I came up with this pattern, and it works well enough for me. If you try it out, I would appreciate any feedback you could give me on how it fit, problems you encountered, etc. so that I can make it more generally workeable.
1.) Take your measurements. You'll need:
2.) On a piece of large paper--newsprint, a cut-open grocery bag, etc.--take a ruler and pen, and mark out the following pattern:
Mark this point A. Take that same measurement of one, two or three inches, and measure down that far from the left end of the horizontal line. Label this point B. Then measure from the front center out leftwards to 1/4 the length of the horizontal line, and mark this point C.
If you want straps:
If you want a corset with straps, measure along the top curve of your pattern three inches out from the top front center. Mark it. Measure another inch out, and mark that place too. Now draw two five inch long vertical lines up from these points, perpe ndicular (90 degrees) to the curve, five inches long.
Measure in three inches from the back center, mark it, measure in one more inch, and draw another set of five inch long parallel lines perpendicular to the top curve. (see diagram)
Now Check the Pattern.
Using this half-pattern, fold a piece of cheap fabric in half, lay the front center of the pattern against the fold, and trace around the pattern. Cut it out of the folded piece of cloth, open the fabric up, and fit it around you to see if it fits.
Make sure that the underarm curves and hip curves are large enough so that they won't rub against your arms and hips. You may have to move the underarm/hip curve slightly to the front or back to get a perfect fit.
Make sure that the pattern comes up high enough in the front. It should not close completely in the back; there should be a one to two inch gap, some of which will disappear when you lace the actual corset on.
If you made a corset pattern with straps, have someone pin them together at the top of your shoulders. Make sure that they are pulled tight enough to provide the bust support you want. If they're too close or too far apart for your liking, change the ir placement on the pattern. Mark each strap where it meets over the shoulder. When you take the cloth pattern off, place the paper pattern beneath it and cut off the strap on the pattern at the place where it met the other strap over the shoulder.