Using Your Duct Tape Sloper to Modify Flat Pattern Pieces (Part 2/2 – Duct Tape Sloper Series)

Disclaimer: I’m not a professional sewist or pattern maker. This tutorial simply describes an approach I find helpful.

Okay, so you’ve made yourself a sloper – now what do you do with it?

You can lay your sloper pieces over flat pattern pieces to help you work out a few important details:

• Which pattern size to use, and whether or not to grade between sizes/
• Which fit alterations you want to make.

This comparison technique works really well for simple pattern pieces which correspond with your sloper pieces and their dart placement. If your pattern is for a top with one bust dart, compare it to your bodice sloper with one bust dart. If your pattern is for pants with front and back waist darts, compare it to your pants sloper with front and back waist darts. If your pattern is for a dress, compare it to your bodice sloper and skirt sloper which you overlap at a horizontal reference line, such as the waist line.

This comparison technique doesn’t work well for more complex patterns with multiple panels or unusual pieces that do not correspond to your sloper pieces.

Comparing your sloper pieces to flat pattern pieces

Use the following general steps to adapt flat pattern pieces using your sloper:

1. Align the pattern piece and sloper.
2. Choose your size(s).
3. Make any pattern adjustments.
4. Make a muslin.

Step 1: Align the pattern piece and sloper

For bodice comparisons, I align the centre front or centre back lines. Next, I place the shoulder seam on my sloper 1″ (plus seam allowances) below the shoulder seam on the pattern piece. The extra 1″ provides vertical pattern ease through the armhole. Personally, I find 1″ is a comfortable distance for vertical pattern ease at the shoulder/armhole. Some people prefer ½”.

For skirt comparisons, I align the centre front and centre back lines, then align the waist line. No vertical ease is required.

For pants comparisons, I align the centre front and centre back lines. Next, I place the base of the crotch on my sloper 1″ (minus seam allowances) above the base of the crotch on the pattern piece. The extra 1 inch provides vertical pattern ease through the crotch. I find 1″ is a comfortable distance for vertical pattern ease at the crotch.

Step 2: Choose your size(s)

Compare the pattern sizes to your sloper (plus seam allowances) and the amount of horizontal ease that you want, which might differ from the ease included in the pattern. For example, I like a closer fit over my bust and a looser fit over my hips, so I allow less horizontal design ease at the bust and more at the hips than the standard recommendation.

Note: There are standard recommendations for the amount of horizontal design ease to allow depending on the type of garment, type of fabric (woven v knit, amount of stretch) and whether any closures are used. The book Professional pattern alterations made easy by Kerstin Martensson (1976) is my go-to guide for this measurement.

When you compare the pattern sizing with your sloper, seam allowance, and ease requirements, you might find that your sloper corresponds comfortably with a single size, or you could find that your sloper spans one or more pattern sizes.

If your sloper spans multiple pattern sizes, consider whether you want to grade between sizes, make some pattern adjustments, or both!

Step 3: Make any pattern adjustments

Here are some common pattern adjustments you might want to make:

• Adding or removing vertical length between bust, waist, and hip lines.
• Raising or lowering bust dart.
• Raising or lowering armhole.
• Shortening or lengthening darts.
• Aligning waist darts under the bust apex for front pieces, or shoulder blades for back pieces.
• Increasing or reducing the shoulder slope.
• Horizontal adjustments: Full bust adjustment, full/flat tummy adjustment, full/flat bottom adjustment, narrow/wide shoulder adjustment.

The CSC Curvy Tutorials have fantastic step-by-step instructions for common pattern adjustments.

Use the comparison of your sloper with the flat pattern pieces to help you to decide how much of an adjustment to make.

Step 4: Make a muslin

Yep, I still make a muslin to try out my size grading and pattern alterations using the same or similar type of fabric that I plan to use for the final garment. Even with the help of my sloper I don’t know exactly how the fit will go until I make the pattern up in a specific type of fabric. I find a muslin particularly important where high levels of stretch or drape are involved. The fit of the muslin is usually much closer to my ideal fit if I made size and alteration decisions based on a comparison of my sloper with the flat pattern pieces.

Examples of garments that I’ve adjusted with my sloper

Here are some of my experiences using my sloper with some simple patterns.

Example 1: Comparing my bodice sloper with a pullover dress pattern

I learned to sew with Kwik Sew 2982: a pullover dress in a boxy style with a scooped neckline. The size range is XS – XL.

Kwik Sew 2982 – Misses’ pullover dress

This pattern is very straightforward. I only wanted a top so I cut the pattern pieces to hip length. What could go wrong?

The first time I made it, I followed the instructions in the packet on how to pick my size, and chose size L. When I made up the top, the shoulders were too big, the hips were too small, and the top just hung like a bag over my curves in all the wrong ways.

Let me show you why this was so unsuccessful. Here are some photos of my bodice slopers overlaying the front and back pattern pieces. The seam allowances are all ½ inch and I’m aiming for 2 inches of ease in the bust and hips.

Comparing my front bodice sloper with the front pattern piece, my shoulder width is XS, bust is M, waist is L and hips are XL plus a little bit more.

Comparing my back bodice sloper with the back pattern piece, my shoulder width is M, underarm and waist is L, and hips are XL.

 The reason the top was so unsuccessful was that I cut a straight size L, instead of grading between sizes to fit my curves with a more appropriate amount of horizontal ease. I can’t even show you any photos of me wearing that first attempt; it went straight in the bin.

Comparing my sloper with the pattern pieces, I tried again and graded size S for shoulders, between M and L for bust, L for waist, and XL plus ¼ inch for hips.

Here are the results!

Here is K2982 made up as a top with size grading informed by my sloper. The fabric is a double gauze.

