Swimsuit Sew-Along: Basic Construction

This post is one part of a Swimsuit Sew-Along series! If you missed the previous posts and would like to join in, just click below!

I hope you had a great, productive weekend. I was able to tie up some loose ends and clear the way for me to work on this swimsuit! If your swimsuit is cut and ready to sew, this post is for you! Hopefully by Friday you will have all the information you need to finish your swimsuit!

Because a swimsuit is made with stretch fabrics/knits, you will need to construct it with a stretch stitch. If you use a traditional straight stitch, it might sew up ok, but the wearing will be another story – in fact, as you pull it up, your fabric will stretch, but your stitches will not and you’ll find yourself with popped seams! So I’m going to show you two stitches you can use on a regular sewing machine that will give you the stretch you need. On my machine, they are stitches 2 and 3 (below). I know we talked a little bit about it when we discussed machines, but this is where the rubber meets the road so let’s look at it more detail.

Stitch 2 is more formally called a Stretch Straight Stitch, and less formally called a Lightning Stitch. On my machine it has a left needle position. I tried to google the reason for this but must not have been using the right combination of wording because nothing came up so here’s my best guest. Typically seams on knits are narrower than the 5/8″ included in most other patterns. The left needle position would allow you to use the right edge of your presser foot as a guide for the fabric edge. Otherwise, I’ve always found it strange. If you know the real reason, feel free to share! Some machines have three stitches for this one stitch – one with needle position left, one center & one right. If yours only has one choice and your pattern’s seam allowance is larger than 1/4 or 3/8″, just measure out the distance from the needle position to your required seam allowance and make note of the line to follow. If your stitch plate doesn’t have marked seam allowances, you can use masking tape and a ruler to make your own line. I’ve also seen on pinterest using a rubberband as a seam guide (placing it around the free-arm of your machine).

The Stretch Straight Stitch is not straight – as you can tell from the picture on my machine and the stitches below. It zigzags back and forth in a tight narrow formation to allow for give while still providing a strong seam. While using this stitch you do not need to stretch your fabric as you sew since there is stretch built in to the stitch.

If you do not have this stitch on your machine, not to worry! The second stitch in the picture above was made with a regular zigzag stitch, adjusted to mimic the stretch straight stitch (and I didn’t sew crooked, I just didn’t press the fabric after I stitched & before taking the picture so it has a few little waves). 😉 My machine has computerized controls, shown below, but you can get the same settings on a manual machine just by choosing a narrow stitch width and length.

Stitch Width (right) set to 1.0 and Stitch Length (left) also set to 1.0

These stitches are strong enough to use without finishing the edges, but if you would like a professional finish, you can use your widest zigzag to encase the edges after your seams are sewn. You can also use your serger to finish the seams.

And that brings us to construction on a serger. If you are using a 5-thread serger, you also have a choice of a few stitches. You can use a 5 Thread Safety Stitch, which creates a seam and seam finish simultaneously.

If you prefer not to switch the stitches on your serger or if you have a 4-Thread serger, you can use the 4-Thread Overlock Stitch. This can be used to finish the seam after you sew it on your regular sewing machine or it can be used to sew the seam all by itself. It is a sturdy stitch used on most t-shirts (just turn yours inside out and look at the seam!).

Your manual should be able to tell you how to thread up each stitch. Just be sure to follow your stitch plate for your pattern’s seam allowance and you can zip right through making your swimsuit. Word of warning if you’re using a serger: If you are very familiar with your serger, you already know this, but it is a bad idea to use pins while working on a serger. The cutter will chop right through them or become dull trying! If you need to use them for a tricky spot, be sure to stop before the pin reaches the cutter and pull them out as you go.

So once you have chosen your stitch, you are ready to get going! All your seams will be made with your desired stitch. However, if you have gathering or basting to do, you will use the regular straight stitch with the longest stitch length. Since these stitches are temporary, their stretch-ability isn’t important.

Next post we’ll cover sewing your elastic to the arm & leg holes and wherever else it might be necessary. You are almost there! If you need help with any instructions or construction techniques that come up in your particular pattern, just let me know! I’d be happy to help. Thanks for following along.

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