Adding a Ruffle Bum to your Swimsuit: Tutorial

Hello, it’s Marnie here in freezing cold Sydney wishing that I was experiencing summer like the Northern Hemisphere. And even though it’s too cold for swimming here, I just had to get in on the fun of kids swimsuit week, because I love sewing swimsuits. Today I am going to share a tutorial with you on how to make a swimsuit with ruffles across the bottom - it is one of my most requested items as far as swimsuits are concerned and they look really cute.

For my tutorial today I am using my favourite swimsuit pattern - the Boo! Designs DYO Swimmers. You can use any swimsuit pattern for this though (but between you and me, the Boo! one is worth checking out). To start off with, we are going to need to modify the back  pattern piece of your swimsuit.

Take your back pattern piece (traced, not the original if it is a paper pattern) and see the approximate place for the waist - you can usually see this because most swimsuit patterns go in a tiny bit and then kick back out again. We are going to need to insert some height in here. Take your piece and cut it right across horizontally at this point.

Overlay the horizontal pieces onto a new piece of paper or interfacing or whatever you use for your pattern pieces. line them up and then slowly move them apart until you have a 2cm, or ¾” gap between them.

Now trace around the pieces and you have your new pattern piece for the back.

Cut out your swimmers (sorry that is Aussie slang for swimsuit and I’m going to keep using that word, so I may as well explain it now) as per pattern instructions. Additionally, cut 3 strips each 2.5” wide, by approximately 27” long. A few inches less will not matter too much. Also, if you are not fully lining your swimmers, use the back pattern piece and cut out a piece of lining using your ORIGINAL back pattern piece, not the one we just modified above (please note, lining is not pictured below).

First up, decide whether or not you want to hem your ruffles. It is not strictly necessary with material traditionally used for swimwear, and I actually prefer it unhemmed, I think it sits better, but for the sake of this tutorial, and because many of my customers prefer hemmed, I have just done a simple rolled hem on my ruffles, using my overlocker. If you have trouble getting a nice rolled hem, try using wooly nylon in the loopers only (and set your machine tension very very low for the wooly nylon), it gives a really nice finish. If you want them hemmed, go ahead and hem them now along one long side of each ruffle strip. Along the other end, sew a gathering stitch, as we will need to gather them.

Next, take your bottom ruffle and gather it to fit the back of your swimmers. Pin it onto your back swimmers piece and ensure that the bottom of the ruffle is just above the leg hole - this may be really hard to do on very small sizes, but it makes getting your elastic for the legs in far less complicated.

Once you have pinned into place, sew onto the swimmers. You need to use a machine stitch that has stretch to do this as swimmers have a fair bit of stress placed on them horizontally. I have used my coverstitch machine.

Next, take your middle ruffle and gather it to fit the back of the swimmers, Place it on top of the bottom ruffle, about a ½” inch above the bottom one and sew down. Repeat the above process for the third ruffle.

When all three ruffles are sewn on, and you are starting to catch a vision of the cuteness that is the swimmers you are sewing, cut (yes I did say cut) the swimmers across the back in line with the very top of the ruffle.

Take the top of the swimmers back piece that you just cut off and lay it on top of the ruffly piece right sides together, so that the cut lines match up.  Sew across using a stretch stitch and overlocker using a 1cm (just under ½”) seam allowance.

This is the reason we modified the pattern to begin with - to get some room in for this seam here. Sew along and now the back piece is all joined together, but the seam of the ruffles is all hidden and it looks nice and neat. You can topstitch down the top of the first ruffle if you are the sort of person that needs to topstitch everything. I haven’t.

And now your back piece is almost all done. The final piece to the puzzle is to sew the ruffles down at the sides so they they will sit nicely in the side seams. Sew them carefully down, and you will most likely have some excess.

Trim off the excess fabric from the sides, and if you are fully lining your swimsuit, you can proceed as per the pattern instructions. If you are not fully lining your swimmers, the back now has lines of sewing in it from sewing the ruffles, and a seam through it and some children will find this uncomfortable. To avoid this, take the back lining piece that I instructed you to cut out previously, and lie the back swimmers piece on top of it, right sides facing up. Pin around the edges, and gently baste them together at the edges, so that the back inside of the swimmers is fully covered by the lining piece. Treat this now as one piece and continue sewing your swimmers as per the pattern instructions.

The only other fiddly part of this comes with the leg holes. Most swimmers patterns advise you to sew the elastic onto the swimmers, and then turn the seam under and sew down. when sewing the elastic on, you need to make sure any little bit of ruffle that pokes down into the seam edge gets sewn in nicely too. You may need to baste the ruffles down around the leg holes and cut off the excess that sticks out over the basting - see below for picture.

When you turn under and do the final sew, make sure you keep the ruffles get sewn nicely into the seam so that it looks nice and pretty. Proceed to finish the neckline as per the pattern instructions.

Other than that, there is nothing else to it. Other people may have better or different ways of doing this - so do whatever works for you, just remember to use a stretch stitch to sew the ruffles on so that your seams don’t pop. All that is left to do now, is to pop your child into your very cute swimmers and hit the pool…...or just stare longingly at it if you live down under with me.

Thanks for reading along,