As an ambitious garment sewist (I almost called myself a sewer there) with a very large collection of clothes in my closet I am always on the lookout for “bang for your buck” projects. Ones that involve lots of new skills, and/or ones where the materials will end up costing less than buying similar quality off the rack.  Designer swimwear costs a fortune and sewing a swimsuit is a great step along the path to maybe, eventually, possibly sewing a bra.

Department store swimwear separates START at $40 per piece. Swimwear is DEFINITELY a bang-for-your-buck project! And while it may seem scary, once you get a handle on the techniques, it’s a project that chugs along nicely.   So, in this blog post I am going to dive right in with practical advice and techniques to help you troubleshoot the main frustrations and explain reasoning behind the common advice that comes with sewing your own swimwear.


For sanity, I’m going to break this down into 3 parts: Materials, Construction, then Design. Design is last, because I don’t want to make anyone go cross-eyed when they were just trying to figure out why their stitches are skipping.





MATERIALS; More than you ever actually wanted to know:


Why choose Polyester?

Swimwear needs to be able to stand up to UV, chlorine, salt water, sunscreen oils, sweat, and heat. If you’re taking the time to sew your own you want your suit to stand the test of time. So, what fiber content should you look for?

Polyester Nylon
Very little give. Resists shrinking. More elastic, more give. Can stretch when wet. Resists shrinking.
Very resistant to UV Deteriorates when exposed to UV
Resistant to chlorine Deteriorates in Chlorine
Resistant to oil Resistant to oil
Does not absorb water Absorbs a small amount of water

This comparison is for swimsuit purposes. Nylon fiber has give and stretch combined with durability and strength which make it ideal for many applications such as foundational undergarments, backpacks, or even climbing ropes. I will cover a lot more about synthetic fibers in Thread Adventure’s forthcoming posts about natural, synthetic, and man-made fibers.

Polyester is very robust, but its lack of elasticity is why its combined with Lycra in about 10-20% of the fabric makeup.


Why use Lycra?

Natural rubber is resistant to Chlorine but susceptible to UV and rapidly deteriorates when in contact with oil. Manufacturers used to recommend washing girdles with latex elastic immediately after every wear to remove body oils!  Spandex is far more durable and resistant to body oils, but it is still susceptible to Chlorine (which is why you can’t use bleach on anything with spandex).  Spandex’s susceptibility to chlorine is why Speedo and other manufacturers have come out with endurance swim fabric for extending the life of exercise gear. Speedo’s fabric is  50/50 polyester/PBT (a kind of plastic fiber with a natural stretch and recovery properties but resistant to oil, UV, chlorine, and other solvents)  But, anyone that has ever tried on a Speedo endurance suit recognizes the limitations of the material in both comfort and figure flattering capabilities.  If you’re sewing activewear for continual daily use, you might consider using endurance fabric, but for a fashion suit? No way!


Why use SWIMWEAR elastic? Why is it cotton?

Depending on construction it might be right up against your skin, so it needs to be comfortable. Similarly “intimate” underwear elastics are made with soft, woolly nylon, (But nylon will deteriorate in chlorine). So why cotton and not polyester? Remember polyester doesn’t stretch or swell… but elastics DO, and so does cotton!  So if an elastic rope is encased in polyester it will end up like an overtight sausage and cause damage in the form of tiny little cuts that weaken the elastic.  Another characteristic of swimwear elastic is  they have thicker, more robust lines of elastic which will have a longer lifespan.

Swimwear elastic comes in many widths. Dritz sells it in 1/4” and 3/8”. You can find it elsewhere in 1/2”, 1” and 1-1/2”


Unfortunately we don’t have a magic bullet swimwear material, but being mindful of your fabric’s limitations will help you decide how best to care for your suit and extend its lifespan.  My advice is to be mindful of the effects of chlorine and other solvents on your fabric. Make use of the showers to rinse off before your poolside picnic.Thoroughly rinse your suit in fresh water after use. Be careful with the solvents in spray-on sunblocks.  And avoid the high heat and extra high chlorine content of a hot tub while wearing your favorite suit.


