I would like to offer a suggestion for the next time. After you have your flat piece of brass cleaned and softened, cut to the correct length and width, use a metal straight edge and a pointed scribe or nail set and scribe or scratch in the lines or groves at either end of the soon to be pipe. Make them deep. Then wrap your material around your mandrel(I use the shank of drill bit the correct size) and clamp the lower edges in a heavy vice and draw it tight. after they are shaped you can deepen your groves or shape the flats to your desire. You might want to practice on some scrap metal (tin can stock, or such ) so you can see where to bend and adjust you measurements. Good luck, BPRICHARD