There will be a day very soon when I stop blogging about sleeves, but today is not that day.
Reading in the dissertation linked to in yesterday’s post about how surface intersections are approximated using cones and cylinders, I discovered that the method of slicing a cylinder at an angle we used to approximate a 3D armscye/sleeve cap intersection and flatten it to a 2D pattern shape is best suited for straight sleeves on closely fitted designs like jackets.
The sleeve cap is higher for this kind of design, restricting arm motion.
The diagram on pg. 80 (PDF pg. 104) of The Development of a Hybrid System for Designing and Pattern Making In-Set Sleeves by Morris Campbell shows how flattening the crown and widening the underarm length increases range of motion.
The two images comprising this diagram are shown above and below.
This could be part of the reason why my V8543 bodice muslin is too tight at the sleeve back seam when I put my arm into the driving position, although the main reason is that I cut the size too small overall. I plan to cut a bigger one.
Thinking of Goldilocks and The Three Bears, I decided I wanted a “just right” compromise between fit and range of motion, meaning the perfect balance among these three arm positions:
Martin produced curves for these positions.
Here’s what happens when you take the union of these curves to optimize for all three positions.
Smoothing you get this.
And tracing you get this.
These shapes look pretty close to the armscye/sleeve cap shapes of commercial patterns, with a couple exceptions:
1) the sleeve cap has a slightly deeper scoop in front, and
2) the armscye is slightly rotated forward.
My third V8543 bodice muslin will approximate this armscye/sleeve cap design.
What do you think about your own arm range of motion preferences? Do you also want to wear garments optimized for all three of these positions?