I have a barrel/drum that is 14 inches across and 36 inches long I need to cut it into 3 equal parts longways then cut the ends off to form a long continuous 9 foot trough without the joints being taller than each other(even joints as if it was made that way, 9 feet long) so not to jab/cut with the longer point, problem is the barrel has a rounded top instead of s 90 degree points on the edges where side and top meets so measuring is very difficult. Any ideas? Would it be easier to first cut the ends off then divide the round barrel/pipe into 3 parts? I have 15 barrels to cut this way, they really need to match. Thanks