swimwear

May 30, 2025

Sewing Swimwear? Quality counts

There is nothing more timeless (or useful) than a high-quality, well-made swimsuit. I recently had a customer who is an avid swimmer contact me after 10 years to make her another set of swimsuits. Although I usually purge dormant patterns from customers, I still had hers and her shape had not changed much during in the 10 years. The original suits had for the most part withstood the onslaught of chlorine and salt and were just starting to show some loss of recoil in the elasticized edges. This is understandable as the elastic fibers are usually the first to go. But all things aside, 10 years says a lot about the garment. Let’s look at what it takes to make a high-quality swimsuit and then in a future article, delve into staple garments of high quality.

Two tank-style swimsuits created by Kim Larcom with Astrosports Activewear.

It’s All in the Layers

It is important to look at the layers of things to consider in making a timeless swimsuit—or event a garment for that matter. By layers, we refer to the considerations you must ponder for that garment to still be viable in terms length of time of wear and its fashion trend longevity.

Style

The first layer we see is the style of the garment. Visually, a garment will always be in style if it suits the wearer, meaning that it accentuates the figure type. With fashion trends constantly changing, there will be short-lived styles, but a well fitted, high quality swimsuit in a style that flatters the wearer is always in style. Also, remember trends cycle. As a longtime seamstress once told me; 7 years to come in, 7 years in style, and 7 years to go out. By that time, they are back in style. If you are lucky to be around long enough, you will see this trend on repeat.

Fit

If a swimsuit fits the wearer well and is the correct style for the anthropometry (size and stature) of the wearer, the visual results will be positive. There are design details that one can use to flatter the figure as well.

Using gathers to add volume, or using color blocks mixed with colors to create optical illusions are great factors to keep in mind. These details applied to a well fitted tank-style swimsuit will never go out of style.
Within the suit base, you can eye out details of neckline shape, both front and back, shoulder strap width and placement on the shoulder, and the cut and shape of the leg style both front and back.
A slightly higher cut leg can have the visual of creating a longer leg, but without a well fitted seat it can cause the seat or bottom of the back of the suit slide out of place. One thing a wearer does not want to deal with is constantly fixing the back of the bottom of the suit or the straps. So, length, width, and placement all count towards a well-fitting garment. Not only will this flatter the body type but will feel comfortable and be functional as well. Less is not always best when it comes to coverage.
You can add a variety of support mechanisms including a shelf bra, underwires, or sewing cups right into the lining. They are not as hard as they might appear to accomplish. There are a lot of similarities with sewing lingerie and bras to sewing swimwear. Both are very close fitting with little or no ease and have small seam allowances.

Choosing Fabric and Lining

When choosing your fashion fabric, choose exquisite fabrics! The most resilient and brilliant colored spandex fabrics have an 80% nylon / 20% spandex blend. That is not to say that some polyester blends do not work, but they usually will not have the same resiliency and it will affect longevity. When looking at prints, try to look for fabrics that use the wet print method of dying the fabric as opposed to heat sublimation. When fabrics are heat sublimated, the colors fade as the garment is stretched. Try it out when you get a spandex fabric next time. Grab 5 inches and stretch it. Look at the print colors. Do they fade with stretching? If so, that will happen as the garment is worn.

Weight of fabric is also a consideration. Anything less than 5oz. per sq. yd. is too thin and will not last or have the structure needed for a suit to last. Anything higher than 7oz. per sq. yd. might be too heavy when wet so look carefully before choosing. Study your fabric, look at the direction of the print and how that will translate when laying down your pattern. At best, aim to achieve the greatest amount of stretch going around the body; while making sure it works with the print design. You do not want to have sideways designs on the print going in the vertical of the suit.

Lining

You can line the front and/or the back of the swimsuit. The lining plays an important role in a well-made garment as it allows the garment to slide onto the wearer and also protects the fashion fabric from perspiration. It also protects the textile of the fashion fabric from the wear and tear of friction. Lining fabric does have a right and wrong side so study it closely to determine top from bottom. Use a lining that has the same or very close to the stretch coefficient of the fashion fabric. I often use bold colors in the lining as well, because the garment should look as beautiful on the inside as the outside—a ‘tell’ of a high-quality garment! If you happen to be using light colored fashion fabrics such as yellows or whites, then it is best to use a color of lining that closely resembles your skin tone. It may appear that this will show through, but rest assured, it won’t.

