How to Eliminate Crotch Bunching

Wrap shorts were a trend when I was a teenager (they were called “Hawaiian shorts):

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They were a fad decades before (sometimes called “diaper wrap”):

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They’re a favorite sewing project because  the open leg ensures easy fit. No need for a muslin, just sew it up and wear it! And now they’re back, and called Hippie or Boho or Pompom shorts, this time with an elasticized waist, but still simple to make  and no fitting issues at the thigh, crotch, or under the bum:

boho..boho3..boho2

The darling kids’ “Coachella” wrap-shorts pattern was released just as I was discovering pdf-world.  The fanfare was amazing: people grabbed up this pattern and LOVED it, exclaiming how easy it was to sew. It was an instant best-seller and voted as a favorite on sewing blogs.  I wanted to love it too, but the tester photos didn’t look comfortable: there was  always  “bubbling”at the front crotch.. The photos of flats that pop up all over Instagram actually look better than the tester photos on models.

Note!  This is the “hazard of the job” of being a technical designer: my eye goes directly  to fit, no matter how adorable the modeled photos.  Sadly I instinctively overlook the sweet faces of happy kids who love their new mommy-made outfits, the brilliant fabric and color combos, the lovely stitching craftsmanship. Obviously since this is a best-selling pattern and loved by many, it is a fine product “as-is”.  The idea of adjusting it is purely my own professional issue.

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(photo used under Fair Use doctrine for product review)

As time passed, I heard many sewists say they needed to go UP a size or two in Coachellas.  I kept studying the tester-photos: I didn’t see any with fabric straining AROUND the body….my eyes kept going to the stress-lines going from the center-thigh down under the crotch.   And that’s when I realized they were MOCK-wrap.  That’s great for yardage yield, but there’s a downside: because they’re not open-wrap shorts, getting a good fit is much more difficult. All of the competing elements of pants-fitting (rise depth, rise length, rise ratio, and crotch width) must be met.

I could see a fit issue, and going up a size wasn’t  the solution. It wasn’t a different size that was needed but rather a different shape , as I blogged before  regarding other pant styles. From looking at photos I could guess that besides too small a crotch width, there could also be an imbalance in the rise ratios, which I’ve discussed previously. Still I couldn’t be totally sure what the problems stemmed from since hadn’t bought the Coachella pattern . It’s a very cute style, but due to the fit issues I saw in all the photos, I just couldn’t see putting it in my shop.

Things change, and this week a post on Facebook showing a partial area of one pattern piece piqued my curiosity, making me think there might be additional causes of the “crotch bubbling”: maybe the angle of the inseams is too sharp?  I gave in and bought the pattern. I wanted to check 3 things:

  1. Angle of the inseams
  2. Crotch width 
  3. Rise ratio

  1. Angle of the inseams

The first thing I always do with a new pattern is Alpha-Test it: Measure, Walk, True. There are only two seams to walk (the mock-wrap side-seam, and the inseam), and they match up pretty well. The measurements are fine: the body measurement chart is to ASTM standards, the waist garment measure is irrelevant since these sit on the hip, and the hip garment measurements show adequate ease of about 3″ to 4″.  So they are not tight going around the body, and shouldn’t require sizing up.  That confirmed my guess that there’s not a size issue but  instead a shape issue.

Time to see if the pattern is  trued. Coachella is well trued at the rises on both front and back, top and bottom corners….but it’s not trued at the inseam hem (note the obtuse angle in this photo).  Additionally, the angle of the inseams is very sharp (because the Front Rise and Back Rise meet in a “V” not a “U”):

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My gut reaction is to slash and spread, which helps true the inseam at the hem AND adjust the rise from a “V” to a “U” shape:

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But then I had a thought: coincidentally, this sharp inseam angle is what you use for diaper-cover baby bloomers, which get elasticized at the thigh….the photo n the left is the inseam of a muslin of  diaper cover, placed over the Coachella pattern…..the photo below on the right shows the difference in inseam angle between a diaper cover pattern on top and a regular pant pattern underneath (note the difference in the angle of the inseams):

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If I pin a bloomer muslin on a dressform,  the angled inseam wants to shift away from the crotch center and over towards the leg, which is what you want in a “bubble” baby bloomer that will have elastic around the leg and needs to accommodate a diaper:

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But if this were a pair of shorts, the inseam needs to hang straight down, and what happens with this sharp inseam angle is that the  hem “cuts” into the inner thigh. The fabric at the CF and CB hems is forced to relieve the tightness of the inner-thigh hem, causing stress pull-lines where fabric wants to shift towards the inner thigh, resulting in   “crotch bunching”  or “diaper-crotch” (see also the last photo in this post for reference)

IMG_8874….

