The Center Seam Leg Block
Leg Blocks Part Two
This section assumes you've already completed the first six steps of the Leg Block. We'll continue building the centre seam block as step 7.
21: Mark point 21 halfway between 19 and 20. This represents the height of the seam as it passes under the crotch. If you place it higher it'll cut your client in half, if you place it lower it'll restrict movement. It is an arbitrary position however. Square across the entire sheet.
22-23: Measure this line. It is waist to crotch plus half gusset. This is the length of the centre front seam for the next step.
22-23: Draft in a curve the exact length of the centre front seam as determined in the previous step. If you're drafting on paper this is easier to do with a flexicurve ruler. Mark the distance on your ruler and then bend it to a nice smooth curve which ends on the halfway line. If you're using a CAD program there are a number of bezier features in most programs that'll help you maintain the line length while you curve.
23-24: Draw down a straight line from point 23 to point 24 about halfway between the thigh and knee. If you've drafted an even curve for the centre front seam, point 23 should be a right angle.
Mirror the curve from the centre front to the centre back and mark in points 25 and 26. Now look at the illustration below. The left image shows a lengthwise cross section through the body. The dotted line in image 1 represents the height of the thigh at its widest point. The new dotted line in image 2 represents the line between the cheeks. The last image shows how the garment should sit on the body. Note that it pulls between the cheeks and then sits down below the crotch. What you should also note is that the centre back seam is slightly longer than the centre front seam. It's not much (about half of the measurement 20-21 in step seven), but it's significant if you want the inseam to sit in the right place.
Pivot the line 25-26 by rotating it around point 26 in order to lengthen the centre back seam the amount determined in the last step. This is advisable, but only really necessary, if you're making full length leggings because the inside seam needs to sit in the right place. In shorts, the garment will ride and self-adjust because nothing is locking it down. Re-curve the centre back seam as shown. I would leave the original line 25-26 on the block for when making shorts. Lastly, curve off the ankle cuffs so that they make right angles with the seams.
Remove unnecessary guidelines, points and numbers. Cut out or retrace the front and back blocks and true up all curves. Make sure you clearly label your block with a title, panel name, size, date, author’s name and version number. Do not add seam allowance to the block!