There you go. A much larger diameter pipes would work better but it's not necessary since the width of the material being bent is very small. Just insert the sheet between the pipes and push down to your desired curvature. Also if you have a tree trunk that has a nice round trunk with the right diameter, just screw one end of the sheet and wrap it around. Not much effort to bend the sheetmetal being less than 5" wide. The holes in it also makes it much easier to bend.
For sharp right angle, i use this old bed frame.