So I know there’s an issue with the angle of the inseam. But first I need to look at the crotch width. My guess is that it’s too small, and needs to be increased by extending the crotch hook:  this would help eliminate the pulling and straining of fabric  down under the crotch, so that the shorts “pouf” less at center-front crotch and hang more smoothly.


 

 2. Crotch Width: a too-small crotch width is a common cause for stress lines pulling the fabric down under the crotch. Crotch Width is  the horizontal distance between the Front Rise and the Back Rise,  measured  at  2″ above the crotch on the pattern. A pant with Crotch Rises drafted using  a French curve into a nice U-shape, will automatically have a Crotch Width that fits well. In an Infants to Childrens pattern such as this, we’d want a crotch width of about 5″…..but this measures 3″:

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That “V” shape doesn’t look wearable, but when the inseam is stitched (mocked-up here by taping the pattern at the inseams) and the garment is put on a body, the crotch will be forced to open up to accommodate the figure:

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However this  will cause strain lines where the inseam hem cuts into the thigh, same as we saw in the angle of the bloomers muslin above* :

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* Note: for bloomers this isn’t an issue since they are cut very full and then elasticized at the thigh

So I made a muslin. The sharp angle of the inseam makes the inseam hike up:

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When I slide the inseam down to make the hem horizontal, I can see where the angled inseam  stitches are stressed.  When I let go, there’s a “bubble” in the front crotch area:

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Eventually the bubble will create a pouf that drops into a pouch in front that you see in tester photos….what is referred to in industry as  “wadding” or “crotch bunching”:

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The solution is to release the stress on the inner thigh by reducing the angle of the inseam.   Look what happens when the inseam is ripped:

IMG_8932….IMG_8933.

So now I know that

  • the angle of the inseam needs to be decreased
  • the crotch width needs to be increased (and smoothed from a “V” to a “U”)

 

3. Rise Ratio. Imbalanced Rise means that the ratio of Back-Rise length to Front-Rise length is not in the right proportion. The rise ratio can be calculated through basic division:

Back Rise divided by Front Rise : hopefully somewhere from 1.25 to 1.35

The rise ratio here is 1.22 .   Not  way off, but  the back rise needs lengthening so there’s less strain  under the back crotch, pulling the front inseams towards the back. Also a too-long front rise is a contributor to “frown lines” at the crotch in ANY style of pants, no matter what the crotch width or angle inseam are.

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On to the corrections. First thing is to scoop the Center-Front Rise to change from a “V” to a “U”, thereby increasing the front “hook” extension (not enough scoop in the front rise is what expert Kathleen Fasanella calls the contributor to crotch “wadding” in her amazing blog), and blend up to the waist:

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Next: true the Front Inseam at the hem; the added fabric will alleviate the diagonal stress lines towards the Front Crotch:

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Repeat for Center Back Rise:

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True the back inseam, adding a half inch to the back crotch hook (this will correct the rise ratio to 1.26, which is a better balance between Back Rise and Front Rise.):

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Now recheck the Crotch Width: it’s 5″ which is basic for kids’ pants and shorts:

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Time to cut out a revised muslin. Here is the revised graded inseam:

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I cut out a size 4 and rechecked the Crotch Width (original pattern left, revised right):

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Comparing the muslins, you can see that the difference in the crotch (original left, revised right).  I’ll be the first to admit that the original looks cuter in flat-lays.  This happens often in RTW: items have great “hanger appeal” yet have fit issues:

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Since I don’t have a fit-model, I mimicked the effect of having the shorts worn by clipping together the inseams, to see the shape of the shorts when standing with legs together:

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Here is what happens (original left, revised right). As soon as I stand up the muslins, the “wadding” forms in the original, but not the revised muslin:

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Then lay the muslins flat, and the bunching lines remain:

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The magic of making the bunching disappear lies in simple adjustments to the:

  • angle of the inseams
  • crotch width
  • rise ratio

So if you ever have a fitting issue with crotch bunching, these are the three areas to inspect!


 

Pinterest link:  https://www.pinterest.com/pin/23855073006328511/

Coachella copy

 

 

 

 

 

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24 Responses to How to Eliminate Crotch Bunching

  1. Shelley says:

    This is so amazing. I’d never have thought how to analyze patterns this way. I use pattern software so learning a way to test the ‘physics’ of a smaller scale version of the pattern will really be helpful.
    What I’d like to ask is…for adult plus sizes, do these standards change? Like, would the crotch width be more than the standard 7″? Pants are the hardest darn things to fit.

