Summer is here, the weather is hot, and we are finally ready to sew a swimsuit. If you have never sewn one, you might be a little freaked out. Fear not—sewing a bathing suit is only scary if you don’t know what’s coming your way. Let’s make sure to pave the road to success by breaking down the three stages of sewing a swimsuit.
A note on sizing: Knit fabrics are much more forgiving than woven when it comes to fitting. Swimsuit fabric is even more forgiving because of how much give it has. If you are sewing a two-piece swimsuit, you have the extra bonus of being able to choose two completely different sizes. If you are sewing a one-piece and need different sizes, blending—connecting different sizes by drawing new lines—can get you to a better fit without much effort.
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A Word of Caution
Do you know how you are supposed to pre-wash your fabric before you start any sewing project? With swimsuit fabric, you don’t have to! If you want to, though, hand wash it with some mild soap—just like you would do if you just came back from the beach.
The one thing you really cannot do is press your seams. DO NOT PRESS SWIMSUIT FABRIC. It will melt. If you don’t like having to press your seams, this is your one opportunity to keep that iron off.
Stage 1: Cutting your pattern
My preferred way to cut knit fabrics is with a rotary cutter, a self-healing mat, and fabric weights (washers purchased at my local hardware store). This setup allows the fabric to be flat on the mat. Because the fabric does not shift, I can be much more precise when cutting my pattern pieces.
A rotary cutter is not for everyone, so if you prefer to use scissors, ballpoint pins are your new best friend. When cutting, keep your scissors resting on your cutting table for stability, and take your time. Don’t move the fabric around; instead, move around the table as you cut. You want to keep shifting to a minimum.
You will be cutting two sets of pattern pieces, one in the swimsuit fabric, and the other in the lining fabric. It is REALLY important to transfer all markings from the paper pattern to both swimsuit fabric and lining. Precision is key when function depends on it. Also, make sure to mark wrong sides and keep all pattern pieces numbered and properly stored—because pieces can be small, losing a triangle from the top or one of the straps is surprisingly easily (ask me how I know it).
HOT TIP: Before pinning, cut a piece of both fabric and lining and put a couple of pins through it. You want to be absolutely sure that your pins will not snag the fabric. If you are using a rotary cutter and fabric weights, you can skip pinning altogether.
Once you’ve cut, labeled, and transferred all markings, it’s time to move to stage 2, sewing.
Stage 2: Sewing your pattern
You are going to assemble the pattern pieces following the instructions of your chosen pattern. You will sew two swimsuits, one in the swimsuit fabric, and one in the lining fabric.
HOT TIP: Use a scrap of fabric and of lining and try different zigzag lengths and widths to see what works best on the fabrics you chose. I chose a zigzag with 1.8 length and width to sew the elastic to the fabric, and 3.0mm length and width when I folded the elastic over.
Construction instructions will differ, but at its core, every swimsuit is made of an outward facing fabric and a lining. For some swimsuits, you will be placing the wrong side of the swimsuit fabric facing the wrong side of the lining; for others—like the Seamwork Maggie—you will have right sides together as you sew the straps, flip the lining to the back, and then join the pieces.
Baste the pieces; then, sew them together with sewing machine and a zigzag stitch or serge it.
HOT TIP: Baste, baste, baste. You are working with two very slippery fabrics, and you want to make sure that they are joined correctly before you zigzag or serge them. Before I serged any edges, I basted them to avoid the layers of fabric from shifting.
Stage 3: Adding elastic
Every edge of your swimsuit will have elastic. This guarantees that it will never sag and leave you in a compromising position. If you are using a pattern, check the measurements for each piece of plastic.
Select the width of your elastic based on your seam allowance. For the Maggie, the allowance is 3/8”. I used a 1/4” cotton elastic specific to swimwear. This way, I was able to sew the elastic at 3/8” and leave a bit of fabric. When it was time to fold the elastic, there were no bits of it showing—that extra fabric gives the whole swimsuit a nice finish on the inside.
I’ve just learned about rubber elastic for swimsuit. I bought some from Amazon, but it was too wide for my needs. Reading around the Internet, I’ve heard that it is more challenging to work with than the cotton one. I have no first-hand insight to offer, but I’d stick with the cotton one if this is your first swimsuit project.
You will notice that some areas have a ration of 1:1—that is, the length of the edge is the same as of the piece of elastic. For other areas—the curved ones like the top of your bust cups or your back bottom—the elastic will be a little shorter than the edge where you are sewing it to. The elastic will stretch a bit to make that part of your swimsuit snug against your body. No wardrobe malfunctions.
Anything that is flat on the body will get a length of elastic the same size as the length of that section. Anything round will need a slightly shorter piece of elastic.
If you are concerned about sewing the elastic to sections that have both flat and round parts (like the leg opening), do the following:
- Measure the length of the pattern piece that is flat
- Mark that length on your loop of elastic in one color
- Mark the middle of the curved section on your pattern piece
- Mark the middle of the same section on the elastic, preferably in a different color from the flat section
Start sewing the flat section; once you reach its end, stretch the elastic to match both middles. You will get an elastic that is perfectly distributed!
When all the elastic is sewn, you will fold it and then stitch on top of it from the right side of the swimsuit. Make sure to NOT STRETCH the flat sections and STRETCH the curved sections.
Depending on how much you had to stretch the elastic on the curved parts, your swimsuit might look a bit… wrinkly. Don’t judge. Once you wear it, everything will work out.
Take Your Bikini Body Out for a Spin
Now that your swimsuit is ready, head out to the beach and make a splash!