Cut the lining as you did the fashion fabric, so that the greatest amount of stretch goes around the body. Use a 4 way stretch fabric so the tension lines can be created in when the garment is worn. This, of course, presupposes that you have put thought into creating these tension lines in your planning of the design details of the suit itself. I have found after many years of doing swimwear that the pattern on the lining is 1/16^th smaller than the original garment pattern. You can trim the seam allowances of the lining after you cut it out or make an additional lining pattern with these specifications. This is often done on collars in blazers to account for turn of the cloth and a better overall fit of the garment.

Strap Placement

Strap placement and size is a consideration for a functional suit. Straps that are place too far away from the neckline will constantly fall off unless you add a back horizontal support strap. The properties of spandex do help immensely with this, but you must know how to use it to its full advantage. Spandex will support with creating tension lines vertically and horizontally, but the strap must have horizontal tension created by strap width, and vertical tension created by the strap placement with respect the shoulder point and neckline. Find just the right spot so the strap stays put, combined with the best width, allowing the spandex do its work, then add elastic for added security and structure. A comfortable armhole that gives you the coverage you need will help you decide the best strap placement.

Construction of the Garment

It is best practice—but not required—to use an overlock machine to do the bulk of the construction. You can use a lockstitch, coverstitch, or zigzag stitch to do the finish work. I use a combination of these, depending on the suit. You can line both the front and the back, or just the front as previously mentioned.

Sewing the crotch: I never line only the crotch area for all the reasons discussed above about what the function of the lining plays in the overall integrity of the garment. If using both a front and back lining, stack your garments in the following order in preparation to sew the crotch:

Wrong side up of front fashion fabric—to right side up of back of fashion fabric—to wrong side up of back of lining—to right side up of front lining.

In essence, you have stacked the fashion fabric front and back, right sides together, and the front and back lining right sides together underneath. When you have completed sewing the crotch seam, the right side of the front lining should lie against the wrong side of the front fashion fabric, and same for back. The beauty of this is that the crotch seam is encased so the overlocked seam does not lie against the body. Ideally, you can do this for the side seams and shoulder seams too as well. My sewing order is crotch seam sewn, shoulder seams, then side seams. I do this in a chain fashion to save time, then clip the connected trail treads.

Applying the Elastic

Apply elastic to the wrong side of the swimsuit, on the lining side, with an overlock machine or zigzag stitch on your conventional machine. The stitch lengths and widths depend on size of elastic. Use a larger zigzag stitch on larger width elastics; however, a 2.5 width and 2-3 length is a good starting point. Although some use a three-step zigzag, I have found after years of experience that less-is-best when it comes to thread in the elastic as it will allow the elastic to keep its recoil and resiliency. Although I do use the three-step zigzag on lingerie

Type of Elastic

The best type of elastic for swimsuits is cotton braided elastic. It comes in a variety of lengths and has a beige or crème color to it. Knit elastic does not have the resiliency in the high-tension areas, and nylon braided is too thick. You can use latex elastic but if you so, use the no stretch techniques and make sure your patterns are commensurate with that.

Length of Elastic

Learning what NOT to do: Ready to wear now uses a smooth look to elastic. This means the elastic length is almost the same length as the opening. In order to do this, your pattern has negative ease, meaning smaller than the body size so that the garment stretches when on the body. This allows the garment to look smooth on the rack for retail, but is a lesson in what not to do on your custom garment.

Years ago, the elastic was stretched to fit the garment hole and I still use this technique today in certain areas of the suit to get the best secure fit, especially if the suit is used for exercise or competition. In a deep curve area, you stretch the elastic and it can be up to .9 % stretch factor. Measure the area to be elasticized and multiply by 0.9 — this will give you the elastic length. You can match one to one on straight lines, then stretch over curves. A perfect example of this is the armhole area. The strap has straight lines so keep the elastic one-to-one there but pull it to fit the length when going around the underarm. Don’t stretch the fabric, only the elastic. It is not hard and a technique you will acquire by practice and tenacity.