Here is K2982 made up as a dress with size grading informed by my sloper. I added a casing with soft elastic at the back waist for more shaping. The fabric is a light viscose.

The fit was so much better when I used my sloper to inform my size grading. Okay, it turned the pattern from a boxy silhouette into an extreme A-line silhouette. But when I wear the finished garment, it just looks like a plain sleeveless top or dress that fits me. It doesn’t draw attention to its acute shape and I think that’s because overall, the horizontal ease is evenly proportioned. Nowhere is too tight or too loose for me.

However, an inescapable problem with this pattern is the lack of bust dart. In the photos of the top, you can see the side seam is pulling under the armhole. Also, I like more shaping over my bust and sometimes through the body, too. This is where my bodice sloper can really sing.

Using my bodice sloper to re-draft the pullover dress pattern

Just like pattern companies, I can use my slopers as the base to redraft clothing patterns. I just need to add pattern ease, design ease and design features.

To get a better fit with the K2982 pullover dress pattern, I used my front bodice sloper with a bust dart and back bodice sloper with the fish eye dart as the base, and then added the following:

• ½” seam allowance to shoulder seams and side seams
• 1″ vertical pattern ease to shoulder seams
• 3/8″ horizontal design ease to side seams
• Neckline and armholes from the pattern K2982, aligning centre front/back lines and shoulder seams as reference points (taking into account shoulder seam allowances and 1″ vertical pattern ease through the shoulder).

This top was drafted from my front bodice sloper with a bust dart and back bodice sloper with fish eye darts. It has the armholes and neckline from K2982. The fabric is a cotton lawn.

This time, the fit of my top was spot on because it was made for me, based on a cast of me, with darts exactly placed for me. Since then, I’ve made so many variations of this top by adding different necklines from other patterns, additional darts for shaping, back yolk, side hem line splits. There are so many possibilities. I generally don’t bother making a muslin for these variations because I already know what the fit of the sloper it’s based on is like in a non-stretch woven fabric.

This white linen top was drafted from my front bodice sloper with a bust dart and back bodice sloper with fish eye darts. I didn’t sew the back fish eye darts because I wanted extra ease to compliment the linen. It has the armholes from K2982 and the neckline from Kwik Sew K3601. I drafted the back yolk using the Cashmerette Springfield top.

Example 2: Comparing my pants sloper with a pull-on pants pattern

I love to wear linen pants on hot days and Tessuti’s Laura pants is my go-to pattern. It has a high elasticised waist and tapered leg. I first made this pattern before I’d created my pants sloper, but I knew about grading between sizes. I compared my body measurements to those recommended on the pattern sizing, and selected a size XL waist grading to size L hips. For my first attempt the hips were too snug, and there was too much fabric at the centre front and centre back crotch seams. I couldn’t understand how that was happening – why couldn’t that extra fabric just move sidewards to where it was needed?

Later comparisons of my pants sloper with the pattern pieces showed me why this happened. My hips are really wide and my crotch depth is comparatively shallow. Crotch depth gets bigger with larger sizes. I only needed the larger size to accommodate the width of my hips, not an increased crotch depth. I can use a much smaller size for the crotch depth.

Based on the recommended 1 ½ – 1 ¾” horizontal design ease for hips in pants made from non-stretch fabric, I used the XS crotch depth, took ½” from centre front and centre back seams, and added ¼” to the XL side seams.

Here is the result.

Here are my Laura pants, which I altered based on my sloper. The fabric is a medium-weight linen.

I was really pleased with the result. The horizontal ease through the waist and hips is even, so the side seams hang straight down, there’s no extra fabric in the crotch seams, and when I sit down the pants are snug, but not too tight

Why some styles work better for my curves

This process has taught me a lot about my body shape and why some styles work better for my curves.

As an observation (not a negative comment): my shoulders are narrow, my bust is generous, my waist is very high and sits close to my under-bust, and while I have a full tummy, this is overshadowed by my wide hips. Overall, I have an A-line silhouette.

So to get a pattern to fit me nicely I generally need to do the following:

• Grade between 2 – 4 sizes from my shoulders to my hips
• Narrow shoulder adjustment – if size grading isn’t enough
• Full bust adjustment (unless the pattern has cup sizes)
• Raise waist height, or get rid of waist shaping by straightening the side seam from my under-bust to hips
• Reduce crotch depth

I can make all of these alterations to my pattern, or I can use my sloper as the base to re-draft the pattern, simply adding seam allowances, pattern ease, design ease, and pattern features. For simpler patterns, I find re-drafting the pattern based on my sloper is often easier than making multiple pattern alterations.

Since my silhouette is A-line, I’m going to have trouble achieving a fit-and-flare silhouette. For a fit-and-flare dress to fit me properly, the waist is going to become an empire line, or it’s going to be more of a flare-and-flare-more silhouette (which means back to the A-line). That’s not going to stop me sewing these styles. I love my Cashmerette Upton dress in quilting cotton. But I’m not going to be too hard on myself that the silhouette of this dress has less fit at the waist than the pattern intended.

Here is my Cashmerette Upton dress made in a quilting cotton. The bodice is a 12 E/F in the shoulders and bust, graded to a 16 in the front waist and 14 in the back waist.

Given my A-line silhouette, I’m also going to have trouble fitting a boxy silhouette like the K2982 pullover dress. If I cut a straight size, either the bust is going to be too voluminous and the shoulders too large, or the hips too small. I still use boxy patterns, but with my modifications, they gain a distinctly A-line shape to better fit my curves. And that’s all okay. Because when I wear clothes which fit me well, I feel more comfortable and confident.

Using my own sloper has helped me to fit clothes more successfully, understand my personal fit, and make better pattern choices. This knowledge means happier sewing and happier wearing. And that’s what it’s all about.