Lay out your fabric well in advance and allow it to rest flat at least a few minutes, carefully graining your fabric. Read about the MPD help article about swimsuit fabrics for more information on suppliers and tips for working with swim fabrics.

Prepare the pattern:
I color over the important fold and mark lines so I can see them clearly and not “forget” something.

Note that Seam Allowances for swim wear is ¼ inch NOT 5/8ths.

Adjust the closure depth for the type closure you desire.

The circle represents the swim or molded cup placement at true under bust and bra band.

General Notes:

Thread: Polyester threads are ideal so sewing on most swim fabrics. I often suggest organic thread with organic fibers and synthetic with synthetic.
Your swimwear may be subjected to chlorine and or salt which are very destructive to organic threads. (Hint: the “chlorine out” type shampoos may be used to wash your finished swimsuit and will extend its life!)

Elastic:

Have on hand sufficient thin lingerie elastic or rubber swim elastic to use on the armholes, leg openings and possibly around neckline to snug in the swimsuit to the body.

Elastic may be ¼ to ½ inch.

Swim Hooks: (or water resistant Buckles!) May be used.

Sewing machine stitches: It is important that you use a stretch stitch when constructing your swimwear. There are two types available the zigzag stretch stitch and the elastic stitch. I use both in the same swimsuit. Use the zigzag stretch stitch to apply elastic around the armhole, legs and often at neckline.

The stretch elastic stitch often represented as ||| three dashed lines is used for connecting side seams and shoulder straps and crotch pieces.

If you use a straight stitch the spandex will stretch- the stitch wont and you will have popped seams.

You may also serge your swimsuit pattern pieces together. However, I think you will find the stretch zigzag stitch is your best friend at the legs and armholes.

Always take a scrap of fabric, set your machine(s) stitch, and tensions as needed and do a test!



Linings:

After deciding on your pattern style, decide if your suit will be fully or partially lined. Use the same pattern pieces for the lining IF the stretch factor is the same. If the stretch of your lining varies from your fashion fabric, before closing the pattern out, change the stretch factor and reprint a separate lining pattern!

Also decide if a swim cup is adequate or if you need a molded cup.

Tip: Some swim fabrics and even linings are very slippery and cutting them out directly will leave “choppy” edges. To avoid this lay white wrapping paper tissue on your cutting table then the fabric then another layer of tissue. Weight well. Sewing weights, hardware store large “washers” even tuna cans work. Use the smallest thinnest, sharpest straight pins you have and pin only in seam allowances! Click here for more on sewing with slippery fabrics.

The example will be for a full front lining. Make sure to print your pattern with the reference lines on so you have guide points to help map your placement.

Use  colored pencils and rulers to trace off a full or partial lining and accurately place your swim cups once you have drawn them on your main pattern pieces.

The bottom may be a partial lining set the height based on the waist line position and trace off the lower half of the suit.

Find the bust apex and color over so it is very visible.

Mark down from apex to the true under-bust the amount of the bust radius from your chart. Draw a line.

Then add ½ inch seam allowance (or a bit more) for an under cup bra band.

For the bandeau simply cut on the cut line of the seam allowance line, you will then have from top of strap to the bra band as an insert or partial front lining.

These marks will help place your cups and bra band.

Center the cup on the pattern and press inwards to let the cup stand on the apex center. When centered allow the cup to stand as it will wear.

Trace around the cup

Transfer these marks to your lining fabric. You may use graphite paper, dressmakers tracing paper, chalk or basting tack stitches( even washable markers)

Make sure to mark the bust apex point on the lining!

You will be centering the “cup” apex UNDER the lining.

Remember the “right side” of the lining will be facing in towards you!

Carefully lay out the swim lining.

First place the cup CENTER under the apex and make sure you have the span and the cups level!

On molded cups press in at center and the cup will “stand” on the apex. If the cup is darted from the bottom make sure to check placement.

From the “wrong side” pin the cups in place over your marks.

Flip over and stitch from the “right side”.

Pin around the cup and using a straight stitch sew the cups in place.

You may wish to do a few basting stitches first and try the front lining on you or your dress form to make sure they are level!

Stretch slightly as you stitch but be careful not to offset the cup!

Once this is completed and on your table again, the lining will sit like saran wrap on a bowl.

Trim away the lining from the cup itself.
 

Zigzag around to finish the edge using the stretch zigzag stitch.

You may wish to add a length of bra band elastic under the cup to snug it to the body. Cut the band two inches less than your front under bust measurement and stretch as you stitch. Place the band so it is on the true under bust line within the seam allowance (or extending slightly below it.)

Sew the side seams; you may leave shoulder seams open and crotch open! Add the back to the front lining.

Now construct the fashion fabric swimsuit. Again, leave shoulder seams and crotch open.

Insert the lining into the swimwear.

Finish the neck, armhole, and crotch with lingerie or swim elastic. Refer to the MPD help article on this topic for more detailed directions.

Adjust the shoulder straps if necessary and stitch.

Enjoy your custom fit swimsuit!