An alternative is to get machine feet or tension mechanisms to do the work for you. Personally, I find that you need various stretch techniques within one garment… and who has time to keep changing feet or attachments! If you use the stretching elastic technique, you will see the results in the garment when it’s off the body; however, remember that a swimsuit is worn on the body which is where it needs to fit well, be functional, and look good so don’t worry about the gathering effect that stretching elastic causes. Paying careful attention to this in the leg opening means a successful swimsuit. Stretch the elastic to fit over the backside of the swimsuit with less stretch in the front of the leg line. This helps the back “cup” over the derriere.

Practice with your elastic:

Anchor a 5” piece of elastic to a table via tape or pin it to a garment, with a tape measure underneath.
5″ x .05 (5 percent stretch) =.25, so 5″+ .25 = 5.25.” Practice stretching the elastic from 5” to just under 5.25.“ Then practice stretching 5” to 9.5,” which is a 90% stretch, etc.
You can calculate for any stretch coefficient you want. Oftentimes, lingerie will use a 3% strech, which is a very little bit but a good technique to practice when using very little stretch.

Neckline Elastic

Neckline elastic application for both front and back will use a combination of stretching elastic to little (3%) or no stretching, depending on the style lines.

I will often time write my cutter’s “must” measurements for each swimsuit on the patterns:

Neckline opening, cut elastic _______
Armhole opening, cut elastic _______
Leg line opening, cut elastic ________

The Order of Things

The order for applying elastic to your swimsuit can be varied. I usually do neckline, armholes, and leg openings. Sometimes there is a back opening as in a keyhole back. When overlocking the elastic to the opening, it is placed on the wrong side of the garment, with the elastic side up, and the right side of the garment against the feed dogs.

You can also bind elastic edges to have a contrast look to your suit. When doing that, cut off the width of elastic for the area; for example, if using ¼” elastic, trim off ¼” from that opening. Then remeasure the area, cut a strip of binding the length of the opening (or you can use the stretch coefficient plus ½’ seam allowance). Sew the binding strip in the round technique and then pin to the opening right sides together. Cut the elastic at 90% stretch length, plus ½” overlap, and pin to the opening. You will have to stretch the elastic in the appropriate areas as you are sewing both the elastic and binding to the opening and trim off the excess after topstitching (see below.)

Topstitching to the Finish

Next on the list is topstitching. Turn the elastic to the wrong side when topstitching with either a zigzag or coverstitch machine. The right side of the fabric should face up and the elastic side should face the feed dogs. You could also stitch with the right side against the feed dogs and the wrong side up if using a zigzag stitch. If using a zigzag, zig on the elastic, then zag just at the edge or just off the edge, using the edge of the pressor foot as your guide depending on the width of elastic used. If using a coverstitch machine, keep the needles close to the outside edge of elastic so it will hold it down. Whichever way you decide to orient the fabric with respect to the feed dogs, use your left (or non-dominant) hand to hold the fabric in a perpendicular line to the line of the stitching. This will help keep tension on the spandex fabric so it is held snug to the elastic and you will not get any rippling. You may need to pull on the elastic as you go around the curves just like you did when inserting the elastic. Topstitch all the elasticized edges in any order you want. I typically do the neckline, then armholes and, finally, the legs.

If you need to do tacking of thin straps, then use a bar tack or a small-width, short-length zigzag stitch.

If you have decided to bind the elastic edges, you would need to trim off the area to be elasticized an amount equal to the width of the elastic on the garment itself. Remember you will not be turning under the elastic but rather turning the binding over the elastic and topstitching it from there. You can use a variety of methods to topstitch; zigzag, coverstitch, etc. Use your hands to pull the binding snugly over the elastic and around the wrong side of the garment by holding the edge of the binding with your non-dominant hand, and manage the topstitched area with our dominant hand. For example, I am right-handed, so I use my left hand to hold taught and slightly pull it perpendicular to the line of stitching while my right hand guides the garment. Sometimes your left hand (or non-dominant hand) will be underneath a part of the garment which is ok – you will get used to doing it with practice. Be especially careful around curves to keep the binding tight around the garment and the area being bound for a nice, smooth, topstitched finish.

