Drafting separate front and back knit skirt pieces
Building off last week's tutorial, I'll share how to customize the pattern pieces for a curvier shape.
Last week, we drafted a simple knit skirt that is fitted by using negative ease and stretchy fabric. The draft uses the same pattern pieces for the front and back which makes drafting easy but it may not be the best fit for you. If you are curvier in the bum or the tummy, you may want to draft different pattern pieces for the front and the back. This will help ensure that the side seams stay on the side of the body and aren’t pulled askew. For example, if you have a more shapely bum, but the pattern pieces are the same front and back, then the side seams may creep towards the back of the body.
If you haven’t read them already, you can catch up on the previous posts in this series at the links below.
A little note on fitting
Scratch that. Let's call it customizing. Humans have so many different measurements and proportions that there is no true "average" size. That's why most people benefit from making adjustments to their sewing patterns. We're all different by nature. There's nothing wrong with your body (or even with a sewing pattern) if you need or want to make an adjustment.
I truly hope that in addition to helping people make their own custom sewing patterns, that this Substack will help people feel more confident in their clothes, in their body and in their skills.
By the way, I heard this episode of the podcast 99% Invisible years ago about “average sizes” but it's really stuck with me. Click here to read the transcript. Around paragraph six, it starts to talk about how the military built airplane cockpits to fit an "average" size. But after many pilots died while flying, they discovered no one (yes not a single person) was actually average size. I find this very encouraging.
Our approach to today's lesson
Part 1: Measure Front and Back separately
Part 2: Draft the waistband pattern pieces
Part 3: Draft the skirt pattern pieces
Part 4: True the side seams/Add a dart if needed
Part 1: Measure Front and Back separately
For this approach, you'll need to take body measurements for both the front and back of the body—as opposed to the entire circumference. It might be easiest to have a friend help you take measurements. Or, you can create a visual guide by tying pieces of elastic at the waist and hip points. Then using a fabric pen, mark your ideal side seam location on the elastic. Then measure with a flexible measuring tape using the elastic as a guide.
In the graphic above are two example bodies. In example 1 the bum is curvy with a smaller waist. In example 2, the tummy is curvy with a narrower hip. The gray line represents the side seam and is placed in the middle of the leg. The red line represents the waist measurement and the blue line represents the hip. The dots on the side seam show where you will start and stop measuring.
If you have a curvier tummy and narrow hips like in Example 2 and the Front Waist is larger than the Front Hip, I recommend using the Front Waist measurement for the Front Hip measurement. This will help the skirt hang straight down from the waist. This blog post from Itch To Stitch does a good job of explaining this idea.
To keep things clear, the only measurements I’ve changed names and letters for are the waist and hip measurements. The Front measurements will use the Roman A and B. The Back measurements, will use the corresponding Greek letters α and β .
A Front Waist
α Back Waist
B Front Hip
β Back Hip
Part 2: Draft the Waistband Pattern Pieces
The formulas are very similar to our last lesson. But, instead of dividing the waist circumference in half equally, we are using our separate measurements for the front and back. The formula for the Length of the waistband pattern piece is the same as before and it is the same for the Front and Back.
Front Waistband Width = A×F + I×2
The Width of the Front Waistband is A Front Waist times F Negative Ease Multiplier plus the I Seam Allowance on each side.
Back Waistband Width = α×F + I×2
The Width of the Back Waistband is α Back Waist times F Negative Ease Multiplier plus the I Seam Allowance on each side.
Front/Back Waistband Length = (G+H)×2 + I×2
(No change to this formula)
Let’s look at an example where the front waist measurement is larger than the back waist. The example patterns in the graphic above are drawn to scale and you can see that the Front Waistband is wider than the Back but the Lengths are the same.
A Front Waist 18”
α Back Waist 14”
F Negative Ease multiplier .97
G Elastic Width 1.5”
H Elastic Casing Ease 1/8"
I Seam allowance .375”
For the Front Waistband, the Width of the pattern piece is:
A×F+I×2 = 18×.97+.375×2 = 17.46+.75 = 18.21"
For the Back Waistband, the Width of the pattern piece is:
α×F+I×2 = 14×.97+.375×2 = 13.58+.75 = 14.33"
For both the Front and Back Waistband, the Length of the pattern piece is
(G+H)×2+I×2= (1.5+.125)×2+.375×2 = 3.25 + .75 = 4"
Part 3: Draft the Skirt Pattern Pieces
Drafting a separate Skirt Front and Skirt Back is very similar to our last tutorial. The main difference is that to draft the pattern we will divide the Front and Back measurements by 2 instead of dividing the circumference by 4.
For this tutorial, I’m only covering Part 1 of the skirt drafting. Please refer to the last post for more details.
To draft the Front Skirt block, we’ll use the measurements A Front Waist and B Front Hip. The width at the waist is (A/2)xF and the width at the hip is (B/2)xF.
To draft the Back Skirt block, we’ll use the measurements α Back Waist and β Back Hip. The width at the waist is (α/2)xF and the width at the hip is (β/2)xF.
Part 4: True the Side Seams and/or Add Waist Darts
Note: If you are planning to draft an A-line skirt or a skirt with more ease through the hips, then you might want to make that adjustment before trueing the seams.
The tricky thing about drafting separate Front and Back pattern pieces for the body of the skirt is that we are not guaranteed that the side seams are equal and that they will sew together nicely. I foresee two potential situations here and I believe it hinges on the waist to hip ratio in front vs back.
Start by laying the Front and Back Skirt pattern pieces on top of each other and compare the side seams. Ideally, the side seams will be equal in length and shape. To a certain extent, you can ease the side seams together while sewing. But, I wouldn’t want to ease more than about .25”.
Example 1: Waist to Hip Ratio is Equal (or nearly equal) in Front and Back
If the ratios are similar, then you shouldn’t have to make big adjustments to even out the side seam. In the example above, the waist and hip ratios are the same in the front and back. But, the backside is wider than the front.
If the side seams are not exactly matching up, you can add a little bit here and there, and you’re good to go. Just make sure that any changes that affect the waistline are applied to the waistband. I would also try not to subtract anywhere because we’re already working with negative ease.
Example 2: If the waist to hip ratio is very different from front to back, then the curve along the side seam will be very different between the two pattern pieces. If this is the case, I recommend using waist darts to shape the skirt.
For this example, I’ve labeled our curvier pattern the Back and it’s shown in red. The Front pattern piece is in blue.
Lay your pattern pieces on top of each other aligning the hip point (the distance C from the top). Measure the difference between the front and back at the waistline. We’ll call it “X”.
Redraw the Back pattern piece using the side seam curve from the Front. Then add a dart that is “X” wide to the Back waist. The dart narrows the skirt to fit the waistband while allowing the side seam curves to match.
Darts are not generally used with knits but there are cases (like this) when they're helpful. I first used darts with stretch when I made the Seamwork Maggie swim top (blogged here). I was a little skeptical but it worked so well that I made a second one. I've also drafted a sports bra with under bust darts that I've been wearing for a year plus with great success.
I would just check that the fabric has enough stretch to go over the hips. And remember to use a stitch that stretches as well.
To finish your pattern, you’ll want to add any desired shaping to the hem, as well as the Seam Allowance and Hem Allowance.
I hope that you enjoyed this tutorial. Next, I’ll share how to draft a slit with a mitered facing and (hopefully!) my own version of the skirt.
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Happy mathing!
Beth
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