



 
Hi John, Most of the information you need is in Edwards response to Neal's question and my response to Al's question. Suppose the diameter of the pipe is d units and the pipe is sliced by a plane in inclination φ degrees, in your case 150 degrees. Following Edward's development the equation of the intersecting plane is z = tan(φ) x which in your example is z = tan(150^{o}) x = 1/√3 x. The equation of the curve you need is then
where the angle 2x/d is in radians. In your case where the plane that slices the pipe has an inclination of 150^{o} this is
For example I took d = 10 units, graphed one period of y = 5/√3) cos(x/5) cut it out and rolled it up to form the pipe Harley  


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