Ironing It All Out

I iron my spandex when all is complete using a piece of silk or polyester organza over the garment which allows me to see the garment area to be pressed. Use steam over the elastic and allow it to recoil to its original (or mostly original) length. Finally, I always tell my customers, that to preserve the longevity of their garment, they should wash it in cold water, with clear, gentle detergent. Rinse it well, and hang the garment dry out of direct sunlight to preserve the elastic fibers.

Like any other type of garment, it will take practice to get acclimated to working with stretch garments but just think of all the suits you can make while trying. Not wearing swimsuits anymore? I am sure there are plenty of willing subjects who would be delighted to reap the benefits of your swimwear sewing musings! Long-lived and long-loved swimsuits is the end result.

~Kim Larcom, ASG Member (Boston Chapter), known as The Bridgewater Seamstress, is the Entrepreneur for Astrosportswear Activewear. She graduated from the Master Seamstress certificate program at the University of Rhode Island and owns her own custom activewear business.

August 9, 2019

Sewing Swimwear – Tips of the Trade

DIYStyle® for the Millennial Sewer

by Cindy Cummins

Editor’s Note August, 2022: This article has been updated to remove links that are no longer operational

To say that I’m passionate about sewing is an understatement. With more than 35 years’ experience in the industry, from working in sewing education to designing some of the first serger patterns, I’ve gained some valuable knowledge to pass down to young sewists. This is one of the reasons that I launched DIYStyle® along with designer (and my daughter) Allyce King. We frequently offer tips on anything and everything related to sewing, but we are particularly qualified to give tips on a certain subject: Sewing Knits & Swimwear.

History

In addition to working together at DIYStyle, Allyce and I made up part of the team at Allyce King Swim, a custom swimwear company that focuses not only on suits for the pool, but suits for the stage. Our line was worn by competitors nationwide, including Miss USA, Miss America, Miss Teen USA, and Mrs. United States, just to name a few.

Allyce first started learning swim and activewear design and sewing techniques in fashion design school, graduating from Stephens College. She later honed her designs and techniques with seamstresses in the sample workroom, and in production. Design, line, fit, color, and optimal style for body type are of key importance with these discerning customers. Allyce was one of only a handful of designers in this niche, and many clients won in Allyce King Swim suits.

Our Swimwear Creation Tips

It all starts with the best tools, good lining, and best quality 4-way stretch fabrics. These are a few of our favorite notions/tools and tips that are important as we are creating new sample pieces.

Use clips instead of pins for most all construction, including applying elastics. We especially like the pointed ones for ultimate control in tight places.
Tech Elastic works best for swim and activewear as it is latex free, does not break down with chlorine or sweat, and does not have that messy powder like some other rubber elastic tapes. We discovered this while Allyce did pageant swimsuits, as many of the girls had latex allergies. We use this for all of Allyce King Swim pieces.
Use a chalk liner for markings. It brushes off most swim and activewear fabrics. Test color first on a swatch. We most often use white and pink for most colors.
Texturized thread is great for ultimate stretch with 4-way stretch fabrics and the movement swim and activewear garments require. This thread is nylon or poly, and is crimped. It has some “spring” to it, making it stretch and recover–just like the S-T-R-E-T-C-H knit fabric.

Tips for Swim/Activewear Construction

Cut with precision. A 1/4” difference is a LOT in swim and activewear. Use a set-up that does not distort or stretch the fabric when cutting. Our magnetic DIYStyle Pattern and Cutting System works great for this! The low-profile magnets hold slippery fabrics like swimwear in place, while keeping the fabric from pulling and stretching. We also use our Pro T-square for cutting straps and bands precisely. We’ll give you more information on our system below.

An ongoing debate with sewers! Are you team Rotary cutter or team Shears? We lean to the rotary cutter in our studio, as we feel it cuts faster and is accurate for our needs. But some sewers feel more comfortable with a great pair of sharp shears. As long as you are not lifting up or moving the fabric as you are cutting (thus distorting the cutting line) both work just fine. Especially helpful with either method our FabricMagnets™ (in lieu of pattern weights) along with the magnetic mat, hold everything in place for cutting precisely.