  2. 7pinedesign@comcast.net says:

    Good question! Another inch in crotch width would probably be better for plus sizes, but I haven’t tried it. Pants are definitely the hardest thing to fit because there are so many factors involved. And of course plus sizes make it even more complicated because we all add weight in different areas. Which pattern software do you use? Do you like it? I love the idea of being able to plug in measurements, but I can see that it doesn’t explain the “why” of fitting.

  3. Diane says:

    your transformation was fascinating, I especially loved seeing it in fabric, thank you so much, your blog has become one of my favorites

  4. Tibeca says:

    I’m going to have my husband reprint this one for me. I thought it was a lost cause, but I can’t wait to have them as great fitting shorts!

  5. 7pinedesign@comcast.net says:

    I’d love to hear if they come out better! I think these are pretty simple adjustments….

  6. 7pinedesign@comcast.net says:

    Thank you so much! Playing with fabric, and seeing what it will do, is fun for me

  7. Sarah S says:

    Okay, this is going to be my project this afternoon if my son will agree to take a nap. My daughter is wearing a pair of Coachellas today where I made some adjustment to the shape of the crotch and it did help, but this will be even better. Thank you for the thorough explanation!

  8. Cheryl says:

    Thank you! I have made 2 pairs & both have the bunching problem. I just fixed the pattern for a size 12. Hopefully the next pair will be better.

  9. 7pinedesign@comcast.net says:

    I hope it works for you, it’s SUCH a cute design!

  10. 7pinedesign@comcast.net says:

    It’s worth the effort, since it’s such a cute design!

  11. Hilary says:

    Thank you! My French curve came this weekend, and I’m getting so excited to try a out re drafting the pattern and making my fit test shorts tonight!

  12. Cassy says:

    I would like to download all of the knowledge about pattern making and fitting into my brain… ASAP!

  13. Jenya says:

    Thank you for this article! Such useful information!

  14. 7pinedesign@comcast.net says:

    Thank you!

  15. 7pinedesign@comcast.net says:

    Hi Cassy! I’m sure you learn more than you know with every outfit you make. PS: I love LOVE your little one’s Independence Day outfit!

  16. 7pinedesign@comcast.net says:

    You’ll soon wonder how you lived without one!!

  17. Janelle says:

    I’m actually considering buying this pattern, knowing that it’s flawed. Which I think is crazy.

  18. 7pinedesign@comcast.net says:

    Haha well I bought it, knowing from the photos that it was flawed….I was so curious to see what was causing the problems. I looked at this pattern for two YEARS, thinking am I crazy to spend money on this? But the truth is that it’s really such a cute IDEA….and with a bit of tweaking it’s very wearable. Go for it!

  19. Carolyn says:

    I don’t make children’s clothes but this post is fascinating. I have spent years gazing at my butt in the mirror trying to fit the crotch of pants patterns without managing a consistent solution. Your post has really given me an AHA! moment and I can’t wait to pull out some patterns again and measure those crotch curves. Thank you for the considerable time you must put into these posts they are HUGELY appreciated. From a reader in New Zealand.

  20. 7pinedesign@comcast.net says:

    Hi Carolyn! Yes pants are definitely the “grail” of fitting…so many inter-connected elements. Also since we are all have out own unique shape, it’s not simple, that’s for sure! But every time you try a pattern, and every time you edit your closet (trying a new style, donating an uncomfortable-to-you item to charity) you get closer and closer to what suits you. Even if the examples I use are for children’s-wear, the same concepts apply to adults patterns. PS: we are visiting New Zealand in 2018!

  21. Mel says:

    Oh my goodness. I put a neutral-almost-negative review of the Coachella Shorts pattern up on PatternReview as, IMO, there are flaws in how the pattern goes together (no notches, no waistband pattern or measurements, and similar). And while my daughter loves her Coachella Shorts, every time I look at them I see the poufy front and it bugs me. It hadn’t occurred to me that it was bad drafting. I’m going to take this and redo the pattern before I make her next pair for summer!

  22. Kathleen says:

    I have just discovered your blog and can’t thank you enough for reviewing these shorts . I made them for my daughter and had that exact bunching and I really didn’t like her wearing them (although she loved them ) as I couldn’t work out why they were bunching like that . As a result I only ever made the one pair and never picked up the pattern again. I am now going to try and work through your corrections to see if I can get a better fit ( my first time at trying to alter a pattern !)

  23. 7pinedesign@comcast.net says:

    You can do it! It IS a really, really cute design, you’ll love it when it’s “tweaked” a bit. Your daughter won’t notice the difference but you will!

  24. 7pinedesign@comcast.net says:

    Mel, I hear the same story often: daughter loves them, mom sees fitting issues. You can fix this!! It’s such a cute, cute design…totally worth making a few changes so that you’ll both be happy with them!

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