Have you ever wanted to lay out the frustum of a cone on a flat surface?” “A what?” “A frustum, the part of a cone that is left when you lop off the top.” “Oh, yeah. If I had a nickel… sadly, I’m still poor.”
It can be a little intimidating if you’re not familiar with the concept of how to go about it. Our draper came to me wondering how she could accurately lay out a dress based on an actor’s measurements. (Apparently the traditional layout method wastes fabric.) So I came up with this simple excel sheet that does the calculations based on the following measurements: waist (small circumference), hem (large circumference) & inseam (height of the frustum.) It gives back the details needed to lay the cone frustum out on a flat surface. The diagram below gives the general gist of what’s what. There is a larger version of the image in the excel document.
Frustum.xls From fabric to sheet goods, I hope this calculator finds some use.
Update: There is a great description of how to flatten a frustum in AutoCAD over at Woodweb.