Make a stretch muslin. We use fabrics that are similar stretch to the finished design to judge the fit and design of a garment. It’s so much easier to make adjustments on the muslin than to fit and reverse sew the fashion stretch fabric! Once the muslin is fit, sewing the final piece goes so much faster.

Linings are important in swimwear. Don’t ever leave out the lining. We have a special lining that we use for the Allyce King Swim line that is heavier for our pageant (stage) clients. For a suit worn in the water, the lining must have similar stretch as the fashion fabric to fit properly. White swim lining makes fabrics look brighter, nude is another choice standard, and black for dark fabrics. And interlining with a stretch mesh adds another layer of control, hugging the body and smoothing lumps and bumps. Cut this the same as the lining, sandwiching between the swim (or activewear) fabric and lining.

Use Tech elastic to control edges, and where elastic is needed. We like 3/8” wide for all of our suits, and it’s most appropriate for all swim and activewear. Here are the steps we use for applying and finishing elastic quickly and neatly.

1. Apply Tech Elastic to edge. We use the serger for a professional application. The edge of the elastic tape rides along the seam line (our patterns have ½” seam allowance, so we trim a scant 1/8” while applying. Use a 3-thread wide stitch with a 2.5 stitch length.

2. Fold over and secure. We prefer the coverstitch for this step, but you can also use a multi-step zig-zag or regular zig-zag for finishing. A wide or narrow coverstitch can be used, with a 2.5 stitch length. This is also where the texturized nylon thread works great in the looper for ultimate stretch. Be sure to fold over, then stretch the elastic up to the fabric, but do NOT stretch the fabric as you are securing the elastic. Stitch close to the inside edge of the elastic, with both needles penetrating the elastic.

3. Prevent tunneling (that ruffled looking edge) by pulling elastic taught, while smoothing the stretch fabric at the same time before securing.

Ongoing debate #2! Sewing machine vs. Serger for sewing swim and activewear. While we prefer the serger and coverstitch combo, you can definitely sew swim and activewear with a sewing machine that has just straight and a few zig-zag stitches. Because you are sewing a stretch fabric, you will need a stitch that gives and recovers with the fabric. The only time we use a straight stitch in swimwear is for basting linings, gathers, and stabilizing areas with twill tape that we do not want to stretch. A narrow zig-zag is appropriate for seams, while a multi-step zigzag is best for applying elastic and finishing.

Speaking of seams, watch the exact seam (stitching) line as you are sewing. As stated above, ¼” is a lot in swim and activewear! As you are sewing or serging, be sure the needle is directly on the seam line. If serging, engage the knife so the excess is trimmed off. If sewing, trim the excess after, close to the zig-zag stitching. For serging use a 3-thread wide stitch, 2.0 stitch length. For sewing, use a multi-step zig-zag, with 2.5 stitch length, and 3.0 width.

Straps need elastic! Fabric tubes alone are not sufficient for hold and stretch on a swimsuit (or workout garment), especially once that suit hits the water! We use a French-filled strap method for creating all swim and activewear straps. This creates a professionally finished and pretty strap, filled with elastic.

Creating your own swim and active pieces is actually faster than shopping for a swimsuit (and we know how we all dread that)! Using these tricks of the trade, and you will be on your way to adding your own custom suits to your wardrobe.

Saving Time—Increasing Accuracy

Along the (sewing) journey at Allyce King Swim, we invented a new system and method for cutting fabrics fast as well as making patterns efficiently. Used in our studio for a few years, we recently brought our new Magnetic DIYStyle Pattern and Cutting System to the home sewer.

With this new magnetic set-up, you can cut fabrics in 2/3 the time, as well as increase accuracy in cutting (1/4” is a LOT in swimwear). No more pins! This is especially important in producing a line for customers–reducing time spent in the prep is key.

We also use our specially designed Pro T-Square for aligning pieces, as well as cutting strips. We are extremely proud to have our DIYStyle Pattern and Cutting System made in the USA. In doing so, we employ several individuals with disabilities, as well as veterans.

With the addition of this new product, DIYStyle® revolves around designing, developing and promoting new products that help the home sewer and small design businesses. And we continue to offer the on-trend fashion projects creators love.

~Cindy Cummins, DIYStyle