14 Jun 2022 • • by Amy

Beginner Tips for Sewing Swimwear!


While we absolutely love sewing swimwear like our new pattern Faye (almost as much as we love not having to buy swimsuits in fluorescent lighting) a lot of people are hesitant to start. We thought we would pipe in with an encouraging reminder: ANYONE CAN SEW SWIMWEAR! It is not hard. You do not need any special equipment. If anything, sewing successful swimwear is more about using the right fabrics and notions than it is about using a fancy machine. That said, there are a few tips to make your experience easier and that's where we come in! In this post we will give you our top ten tips for a successful swimwear sewing experience; you'll be splish splashing in no time!


You will need: 

  • Your swimwear pattern of choice (these materials are for the Faye Swimsuit)
  • 1/2 yard - 1 yard of swimwear fabric
  • 1/2 yard - 1 yard of swimwear lining fabric (or self-fabric)
  • Elastic designed for swimwear - we prefer rubber swim elastic
  • Stretch or ballpoint needles
  • High quality polyester thread in matching colour



One thing that is important to know about sewing swimwear is the "ease" factor. Unlike woven garments which generally have no stretch, swimwear is meant to fit very close to the body. Because the mechanical stretch is built right into the fabric, you can make a size that is exactly your measurements (or even a little less) and it will still fit. If you are between sizes we suggest going with the lower size. If your bust measurement is within 1-3 inches of the size range, you should be able to avoid any full bust adjustments. As always, we suggest grading between sizes for the best fit. Bikinis make this easy since you can make the exact size you need for your upper and lower body!


The most important factor when choosing an appropriate fabric for swimwear is the amount of stretch. Look for a knit with four-way stretch of at least 50% in order to make most swimwear patterns work. Beyond that, the fibre content is also very important when making a suit that will stand up to chlorine and salt. You are looking for either nylon or polyester with a minimum of 8% spandex. This collection of soft, smooth knits made from recycled nylon and spandex have everything you're looking for in a high-quality swim fabric: excellent recovery, UV protection, colourfast shades, and a firm stretch. 


Lining your swimsuit is key. Since swimsuits are worn so close to the body, you want and need that extra layer of protection. There are a few options when it comes to lining a swimsuit like Faye. For a lightweight, "invisible" option, look for a nylon lining designed specifically for swimwear. Generally 100% nylon, we are carrying a black and tan option  in the Core Fabrics shop that are made with 100% recycled nylon for an extra feel-good factor. You can also use swim fabric for a lining, but note that this will add a bit more bulk. It's also possible to create a fully reversible swimsuit, and we have a tutorial coming on that soon!


Please, I beg of you, don't use regular polyester elastic for sewing a swimsuit! Once you put all that work into sewing your perfect suit there is nothing more disappointing than hearing that crinkle sound of disintegrating elastic. Chlorine, salt and sun are all very hard on elastic, so you want to make sure you're using one up to the task! The two most common options are a cotton/poly swimwear elastic blend and natural rubber. We prefer rubber around here since it has a very flat profile and is easy to work with.  The one we have in stock at Core Fabrics is perfect, and will ensure a suit that looks great today and for many summers to come.


While this is something we recommend for all your me-mades, it is especially important when it comes to sewing swimwear: don't skimp on thread! Using cotton or low-quality thread will result in skipped or broken stitches, especially given how much stress is on close-fitting swimsuit seams (let's ensure you don't get an unintentional reveal pulling on and off a wet bathing suit!) Look for 100% polyester thread from a reputable company like Gutermann or Mettler. We carry tons of Gutermann thread in stock (including recycled poly thread) so you can get a perfect match. If you're using a serger, choosing a high quality serge thread will ensure a longer life. You may also want to experiment with wooly nylon thread in the loopers for a softer feel against the skin.


While you don't need a serger or any special machine feet for sewing swim, we do recommend a fresh new stretch needle in your setup. Stretch needles are designed to slip in between the knit weave of the fabric and will prevent skipped stitches and holes. You can also use ballpoint needles, but we suggest stretch needles for dense knits like swim fabric.  Hot tip: I like to put a little post-it on my machine when using a specialty needle so when I sit down to sew a woven I remember to change my needle back.


Since swimwear fabrics tend to be shifty, we recommend cutting on a single layer. Swimwear pattern pieces are small, so taking this extra step isn't much of a time burden and will end up saving you headaches in the long run. In the case of things being cut on the fold, don't skimp on the pattern weights! Rocks, cans or metal hardware can work in a pinch; lay them close to the edge to ensure maximum accuracy. We suggest using a rotary cutter with a fresh blade, and of course, caution... get your finger out of the way! 


Try to avoid using straight stitches on knits, unless you're a fan of popped stitches! The all-purpose swim stitch is a good ol' zig zag, and you can assemble an entire suit on a regular machine using nothing but a zig zag stitch. Any reputable commercial pattern should provide you with the right stitch settings - we like a medium zig zag  (3mm x 2mm) for attaching elastic, and a wider stitch (5mm x 1.5mm) for sewing a "mock" serged stitch when attaching seams. Of course, you can also use your serger for seams - make sure you're set up for a 4 thread overlock stitch for best stretch. Lightning bolt stitches or triple straight stitches can also work in lieu of a serger or overlocker. Just make sure to test, test, test! Setting up properly right from the get go will save you a lot of trouble down the line. 


When sewing stretchy fabrics it's hard to know exactly what kind of tension to use. Too much and you'll end up with rippling seams, not enough and your fabric will pucker and shift. The most important thing to keep in mind is not to pull stretch fabrics as you're sewing them. Since you are either sewing stretch fabric to elastic or another stretch fabric, you want your seams to be flat and as undistorted as possible when going under the needle. If you're struggling getting your fabric to feed evenly through the machine, two things will help. First, a walking foot is incredibly helpful for sewing knits since it ensures both layers feed through evenly. Second, if you can loosen your machine foot pressure, this can sometimes help bulky knit seams pass through more easily. Most importantly, don't hesitate to practice a bit before sewing your final garment if this is new to you. Test stitches and machine tension by sewing scraps to elastic before starting with your final suit, and you'll be rock and rolling in no time!


Since swimwear fabrics and notions are all made of some version of rubber or plastic, they don't really love heat. While you can use a little well-placed steam if you are finding your seams behaving badly, a finger press will go just as far in most cases. You can also use well-placed top stitching or bar tacks to make seams flat. The instructions for Faye take this into consideration and the unique, clean finishes look totally professional with just a simple zig-zag stitch. It's basically magic!


If you would like to take an online class with lots of help, our Sew Your Dream Swimsuit class includes our Sophie Swimsuit pattern (sizes 0-20) and allllll the cup sizes to craft the perfect supportive one or two-piece for your body! Heather will walk you through all the swim sewing tips and every stage of fit and construction.


Our first pattern EVER was a swim pattern (Happy Anniversary Bombshell swimsuit!) so swimwear is close to our hearts. Whether you're looking for something vintage inspired, super supportive, or fun and sporty, we've got you covered! We also have a full, free sewalong for the Bombshell!

That wraps up our tips for sewing swimwear! Do you have any tips of your own you'd like to share!

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