This section is from the book "The Tinman's Manual And Builder's And Mechanic's Handbook", by Isaac Ridler Butt. Also available from Amazon: The Tinman's Manual And Builder's And Mechanic's Handbook.
But there is a greater simplicity in cutting it, when the angle is 60°. For instance, take AC equal to the slant height, describe an indefinite arc AO; with the same opening of the dividers measure from A to B; draw BC and we have the required sector. This would make the angle C equal 60°. This angle may be divided into two or four equal parts, and we should thus have sectors whose angle would be 30° or 15°, which would not make the vessel very flaring. The accompanying figure gives about the shape of the flaring vessel when the angle of the sector is 30°.