Besides that, what do I need to make a designer quality suit?

Powermesh –  It’s a bit thicker than swimsuit or lining material. It is a mesh material that initially stretches easily because of all the little mesh holes, but reaches a limit where it then HUGS. It’s the perfect fabric to use as a panel to smooth and compress across your tummy, but maybe not so great to smooth and compress across your boobs.

Silk or polyester organza – when you have an area that MUST NOT STRETCH, like right between your boobs on a bra-like suit, such as mine.

Moulded cups – They also come in push up. A great way to give your girls a little more shape when confronted with the pancaking effect of swimsuit fabric. Also, to hide any nippage. You can sew them into a layer between the lining and fashion fabric, or you can leave an opening in the lining so you can slide them in-between the layers.

Featherlite boning – Use it where you need to make sure there’s no rolling or buckling.. Like in a bandeau-style top.  You can use thick zip-ties with their edges trimmed smooth (or filed down) as an alternative.

V-wire –  If you want a fancy low cut one piece suit or a bandeau with cleavage this will give you a professional looking result and make sure you don’t have any issue keeping the suit in the shape its supposed to be



Clover clips, silk pins, or ballpoint pins –  Avoid snagging your fabric by using very fine silk pins, round-tipped ball point pins, or  clips (get a whole bag of off-brand clover clips for cheap).  If you use regular or silk pins, only pin in the seam allowances in case there are snags.

STRETCH NEEDLE – I managed to use a ballpoint jersey needle, but my friend had TONS of skipped stitches until she broke down and bought a stretch needle.

Polyester thread – This is NOT the project to use cotton thread on.

Wooly nylon overlocker thread –  I didn’t use it, but its common in swimwear because of the added comfort.

WALKING FOOT – This is a must-buy, in my opinion. The sandwich of slippery fabric needs all the help it can get, and it can be pretty inexpensive. Don’t bother buying fancy or expensive versions. They’re all made of plastic, and they all break in the same way after lots of use.





CONSTRUCTION; If you want a tutorial, go somewhere else.

REALLY!! There are a lot of fantastic tutorials and sew-alongs for swimwear, so I’m not going to reinvent the wheel. I want to cover a few pieces of advice that the tutorials don’t


Here are some great tutorials I used in my own learning process:

Sewing in elastic edges

Using tension to get perfect edges

3 ways to finish edges

Contrasting edges

2 ways to sew straps

And if you’re really nervous, find a pattern that has a good sew-along blog series so you can follow along!!


The best advice I can give is to buy extra fabric and practice before you jump into your suit.  I sewed a pair of underwear in preparation for my swimsuit, and I was very glad to get an idea of what techniques I needed to perfect and failures I needed to address before I was “in the groove” with my swimsuit and therefore BEYOND frustrated to find out that everything wasn’t behaving as I imagined it should.


Zig-zag stitch; why do you use it?  When can you use a serger?

Your swimsuit is going to stretch A LOT, like at a bare minimum 10%, so you need a stitch that won’t break and pop out. So, you’ll need to piece it together with either a serger or a zigzag stitch (swim fabrics don’t unravel, so edge finishing isn’t a factor) and then you’ll need to do your top-stitching with a stretch stitch.  When sewing knit dresses you might use a twin-needle to sew a hem, but I don’t recommend this for sewing a swimsuit. The twin needle is pretty temperamental, the stitch isn’t as strong because its not as even (comparing the top side and bottom side of the stitch), and you’d have to switch back and forth in machine set up to top stitch throughout the project.

How do you get the perfect zig-zag stitch over your entire project? You can’t!! The nature of pulling a stretch fabric taught to sew it will create a little variety in your finished stitch length. It doesn’t detract from the beauty of your suit!


How do I figure out my stitch settings?

Create a sampler!

