I need to make a cone but am unsure how to work out the curved ends when cutting the sheet. is there some kind of equation to work it out. The cone has to be 36" high with a 6" hole at the base and a 24" hole to the top.
You can have a copy of my Excel cone calculator if you want it, it does the maths for you just, fill in the yellow boxes with your measurements and it will calculate the frustum angle for you.
PM me and I'll tell you where to find it
I normally draw it like in Paul's picture above, but instead of calculating angles, I measure round the curve, mark off the length, found from the circumference of the ends of the cone. Probably an easier and more accurate way on bigger ones.