A student decides to build a boiler for a model steam engine. He cuts some thin sheet metal into a strip, rolls it into a spiral, and puts on end caps, as shown in the diagram. The diameter of the cylinder D = 34 mm and wall thickness t = 2.9 mm. The student has some fancy glue, and uses it to secure the spiral seam.
After applying the glue, he applies a torque T to clamp the edges of the seam shut. With the torque still applied, he puts some water inside, heats the boiler, and a steam pressure p = 126 kPa is created. After a while, the student notices that the heat has caused the glue to melt and run out. However, even when the cylinder is pressurized, the torque T is still sufficient to keep the seam closed so that no water leaks out. Determine the angle theta degrees that requires the minimum torque T to keep the seam closed. (Hint: use Mohr's circle). Give the answer in degrees.