Frequently when I tell someone that I make pourpoints I receive a response along the lines of “Wow, aren’t those sleeves really hard to figure out?”, so after considering this response I tried to figure out what part of making a pourpoint was stumping so many people who are otherwise strong sewers. The body of the garment is either three or four pieces, two front pieces and one or two back pieces depending on whether it is cut on the fold, there is an upper sleeve with added gussets and a lower sleeve, in all seven separate pattern pieces.
This image shows the front, two back pieces and the base for the upper sleeve. The best place to start with creating your pattern is to start with a body block that fits quite tightly around the body and to the neck. With the body block tightly pinned on the body mark the half way point on the top of the shoulder, the center of the pectoral muscle (just to the outside of the nipple), and about halfway between the old armscye and the spine on the shoulder-blade, finally mark about 2” down under the arm on the side seam. Now connect the dots with smooth curves. You should now have approximately the right shape for setting your grande assiette sleeve.
To create the sleeve itself you need a few easy measurements and the willingness to retry it a couple of times!
Bicep measurement, plus 1” of ease: _________
Shoulder point to above elbow: _________
Shoulder width: ________/2=_________
Arm measurement above elbow: _________
Now you can plug those measurements into the basic pattern! Don’t forget to add 1/2” seam allowances to everything! Make yourself a mockup and try it on, ideally you should have a full range of motion when the garment is fitting tightly.
Adding the gussets: There are a couple of ways to do this, the first is to cut out all of the pattern pieces for your first mockup, sew them all together and fiddle with the pieces once you have it on. Another way to determine the size of your gussets is to sew in the sleeve without the gussets and determine the gusset sizes that way. The best way to line up the sleeve into the armscye is find the point half way between the front gusset cut and the edge on the other side from where the underarm gusset is and match that point at the top of the shoulder. Then attach the sleeve across the top of the armscye from the back edge to the front gusset. Line up the underarm gusset so that each side of the cut in the sleeve is about 1” from the side seam and finish attaching the sleeve to the armscye.
Before starting to attach the sleeve you should put a minimum length cut for both the front gusset and the underarm gusset into the sleeve. The front gusset should not pull, if it does lengthen it slightly until it does not pull. It should not go more than 1/2” past the arm/shoulder crease at the front of the arm. Likewise the under arm gusset should not go more than 1/2” into the armpit. Finally, remember when measuring for the gussets that the Front and Underarm gussets slashes will have 1/4” seam allowances, and the back gusset will have a 1/2” seam allowance.