How to sew a swimsuit - Sewing technical tutorial

What is Lycra knit?

A swimsuit fabric is a knitted fabric, stretchy in both directions (height and width), with at least 15% spandex. This type of fabric is called Lycra knit. It dries quickly, resists chlorine, salt, and sun. In short, it’s a fabric meant for the water! There is a wide variety: shiny or matte, solid or printed. Some Lycra knits, like the ones we offer, are also UV-resistant, making them perfectly suitable for sewing protective clothing in addition to swimsuits. At Ikatee, we prefer matte Lycra knits as they slip less during sewing.

What to sew with Lycra knit?

Lycra knit can be used for various projects: obviously swimsuits, but also UV-protective clothing, skating outfits, or gymnastics wear. You can probably use patterns you already have in your pattern library: sewing patterns for T-shirts or leggings transformed into sun-protection clothing, body patterns for dance or baby swimsuits, jumpsuit patterns to protect children from the sun...

At Ikatee, we offer you two dedicated swimsuit patterns: Paulette, a one or two-piece swimsuit for little girls, and Sébastien, an underwear pattern for boys that you can adapt into a swimsuit.

Which Haberdashery for Sewing a Swimsuit?

Swimsuit Lining

For comfort, as swimsuits are worn close to the skin, garments sewn in Lycra are often lined. For the lining, you have several options: line with the same fabric for a very neat result, or line with special swimsuit lining or Claudia foam. Very thin and stretchy, it comes in several colors: white, black, or nude. It allows you to opacify your fabric if needed and is less expensive than Lycra knit. However, you will need to reduce 5 mm from all edges of your Claudia knit pieces: being very stretchy, this fabric will stretch more than your outer fabric when wet.

Laminette: A Specific Elastic

As swimsuits are made to go in the water, you will need to opt for an elastic that is resistant to chlorine, salt, and sun. This elastic is called laminette. It is a rubber elastic that comes in different widths depending on your project. 6 mm is a sufficient width for swimsuits. Laminette is a fairly firm elastic that will help the swimsuit fit well against you. Don’t worry about comfort; it will never be in direct contact with your skin.

Microtex Needles

To avoid damaging your fabric and to respect its weave, we recommend using microtex needles. They are fine and sharp, not only to penetrate the fabric cleanly but also to attach the laminette with precision.

Foam Thread

Given the proximity of the swimsuit to the skin, we recommend opting for foam thread. It is a fluffy and thick thread. It is stretchy and soft against the skin. This thread should be installed in the bobbin of your sewing machine or in the loopers of your serger. It will allow you to give elasticity to your stitch while maintaining comfort against your skin.

How to Sew Lycra Knit?

Now that you are equipped, it’s time to start sewing Lycra knit. This fluid and slippery material can be intimidating at first, so here are all our tips to help you assemble your garment. Precision is key!

Lycra knit can be sewn both on a sewing machine and on an overlocker. The key is to have stretchable seams so they don’t break when you stretch them! If you are assembling your swimsuit on a sewing machine, you will use two different stitches:

• The stretch stitch, which is stretchy and looks like a lightning bolt (see video) for assembly seams,
• The zigzag stitch for the laminette and visible seams.

Swimsuit fabric does not fray, so it is not necessary to serge!

You can also completely assemble your project on an overlocker; the stitch will automatically be more stretchable, which is perfect for a swimsuit. Don’t forget to use microtex needles and foam thread in your sewing machine bobbin or in the loopers of your overlocker, making your garment more comfortable.

Attaching the Laminette

This is probably the most technical aspect of sewing Lycra knit. The laminette is generally attached at the thighs, armholes, and necklines according to your needs. As well illustrated in the video, the laminette is placed edge to edge on the wrong side of your fabric with a 2.5 mm wide zigzag stitch. The trick is to slide the swimsuit fabric under your presser foot and start sewing to plant the needle in the fabric to hold it in place. Once this is done, you can lift your presser foot without fear because the fabric is held by the needle. Then slide the laminette right in front of your needles, edge to edge with your fabric, and resume sewing. This trick will help you avoid struggling with fabrics that slip and escape from your hands before they are under the presser foot.

While sewing, you will need to slightly stretch the laminette to slightly gather the fabric so that it fits well against your skin. We recommend doing some tests beforehand because if you stretch the elastic too much, the fabric will form unsightly folds. Rest assured, you will quickly get the hang of it.

Once the laminette is attached with the first seam, fold your fabric on the wrong side so that it is “sandwiched” in your fabric. Topstitch with a zigzag stitch on the sewing machine along the entire length.

We hope this video and the accompanying article have provided you with all the details necessary to start sewing your swimsuit or any other Lycra knit project. Now, you just need to dive in. Show us all your beautiful creations with #ikateecouture.