Fabric grain is a pain in the ass. If your waist and hip measurements are within a few inches of each other, you don't need to worry about this; but if the difference is any greater, the waist-to-hip section of your skirt pattern is going to start to look pretty diagonal. And diagonal is bad. Diagonal means bias, and bias means stretch, and stretch means the side seams of your skirt are going to be unstable. Unstable is bad! Unstable looks like this:
In order to correct this, we're going to add some darts. Darts take that nasty bias seamline and correct the shit out of it, making it nice and straight like this:
I'm going to show you how to add darts in the pattern that I like: one at each side of the front waist, two at each side of the back waist, down to the hip line. That means we'll be putting one dart in our Front pattern block and two in our Back pattern block. If there's less difference between your waist and hip measurements, you may not need two darts in the back; just strike one of 'em and center the other. If there's more, add another dart in the Front block.
So! We're going to start with some math. Take your waist measurement and subtract it from your hip measurement to get the difference between them. Now divide it by four. This is the total amount we need to take out between waist and hip line on each pattern block. We'll take a portion of this out with our darts, and the rest by curving in the side seam. (If this number is less than an inch and a half or so, you're probably good without darts; go ahead and skip to Step Five.) Get your Front block in front of you and decide how much difference you're going to take out with the dart. I like one-inch darts; any deeper than that and the dart itself is sewn too far on the bias and you get the same problem you're trying to correct on the side seams. Assuming you're making a one-inch dart, you're going to move your Waist Line mark one inch further out:
Then you mark your dart. I like mine centered, so I just find the center of my Waist Line measurement and put two marks half an inch to either side. If you have a round tummy you don't want to emphasize, though, you can place your darts further out toward the side seam. Supposedly this helps. Anyway, once you've marked the top two points of the triangle that will be your dart, you need to mark the third point. You'll want the dart to end at the hip line--it's most flattering that way, I think--and you have a few alignment options.
Option one is straight down the middle:
Option two is with the center line:
Option three is with the side seam:
They'll all give a slightly different appearance to the finished dart, but it's up to you which you prefer. I generally go with straight down the middle because I find it looks more symmetrical.
Now your Front dart is finished! You're going to repeat this process with the Back darts. Let's say you're using two one-inch darts: now you'll add two inches to the length of your Waist Line. Placement is a little trickier, since there are two, but I usually find the one-third and two-thirds points of the line, and mark half an inch to either side of each point. You'll end up with a pattern that looks like this:
Now, there are two things you need to pay special attention to on the Back darts. Firstly: the shape of your rear areas will affect how the darts fall. I usually plan my inner dart to fall about an inch and a half short of the Hip Line; on the finished skirt, this makes the two darts appear to fall on the same horizontal line across my body. Since every body is different, you may want to tentatively mark this dart at the hip line and then adjust the length when you're fitting the garment.
And secondly, dart alignment is important here. I put the outer dart with the side seams and the inner dart straight down the middle. Here's what my Back block darts look like:
And that's it for darts! They're beastly complicated, but knowing how they work and how to manipulate them is really, really useful.
Step Intermission: Draw Those Lines!
Time to connect the dots. If you've got a plastic curve ruler thingy, use it now. I just freehand. You're gonna end up with something that looks a lot better than this, no matter how you do it:
Once you've connected the dots on both your Front and Back pattern block, you've got a basic pattern in front of you! The rest of the steps will cover adjustments and additions you can make to your pattern in order to turn it into a real garment. Pat yourself on the back at this point, though--you're a real badass who just drafted a pattern.
(Note for seasoned pattern-drafters: you'll note that this pattern has a straight-across waistline, which will of course fit a curved human being very poorly. I usually correct for this when I put the waistband on. This is because I am lazy and cut corners something awful. If you don't want to be lazy like me, jack the top outer corners of your Front and Back blocks up about two inches. Congratulations, you're a professional.)
Keep your eyes peeled for Parts Three and Four, which will be up next week. Rock it, guys.