction, but a chunk of rail or I-beam set into a stump works fine. Ask at your friendly neighborhood scrapyard. Actually, most BIG vises have an anvil right on 'em, so you can do an ergometric analysis of which technique is most efficient.

[Alpha]

I wouldn't recommend squishing the ends of PVC -- you're taking pretty much all the strength out of it, and it just might come down on your head when the wind blows. The same goes for EMT, to a lesser extent. Sliding the round struts into a disc at the vertex is a better solution, and even better than that is to make pegs for the disc that slip into the struts. I'm going to try that for my EMT dome this year, by making an 8" disc for each vertex and using dowel rods that match the ID of the EMT.