Make a series of lines on a piece of scrap fabric and list a series of stitch widths and as you sew, increase the width to match the listed number. Pick your preferred with.  THEN make a series of stitch lengths and sew through the options at your chosen widths and determine the best looking length. Finally, do this exercise on your chosen swimsuit fabric and go through tension settings. You might need longer sections at each tension to be able to determine, but it helps to pinpoint what falls right in the middle of acceptable, which can be difficult when you’re dealing with so many variables.


Here’s a mediocre drawing of my method:



Dealing with slippery fabrics

Take your time. Use lots of pins. Feel free to baste the fabric sandwich, then remove the basting stitch after the zig zag is sewn. Only cut out a few pattern pieces at a time to avoid mix up or frustration.



Skipping stitches

Thread tension issues and needle issues will team up and break the kneecaps of any swimsuit project. You need to sew enough “samples” using your material to make absolutely certain that stitches aren’t skipping. If they are skipping make sure your needle is a stretch needle. After that, make sure your tension is correct. Re-thread your machine and do the tension “sampler card” again to see if your choice of tension is still the best.  If its a particularly fussy part of the pattern that seems to demand being eaten by the machine rather than behaving nicely: Try “interfacing” or backing the stitch with receipt paper. Receipt paper is rather brittle and much easier to tear away cleanly than regular paper. You can find it at an office supply, or just buy something from CVS and they’ll give you a yard and a half of extra receipt printed with  coupons. 😛


Sewing with elastic

Go back to that list of tutorials I posted at the start of the section. All have great advice.  To get my machine to feed cleanly I had to stretch the fabric in front and behind the needle, which lead to having to play around with how much I “push” or “pull” the fabric into the machine…. This learning curve is why sewing a pair of underwear first was so valuable.



Design: Is there a method to this madness?  You’d like to think so, wouldn’t you…..


I started off with a commercial swimsuit pattern and modified it heavily. I also referred to my waaay too expensive, but oh so cute, and I deserve to look hot betsey johnson swimsuit for construction details. I always look at my favorite ready-to-wear clothing for construction and design advice in my projects…. I also surfed the web and looked at HUNDREDS of swimsuit ideas…. And you know what? It would be a LOT easier to decide if a swimsuit would look good over this curvy girl’s tummy “situation” if swimsuit models stood straight for one of the photos instead of arching their backs and sticking their bums out in every single photo! God bless sewing bloggers and their realistic bodies and realistic photos.


The patterns I started off with were the Reno top and Dakota bottom swimsuit separates from Seamwork magazine. ^  I used the Reno top to help guide the cup shape in my bandeau style design, but not much else… I mostly referred to my Betsey johnson suit for other measurements. There’s not much to describe the design changes because I really only used one element of the pattern, but here’s an image describing what I did:

I based the bottoms design much more heavily on the Dakota pattern. I looked at a lot of sewing reviews and saw that the fit was too high in the back waist, and way more conservative than I wanted.  I wear a speedo three times a week for my workouts, so the conservative cut felt quite matronly to me.  My method for making changes and deciding where I put the strappy cutout panels was to cut a muslin of the bottoms out white of 4-way stretch jersey that I had on hand. And yeah, it was SO BIG and SO CONSERVATIVE. It looked like a BIG ol diaper.  I marked where I wanted the leg holes to go and the panels with fabric markers and translated my changes to the pattern.  I’ve made an illustration of my design adaptation:



And I did end up making my bottoms twice! UGH! But, I learned some stuff along the way!!! Like if you put swimsuit elastic in the strappy bits they pull too hard and the sexy cutouts look more like your horrendously fat backside is barely being held back from bursting out of its fabric cage.  I also learned that it’s a good idea to sew length of elastic in the seam along the edge that the straps are attached to reinforce the edge and give it a better line. You can see the difference.


My advice is to just GO FOR IT. Buy some extra fabric and go crazy!  Feel free to ask me advice!! I’d love to see what you’re working on!!

One thought on “The Big Scary: Sewing a Custom Swimsuit

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