In my last post I promised to give some hints to prevent gaping at the back waist of the Jalie 2908 jeans. But the same principles could even be used for skirts or other pants with a back yoke. Then I decided I needed to test out my alterations, thus the wait.
I'm giving a lot of information so you understand why you should add here and subtract there. You will have more of the facts you need to boss your pattern around, covering your ass without baring your back waist!
First off, some geometry
The reason a lot of of have this problem is that the derriere needs a lot more fabric to encircle it than the waist does, especially at center back. If not enough fabric is removed at waist back, then then the fabric goes up in a cylinder shape (instead of a cone) and sticks out from our body.
The bigger the difference between the oval that represents your waist measurement, and that of your high hip, the more challenging it becomes to provide enough fabric to cover your butt and remove it to hug your waist. Here is a really odd (but enlightening) perspective of the body that I copied from the Fashion Incubator blog that illustrates the back side of the body as several horizontal slices.
Remember too, that it takes more length to travel out and around the behind and back in—especially when you are sitting down.
Dart Manipulation for jeans
In most pants the extra fabric in the back waist is removed with two vertical darts.
Here is a little model to illustrate where the darts typically are, with the future jeans yoke drawn over them. The larger the darts are at the top the more fabric is removed from the waist and released over the fullest part of your rear.
To make the jeans yoke, that top section is cut off making two back pieces: the pants back and the yoke. When the yoke darts are closed, the fabric that would have been in darts is moved to a negative space at the side between the bottom of the yoke and the top of the pants back. (Shown between the yellow lines.)
So the larger the original darts, the more fabric will be subtracted between the yellow lines, and the more the red line will curve up and in to accommodate a smaller waist circumference.
By closing of the remainder of the darts in the pants back, the center back is raised up and a wedge of fabric added the the center back right where we need a little extra length to travel out over the rump and back in at the lower back. Then the the center back seam is redrawn, scooping out the center back crotch seam a bit to make room for the gluteus maximus. This puts that center back seam more on the bias which gives the center back a bit more wiggle room thus avoiding the dreaded mono-butt look. At the same time it will subtract the amount of fabric covering the rear, so an equal amount should be added to the side.
Altering for your rounded rump
Usually we choose a pattern based on hip size. If we have a curvier rear, then the waist is typically too big.
To alter your yoke for a smaller waist, make a vertical cut (about a third of the way from the center back) from top to bottom leaving a hinge at the bottom. In the photo above it looks like a thin black line between the two closed darts. Overlap and tape. Below I traced what my Jalie 2908 yoke looked like before (line with Xs) and after I altered it with the pants back drawn underneath it. You can see how much larger that side dart became, and how much more the top line curves up. I also took a tiny wedge out out of the center top.
Now its helpful to add a tiny dart to the top of the jeans back. The easiest way to do this is to just cut a rectangle from the center top back leaving a hinge right above the fullest part of your tush, as seen below.
Now fill in the wedge and smooth out that center back curve as shown in the black line. You could even take more out at the top center than I have shown here.
To figure out how much to take out, I checked my butt curve with the flexible ruler (below) and came up with this. I didn't remove quite that much, but I did take out about 1/4". I had already added a bit more than this to the side edge for my wide hips, so there was enough fabric in width to keep me covered. I suggest cutting the front and back sides a size or two larger than you need at first and taking them in as needed while figuring out all the alterations to the behind.
It's very tempting to keep tweaking the pattern endlessly, but jeans already fit so much better than most jeans that I am very happy.
Hope this didn't bore you to death.
Does this make any sense at all? Any other fitting ideas?