When I need something like this, I draw an arc. Nearly closed in sheet metal:
This tube can be flattend.
Further to normal [just as I would do this] solution offered by Joris, and because there is usually at least a couple of ways to accomplish tasks in Solid Edge, you could also draw a pizza segment [obviously, you'd need to dimension accordingly, to have a smaller gap than I have used for illustration] to one end, and use it as a cutout to the full length of the tube, then switch to "Ordered" mode > run "Convert to Sheet Metal" > "Flatten". Done!
Design Manager Streetscape Limited
Solid Edge ST9 [MP3] Classic [x2 seats]
Thanks guys still having a couple of problems. Ive got my tube (3mm wall thickness) and cut out a 0.1mm pizza shape all the way through. Then switched over to sheet metal to flatten and this problem occurs. Please see image below.
First of all, start in sheet metal, a sheet metal part is drawn in the sheet metal environment.
Than, the easiest way is draw a nearly closed arc when creating a "Contour Flange".
In my prior screenshot you can see all the steps I think.